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bevel cut problems

Posted: Fri Sep 04, 2020 11:04 pm
by saminmn
I am trying to make boxes that will slide over Kleenex boxes. The plans call for the four sides to be 1/4" X 5" X 5 1/4" and there is a 5" X 5" top. I will attach scroll saw overlay pieces to the box sides. The plans use metier joints between the side faces.

I resawed a 30" 1 by 6, cut the 4 sides a little big at 5 1/8" width, and sanded to 1/4" thickness. Then I set up for 45 degree bevel cuts. Then the problems. 2 out of the 4 did not cut a 90 degree angle to the adjacent side and on one of those the cut edge had a stair step indicating a shift of the work piece. While I did not feel the work piece move, this must be what is happening. I kept retrying the cuts a time or two (till extra width was gone) without success. Something wrong with my technique. Open to suggestions...

In the morning I will start fresh with the other half of my resawed board, but I will "cut" the bevels with Disk sander.
Sam

Re: bevel cut problems

Posted: Fri Sep 04, 2020 11:57 pm
by edflorence
saminmn wrote:Open to suggestions...
Sam

Couple of thoughts:

1) Miter slots aligned parallel to the saw blade? If two of the cuts were OK this is probably not the problem, but worth checking. Your idea that the workpiece shifted during the cut seems like the most likely cause. So...
2) Attach an extension face to the miter gage and adhere a piece of sandpaper to it to reduce movement of the work piece. And...
3) Use an additional clamp on the miter gage face, sort of like a featherboard, to hold the workpiece flat to the table and hopefully reduce slippage.

I think all the above will apply even if you try to make the bevel with the sanding disk.

Hope this is of some help.

Re: bevel cut problems

Posted: Sat Sep 05, 2020 12:18 am
by edflorence
Sam;

One more thing...
Assuming the table alignment is good, and assuming the workpiece isn't slipping, then I wonder if there might be some play in the miter gage itself? Probably not likely, but it is another possible link in the chain. You might consider checking the 90 degree setting before each cut to be sure it hasn't shifted at all. Miter cuts are fussy and it doesn't take much.
Likewise the table setting; how are you setting the 45? I use a metal draftsman's triangle to set 30's and 45's. After setting the table angle it might be worth making a few test cuts on scrap pieces before cutting the bevels on the good wood. And is it possible that the table shifted during a cut?

Re: bevel cut problems

Posted: Sat Sep 05, 2020 7:53 am
by nuhobby
For jobs like this I used the tablesaw mode early on. In later projects, to reduce stress on myself, I rough-cut the bevels on the bandsaw, and true them up very precisely on the Disc Sander, with table tilted and with some extension on the miter gage.

Re: bevel cut problems

Posted: Sat Sep 05, 2020 9:33 am
by JPG
IIUC you are using the miter gauge to establish the bevel angle or tilting the table to do so? @5" I assume table tilt. I do not understand 2 of 4. There should be 8 bevels.

Pix of setup and resulting workpieces may help.

Re: bevel cut problems

Posted: Sat Sep 05, 2020 9:54 am
by DLB
The precision needed for these mitered sides is extremely high, so there are a lot of places for this to go wrong. Any edge or face you use as a reference during a cut needs to be essentially perfect as do all of your setups. One thing I would look at is if your resawn boards are still flat, and if you are using the sanded side as a reference it must be truly flat and truly a parallel plane to the other side.

Personal opinion here, I would 'improve the design for manufacturability.' Dovetails would be great, but not everyone likes the look and it is time-consuming. I think in this case I'd use butt joints or a variation and cover the end grain with a plain "L" molding the thickness of your planned scrollsaw overlays and 3/8 to 1/2 wide. More attractive, IMO, and a heck of a lot easier to make.

- David

Re: bevel cut problems

Posted: Sat Sep 05, 2020 1:14 pm
by chapmanruss
One thought and something most of us have forgotten at least once. Is the Quill locked?

Re: bevel cut problems

Posted: Sat Sep 05, 2020 1:34 pm
by algale
Or carriage lock unlocked. I've done that one or twice and ended up with uneven cuts as the carriage drifts towards or away from the blade.

Re: bevel cut problems

Posted: Sat Sep 05, 2020 5:46 pm
by JPG
Ah yes the two most likely cause of a 'step'!

Re: bevel cut problems

Posted: Sun Sep 06, 2020 12:34 am
by saminmn
Thanks for all the ideas and support. The metier gauge's hold-down might be slipping and I do not know how to get a better grip other than more force on tightening knob. I noticed today, when making cross cuts on the other half of the resawed board, that the metier gauge's hold-down needed readjustment after making a cut. I quit after sanding boards flat, but they are the fat half of the resaw and average about 3/8" thick. So I need to remove an other 1/8". Maybe I will get them down to size tomorrow. Any way to know when to replace belt sander belt?

edflorence - Liked you suggestions ,but.... when I sand the bevels I will use fence and quill advance. I don't think I had alignment issues with metier gauge as I just aligned (of course with my vision problems you never know).

nuhobby - had not thought of cutting bevels on bandsaw. Do you put the board on edge or tilt the table to cut the bevel?

JPG - You are correct there should have been 8 bevel cuts. 4 first cuts and then 4 more at 5" and a bit for sanding. Since my first cuts left me no reference edge on half the sides, I did not try the other 4 cuts. The cuts were bevel cut with metier gauge at 90 degrees.

DLB - Yes as looked as the edges I had and thought about gluing them together I could see the requirement for surfaces to match up closely. The bulk of the box's strength will be in the but joints between the top and sides. I will make a couple of more tries with the current plans before giving up on them.

chapmanruss and algale - Boy, I thought you guys had nailed it, but then I remembered I was using a zero clearance table insert. not a lot of way for the blade/table to move out of line. It is certainly the kind of error I would make.

again thanks to all.