# How to Cut 45 degrees



## kolias (Dec 26, 2008)

Making a box 24”x8” out of 5/8” plywood and I want to miter the edges at 45 degrees to hide the plywood looks.

I haven’t used my router in ages and even back then I was never good at it. The attached pictures shows my setup, the router is part of my table saw table and the fence does a dual job (either for the saw or the router).

The other picture shows the bit I have. It’s from a set I bought perhaps 20+ years ago and never used any bits. I just want to show what I have.

The last picture is my setup. The plywood to be cut is shown with the wrong end to the bit just to see what I want. When I will start, I will move the fence closer and push the plywood against the bit in small depth cuts per pass until hopefully I will have a nice 45 degrees edge.

Is it correct and safe what I plan to do?

Thanks


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## Biagio (Mar 2, 2013)

Hi Nicolas,
Essentially, yes. However:
1. That bit, though nice and solid, may be too small - I cannot be sure from the picture. The carbide edge should be long enough to do the final pass(es) in one go, without adjusting bit height. It will be enough to adjust the fence progressively back between passes, without fiddling with bit height. You can work out whether the carbide edge is long enough, by using Pythagoras' theorem.
2. I know you said the wood is the wrong way around, but it bears remembering that you will be moving the wood from right to left.
3. That setup is fine for long edges, such as you show. But if you want to do short edges, you will need some kind of support, to stop the wood rocking during the cut. The simplest would be a plywood right-angled "triangle", with a piece of wood glued/screwed under one short edge. This rail would run along the front edge of your table, keeping the workpiece at 90° to the line of cut. Or you could use a piece of square timber, making sure you keep it pressed along the fence.
4. Be aware that you may well get tear-out at the end of each cut, so you would want a scrapwood backer, that the bit could cut into (reusable for the final cut). If you are cutting short edges, the "triangle" or square guide can serve as the backer, provided it reaches close to the fence.
5 . Keep your fingers well away from flippy-spinny things, use push sticks and feather boards. You do not have grooves for feather boards, but they can be clamped to the table and the fence, especially if you make them yourself, and make them long enough. The goal is 10 in, 10 out (fingers, that is).
6. For efficiency, rout all the edges at a particular fence setting, before moving the fence back.
7. It pays to rout an extra board in each size, in case of snafu's.


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## DesertRatTom (Jul 3, 2012)

Good luck. This is really a job for a table saw, and I have never gotten that clean a cut on Chinese ply. This is something where you don't want any chip out. You want as many layers as possible, which only happens with some premium big box ply, or Baltic Birch, or ApplePly, a premium hardwood ply made in America.

You are also likely to have some issues with holding the box in place when you glue up the corners. That can be alleviated by using wide tape, face up, and laying the outside pieces end to end and just touching. You can fold this up so the tape holds the joint in place.

It is a very weak joint. Pre glue the ends, then add more when you put them together. That will help some, but half the ply shows the endgrain, so the adhesion is a little spotty.

If you have a table saw with a really good blade, you would first make a groove for the bottom on the inside of all four pieces. Be sure all four pieces are grooved the same. The bottom cut will be hidden at the corners after glue up. Cut the miter on one end, then use a stop block clamped to your miter gauge's fence and cut the other end. You can do this on your table with a miter gauge, or by clamping the stop block to whatever you're using to push the piece through. The piece will want to fly away when it hits the bit, so make sure it's secure.

On a router table, you can likely do this by butting the end of a piece precut for length against the fence, and aligning the fence to the center of the cutter. Instead of making so many passes and getting it just right. Set the fence for the final cut, and move the workpiece up toward the bit a little closer with each pass. Don't move the fence!

Unstead, put some sticks at the end of whatever you're using to hold the workpiece. Place them between the fence and carrier. That way you can control depth of cut and have it be the same for every piece. If you move the fence, you'll never get your pieces to match.

For real strength, you can use splines, see pix, either vertically inside the miter cut, or cut into the corners after assembly. For the pictured spline on a router, you will need a carrier you can get to 45 degrees. That means a jig of some sort slanted to 45 degrees and a small straight bit to cut the vertical groove.









