# Puzzle - best way to straight & parallel...



## AshleyJ (Dec 1, 2017)

The problem: Starting with a sheet of plywood, I need to cut a full length piece with two perfectly straight and parallel edges.

Sounds easy right... that's what table saws are for? Ah, but there's no table saw available... The challenge is to do this with no power tools other than a cordless circular saw, a cordless drill, and a router. And just to make it interesting, the longest available straightedge that I trust is only 36".

Additional context... When I say "perfectly" straight, that begs questions about acceptable tolerances. Think tool-worthy tolerances rather than furniture or construction quality. The pieces I'm cutting will become references for other projects and/or pieces of jigs/tools.


The crazy solution I'm considering...

First, either trust a factory edge, or (my choice) make one edge straight as follows...

When oriented right, my Bosch RA1054 edge guide looks remarkably like a jointer, so add a thin piece of laminate to the "outfeed" side of the guide using double stick tape.
Put a 1/2" spiral bit in the router
Align the router bit with the shimmed outfeed side
Use the router like a jointer - making a few passes along the length of the plywood.
Although the edge guide's "infeed" and "outfeed" fences are only 5" long each, we're starting with a factory edge, and a few passes "should" leave that edge as straight as possible within the tool constraints.

Second, make a cut, perfectly parallel to the reference edge...

Remove the laminate shim (see step 1) from the edge guide
Insert a 1/4" spiral bit (or perhaps 1/8"?)
Set the edge guide to cut at the right width
Then make a series of increasing depth cuts to cut off the piece - referencing from the previously straightened edge.
 

The questions I'm asking... since ya'll have more router hours than I have router seconds...

Is there any reason this can't or shouldn't work? Any safety concerns?
What changes would you make to the above procedure to improve safety, precision, or anything else?
Is there an entirely different procedure you'd recommend? (Like buying a proper straightedge and using it as a saw guide instead of using a router for a saw.)
What should I be asking that I'm not asking? (ie the things I don't know that I don't know.)


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## Stick486 (Jan 4, 2013)

time to get you a quality clamp on straight edge...


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## DaninVan (Jan 1, 2012)

Re the router edge guide;
Ashley, I don't have mine handy, but I think there's screw holes in the two flat metal edge guides (either side of the bit cutout).
You could mount aluminum extrusions on either side to extend the length of your straight references...say maybe a foot either side.
I had wooden extensions on my old Craftsman edge guide for years.

Forgot to mention, my old wood shop teacher warned us to not ever trust the factory edges on plywood. Mind you technology has changed dramatically in the last 50 years. No idea whether modern plywood is guaranteed perfectly square and straight...


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## JOAT (Apr 9, 2010)

I would imagine you could always go to a local woodworking shop, and have them do it, if nothing else. I'd likely just use the edge off of a sheet of plywood.


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## DesertRatTom (Jul 3, 2012)

I think the factory edge is pretty straight. Now, the question is how do you get the inside edge equally straight? Well, you have two strait factory edges. Buy some excellent ply to start with, not the cheap stuff that will splinter on you. If you're using a circular saw, work face down. Place painter's tape along the cut line, preferably on both sides. Now, cut the sheet down the middle as straight as you can. Now you have two straight edges to work with. Cut a couple of wooden blocks the width of the final straight edge you want, adding the offset for the saw blade. My 18v saw is offset by 1 1/8 th inch, so if I want a 6 inch wide strip, I'd cut the squares 7 1/8th inch. 

Lay the blocks onto the edge of the bottom piece, butt the straight edge of the other half up against the blocks. That's going to give you a good cut line. Clamp it together and make the cut being very careful to make the cut straight. Draw arrows toward the factory edge, otherwise you'll forget.

Now, you have two straight edges. Use them to trap the saw's base and your cuts will be very straight. Cut as many straight edges as you want. Do trap the base, it is really a challenge to cut a truly straight edge without trapping the saw.

Now I have a track saw, but this is how I have done it before the that, using my nice little DW 18v saw. I have an 8 ft aluminum L beam that cuts a fairly straight line, but it is not a perfect straight edge. 

Last thing, if you can get a premium saw blade, full kerf if possible, or if your saw will accept it. Hope this helps.


