Blade behaviour advice

[Zog]

Hi,
I am experimenting with blades to cut jigsaws and so far have only tried the pinned type. I thought that a blade, such as Sealey SM43B25 25TPI, which is less than 2mm depth and quite thin would help get tight corners.

But I find that the blade twists as I cut a corner (sometimes up to 90 degrees).
Is this normal?

If I try a pinless 2/0 blade will it also twist?

Thanks
Chris

 

[StevieB]

Any blade which is deeper than it is thick will twist in a tight turn. Think of trying to turn a car round a corner in an alley the width of the car. Not possible!

You can only really do this in one of two ways. The preferred method is to go to a smaller blade, which means pinless really. Some of the fine ones are as thick as a human hair and not much deeper. The second way is to slow the turn down so the blade cuts round the corner. This will give you a slightly more rounded corner than a sharp 90 degree bend but is the only way to stop the blade twisting. When cutting a sharp angle on a shape you are cutting out from a waste piece you can run into the waste area, do a loop and come back up the next side of the shape to create a sharp angle. Unfortunately this is not possible in a jigsaw as there is not waste areas for the internal pieces. It would still work for edge pieces if you wanted crisp edges however.

HTH,

Steve.

 

[Gill]

Hi Chris

Although 2 mm might seem fine, Flying Dutchman puzzle blades are only 0.38 mm deep!

Steve has already given some very sound advice and the only additional point I would add is that some scrollers make their blades more manoeuvrable by filing away part of the back. They fit the blade, switch on the saw, then file the back of the blade paying particular attention to rounding over the square corners.

I have never tried this technique myself, preferring to switch to a finer blade instead.

Gill

 

[Mike M]

Below is what I have on my web site under "Q & A".
How about cutting corners?

Some people just spin the blade around, this will leave a round corner. I don’t like that. If you do spin the wood, make sure you stop cutting, but keep the saw running. Don't turn the speed down too much. Then, turn the wood with pressure on the back of the blade so it won’t remove any wood while turning.
I like to do it different. There are two lines: line “A” going into the corner, and line “B” going away. Cut on line A all the way to the corner. Then, back out about a 1/4” and turn the blade with the teeth into the waste, start cutting a curve towards line B and then to the corner. A small piece will fall out. This gives you room to turn the blade, put the back of the blade in the corner and start cutting on line B. Try to have the open space to the left of the blade. The right side of the blade has this little burr and will grab faster into the wood. Be careful that it does not get off the line. With some experience you can even utilize this burr to do some sanding if you have a little bump. Some people like to round the back of the blade. This is done by running the saw while holding a wet-stone against the back of the blade.
Mike

 

[chrispuzzle]

Any blade which is deeper than it is thick will twist in a tight turn. Think of trying to turn a car round a corner in an alley the width of the car. Not possible!

You can only really do this in one of two ways. The preferred method is to go to a smaller blade, which means pinless really. Some of the fine ones are as thick as a human hair and not much deeper. The second way is to slow the turn down so the blade cuts round the corner. This will give you a slightly more rounded corner than a sharp 90 degree bend but is the only way to stop the blade twisting. When cutting a sharp angle on a shape you are cutting out from a waste piece you can run into the waste area, do a loop and come back up the next side of the shape to create a sharp angle. Unfortunately this is not possible in a jigsaw as there is not waste areas for the internal pieces. It would still work for edge pieces if you wanted crisp edges however.

HTH,

Steve.

That is what I do for corner pieces at the edges of the puzzle although my edges are not straight lines. For sharp corners inside the puzzle, you can manage it if you are prepared to have three or more pieces meeting at the corner. In that case you are really doing a loop as Steve suggests but your loop is another piece of the puzzle in its own right.

This is where a little planning is a great help. However if you are cutting out figure pieces with several sharp corners then you just have to develop a very deft touch with a very fine blade.

I find that very sharp, narrow points have a greater tendency to flake or splinter on one or more layers of ply and try to avoid them. If it is a narrow shape like an animal's tail, it may be better to deliberately round the end in order to protect the corner from getting damaged. You have to pay some attention to the sort of treatment these pieces will receive when the recipient makes up the puzzle.

 

[Carter Johnson]

Good advice from everyone above. If you are cutting puzzles from 1/4" wood, which is the preferred thickness, you should use a very thin blade with what's called a "narrow kerf". The Flying Dutchman "Superior Puzzle" blade is ideal. It, and similar blades, will never twist with the turn, PROVIDED the tension on your saw is as high as you can work with without breaking blades.

Best wishes...and have phun....

Here are some puzzle ideas:

http://www.picturetrail.com/carterj

Carter