Let's talk about miter cuts

[Craig Zettle]

I have been making alot of miter cuts lately, on my 12" Dewalt SCMS and on a pair of 10" Makita SCMS at work. All the cuts at work are for decorative frames for custom doors, and the cuts on the Dewalt are for trim I am running on a separate job.
Anyway, I have been experimenting with the best method for making a flawless cut on a SCMS. It seems that so far I am getting the best results by making the first cut close to the mark, then sneaking up on the mark, and slowly making the final cut, with a chopping motion if the board is not too thick. It USUALLY works, but I want 100% tight miters with these saws, and I am probably at 75%. There always seems to be a gap or a nick turnung up somewhere on occasion, and this just slows me down, because I have to fill in and touch up the offending marks.
These saws seem to have a tendency to draw the trim piece in to the blade when pushing the blade through the cut, so I am avoiding that method in favor of the chop cut. I believe that if the trim piece could be held tight enough to not move during the cut most of these errors could be avoided, but in a production setting where mechanical hold downs are not time-efficient, I have to hold the trim as tight as I can and throw up a prayer.
Any of you miter pros have a secret tecnique or 2 you want to share?

Craig

[Loren Hedahl]

I've had the same problem. Several ways to minimize it:

1. Glue sandpaper to your fence. I'd go with 60 to 100 grit.

2. Use a stop.

3. Use a table saw or radial with a dedicated miter sled.


My uncle did quite a lot of finish carpentry. His favorite was to cut a bit 'fat' as you are doing, then true the cut up with a stationary disc sander. He's in his mid 80's now and pretty infirm, but showed me in his shop last summer. I believe I counted half a dozen disc sanders. Even his band saw had a sanding disc attached to the large pulley.


Hope this helps.

Loren

[Ed Hilton]

Agree on the sandpaper, but I would use 120-150 and put it both on the fence and the table. Buy some self-adhesive sanding paper for a pad sander, and cut the pieces to fit.

[John Gornall]

If you cut a small trim moulding with common size of 1/2 x 3 inches laid flat on the scms table using a sliding cut the first teeth to contact the wood are actually cutting up from below the table trying to lift and/or twist the workpiece. On this size workpiece even a chop cut has the teeth going down into the wood and then comming back up and out. Lower your blade onto a piece and have a look at the tooth contact and geometry during the cut. On chop and scms saws the design is based on maximum cut capacity and is a poor tool design for precision cuts. I have a double miter cutoff saw designed for precision cuts. It has 2 motors and 2 blades which come down together when I step on a pedal. The blades are 10 inch and the max cut is about 3 inches wide by 2 1/4 inches high. If you look at the face of the blades with the blade turning clockwise the wood is cut at the 3 o'clock position. The blade teeth are always cutting down through the wood towards the table so no tendancy to lift or twist the wood. The fence is reversed so that I hold it by pulling the stock against the fence towards me, not trying to push it away to a back fence.

Of course if the stock is not precisely straight, flat, and square there's not use having a precise cut anyway. Have you ever felt the stock move just a little as the cut completes? - it wasn't flat against the table, or the fence or both because it was not straight and so the cut can't be precise. Cut all the pieces a little oversize and then trim to size - this can reduce the effect of unstraight stock.

[Craig Zettle]

Yes John, I have felt the stock being pulled in to the blade, and I would like to glue some sandpaper to the saws, but they are not mine and I don't know if the company would go for it, but that is an option. I completely agree that these saws are not the ideal tool for the job, but that is the tool I am given, so I have to make the best of it.
Thanks for the suggestions, keep 'em coming!

[Ben Grunow]

Are these cuts for interior trim or picture frames?

[Dave Richards]

Perfect miters every time, minimal waste (less than with a saw blade) and quiet. :D
http://www.tech-mark.com/images/morsofc-big.jpg

MORSØ-FC (http://www.tech-mark.com/morso-fc.htm)

[Cliff Rohrabacher]

[...] but in a production setting where mechanical hold downs are not time-efficient, I have to hold the trim as tight as I can and throw up a prayer.
Any of you miter pros have a secret tecnique or 2 you want to share?

you need a better way to clamp - period.
Either spend some time strengthening your mitts or get some of those toggle clamps.

[Craig Zettle]

Cliff, you are right, but I am at the age where if I start a hand strenghening program I would probably accelerate arthritis. I used to rock climb in another life and after thouuosands of finger tip pullups I had to have tendon surgery on both hands. I completely agree, though.
As far as the sandpaper goes, I was thinking that the "shaving" process might not work as well with sandpaper on both the fence and the table. (meaning the trim might be hard to advance a hair at a time in to the cut to sneak up on it).
I have used those dedicated miter cutters when I worked at a picture framing shop, and man are they slick. Maybe I can talk my boss in to one?
Ben, I am cutting decorative frames for high end doors as well as running trim in houses. Right now I am doing a little bit of everything and doing it commercially, so I have to be as efficient as possible, but dead on accurate. Simple, huh?

[Dave Richards]

Craig, for what you're doing, I would expect it to be easy to justify one of these trimmers. Or a Pistorius. You know how well they work and how perfect the miters are. Figure out how many frames you'd make in a year and multiply that by .5 to figure out how much wood you'd save in linear inches. That'll help, too.

[Jim Becker]

I stoped trying to get perfect miters with the CMS long ago. I do get them with a sled on my TS...and feel more comfortable doing it, especially when the workpieces are small.