For edge splines, you need a carrier that holds the box at 45 degrees. I generally use 1/8th inch blades and the the same thickness material for the splines, but you can make them any size you want.


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## CharleyL (Feb 28, 2009)

I find it easy to make mitered boxes using my table saw, but set the blade angle with a Wixey blade angle gauge for exactly 45 deg. I frequently then spline these mitered joints full length with cross grained splines that I make using my table saw and a tenon jig, but setting the jig so it cuts the spline from what would normally be the waste between the jig and the blade. The resulting tenon becomes scrap when chopped off with the miter saw. I can then flip the board over to cut another identical spline from the opposite side, then flip the board end for end to cut two more splines from the other end of the board. I then use my miter saw set to 90 deg with a stop in place so as to cut each spline to the correct width (2x the spline cut kerf depth) off the end of this board. This yields 4 cross grained splines, but then I can go back to the table saw and tenon jig to make 4 more cross grained splines and repeat the whole process to get as many, plus spares, as I need (being cross grained, they break in the grain direction easily, but you can stack pieces in the joint to produce the full kerf spline. It doesn't need to be just one long spline). I make these splines about the thickness of my table saw blade kerf, so I can make the slots for the splines using just the table saw and blade.

Careful positioning of the table saw fence and flipping the mitered box sides over allows cutting the kerfs for these splines at 90 deg to the mitered box ends.

The photo shows the final result of one corner of a box that I built this way. The spline keeps the mitered box corner from slipping off position as the box is being glued up. Keeping the grain in the spline running crosswise, and in the same direction as the box sides, makes for a very strong glued joint.

On the first try, cutting these mitered box corners and then cutting the kerf in each mitered end is a bit of a mind bender. Then making the cross grained (not long grained) splines poses a bit of a challenge too, but once you have made your first joint this way and you get your head wrapped around the process, it all becomes quite easy and relatively quick. This spline shown in the photo runs the full height of the joint. Looking at both the top and bottom, you will see that the spline shows from one end of the joint to the other, so the image will look the same.

Charley


Edit - Tom posted the same joint (just before me) with a great photo (his first photo). So now you have good info from both of us on this type of joint. His second photo is another way to achieve strong mitered corner joints, but different jigs and process are required for this joint. With both methods, the grain of the spline needs to run in the horizontal direction and in the same direction as the grain in the box sides. Running the grain top to bottom in the spline will produce a very weak joint.


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## kolias (Dec 26, 2008)

Thank you all for the help

I thought that the bit is kind of small but that’s all I have now. On the other side of the fence I do have slots for feather boards and I plan to use them.

I was thinking to use the table saw but the handle to tilt the blade is stuck and in any case I thought the router may be the way to go


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## DesertRatTom (Jul 3, 2012)

kolias said:


> Thank you all for the help
> 
> I thought that the bit is kind of small but that’s all I have now. On the other side of the fence I do have slots for feather boards and I plan to use them.
> 
> I was thinking to use the table saw but the handle to tilt the blade is stuck and in any case I thought the router may be the way to go


Hi, try cleaning out the sawdust inside the saw. It gets packed in there pretty tight. Use a dry lubricant, not an oily one. This works for me when I can't tilt the blade just right.

And DO get a Wixey angle gauge or you will never get the exact 45 you need. Using the table saw, once you set the 45 on the blade you use the same setting all the way through the process. You just raise or lower the blade as required. The Wixey is just $30 on Amazon, but I never got perfect cuts until I got one. The new ones run on AAA batteries, so they don't have the problems the flat batteries had.


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## CharleyL (Feb 28, 2009)

Here is a good Stumpy Nubs video showing another way to do it that will work both on a router table or table saw.






Charley


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## kolias (Dec 26, 2008)

Thanks Tom, yes doing a tune-up on the saw is well overdue and its on my list. Last time I did it was a very long time ago. The Wixey sound like a good tool to have.


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## kolias (Dec 26, 2008)

CharleyL said:


> Here is a good Stumpy Nubs video showing another way to do it that will work both on a router table or table saw.
> 
> 
> 
> ...


Very interesting video Charley, thanks


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## DesertRatTom (Jul 3, 2012)

CharleyL said:


> Here is a good Stumpy Nubs video showing another way to do it that will work both on a router table or table saw.
> 
> 
> 
> ...


