# Making Perfectly Squared Pieces



## Careysub (May 7, 2011)

Hi:

I am starting on a series of telescope building projects and am still getting my tool and skill set together. Telescope bodies are made from top quality plywood, and because it is a precisely aligned piece of optical equipment the pieces must be squared up accurately as well.

I have limited space for tools (no permanent set-up table, and my tools are all stored on shelves, the heaviest ones like my disk sander on the bottom shelf).

Currently I have been cutting square pieces using a portable router and top or bottom bearing bits. I just finished cutting 8 pieces, being as precise as I could manage, and I did a pretty darn good job. But - it was painstaking to do and the pieces weren't perfect (though only a close inspection with a square on the stacked boards reveals that)

Looking through box-making forums and websites I see that the use of a jointer and a table saw together is accepted standard practice for doing this - neither of which I own, would have trouble finding space for even in smaller bench-top versions, and would prefer not spending the money on if I can avoid it. Also I would rather not use a table saw for safety reasons.

I am thinking that a table router set-up will allow me to make the straight square cuts I need quickly and efficiently. 

Does anyone have any advice about the best way to do get a set-up that will do this?

Since my needs are somewhat specialized I am thinking a custom built rig is the best way to go. I am looking at getting a router plate and installing it on a sheet of MDF or melamine particle board (for the nice slick surface); getting a length of large (3"?) aluminum angle and facing it with melamine board for an accurate straight and vertical movable fence, and making a small separate zero-clearance fence for safety so that only the cutting edge is exposed on one side. 

Not sure how to mount the movable fence however, and while this will get me straight parallel edges, I am not sure how to make the pairs of parallel sides an accurate 90 degrees.

Any advice is appreciated.


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## harrysin (Jan 15, 2007)

Careysub said:


> Hi:
> 
> I am starting on a series of telescope building projects and am still getting my tool and skill set together. Telescope bodies are made from top quality plywood, and because it is a precisely aligned piece of optical equipment the pieces must be squared up accurately as well.
> 
> ...


There are a number of ways to achieve what you require, but with your limited resources, the method shown is probably the simplest. Make an accurate sample of what you want out of 3/8" MDF or whatever material you have on hand,then rough cut as many pieces of your chosen material, slightly bigger than the sample, which is in fact a male template. Pin or stick using double sided tape, one at a time the pieces to the template and, using a starting pin or better still the fence, guide the assembly over the straight bearing bit from right to left, this is VERY important.
I realise that the photograph shows a round template stuck to a piece of Acrylic but the principle is as outlined above and because it's 10.00pm here and cold out, it's saved me from going into my shed to take some photographs. By the way, welcome to routerforums, where all your questions will be answered by many knowledgeable members.


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## Quillman (Aug 16, 2010)

This is the answer (A & B) but it is not trivial, an all router table approach. The sled slides against a special pivot fence (somewhat viisible in A). The 10 pound aluminum sled holds work in such a way that it cannot move. Nothing deflects.The fence on the sled is calibrated to 90.000 and indicated. Provision is made for blowout prevention on every cut, and ply splinters as bad as any wood product. Does it cut square? It does and consistantly. I cut wood, plastic and metal to ~+ or - .001 in width and length. Fast? Maybe 2 or 3 seconds/slice and a few seconds to reload the work. So expect a couple samples/minute.
Plans and support for such a thing exist? Nope, just a few ideas for you.


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## Phil P (Jul 25, 2010)

Hi Pat

I suppose the question has to be what amount of investment is that? On installs I typically saw or rout a straight edge by holding/clamping a Speed Square (7in or 12in) with the lip against the straight edge furthest away from me. This technique is shown in this YouTube video at about 0:37 (with a circular saw, router works in a similar way). The technique works acceptably on thinner Corian (which requires really tight joints) but you do need to buy a good quality Speed Square and make sure that it's absolutely square first, and it helps if your router can be used single handed. Fortunately I have a Festool router which fits the bill, although I imagine a D-handle or body grip router such as those by Porter-Cable or Milwaukee would do just as well

Regards

Phil


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## istracpsboss (Sep 14, 2008)

Hi Phil

Are Speed Squares available in the UK?