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## Danman1957 (Mar 14, 2009)

Ashley,

You didn't mention if you own/use a square or a T square to check how straight the edge is. That would be my first stop. I have a 4ft T square that I use for drywall marking and cutting, and also to check squareness on large sheet goods. I ran a business several years ago and our neighbour was a wholesale sheet goods vendor that had a wide variety of sheet goods. During a discussion with the manager, he stated that while the sheet goods manufacturers AIM for perfect 90 degree square edges, reality is they cannot guarantee it. A perfect example is some sheet goods come in 49'' x 97'' to allow for both slight damage caused by handling and also for out of squareness. I check this when it is to be used for furniture or jigs etc... and to be honest, I have not come across a sheet that was enough out of square to merit an adjustment cut. In my humble opinion, using a circular saw or a router are both possible, the choice is which one are you more comfortable and confident during use.

Dan


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## DesertRatTom (Jul 3, 2012)

My suggestion above will work about as well with a router. My only concern is that you used the word "perfectly" and "tool worthy." We work with wood, which moves, twists, is under unseen tension, and variances in straightness and thickness, wierd grain patterns. Prefect can't exist in woodworking. A precision straight edge is expensive. A 96 inch precision straight edge is a deal breaker for most of us. You'll find that even your carefully cut ply straight edge will make it almost impossible to draw a perfectly straignt line with a pencil. But for jigs and guides for woodworking, it will be good enough. I visited Laguna a few years ago and in the process they brought out their macined straight edge, which they kept carefully packaged to prevent dings. I hate to think what they paid for those four foot straight edges.

To tell the truth, that's my main reason for buying the track saw. Although I could cut a nice edge with my table saw, hoisting and feeding a 4x8 sheet of 3/4 ply through the saw is just not going to happen anymore. I got a Triton track saw--great, straight, no-tearout cuts, middle price range. Add a premium full kerf blade, a fine lead mechanical pencil for marking, and you have the right tools for the job.


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## chuckgray (Aug 2, 2015)

You could buy the plywood sheet at one of the big box stores and have them make the cut for you on their panel cutting saw. I don't know what the tolerances are for the saw, but all the cuts that I've had them do seemed to be pretty accurate/straight.


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## AshleyJ (Dec 1, 2017)

Hmmm, it seems we're split on whether the factory edge is a trustworthy straight edge. If we assume it is, then Tom's technique is perfect... simple, obvious in retrospect, but I was stuck at the incorrect mental assumption that cut #1 had to be perfect. By allowing cut#1 to be imperfect, I get two straight edges from the outside edges of a single sheet and from there everything falls into place. (Thanks Tom for a nice whack on the side of the head!)

If we don't assume the factory edge is perfect, then Dan's suggestion (use aluminum extrusions to lengthen the edge guide) improves my router based jointing approach and gets me the two straight edges needed to use Tom's technique. And, it allows me to use the saw to saw and drop that second step with the router-as-saw.

Stick and Dan, I like your suggestions for straight edges as I trust them more than a factory edge, but I'm not aware of either solution in lengths sufficient for ripping an 8' sheet. I have a ten or twelve foot length of 2" angle iron for this purpose, but it's in a storage unit a couple states away.

Unless someone else pulls another rabbit out of their hat, I'll probably do two things...

Use a tight string to be picky about the edge when selecting plywood... then use Tom's technique... then test my newly cut edges against each other to see how good they are. I'm OCD tempted to use feeler gauges, but they're in the same storage unit, so an index card will probably be the gauge.
If the results are too sloppy, and if I believe the factory edge is the issue rather than my technique, then I'll order some extrusions (like this or this or this) to extend my edge guide, and use the router to get two straight edges before using Tom's technique to get the parallel edge.

Tom, you have my number with that track saw. Although I'm not ready to buy one yet, my first use for a long straight edge is turning my saw into a DIY tracksaw so this problem is solved well enough to stop missing my table saw. I don't really want to replace it since I have at least one more move in my near future.


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## DaninVan (Jan 1, 2012)

Ashley; it doesn't necessarily have to be metal extensions, it's just that would be my preference...no flexing. Aluminum is lighter but steel would also be fine, except that would add a bit of unwanted weight.
Wood works just fine... a couple of 3/4" x 1" strips of Birch or whatever you have.


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## DesertRatTom (Jul 3, 2012)

I agree on fitting two sheets together on edge to test for straightness. I used an aluminum L shaped angle iron for awhile, but it flexed a little with the saw against it. Never thought to test it with a string or thread. 

Take a strong friend along with you to wrestle the sheet goods. You'll want to pick some a few sheets down the stack to avoid damaged or warped sheets. The concrete floors are reasonably flat so shouldn't be a problem. Given your storage and shop limitations, I doubt you'll be using these for long. 