Nice video. My eyes aren't so good anymore, but did I see a little slip between the two beveled pieces? I'll stick to the table saw because with the blade at 45, you don't have to change the angle and you can lay the piece on a sled or a miter gauge with stop blocks.

If you want a hidden spline, you'd have to use a router to stop the slot from going through. Sort of like a biscuit joint. Haven't done one of those for awhile. That biscuit joiner has to be tucked away somewhere. But I think you can set it for angled slots.

One last thing, if you're using wood with visible grain, or ply for that matter, if you start with a piece longer than the four sides of the box, and cut the miters as close together as possible, you get the look of continuous grain all round. Nice detail.

Interesting discussion. Very helpful.


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## jw2170 (Jan 24, 2008)

Some good advice given here, but if you still want to use the router, I would go for a cutter such as this...






Torquata Chamfer Moulding Router Bit


Chamfer bits are great for finishing the edge of your work with an edge at a variety of angles from 15 – 45 degrees.




www.timbecon.com.au


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## mgmine (Jan 16, 2012)

If you can't get a true 45 with the table saw, you could try cutting it as close as possible then trim it up with the router bit.


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## kolias (Dec 26, 2008)

jw2170 said:


> Some good advice given here, but if you still want to use the router, I would go for a cutter such as this...
> 
> 
> 
> ...


That bit reminded me that I do have one which looks similar and perhaps I do have other ones better? As mentioned the set I have is at least 20+ years and never been used.

I never understood how to use the bearing on these bits. I know the bearing will follow a surface but how do you control the depth of cut using the router free hand?


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## TenGees (Sep 12, 2012)

kolias said:


> I never understood how to use the bearing on these bits. I know the bearing will follow a surface but how do you control the depth of cut using the router free hand?


 You adjust how much the bit is sticking out past the base plate.

You would make a terrible mess if you tried to put a 45 on a piece of plywood in one pass! It would take several passes, cutting a little at a time. You still would have a hard time to get a decent edge on the plywood and you'd be turning the whole waste into sawdust instead of just a saw blade width. If both sides of your plywood is okay, you may be able to use the 45 that you sawed off on your next part.


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## kolias (Dec 26, 2008)

kolias said:


> Making a box 24”x8” out of 5/8” plywood..........When I will start, I will move the fence closer and push the plywood against the bit in small depth cuts per pass until hopefully I will have a nice 45 degrees edge......
> Thanks


Don’t think it will be a total waste, as long as I go slow it should be acceptable. In any case this is not a jewelry case, just a box to keep certain tools in order


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## DesertRatTom (Jul 3, 2012)

TenGees said:


> You adjust how much the bit is sticking out past the base plate.
> 
> You would make a terrible mess if you tried to put a 45 on a piece of plywood in one pass! It would take several passes, cutting a little at a time. You still would have a hard time to get a decent edge on the plywood and you'd be turning the whole waste into sawdust instead of just a saw blade width. If both sides of your plywood is okay, you may be able to use the 45 that you sawed off on your next part.


True, about multiple passes, HOWEVER, you will have a heck of a time getting all four corners to match IF you move the whole fence. You can make moving the fence work if you secure it on one end, and move only the other end. You can make successive cuts until you get the final cut right, then mark the loose end of the fence's position on the table top.

If you put a peg as the fulcrum at the fixed end of the fence so it would not shift, then your marks and resulting cuts will be identical. The peg can be temporary, removable, like a short steel rod. You can make a mark for each of the interim cuts. 

Using a table saw with a good blade will do the job in one pass.

I'm going into detail for anyone thinking of doing this.


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## CharleyL (Feb 28, 2009)

You should also look into Lock Miter bits, if you are set on cutting the box corners at 45 degrees with a router. The Lock Miter Master Gauge from Infinity tools makes setting the height of the bit and the fence position based on a center line on the thickness of the work pieces. A locked together joint as well as a perfect 45 degree cut are possible when using these bits, but you need a follower scrap piece to keep the bit from splintering the trailing end of the work where the bit exits the cut. Don't try to cut full depth in one pass either. Use shim boards between the fence or table to make a light pass before cutting full depth.

