Acute Angle Jigs for Trim Work

Rigging a chopsaw to accurately cut angles sharper than 45 degrees. May 23, 2011

I'm pretty much self taught when it comes to trim carpentry, and even though I've asked many more experienced trim carpenters this question, their method isn't much different than mine. What's a good repeatable way of cutting sharp (55-75 degree) angles on a job site? I usually use a shim against the fence to compensate for angle past the max of the miter saw. This works for the situations I usually find myself in (mostly paint grade house trim, nothing fancy, and never a miter, usually just butting an angled wall or something) but I was wondering how you guys that do really high end work accomplish this if a job is expensive hardwood molding and involves many or at least multiple miter cuts where the profile must line up correctly.

Forum Responses
(Architectural Woodworking Forum)
From contributor W:
We make a jig and it starts with a piece of thin plywood the same size of the chopsaw table. On the plywood attach a fence to the right and left of the blade where you set the fences - it depends on the angle youíre looking for, maybe 20 degrees off the blade. Now your moulding end will be out towards where you stand. Move the blade left or right to dial in the angle you need. Itís simple and safer than shimming off the fence.

From contributor M:
I always did what you describe. Shim the stock out until I get the desired angle, clamp it down and chop. If I had a lot of this to do I would make a miter box using a circular saw. Basically it is a box with guides on top to run the saw straight. Then the stock is placed inside (under) the box and clamped at the correct angle. This is potentially dangerous because the saw is going to try and pull the stock off the bed. Make sure the piece is well secured and it is ok. Better than that is to use a table saw and a sled. I assume you do not have a table saw on the site. Even a portable saw would do the job.

From contributor L:
I bought an old 8" turret RAS for a song and use that for the occasion that I need odd angled trim. Use one once, and you will never use shims or any other method of cutting those odd angles

From Gary Katz, forum technical advisor:
Make an acute angle jig. It's easy to do. It's a lot safer than shimming the material from the miter saw fence, and it's deadly accurate. Both of which make it a lot more fun to use!