Get a 4x8 sheet of insulating foam while you're there. Makes cutting easier when the ply is sitting on the foam, laid out on the garage floor.

I find it fun to think these things through.


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## hawkeye10 (Jul 28, 2015)

chuckgray said:


> You could buy the plywood sheet at one of the big box stores and have them make the cut for you on their panel cutting saw. I don't know what the tolerances are for the saw, but all the cuts that I've had them do seemed to be pretty accurate/straight.



Chuck, that sure isn't true where I live. You are lucky my friend.


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## tomp913 (Mar 7, 2014)

DaninVan said:


> Ashley; it doesn't necessarily have to be metal extensions, it's just that would be my preference...no flexing. Aluminum is lighter but steel would also be fine, except that would add a bit of unwanted weight.
> Wood works just fine... a couple of 3/4" x 1" strips of Birch or whatever you have.


Back when I was making solid surface tops, I had a straight edge that was made from a piece of 3/8" thick x 5" wide aluminum flat - sneaked it in the back door at work and they kissed the one edge flat to within less than .005" on the big mill. Sure wish I still had that.

You can check a straight edge with a string line, or with a laser if you have one. The straight edge doesn't have to be super stiff/heavy - I've seen a metal stud recommended for this use - all you need to do is clamp a couple of ply strips to the material being cut to butt against the back of the straight edge and prevent deflection - I've used 3" wide strips of plywood, long enough to run from the opposite edge of the sheet and butt up against the back of the straight edge. It goes without saying that the blade being used should be sharp, and the work area set up so that the cut can be made in one nice even pass, nice even feed rate, no stops and starts.


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## Cherryville Chuck (Sep 28, 2010)

The method for checking squareness of a sheet:
Measure the length of each side. If parallel sides are not equal in length then the sheet is not square.
If parallel sides are the same lengths measure across the diagonals. If the diagonals are equal then the sheet is square.


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## Nickp (Dec 4, 2012)

I would recommend getting a good straight edge rather than reinventing the mouse trap...routers are not good at cutting like a saw is intended.


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## woodknots (Mar 7, 2012)

This is my version of a "track saw". An 8 foot length of 1x2 poplar on a 1/2" piece of birch ply. I attached the poplar on the ply, leaving a little wider than the base of my circ saw, then using the poplar as a straight edge, cut the ply to the exact with of my saw base to the blade. Clamp the straight edge to the sheet goods on the cut line and rip away. The guide is marked with the name of the saw used to make it. I've got one in a 4 foot length as well.


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## DaninVan (Jan 1, 2012)

"The guide is marked with the name of the saw used to make it"
-Vince

OMG! You name your tools?!


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## Stick486 (Jan 4, 2013)

DaninVan said:


> OMG! You name your tools?!


you have a problem w/ this???


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## woodknots (Mar 7, 2012)

DaninVan said:


> "The guide is marked with the name of the saw used to make it"
> -Vince
> 
> OMG! You name your tools?!


Nope, just the jigs:grin:


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## AshleyJ (Dec 1, 2017)

DesertRatTom said:


> I find it fun to think these things through.



Yes, what an adventure! That's the other reason I'm not in a rush to replace my table saw - I'm exploring how much I can bootstrap with the minimal tools I have on hand. I enjoy figuring out what can be done, what sequence is necessary/optimal, and how to maximize precision. That makes up for my withdrawals from the amazing shop I used to use at the Dallas makerspace.


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## Stick486 (Jan 4, 2013)

Ashley...
you need a quality straight edge...


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## DesertRatTom (Jul 3, 2012)

vchiarelli said:


> This is my version of a "track saw". An 8 foot length of 1x2 poplar on a 1/2" piece of birch ply. I attached the poplar on the ply, leaving a little wider than the base of my circ saw, then using the poplar as a straight edge, cut the ply to the exact with of my saw base to the blade. Clamp the straight edge to the sheet goods on the cut line and rip away. The guide is marked with the name of the saw used to make it. I've got one in a 4 foot length as well.


This method works pretty well, but you need a really straight 1x poplar. Best way to do that is with a jointer. Can also be done with care with a hand plane. This jig is for cutting a straight line with a circular saw, it is not a straightedge. 

BTW you can turn a router with a split fence into a jointer by placing a small amount of padding 2-4 playing card thickness material behind the left fence half. Align the straight cutter to the protruding half with a short straight edge. This becomes a limited jointer with which you can straighten the 1x. If you do this, fasten the 1x to the 1/4 backer right away, start with as straight a piece of poplar as you can find. 