Cheers

Peter


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## The Warthog (Nov 29, 2010)

Coincidentally I am also starting a telescope, an 11.5" truss-tube dob. You can make a straight edge for cutting with a circular saw. I have a 5' one that I use for cutting sheet goods. This one How to Build a Simple Circular Saw Guide for Straighter Cuts - Popular Mechanics is very similar to the ones I use, except that I used plywood for the guide edge and clamp them in place after drawing my cut line. If you put a cleat on as shown in the pictures, that will square up your cut automatically. I used plywood for the guide edge as a 1x4 is not guaranteed straight, as the cut edge of plywood or MDF always is.

Let us know how your telescope progresses.


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## Phil P (Jul 25, 2010)

istracpsboss said:


> Are Speed Squares available in the UK?


Hi Peter

Yes they are. Even B&Q do a cheap one. I got a 7inch one there for £3, which I now use for rough framing (with a Makita cordless saw - no need to drag a chop saw about), but for a decent one (e.g. a Swanson) you'll need to go to Tool Venture, although they do cost a bit more

I might as well mention in passing that for truly straight edges on long edges of sheet material you can't do much better than a Festool TS55 plunge saw and one of their guide rails. I use just such a set-up regularly and it really is worth its' weight in gold to me. Although as BobJ might say, "Whew! What a price!"

Regards

Phil


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## bobj3 (Jan 17, 2006)

Hi Phil

I bet you wish you could buy tools from the USA.

http://www.amazon.com/Swanson-SO101...ref=sr_1_1?s=hi&ie=UTF8&qid=1309365451&sr=1-1

http://www.amazon.com/gp/product/B000056C0D/ref=noref?ie=UTF8&s=hi&psc=1
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Phil P said:


> Hi Peter
> 
> Yes they are. Even B&Q do a cheap one. I got a 7inch one there for £3, which I now use for rough framing (with a Makita cordless saw - no need to drag a chop saw about), but for a decent one (e.g. a Swanson) you'll need to go to Tool Venture, although they do cost a bit more
> 
> ...


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## Phil P (Jul 25, 2010)

bobj3 said:


> I bet you wish you could buy tools from the USA.


Well Bob, I suppose that's the price of living in a more socialist society with free health care, etc. :cray:

Regards

Phil


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## The Warthog (Nov 29, 2010)

Well, Phil, come to Canada, it is a more socialist and therefore freer society, and you can buy all the stuff the Americans can, except guns.


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## Phil P (Jul 25, 2010)

The Warthog said:


> Well, Phil, come to Canada, it is a more socialist and therefore freer society, and you can buy all the stuff the Americans can, except guns.


That sounds ideal in many ways. How many hours sunshine do you guys get each year? Only joking! I reckon I'd be too old to get in now anyway. Ho, hum.......


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## bobj3 (Jan 17, 2006)

Hi Phil

hahahahahaha maybe if you save more money on buying tools right so you can pay your own way and not count on the Gov. to give you help on health care ...

" socialist society " = ???,,, free in the USA and many must think so, we take in many,many in the USA unlike the UK..

I'm sure that will open a new can of worms 

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Phil P said:


> Well Bob, I suppose that's the price of living in a more socialist society with free health care, etc. :cray:
> 
> Regards
> 
> Phil


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## Careysub (May 7, 2011)

Quillman said:


> This is the answer A & B... but it is not trivial, an all router table approach. The sled slides against a special pivot fence (somewhat viisible in A)....
> Plans and support for such a thing exist? Nope, just a few ideas for you.


Thanks - I was thinking of some sort of sled to get the right angle cut (only need one per board, because pushing the right angle side along the fence with makes the other perfectly parallel). Your example gives me some ideas, like the use of toggle clamps.

Right now I envision a melamine surfaced table, a fence made from 3 inch aluminum angle faced with melamine board sliding on two T-track rails; a sled based on a couple of inches of 6 or 8 inch aluminum angle (providing the right angle) attached to the edge of a 18 mm baltic birch square, which rides in turn on a sheet of Formica, the Al angle edge against the fence would be faced with a polyethylene board strip.

