Chopper Technique

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M

Matoaka

MGF, Master Grumble Framer
Joined
Apr 28, 2002
Posts
519
Loc
Albuquerque, NM
Any advise on reducing the displacement of wood when chopping? Anyway, I think this is what's happening... When I join my chops I can get a clean fit on the top of the moulding, but I usually end up with a small spread on the bottom. Should I just start investing in more wood putty, or am I doing something wrong at the chopper?? :confused:

Thanks,
Susan
 
Could it be that your rabbet supports aren't adjusted properly and your moulding is rocking?

If all else fails, get a miter sander.
 
What type of joining system are you using?

Is this with all moulding or just a few?

1st check moulding is laying flat when cut. Some moulding backs are not square to the bottom, when pushed to the back fence the bottom might be held up by the rabit supports and cause this.

framer
 
Originally posted by Matoaka:
.....or am I doing something wrong at the chopper??....
Click to expand...
Susan,

When you lay the two mitred sticks on a <u>flat</u> surface and put the cut pieces together, do you still show the gaping at the bottom? If so, this would indicate that your rabbet supports are set too high.

Adjust these supports 1)While the blade is in its most inward position and 2)While you're maintaining good downward pressure on the moulding. Bring the supports up until they just "kiss" the surface of the rabbet.

Remember to check again after each stick of moulding is cut, as rabbet height can vary from stick to stick.

John
 
Once again, Grumblers "nail" the problem. I've been putting too much horizontal pressure on the stick, instead of using downward pressure. I'll start kissing the rabbet (I see a new sit-com here... "Sex in the Frame Shop").

Thanks again.
Susan
 
Susan,

I am going to approach this problem from an entirely different angle. (Sorry for the apparent pun.)

Many times, when you set your underpinner to drive the V-nail at the outer point of the miter, you may have a tendency to place the V-nail too close to the edge of the corner. In this case the V-nail, as it enters the wood, will displace and push the wood fibers away from the entry point. If you are too close to the point of the miter, say 1mm - 3mm, the V-nail will actually push the corner apart in an attempt to displace the wood that is in its path into the miter.

Is the spread of the lower part of the miter (the gap that you see) about the same height and approximate thickness as the size of the V-nail that you are using? If so, trky setting your outer stop of your V-nailer further in from the point of the miter. I use a Euro underpinner and I have found that, when I see this problem when joining a frame, it disappears as soon as I move my outer stop a little bit inboard and place the V-nail further away from the outer point of my frame corner.

This doesn't occur anywhere else on a miter joint because there is enough strength in the thickness of the wood to allow the wood fibers to compact within the miter as the V-nail is forced into the joint.

This or any of the other suggestions made above may just be the answer to your problem.

Framerguy
 
Susan, How much material are you cutting on your final chop? Sometimes the larger bite will result in the "compressed wood" syndrome.
 
More good points. Thanks! I think my v-nailer settings are OK, but I'll double check. I have, however, been taking too large of a chopper bite at times. I'll correct that.

Thanks again,
Susan
 
It doesn't help that your equipment is as old as you are. You're going to have to fiddle with things and learn their quirks.

One simple thing that helps with the chopper is to brush away the wood chips often. A little bit of wood jammed in somewhere can make trouble.
 
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