Once jointed straight, get the 1x parallel to the cutoff edge, but make sure the backer is wider than you need. The first time you use this, the saw will cut off the excess and you'll know exactly where the cut line will go. It will also reduce tearout.

Put some painter's tape on the cutline to further reduce tearout, and/or make a very shallow scoring cut (1/16th deep), work face down and use a good blade and you'll have a decent jig for cutting ply sheets. Make a continuous, no-stops cut. 

Have you noticed how many times the word straightedge comes up? :wink:


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## woodknots (Mar 7, 2012)

DesertRatTom said:


> This method works pretty well, but you need a really straight 1x poplar. Best way to do that is with a jointer. Can also be done with care with a hand plane. This jig is for cutting a straight line with a circular saw, it is not a straightedge.


Not sure if this is directed to my response, which you quoted, or posted for Ashley's benefit.

*Tom, a jig for cutting a straight line IS a straightedge Whether it's a store-bought, clamp on version or homemade like mine is of no consequence. It still functions as a straight edge.*



DesertRatTom said:


> BTW you can turn a router with a split fence into a jointer by placing a small amount of padding 2-4 playing card thickness material behind the left fence half. Align the straight cutter to the protruding half with a short straight edge. This becomes a limited jointer with which you can straighten the 1x. If you do this, fasten the 1x to the 1/4 backer right away, start with as straight a piece of poplar as you can find.


*Been there done that, and posted several pictures of my router table fence, as jointer in previous threads*




DesertRatTom said:


> Once jointed straight, get the 1x parallel to the cutoff edge, but make sure the backer is wider than you need. The first time you use this, the saw will cut off the excess and you'll know exactly where the cut line will go. It will also reduce tearout.


*The 1x doesn't need to be parallel to the cut off edge. The first cut will make the backer parallel to the 1x*

Put some painter's tape on the cutline to further reduce tearout, and/or make a very shallow scoring cut (1/16th deep), work face down and use a good blade and you'll have a decent jig for cutting ply sheets. Make a continuous, no-stops cut. 

Have you noticed how many times the word straightedge comes up? :wink:[/QUOTE]


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## Cherryville Chuck (Sep 28, 2010)

I have a cutting guide just like Vince's but I used 2 pieces of ply for mine. One for the straight edge and the other thinner one for the base. I think the edges of panel boards are pretty straight these days. If you've ever seen video of the process that trims the sheets I don't know how they would not be straight. The ends years ago might not be straight. They were cut on the fly and if the chain or belt carrying the panel was out of phase with the cutoff saw then the ends wouldn't be square to the sides. I haven't seen that in quite a while and I do check periodically when it does matter to what I'm doing.

Vince didn't really make a point of pointing out that you make the base part wider than the saw cuts and on the first pass with the saw you cut the excess off which shows you precisely where the blade will cut (depending on using the same saw and saw blade). That allows you to mark the cut you want without having to calculate the offset of the base to the blade. The only thing you have to remember is which side of the marks you make you want the saw blade to cut on. This method is way easier and more accurate than using a straight edge because it eliminates measuring that offset.


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## Danman1957 (Mar 14, 2009)

Vince and Chuck,

I am planning to build a jig like that but in a magazine the plan calls for the hardwood piece to be 107'' long. Would this be a special order from a sawmill ? I don't think they would cut only one board to a specific length. Do you guys use something longer or just use 96''

Dan


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## Stick486 (Jan 4, 2013)

a 10' stick of VGCF will work...


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## woodknots (Mar 7, 2012)

Danman1957 said:


> Vince and Chuck,
> 
> I am planning to build a jig like that but in a magazine the plan calls for the hardwood piece to be 107'' long. Would this be a special order from a sawmill ? I don't think they would cut only one board to a specific length. Do you guys use something longer or just use 96''
> 
> Dan


Dan - an 8 foot piece will be long enough - that's all I used. Remember that the shoe of your saw will make up the small difference. The hardwood piece doesn't have to extend past either end of the sheet goods.


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## DesertRatTom (Jul 3, 2012)

@vchiarelli Vince, if you don't have a perfectly straight piece to guide the saw, you won't necessarily have a straight edged cut. I'm differentiting between a straight edge and an edge that's straight. A straight edge in my thinking is something near machine perfect or within a few thousandths. Yes, if you use something really straight as the guide, the first cut will make it parallel, but not automatically straight. 