The sled would have two small toggle clamps to hold the stock sheet down on the Formica keeping its edges flush; I might need rollers that clamp to the back of the fence to keep the sled flush against it, but I'll see (provision will be made int he design).

This looks like it would allow me to make repeatable parallel and right angle cuts quickly.

Not a cinch exactly, but that bad either I think.


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## istracpsboss (Sep 14, 2008)

Thanks Phil. Usual story. Priced in Pounds what they sell for in Dollars in the States, even with the alleged discount !

For straight line cuts I've a Bosch on a base that fits my clamp guides. Muuuuch cheaper than Festool and does the same job. That Bosch even plunges vertically rather than in the usual arc.
Buy ProGrip Universal Base from Axminster, fast delivery for the UK

Cheers

Peter


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## Careysub (May 7, 2011)

The Warthog said:


> Coincidentally I am also starting a telescope, an 11.5" truss-tube dob... This one "How to Build a Simple Circular Saw Guide for Straighter Cuts - Popular Mechanics" is very similar to the ones I use...
> 
> Let us know how your telescope progresses.


Thanks - I have been using edge guides to cut with circular saws, but have been somewhat dissatisfied with the accuracy of the cuts I get - adding the plywood guide surface that is flush with the blade might be just the ticket.

This doesn't address the right angle cut problem though (I'm thinking off a special sled and a table router set-up for this).

The scope I am building is a 13.1 incher. Next will be 16 inch (or maybe a 17.5 inch).


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## Careysub (May 7, 2011)

With further research I think that using a length of Rockler multi-track for the fence and tapping the sled 6 inch aluminum angle for T-bolts will simplify it a bit and give me a zero-slop horizontal slide action.


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## TWheels (May 26, 2006)

I have a life-long interest in astronomy, so I am following this thread with great interest. May I ask why a square body?

Carey, I have a "shop(pe)" very much like yours, and the problem of perfectly (within practical limits) is not restricted to telescopes. I am very interested in the responses you get. The double-sided tape and square as suggested by Bobj3.

I have used a coping sled.


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## Careysub (May 7, 2011)

mftha said:


> I have a life-long interest in astronomy, so I am following this thread with great interest. May I ask why a square body?
> 
> Carey, I have a "shop(pe)" very much like yours, and the problem of perfectly (within practical limits) is not restricted to telescopes. I am very interested in the responses you get. The double-sided tape and square as suggested by Bobj3.
> 
> I have used a coping sled.


It is quite true that this is not restricted to astronomy, my comments at the start about the necessity of a jointer and table saw are from general woodworking forums regarding box building.

I specified my application to telescope making to define the problem more exactly - in the more general box building context a jointer/planer may be desired or essential because the faces of the stock may not be flat. Since I work exclusively with factory-made sheet goods this is not a problem for me and removes a key reason for using a jointer/planer. (It also means I am not making small square pieces, but ones with long dimensions of the order of 12 to 24 inches or so.)

The reason for being square is due to the use of digital encoders for tracking the telescope movement. A 10,000 step digital encoder has an angular resolution of about 0.6 milliradians (~ 1/30 degree) and to get the best performance out of these the telescope body itself needs to be squared with this level of accuracy. (This overstates the accuracy needed a bit, I may use a 4000 step encoder instead, and the field of view is going to rarely be as small as 0.1 degrees or so anyway, more typically 0.25 degrees or more, so a small misalignment will still put the sought object on the FOV).

Thanks for mentioning the coping sled, looking this up I see that I have basically reinvented the coping sled in coming up with a sled design for my table set-up. I will probably build my sled (I already have all the parts), but a commercial sled will be a backup in case I don't like some aspect of its performance.


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## Chris Roeder (Oct 3, 2010)

Carey, I built my third router table, I buy my hardware from Rockler Tee slot track, Tee slot bolts, lockinng knobs and miter track . Go to Rockler.com it's a candy store.