This is why I prefer not using these bits and just cutting slots in 45 deg ends for the cross grained splines. It just goes faster and easier, with more accuracy for me, but lock miter bits do work and produce good joints, if you can work through their splintering problems.

Charley


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## DesertRatTom (Jul 3, 2012)

CharleyL said:


> You should also look into Lock Miter bits, if you are set on cutting the box corners at 45 degrees with a router. The Lock Miter Master Gauge from Infinity tools makes setting the height of the bit and the fence position based on a center line on the thickness of the work pieces. A locked together joint as well as a perfect 45 degree cut are possible when using these bits, but you need a follower scrap piece to keep the bit from splintering the trailing end of the work where the bit exits the cut. Don't try to cut full depth in one pass either. Use shim boards between the fence or table to make a light pass before cutting full depth.
> 
> This is why I prefer not using these bits and just cutting slots in 45 deg ends for the cross grained splines. It just goes faster and easier, with more accuracy for me, but lock miter bits do work and produce good joints, if you can work through their splintering problems.
> 
> Charley


I have the Infinity gauges and they make the bit much easier to use. Without them you have to do trial, trial, trial, error, error, error and toss the bad pieces. I use it with the Rockler center marker. Pix of both below. One shows the joint finished, the other shows how to align the jig with the wood's centerline. The jigs are held in place by small but strong magnets. The bits come in two basic sizes, so do the jigs, although they are really easy to misplace.


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## harrysin (Jan 15, 2007)

This is one method that I have used successfully. I've also used the lock-mitre which is the ultimate corner joint


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## ebill (Jan 17, 2009)

DesertRatTom said:


> ......And DO get a Wixey angle gauge or you will never get the exact 45 you need.


- amen to that. And when you re-set your saw to 90, use the gauge again to make sure its really 90 degrees to the table.

- ebill


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## DesertRatTom (Jul 3, 2012)

harrysin said:


> This is one method that I have used successfully. I've also used the lock-mitre which is the ultimate corner joint


Holy cow Harry, that's a really great looking box!


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## jw2170 (Jan 24, 2008)

kolias said:


> Thanks Tom, yes doing a tune-up on the saw is well overdue and its on my list. Last time I did it was a very long time ago. The Wixey sound like a good tool to have.


 How did you go with that tune up?


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## kolias (Dec 26, 2008)

jw2170 said:


> How did you go with that tune up?


Its on my list, most likely a winter project


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## bfblack (May 2, 2012)

I use a table saw with a shop built jig as described in the articles below:
Fine Woodworking #129, 1998, pp 62-65, Steve Latta
Fine Woodworking #231, 2013, pp 56-61, Bob Van ****
Fine Woodworking #237, 2014, pp 60-65, Bob Van ****
Fine Woodworking #290, 2021, pp40-47, Bob Van ****
Some people refer to this construction technique as miter folding.


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## harrysin (Jan 15, 2007)

I just came across this shot of a simple jig that I used to make picture frames during the years that I had a radial arm saw.


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## ScottyDBQ (Jul 5, 2008)

Thanks for the great tutorial Harry


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## harrysin (Jan 15, 2007)

ScottyDBQ said:


> Thanks for the great tutorial Harry


You're welcome Scotty. Here is another mitre jig that came with the Triton saw table many moons ago. It was just unearthed as my son was packing everything in my shed to be transported to his place, I'd long since forgotten about it. I vaguely recall that I preferred the home made one shown earlier.


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## jw2170 (Jan 24, 2008)

Hi @harrysin . I trust you have suggested to your son that he join the forum.....


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## harrysin (Jan 15, 2007)

Yes, but even though he is a 65 year old very handy guy, he isn't interested in wood or metal working BUT, his wife is! she has joined the local turners club just a five minute walk from home and the main teacher is no other than my very good friend and professional turner John. Her first project is a rolling pin.
The metalworking equipment including the lathe is going to Trevor who I've known since he was 13 and he is now 65 + and has used the facilities of my shed MANY times.
My son's son-in law will almost certainly be using the equipment as he too has used it in my shed many times.
I still have a huge number of photographs taken during the making of heaps of projects and will, as in the past use them when necessary to illustrate an answer that I'm giving a member.


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