My suggestion about being careful about laying the guide piece as close as possible to parallel with the edge you'll cut off is just good practice, but I'm quite fussy about such details. You use a really accurate straight edge for many different purposes, including using feeler gauges to check for flatness. This happens rarely, but I'd never trust a saw cut edge for such purposes. Again, laying the guide close to parallel to the cut off edge is largely a matter of my fussyness about making things like this jig. If your jig is off, everything you make with it will be off. 

Last thing: If you have a long hand plane (#6 or #7), you can clamp the 1x to the bench side and plane it quite flat, but that's a costly solution compared to using either an existing planer or setting up the router as a planer.


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## Cherryville Chuck (Sep 28, 2010)

Tom the sole plate of the saw is close to a foot long. Any small imperfections it will average out and as I said, if you've seen the process where the sheets are trimmed then I don't know how they would not be straight. If you aren't sure then lay 2 sheets side by side and see if there are any gaps between them. My bet is that there won't be.

My guide is also only 8 feet long too so just standard sheets of ply. One way I did screw up though is not accounting for how low the motor sits and how long it is. It bangs into my clamps if I have the motor set for a deep cut so make the guide wide enough to avoid that.


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## Biagio (Mar 2, 2013)

I have used an idea borrowed from a jig that used to be commercially available in the US years ago: a straight-edge screwed onto a length of MDF, particle-board or plywood - much like Vince's. Rather than cut off the board with a circular saw, the cutting is done with a router, with an up-down solid carbide compression bit. Then a base plate is attached to the circular saw, so that the saw cuts about 2mm outside of the edge of the board. 
The initial cut on a sheet is made with the circular saw, placing the edge of the board on the cutline, as Charles explained. Without moving the board, the final cut is made with the router, with the same compression bit - takes care of any tear-out from the saw, without fussing with scoring cuts, tape, etc. Also, the final cut is properly perpendicular to the face of the board being cut - not always achieved with cheaper saws or non-premium saw blades (you would not believe how much premium blades cost in these latitudes).
Incidentally, if the guide is made double sided (i.e. with the same width of board on either side of the metal straight-edge, any small imperfection in the straightedge will not matter - provided one marks the pieces to avoid confusion, cutting mating edges on either side of the straightedge will give mirror-image edges - gap-free when joined edge to edge.
I have the guides in two sizes, to break down sheet goods lengthwise or widthwise.


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## woodknots (Mar 7, 2012)

@DesertRatTom - Tom - I know my piece of poplar is straight. I used a string stretched tight from one end to the other, then glued and nailed the long piece to the sub base using the string as a guide. Then I cut off the excess to give me an exact width for the saw I used. Keep in mind I only use this to break down larger pieces, then cut to width on the table saw.
@Cherryville Chuck - Charles - when I put the long piece on the sub base, I left some overhang on the left so that I could clamp it down with the hand screws on the bottom and avoid hitting the motor. I raise the blade high enough so that it only barely goes through the sheet goods. This keeps the motor above the hardwood.
@Biagio - Biagio - I made one in both 8 foot and 4 foot for that very reason - lengthwise and widthwise.


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## DesertRatTom (Jul 3, 2012)

Hi Charles, I was trying to differentiate between a functionally straight cut edge, and a real, machined straight edge. I was using something like your jig before getting the track saw. It worked OK, but it didn't take much of a wobble to have a noticeable kink in the cut. The difference for me was made evident when I measured one wing on my table saw with a serious straight edge, only to find out it had a little over a mm bulge and was not flat. Got a replacement saw for my effort and got to see the techs set it up and check with a machined straight edge (bar) and feeler gauges. I used my real straight edge on my fence recently only to discover that it's not really flat across the face. For that kind of thing I have a 4 foot, good quality straight edge. 

I know that the length of the saw's base averages out small variations so you'll cut a relatively straight edge on the workpiece. I was detailing a method to cut an edge pretty darn straight and also suggesting the value of a real, high quality, precision straight edge. Part of that was about getting a solid wood guide rail nice and straight when using a strip of hardwood for the saw guide. Very hard to find a piece like this that's truly straight to begin with. Warps and twists, even if slight, need to be flattened out first. Yes you could cut and use a factory cut edge for that purpose, but not if you're a nit picker like me. 

No offense meant by my posts, we're talking varieties of apple differences, not apples and oranges. Nuff said.


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## Cherryville Chuck (Sep 28, 2010)

Tom there are so many other variables affecting the cut such as the amount of freeplay in circ saw bearings, and you leaning well past your effective reach as just a couple of examples, the idea that you will cut off a piece that is absolutely dead on perfect is the same to me as when Jerry Bowen was absolutely certain that he could duplicate cut offs to .001" accuracy with precise repeat ability.


