Thread: those pesky mitre joints

What about using a table saw?

You are not alone with your frustration with cutting mitres. Just the very act of swinging the RAS away from 90° is enough to generate forces that will move the timber enough to create angles that will not be "right".
In my opinion the bandsaw will be very hard to get a straight cut across your timber. The RAS would be my choice because it has a non-flexing blade and will/ should give a very straight cut. As far as cutting a true 45°, the setting on the saw may not be 100% accurate for the detail work you require. So what to do??? One way would be to to spend some time fine tuning you RAS to give you THE correct angle. Another way and this is what I do and have done during the course of the trade is to "sweeten" the mitre cut with a belt sander. It will take a bit of time to get used to "feeling" where the sander is and how much to take off. When fixing out a house where you have this problem with every door jamb's architraves you do get good at it. One thing though that you have to be careful with is, to keep the sander flat on the cut so the joint is tight both on the top and the bottom.

I prefer the hand held belt sander over a hand plane because its easy to take a "poofteenth" off at a time to get the joints right.

Good luck and remember.....practice, practice, practice

Originally Posted by justonething

What about using a table saw?

That would probably be option #1 but alas, I do not own a table saw.

As I said, I CAN do it, I actually have a 45 degree jig for the RAS, I just find it to be a p.i.t.a.
and am curious to see if some clever Trevor has a method that I had not thought of.

-P.

Originally Posted by P.W.H.

That would probably be option #1 but alas, I do not own a table saw.

As I said, I CAN do it, I actually have a 45 degree jig for the RAS, I just find it to be a p.i.t.a.
and am curious to see if some clever Trevor has a method that I had not thought of.

-P.

Have you tried the 4 cut calibration. I know the youtube uses a compound mitre saw. But the concept should be just as applicable to a RAS I think. After the 4th cut, you know how much your saw is out by, so you could compensate it by setting the angle by an extra amount equal to the 1/4th of the misalignment. Or I completely misunderstand how a RAS can be set or controlled. By the way, would clamping down the work piece help with accuracy?

Originally Posted by justonething

Have you tried the 4 cut calibration. I know the youtube uses a compound mitre saw. But the concept should be just as applicable to a RAS I think. After the 4th cut, you know how much your saw is out by, so you could compensate it by setting the angle by an extra amount equal to the 1/4th of the misalignment. Or I completely misunderstand how a RAS can be set or controlled. By the way, would clamping down the work piece help with accuracy?

Clamping down the work piece, hard, eliminates one source of error. The other source is the leverage that the blade going through the timber exerts on the arm of the RAS. If you're cutting something flat, with the blade tilted, it will climb. If you're cutting something on edge against the fence, the arm will move away from your adjustment just a little. My Evanson saw is really not bad, but it's also not top notch I guess. Rob Muldoon put import restrictions on goods sold in NZ at the time though, that prevented us from bringing in the gear we wanted to use so long as something similar was produced in NZ. So that's what I got. I really wanted a DeWalt (before their Black'n Decker days).

My successful way of doing it has been: do the 2 cut calibration (tested with an engineer's square), then do an 8 cut calibration with some waste, then set things up "right".
Do the real job .... but leave everything just 1 mm longer than needed. Because there will be more deviation, never mind how careful I've been. Then, assuming that the
setting up was correct, shave that last mm off very very slowly and carefully and with any luck it will be right that time because the force on the arm of the saw will be minimal.

Sound excruciating? yeah, right I'm not going into picture framing or box making on a grand scale any time soon, until I get a better setup going!

Yes, you may be right in that a good compound mitre saw would probably work a great deal better than a RAS. But those weren't even available here at the time I set up my shop back in '82 (with lots of advice from the Fine Woodworking magazine). It was a few years later that I saw the first Elu CMS being used.

Oh, and if the job still doesn't come out right after the 'fine shaving'? Weeeeelllll - I leave that to your imagination.
Let's just say that I get verbose.

So far Rod's introduction of the idea of a sander seems to promise the best procedural - getting a stationary disk or belt sander
with a decent mitre fence might just simplify the job nicely.

Ever considered making a shooting board? I don't have one, just thought it could be another option. Oh, and believe me unless you have a table saw or CMS that's the ducks guts you won't be any better off.

Shooting board is the go IMHO. In terms of fine adjustments, you have far more control on a shooting board, able to take 1 or 2 thou shavings. Quality of surface far superior to any saw.

Shooting board it is! Cheaper than buying a big disk sander, too, plus I have a few very nice hand planes that don't get used very often these days...
I found a really nicely illustrated guide by one Derek from Perth on the 'net.

Thanks a lot!

{goes and sticks his waterstones into a large plastic cookie bin}

P,W,H, did you see this thread currently running in another section of the forum - Problem cutting mitres on tablesaw ?
Yep, they're pesky alright!

Cheers,
David

Make the pieces slightly oversize with imperfect miters.

Clamp the imperfect frame in corner clamps with slots (necessary) along the miter line, with the pieces abutting. (Some pieces may completely miss each other at the outset if they're very imperfect).

Cut along the miter line with a back saw or equivalent, so that the blade cuts a little bit of each piece.
The kerfs will at least partially have parallel sides.

Repeat until the entire miter fully cuts each piece.

I posted this trick several years ago, but can't find it now.

Cheers,
Joe

You may wish to experiment with a sanding block on the shooting board - used in the same way as a plane. The advantage with the sander is that it is less likely to cause wooden fibres to spelch (break out). The sanding block must not deform in any way, otherwise you will simply round over surfaces.

Lee Valley offer a sanding block for the shooting board ..



Link: Veritas® Shooting Sanders - Lee Valley Tools

Regards from Perth

Derek

I never realised that such a thing existed Derek, good idea.

Those of us from Australia and N.Z. can't buy from the page you have linked to though, we have to buy from their US site, link here - Veritas® Shooting Sanders - Lee Valley Tools

Cheers,
David

Originally Posted by aldav

I never realised that such a thing existed Derek, good idea.

Those of us from Australia and N.Z. can't buy from the page you have linked to though, we have to buy from their US site, link here - Veritas® Shooting Sanders - Lee Valley Tools

Cheers,
David

I expect a piece of well squared off gum with chamfered edges, some double sided tape, and a turned handle
are all it takes, and Bob's your uncle.