Why is it cutting lopsided??

[Ives]

Does it mean the blade is dull or something? I can't really explain it, but the cut isn't the same all the way through, it's wonky and lopsided and a little squirrel I cut out looks all crooked.

 

[stevebuk]

any chance of posting a photo..

 

[Ives]

It looks extra wonky because I tried to even it out with the sander. I think the top one is the one I attempted to even, the other two show how it cut unevenly. It's on its side.

 

[Mike M]

You might have a blade with a burr on the right side. The blade will cut to the right, to stay on the line you have to move the wood some degree to the right.
You might not have enough tension. The blade should not move sideways more than 1/8". Is that 1 mm? You need more speed. If not enough speed you might start pushing too hard into the blade. You need a very low feed rate, Never push too hard into a blade or it will grab the wood instead of cutting it. Scroll sawing means patience.
You also need a good blade. :wink:
FD Mike

 

[Chippygeoff]

Hi Ives.

I agree with Mike as to the possibility of what can go wrong. It looks as if you are cutting hardwood, how thick is it? The thicker the hardwood the more difficult it is. I had the same problems when I started using hardwoods and over a period of time learnt how to overcome the problems. Even now when I have a new type of hardwood I use an offcut and cut a jigsaw piece and then see if it will slide out both ways. You need a good blade, I use FD ultra reverse. You need good tension and a fast speed and go a bit slower on tight corners. Another cause could be that the blade is not perfectly square to the table. I have just taken delivery of some Siberian Larch which is very heavy and dense. It is 18mm thick but I will cut off a small piece and cut the jig saw piece from it and at the same time I can determine what will be the best blade to use and the speed to cut it

 

[Ives]

It's a FD ultra reverse blade! I think it's a 9, the wood is oak, a tiny bit thicker than 3/4". Lately when I cut with the saw on a high speed it's been burning (on some 3/4" maple, even when this blade was brand new just put in) so I now try not to put it at a very high speed. I'll try a new blade and see what happens. I've cut loads of these in the past few months and this has never happened!

 

[Chippygeoff]

Hi Ives.

You need to put clear packing tape over the pattern on the wood. I get the 2inch stuff fromWilkinson's, its so cheap. Use two layers. This will lubricate the blade, prolong its life, stop the wood burning and you be be able to have the saw on high speed and cut the wood quicker. What you are experiencing is a build up of heat which will obviously burn the wood and also the blade will deteriorate very quickly and break. I have a variety of hardwoods i am using including Ash, beech, Oak etc and since I started using the clear tape I have never had a problem and can cut at full speed. If you are still having problems come back and I will see how I can help you.

 

[Mike M]

Did any see this tread on the Fox forum:
http://www.scrollsawer.com/forum/genera ... /44664.htm
It has to do with silicone spray.
Thanks for the explanatiom Geoff.
FD Mike

 

[StevieB]

This effect is somewhat common in thicker timber and can be caused by a number of mechanisms which give the same effect. The two principle mechanisms are a non square table, or pushing the wood too fast through the cut. Think of it this way - when you cut, you move the timber in line with what you see the blade doing on the top of the piece ie in line with the pattern. You need the entire cut to be vertical, and need to allow time for the bottom of the blade to 'catch up' with the top of the cut (a scroll saw blade will flex from the middle remember, even if tensioned correctly).

To test your table for square, make a small half inch cut into a piece of timber of the required thickness. Then turn that timber round and push the back of the blade into the cut you have just made (ie timber behind the back of the blade). If your table is square the blade should align and go into the cut from the back - if it doesn't, your table is not square to the timber. A very small deviation will have a big effect.

To test whether you are pushing too fast, try cutting an inch or so diameter circle in a piece of timber. This should come out as a column, not a cone. It should also be able to fit into the piece of timber it was cut from via either the front or the back. If it doesn't, your cut is not vertical for whatever reason. If you know your table is square, then the cut may not be vertical because of a number of reasons:

Blade has a burr and this is throwing the cut off (unlikely as this tends to affect the whole cut and cutting to a line)
Blade is worn and not cutting efficiently
Pushing too hard and forcing the top of the cut to be faster than the bottom
Sawing too fast to allow dust to clear, slowing the bottom of the cut

Lubing the cut will lengthen blade life, possibly cool the blade, may help clear sawdust and may incerase cutting speed, but if your primary problem is a square table or too fast a cut rather than the above then lubing will not make much difference.

HTH!

Steve

 

[Ives]

Thanks! I'll try all those things!

This effect is somewhat common in thicker timber and can be caused by a number of mechanisms which give the same effect. The two principle mechanisms are a non square table, or pushing the wood too fast through the cut. Think of it this way - when you cut, you move the timber in line with what you see the blade doing on the top of the piece ie in line with the pattern. You need the entire cut to be vertical, and need to allow time for the bottom of the blade to 'catch up' with the top of the cut (a scroll saw blade will flex from the middle remember, even if tensioned correctly).

To test your table for square, make a small half inch cut into a piece of timber of the required thickness. Then turn that timber round and push the back of the blade into the cut you have just made (ie timber behind the back of the blade). If your table is square the blade should align and go into the cut from the back - if it doesn't, your table is not square to the timber. A very small deviation will have a big effect.

To test whether you are pushing too fast, try cutting an inch or so diameter circle in a piece of timber. This should come out as a column, not a cone. It should also be able to fit into the piece of timber it was cut from via either the front or the back. If it doesn't, your cut is not vertical for whatever reason. If you know your table is square, then the cut may not be vertical because of a number of reasons:

Blade has a burr and this is throwing the cut off (unlikely as this tends to affect the whole cut and cutting to a line)
Blade is worn and not cutting efficiently
Pushing too hard and forcing the top of the cut to be faster than the bottom
Sawing too fast to allow dust to clear, slowing the bottom of the cut

Lubing the cut will lengthen blade life, possibly cool the blade, may help clear sawdust and may incerase cutting speed, but if your primary problem is a square table or too fast a cut rather than the above then lubing will not make much difference.

HTH!

Steve