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## AshleyJ (Dec 1, 2017)

@stick, what's VGCF?
@All, I'm really enjoying this thread. Thanks for caring enough to share so many opinions and differences of opinion.


Sent from my moto x4 using Tapatalk


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## DesertRatTom (Jul 3, 2012)

Hey guys, what's the problem. I use the straight edge for precision setup. I like precision, but understand it's impossible with wood. I'm not disagreeing with anyone, just pointing to the difference. If we're talking about cutting ply to close tolerances using a guide instead of hoisting a ply sheet onto a table saw, then you want a VERY STRAIGHT cutting edge--or at least I would. Which is why I got the track saw. 

Couldn't get that kind of cut with the shop made jig. Maybe you can, but I sure didn't. You can cover a lot of sins on cutting cases by adding a face frame, but as I said, I'm fussy. 

If you're going to cut to rough sizes, then finish on the table saw, then you only need to keep the factory edge against the fence. That's anothe story. 

I'm glad you all are happy with the shop made jig, I was too, until I popped for the track saw. So what's wrong with wanting to use a solid wood guide rail that has been straightened on a planer? Sure you can use the edge of a slice of ply or particle board or MDF, but is there something wrong with wanting the extra stiffness of a solid wood piece? 

We just have a minor difference of opinion about the material and construction method, but we all know everyone has different approaches to this great hobby. Nothing invalid about any of our posts so far as I can see. Just minor differences and every one of us is as right as any other. Whose tag line is it that there are many ways to do anything?


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## woodknots (Mar 7, 2012)

DesertRatTom said:


> Hey guys, what's the problem. I use the straight edge for precision setup. I like precision, but understand it's impossible with wood. I'm not disagreeing with anyone, just pointing to the difference. If we're talking about cutting ply to close tolerances using a guide instead of hoisting a ply sheet onto a table saw, then you want a VERY STRAIGHT cutting edge--or at least I would. Which is why I got the track saw.
> 
> Couldn't get that kind of cut with the shop made jig. Maybe you can, but I sure didn't. You can cover a lot of sins on cutting cases by adding a face frame, but as I said, I'm fussy.
> 
> ...


Tom - there is no problem - hope you haven't taken the responses personally. Not sure if you misunderstood but I use a solid piece of wood as a "fence" to guide the saw. The only ply is the base portion and it is solid enough when it's laying flat and clamped to the sheet goods. I choose not to spend several hundred dollars on a track saw because I don't need one. In my shop I break down sheet goods with my homemade jig. In my buddy's shop we routinely break down full sheets of melamine and mdf on his unisaw, but there's always two of us handling the material and we can rip a full sheet lengthwise and it won't fall off his outfeed table.

What I like about this forum is that people have different opinions/ways of doing things - none of them are wrong - and they are willing to discuss those methods without any animosity (as I've seen on other forums).


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## AshleyJ (Dec 1, 2017)

@Tom, I know you choose the track saw for ease of use, but I think you'll appreciate this commentary on its precision also...

William Ng demonstrates the 5 cut method of checking square on your table saw sled… to skip the sled making and see the test, to to 31 minutes in... 




Same method of checking square with a track saw and mft... 





The tldr is that both methods can have comparable precision. 

When I talked about precision in the opening post, that was what I was seeking. I'm not building a milling machine. I am exploring ways to work without a table saw... without compromising precision. It's not only about the results, it's also about the joy of pursuing of perfection. Why aim lower?

@Danman1957... and anyone else building a DIY tracksaw... Since this type of jig is part of the build sequence I'm pursuing, I'll share a few related sources I find interesting...

Dave Stanton's DIY tracksaw is interesting for its integration with his DIY MFT, and for his unusual build sequence to guarantee all relevant pieces are perfectly parallel. His approach is tailored to using the Parf Guide System, though a similar build sequence is possible without that system. 




Most DIY track saws run the saw's base plate against a guide on one side. As DesertRatTom mentioned in post #5 of this thread, a more effective solution is to trap the saw like a real track saw, so it can't shift away from that guide. One of the simplest approaches I've seen to this is attaching a miter slot bar to the saw base and running it in a dado in the track like this... 





My intended solution will use a dado like the 2nd video but also have a row of holes like the first - since I will use it with a MFT type table for square cuts. I may also route a full length dovetail on the bottom to accept clamps sliding in underneath like a commercial track.