Thank you, Chris


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## david cooksey (Jun 3, 2011)

*Kreg Square Cut*

I use a Kreg Square Cut for small stock


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## Tempest (Jan 7, 2011)

> The reason for being square is due to the use of digital encoders for tracking the telescope movement. A 10,000 step digital encoder has an angular resolution of about 0.6 milliradians (~ 1/30 degree) and to get the best performance out of these the telescope body itself needs to be squared with this level of accuracy. (This overstates the accuracy needed a bit, I may use a 4000 step encoder instead, and the field of view is going to rarely be as small as 0.1 degrees or so anyway, more typically 0.25 degrees or more, so a small misalignment will still put the sought object on the FOV).


It would be nearly impossible to achieve such accuracy with standard woodworking tools. All routers/bits have runout and it's comes down to how much. 

Trying to measure accuracy like this without dial indicators I think would be impossible. Highly unlikely that a speed square is this accurate.

A quality machinist square would be a minimum.


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## Phil P (Jul 25, 2010)

Tempest said:


> Trying to measure accuracy like this without dial indicators I think would be impossible. Highly unlikely that a speed square is this accurate.


I'm beginning to wonder at what would be achieved by resorting to dial calipers on plywood, though. It starts out only passibly flat, it can warp as tensions are released by the cutting process and it will swell or shrink measureably as the relative humidity of the surrounding air changes with the weather. MR-MDF is appreciably better but is much less rigid. Anything built from a timber-based product has to take these inherent "defects" so trying to "engineer" wood seems in many ways counter productive.

Regards

Phil


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## rrlindh (Feb 22, 2010)

Your high taxes pay for your and other freeladers health care


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## Finleyville (Feb 28, 2010)

Careysub said:


> With further research I think that using a length of Rockler multi-track for the fence and tapping the sled 6 inch aluminum angle for T-bolts will simplify it a bit and give me a zero-slop horizontal slide action.


That is exactly what I did for my router fence except I did not need to use the aluminum angle. I wanted to use the Incra-jig for my router table. However, the retail and plans for their fence was only a single piece fence. I wanted a split fence for jointing operations too. All I do is slip some shims behind the outfeed side. The sub-fence is MDF for stability reasons.


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## JOAT (Apr 9, 2010)

Well, I guess I would do it more the K.I.S.S. style (Keep It Simple Stupid). Homemade router table, no fence because for my work I don't need one. I make wooden figure banks, which surprisingly need precise size pieces, 16-17 pieces in each bank, believe it or not. 
Anyway, I make a very precise master out of 1/2" plywood. This means I could modify the first, not precise master, and make a more precise second master. Has taken up to about five redos on complex pieces. Then when you get that dead-on master, rough cut another 1/2" piece of plywood, and glue it to the first master. Then when the glue dries, you rout the second piece, using the glued on first piece as a master. This will give you a very accurate master that is one inch thick. 
The one inch thick master is much easier to handle than just 1/2"; plus then you won't mistake your master for a finished piece and inadvertently use it, then have to make another. Also I use a magic marker and write "master" on it, and any esstential information, like measurements. 
Then I drill a series of small holes thru the master, for tacking the master to the piece to be routed to size. More holes than needed really, because at times some pieces need more nails to hold the piece being routed as vibration will sometimes loosen some of the nails. The nails are very slim, and about 1 1/4", they only need to be tacked in about 1/8". Experience will tell how many nails are needed. 
These can often be just pulled apart when finished, or I found a 6" nail puller at the hardward that works better than anything I have found for pulling loose the nails, or prying the pieces apart.
If you original 1/2" thick master is accurate, all the routed pieces will be accurate also. I use a 1/2" pattern router bit. If I plan on making more than one piece of something it is usual practice for me to make a master. 
I have masters for silhouette chess pieces now also, and those come out nicely. I got very frustrating with hole saws for making round bases, and was going to buy a specialized tool for doing that, then realized I could just make a round master, and make round bases in less than a minute each. Closer to 30 seonds actually. 
Works for me.


