Circle cutting with a jigsaw question

Odd issue I thought I’d put here. I made a DIY cicle jig for my old jigsaw - a Black and decker from probably 1980something. I recently bought a Bosch 470EB barrel grip jig saw. SO I modded my jig - and had high hopes.

Which failed tragically. Well not tragically just 3 broken blades a chipped up jig, and circles cut out of 1/4 birch ply and luan. (yes 2 different sheets) and the 1/4 ply ones all have a bevel to them. Smaller circles were worse than the larger (5 inch radius vs 12 inch radius)

I don’t understand why it works so poorly. The old one with a quality scroll U -shank blade cut a good circle. The Bosch with either scroll blades or the precision wood blades cut with lots of deflection and would break a blade. I even used the base plate and zero clearance insert with my modded jig thinking that would help - no dice and it ate up the insert.

Usually the blade would flex and jump off the guide rollers. I turned the speed down to 2 or so (out of 6) and I kept the orbital set to 0 so straight plunge. Any help would be appreciated.

Can you post an image of your jig?

Nobody is answering, so I’ll just throw this out there.

The only reason I can think of for your issue is that your blade is no longer 90 degrees to the center point of the circle. It might look like it is, but it isn’t.

So the way I imagine it could happen is if your new Bosch is longer than your old B&D. When you put the Bosch in your old jig, the blade is now a few inches further ahead of where it used to be. That throws off the angle, even though the saw itself is still 90 degrees to the arm. So the saw wants to spiral away from the center, but the arm restrains it, so the blade bends and eventually breaks.

So what you can do is take a piece of string and tie it to the pivot point or nail or whatever marks the center of the circle you want to cut, and pull it out to the BLADE of the saw. The blade has to be 90 degrees to that string, not to the arm or whatever.

Good luck!

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Can you borrow or rent one to test if it is the equipment? I poop canned a Ryobi that was worthless for precision cuts and got a DeWalt, the newest one and it is a night and day difference. I went DeWalt as that is my platform but any other high quality brand might be worth a try. Go check reviews also. You might find that what you bought has a reputation for certain things. GUIDES are a key to jigsaw performance.

I’ll try to post a picture.