Enjoy!


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## Cherryville Chuck (Sep 28, 2010)

The track saws are great tools Tom but a lot of members, especially the newer younger ones, don't have $700 to $1000 to buy one with. I have a Unisaw and like Vince's friend I have a long enough out feed table that the cuts will sit there without falling off. But getting a full sheet up on the saw is getting to be a problem so I will often slide the sheet out of the truck onto saw horses and make the intial breakdown to where I can handle it.

And yes I often cut slightly oversize and cut to finish size on the Unisaw but I have also roughed out pieces with the guide and then used the guide to make a finish cut when I was then able to lean over comfortably and cut the entire length in one relatively smooth non-stop motion and the guide will make a good enough finish cut doing it that way. The reason I choose plywood for both top and bottom pieces is that I could count on the ply to be straight and stay straight. Wood can be a crap shoot. Plus using ply is cheaper in the long run because if you plan right you can usually get those strips off a sheet and still have enough for the rest of a project or two without shorting yourself. And the plywood is plenty stiff enough. I think I used some 5/8 D fir sub floor ply for my guide fence.


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## tomp913 (Mar 7, 2014)

Watching the video showing the construction of the "home-made" track saw, I noticed that he didn't address checking that the saw blade is parallel to the edge of the saw base - but then I've never seen one that did. And it may be that it's not a problem - maybe the manufacturers take care of this already - maybe I'll check mine and see how close it is. 

As an aside, the method used to prevent the straight edge from bowing was what I was trying to explain in an earlier post, a quick and easy way to eliminate/prevent any bowing of the straight edge used.

Like Vince, I used a home-made straight edge (1/4" tempered Masonite/plywood fence) for many years, both in 4' and 8' versions - the 8' version was pretty cumbersome as I was working out of a townhouse basement at the time so storage of the 8' version was a problem - and no noticeable deflection as the guide was pretty wide (cut-off width + fence + clamping surface on the back of the fence). I switched over to an aluminum track (2 x 57" lengths) that came with a saw base that mounted to the base of my circular saw, and still have it although have gone in a different direction since then - see photo. There are several manufacturers who offer their version, all for around $200, and who provide a means of adjusting the base parallel to the saw blade when mounting the base to the saw. The photo shows a quick fixture I made whenr moving my base to a different saw - 15 minutes work and no cost as it was all scraps.


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## DesertRatTom (Jul 3, 2012)

Lots of good solutions.


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## AshleyJ (Dec 1, 2017)

@tomp913, I measured my circular saw a couple months ago and was surprised how far off it was. Rather than using the jaws of the micrometer, I placed the part that sticks out when it's opened against the flat of the blade (not teeth), and the joint where it meets the rest of the micrometer against the edge of the base. 

I don't recall the exact measurement, but I was surprised how far off it was. I really expected it to be right on. After a few moments stewing about it, I realized that it was off by less than the difference between the thickness of the flat of the blade vs. the kerf width... and concluded that's probably close enough... but that doesn't mean I'm thrilled about it.

I've considered building an adapter plate for the bottom of my saw, perhaps like the one in the next video. The video doesn't show a specific procedure to get the attachment perfectly parallel, but I think that's solvable.


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## tomp913 (Mar 7, 2014)

AshleyJ said:


> @tomp913, I measured my circular saw a couple months ago and was surprised how far off it was. Rather than using the jaws of the micrometer, I placed the part that sticks out when it's opened against the flat of the blade (not teeth), and the joint where it meets the rest of the micrometer against the edge of the base.
> 
> I don't recall the exact measurement, but I was surprised how far off it was. I really expected it to be right on. After a few moments stewing about it, I realized that it was off by less than the difference between the thickness of the flat of the blade vs. the kerf width... and concluded that's probably close enough... but that doesn't mean I'm thrilled about it.
> 
> ...


 @AshleyJ

Most of the commercially available saw bases that I'm familiar with provide a means of installing the base on the saw with the saw blade parallel to the guide/locating feature of the base - the home-made jig that I showed is similar to what one manufacturer provides with their base - but it's fairly easy to come up with your own version. Let's look at the one shown in the video where two aluminum strips are screwed to the bottom of the saw. Assume that the location of the aluminum strips is determined by the design of the saw base - measure the distance from the blade to the first strip and between the two strips; add 1/4" to the first dimension, this gives you an overhang on the straightedge to trim with the saw at the final step. In addition to your straight edge, prepare a second piece the same length as your saw base and cut the two grooves for the aluminum bar with your router. Now, trim off the additional 1/4" on the second piece - this will give you the required dimension from the face of the saw blade to the first strip. Drill a couple of holes through the plywood, over the grooves and where you want to put the attaching screws for the saw base. Lay the aluminum strips on the saw base and set the plywood over it, capturing the aluminum and move the assembly over until the edge touches the saw blade - you may need to trim the edge where it touches the blade if it interferes with the teeth. Clamp the plywood to the saw blade, drill & tap through the access holes and bolt the aluminum strips to the saw base. Your guide strips are now parallel to the saw blade (no heeling = no burned cuts).

