Cutting Miters Precisely

Equipment and methods that help produce a better miter cut. November 15, 2011

Question
What is the best way to cut the perfect miter? I bought a miter stop for my J.A. Dawley fence and it works perfectly for length. The problem is I can't quite get the miter dialed in on my chop saw. I have batted around a few ideas:

1. Cut slightly long on chop saw and trim to final length using a miter trimmer like a picture framer would use. I've never used one so if anyone has experience with one please chime in.

2. Make a sled and cut on my tablesaw.

3. Purchase a high end miter gauge like Incra or Kreg.

Forum Responses
(Cabinetmaking Forum)
From contributor B:
In my experience, the biggest culprit in ill fitting miters has been a result of blade deflection. Full kerf blades perform better but they will work the saw a bit harder. I also have used guillotine cutters, in particular a Lion cutter, years ago (approx 35) when we did a lot of interior trim which was for the most part pine or similar woods. It performed well on smallish moldings but you may be disappointed with most hardwoods. I donít think the Kreg and Incra toys will help you. If you have a decent chopsaw with good blades and proper setup you should not have any trouble. Remember: perfectionism is another word for slow.



From contributor A:
Buy a Forrest blade. Any decent chop saw should be capable of accurate miters. The real trick is the blade.


From the original questioner:
I agree with you about the thin kerf blades. I own one thin kerf blade and it has a very nice cut except for the slight wobble that ruins it. The saw is a good one. Itís my infeed side fence that I can't quite get right. I took the factory fence off in an attempt to get my Glide stop all the way up to the blade. It works great except for the fact that the right side fence is skewed just enough to screw up my cut. I just didn't want to have to fiddle with my table again. It looks like it may be the lesser of two evils though.


From contributor J:
I always double cut my miters - it's a little bit extra time, but eliminates the blade deflection that usually results in a bad joint. Chop everything at least 1/4" long, and then re-cut all of one side to remove about 1/8". Then set up your stop for the other end, and cut off the last bit. The small amount removed keeps the blade from deflecting, and you get a smoother cut.


From contributor M:
Maybe itís the fault of the blade, but I gave up on miter saws long ago and use my shaper. I made a jig that just slides by a straight cutter head tall enough to exceed the thickness of the stock and always, always clamp the workpiece to the 45 degree angled fence on the jig, and of course pay careful attention to the direction of feed. Not only are the angles perfect, but the surface is smooth and ready for gluing. A little bit of fiber on the trailing/outside corner, but no problem, it sands right off after glue-up.


From contributor Y:
We long ago gave up on the hobby level mitersaws and bought an Omga, huge difference. But even with a real saw if the stock is not straight or the fence is off it wonít work well. The inherent problem with miter stops is they can force the non-straight stock to move in relation to the saw fence. The pneumatic or manual clamps that push the work toward the fence help in two ways, they keep the stock from creeping while being cut and they at least try to take minor curves out of the work and reference it only to the saw fence. The clamps require a very solid fence system.


From contributor S:
You should not be trying to use the full length of the fences to reference. The saws fence is going to be more accurate and easier to adjust. The auxiliary fences should be set slightly behind the saws fence.


From contributor E:
I had the same problem, and had a bunch of mitered doors to make. I broke down and bought the Incra 5000 sliding miter table. It works well, but I agree the blade is key. The only thing with the sliding miter is you have to push it straight. With the miter track you canít be off. As I learned you could be off a 64th plus and then you have a problem with the miters being opened. I finally got my skill down where I can push it correctly. On another note, I like the idea of using a shaper to make the miter, although I use production routers and custom router tables with the Incra split fence.


From contributor M:
I should have mentioned that I cut the pieces on the miter saw first, then just take off the last sixteenth with the shaper. It works ok with shorter pieces anyway.


From the original questioner:
Thanks for the many helpful responses. I decided to try the Incra 3000 miter fence. It seems to be nice and very accurate. Though obviously not for high production, I'm confident it will get me to a successful end to this project. This is my first try at miter frame doors after making thousands of cope and stick doors. I have solved the problems that I figured were big,' like joinery and making the moulding. Cutting the miters kind of caught me by surprise.