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## tbear (Mar 7, 2009)

With all the accuracy you seem to want you might be better off purchasing some machinist measuring tools and setting up your system from there and make each setup for a specific angle etc. You can get some pretty good tools like a "Sin Bar" setup from Grizzly Tools.
They have good dial indicators, if you get any dial indicators I would stick with the analog style, I'm finding that all these new Dial Indicators and Calipers that are digital seem to eat up batteries. A nice set of 1-2-3 blocks is good top have. I found some on Ebay for a inexpensive price. Hope this helps.
Seems to me that if you want that kind of accuracy you might want switch to plexiglass or some other material that will not change with the ambient temperature and humidity.


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## Careysub (May 7, 2011)

Tempest said:


> It would be nearly impossible to achieve such accuracy with standard woodworking tools. All routers/bits have runout and it's comes down to how much.
> 
> Trying to measure accuracy like this without dial indicators I think would be impossible. Highly unlikely that a speed square is this accurate.
> 
> A quality machinist square would be a minimum.


The problem is more tractable than it seems. 

To get the sky tracking system precisely aligned there are really only about three alignment issues - the azimuth axis (the merry-go-round rotation axis) and the altitude axis (for up and down motion) must be orthogonal, the two encoders must be aligned with the axes of rotation, and the telescope optical axis must be (when vertical) align with the azimuth axis.

With an optical to azimuth bearing axis length of 54 inches a 0.1 degree alignment amounts to a 2 mm tolerance. This is a bit tight, but vertical alignment with a plumb bob should be able to meet this without too much trouble. The horizontal axis is much shorter (16 inches say) so the tolerance is no more than 0.6 mm, I don't expect to be able to do that just by careful woodcutting and assembly.

Reasonably priced digital inclinometers ($30-$40 range) can make vertical and horizontal measurements of 0.1 degree allowing post-assembly leveling to that degree of accuracy.

The final arbiter of alignment is the digital tracking system itself. If you align the telescope on a star, spin it around, then realign on the same star the tracking system won't return to the original value if the scope if not closely aligned. But the digital setting misalignment tells you what type of misalignment you have and its relative magnitude. Repeated shimming and testing can then eliminate the problem.

But all this aligning is much easier if the pieces are as square and squarely aligned as possible. A well squared of the pivot box ensures that the pivot wheel are closely co-planar and makes the initial horizontal alignment more accurate and easier to shim.

One thing I have quickly learned is that right jig/tool set up can take a manual process that can give good results only with lengthy painstaking attention, and give a better result fast and (nearly) automatic.


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## Careysub (May 7, 2011)

tbear said:


> With all the accuracy you seem to want you might be better off purchasing some machinist measuring tools and setting up your system from there and make each setup for a specific angle etc. You can get some pretty good tools like a "Sin Bar" setup from Grizzly Tools.... A nice set of 1-2-3 blocks is good top have. I found some on Ebay for a inexpensive price. Hope this helps.


Thanks, yes it does help - I was not familiar with Sine Bars or 1-2-3 blocks and now I have some other tools to investigate.



> Seems to me that if you want that kind of accuracy you might want switch to plexiglass or some other material that will not change with the ambient temperature and humidity.


I do have some laminating ideas that address this - using kevlar or carbon fiber, or bonding plywood to closed cell foam.


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## Careysub (May 7, 2011)

Phil P said:


> I'm beginning to wonder at what would be achieved by resorting to dial calipers on plywood, though. It starts out only passibly flat, it can warp as tensions are released by the cutting process and it will swell or shrink measureably as the relative humidity of the surrounding air changes with the weather. MR-MDF is appreciably better but is much less rigid. Anything built from a timber-based product has to take these inherent "defects" so trying to "engineer" wood seems in many ways counter productive.
> 
> Regards
> 
> Phil


I a using aluminum angle and square tube to provide an internal/external framework for the plywood boxes that will hold them rigid. 

I tried doing a dry clamp-up of the box with the interior aluminum corner angle in place using corner clamps for a one-step assembly process, but it complicates squaring the assembly up. I haven't gone to gluing it yet (I want refinish the edges first) and am considering just gluing it up with butt joints to assemble the box then epoxying in the aluminium angle to give it its stiffness, stability and strength.

In some sense it becomes an aluminum frame struture, with the plywood/epoxy serving as a fabric that joins the framework together.


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