Looking at the video that you posted, you can do the same thing - a couple more steps to set the saw blade parallel to the groove that locates on the raised portion of the rail, and add the rabbeted strips that hold the saw base down as a final step.

FWIW I measured the parallelism of the blade to the locating groove on the assembly I showed in the photos that I posted and it was a hair over .001", was pretty happy with that.

I don't want to push a product, but I'm pretty happy with the set-up I have for ripping 8' plywood (and especially that I don't have to find somewhere to store an 8' straight edge). Take a look at the Eurekazone UEG and consider it as an alternate to a straightedge. Starting with a new sheet, I check the "factory" edge for damage (particularly high spots) and touch it up with an 80 grit sanding block - the fence on the UEG is about 24" long so kind of spans over slight depressions - and make the first rip maybe 1/8" oversize. Flip the part and use the new edge to trim the factory edge to give me finished width and then go from there. The UEG has a little bit of a learning curve - there's definitely a technique involved (but the same thing can be said about ripping on a TS, or even using a circular saw and straight edge) but it's capable of giving nice even cuts.


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## Danman1957 (Mar 14, 2009)

Stick,

What's VGCF ? I know it's not very good coli-flower LOL


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## Stick486 (Jan 4, 2013)

Vertical Grain Clear Fir


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## Job and Knock (Dec 18, 2016)

AshleyJ said:


> [*]Most DIY track saws run the saw's base plate against a guide on one side. As DesertRatTom mentioned in post #5 of this thread, a more effective solution is to trap the saw like a real track saw, so it can't shift away from that guide. One of the simplest approaches I've seen to this is attaching a miter slot bar to the saw base and running it in a dado in the track


However that approach limits the use of the saw to just on the track because every time you remove the bar from the base of the saw (to allow it to be used elsewhere) you will need to go through the set-up process yet again which can be quite time consuming. A real tracksaw has a groove in its' base which allows it to ride on the "hump" in the track - and a way to reproduce that would be to make-up a sub base with a groove in it to fix and leave on the saw. That would stay in alignment but reduce the depth of cut by say 5 or 6mm



tomp913 said:


> Watching the video showing the construction of the "home-made" track saw, I noticed that he didn't address checking that the saw blade is parallel to the edge of the saw base - but then I've never seen one that did. And it may be that it's not a problem - maybe the manufacturers take care of this already - maybe I'll check mine and see how close it is.


They do and I can ay for certain that the Festools and Makitas I've used have ways of adjusting the base to crrect the toe-in/toe-out as well as having ways of tightening or loosening the grip on the track "hump" (effectively a wear compensator) so that the saw doesn't shimmy as it ride the track

One thing I haven't seen here is any comment about useable straight reference edges. The most obvious one I possess is a 6ft spirit level - a very necessary item for any carpenter (or anyone wishing to do accurate installation work of furniture or joinery work) to possess. In order to ensure that your home-made track saw is straight I'd have thought that something like that was essential. far cheaper than any other long straight edge I know of


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## Cherryville Chuck (Sep 28, 2010)

I was getting poor results with my homemade guide and cheap circ saw when I finally decided to check for parallelism like you did. It was way out. One end was riveted to to the sole plate but the other was pinned on. I drove the pin out and filed the housing on the side opposite the direction it needed to move then used a washer to take up the free play. Now I get very good results with it.


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## DesertRatTom (Jul 3, 2012)

*Assumptions lead you astray*



Cherryville Chuck said:


> I was getting poor results with my homemade guide and cheap circ saw when I finally decided to check for parallelism like you did. It was way out. One end was riveted to to the sole plate but the other was pinned on. I drove the pin out and filed the housing on the side opposite the direction it needed to move then used a washer to take up the free play. Now I get very good results with it.


Very good. It sometimes makes a big difference when you check instead of assuming something is set up right at the factory. Even Bosch can screw up (not very often though).


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