Problem=Cutting correct-Top, larger underneath

[Dena F]

I am using the 3/4" plywood for the fish exercise as I use on the cat. The fish cut real nice, had real good sharp points as per lesson. When finished I could not retrieve the fish. My husband finally took a small mallot to push the fish out the underside.

The top cutting was correct, but the under side was larger. What would cause this to happen?

I can put the small loop cuttings back in from under side of board I cut from, but cannot put the fish in from top or under side.

Any help or suggestion appreciated

Dena

[jttheclockman]

Dena

One of two things could have happened. First the blade and the table are not 90 degrees to each other. Do not use the scale on the table to check this. Instead do one of two things. Place a small square preferable a machinist square which is true on the table and next to the blade. You should see no light shining through. You can also use a small draftsman angle. To check that this is true you can take a pice of wood say 1-1/2" thick and saw a kerf about have way through and then take the wood and place it at the back of the saw blade and the blade should line up with the saw kerf exactly. If not adjust table and try again until it does.

Second thing that can go wrong and this is the one I suspect is when you are cutting thick pieces of wood such as 3/4" plywood you have to be aware of your feed preasure and your sideways preasure when sawing. You want to let the blade do the cutting and not push so hard. You can be doing this and not realize it because you are concentrating on following the lines so much. As you do scrollsawing more and more you will become more aware of these things. Also learn to set the scrollsaw speed at a faster speed when cutting thicker pieces and you will not have to work so hard.m Hope this helps. Good luck.

[Jimpask]

Thick Wood

Hi
I agree with John T...either the blade is not square to the table or your applying side pressure to the blade when cutting.

Thick wood will cut very nicely, but we as operators need to slow down the cutting pressure. If we cut out say 1/4" plywood, we generally wouldn't experience any problem. However when cutting 3/4" or thicker wood trying to cut to fast or pushing a little side pressure on the blade will produce a more pronounced problem called undercutting.

The blade flexes when the tension isn't correct or if we push the wood into the blade to hard...this flex causes the undercutting problem you are experiencing.

I'd suggest you use a larger sized blade, perhaps a #5 or #7 when working with 3/4" stock and also a blade with fewer teeth per inch. I blade with 12-13 teeth per inch will cut more aggressively than a blade with only 15-17 teeth per inch. Second, sit directly in front of the blade rather than at an angle to the blade. Third, allow the blade to do the work by not applying to much pressure. A more aggressive blade will help you here.

Hope this helps...good luck

Jim

[Dena F]

John T. and Jim

Thank you both for your replies.
I think I must have been pushing too hard, but didn't think so. I was conscious of trying not too. I was using #7 RV, it is the largest blade I have at the present time. My speed may have been to slow, I don't know. I don't really know how fast each section mark is suspose to be. It starts at 600spm and then section marks, but no numbers until 1650spm. I was in the second second from the 600, but not in a wider section, which I assume is halfway point. I have the Delta 350, if that helps at all in what I'm trying to describe.

Anyway I put in a new blade and squared it to the table and am set to try again.
Dena