Blade wander on Bosch jigsaw - Woodworking Talk - Woodworkers Forum
 
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post #1 of 10 Old 12-16-2009, 01:36 PM Thread Starter
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Blade wander on Bosch jigsaw

Hi,

I own a Bosch PST 700PE jigsaw - not top-of-the-range, but not the cheapest either. See first attached image.

My problem is that I can't get it to cut straight even under the most benign of conditions (thin material, well clamped, guided sole plate, good blade, slow cut, no pendulum action). I've read a few other threads in this forum about similar problems, but mostly there is some factor which doesn't apply in my case (I think). I don't expect to get accurate straight cuts in thick/hard material with this saw, but I sure expected better than I'm getting.

I thought it might be a guidance problem, so I made a a jig out of two parallel right-angle steel profiles, spaced apart at exactly the width of the saw's sole plate. You can see this clamped up, ready to cut a line on a length of laminated flooring in the second attached image. (The laminate is thin stuff, about 1/8" thick, or maybe a bit more, & cuts quite easily with a small hand saw).

In the third attached image, you can see the saw in place, sitting snugly in the guide jig, the blade aligned with the cut mark and ready to go. I'm using a Bosch blade, and the pendulum action is OFF. I've removed the plastic blade guard to better see what's going on.

I advance the saw SLOWLY and continuously, at full blade speed. I know from the centre-point mark on the front of the sole plate that the guide jig is keeping the saw body on-track. But after about 2" the blade - although still moving up-and-down within the groove of the guide wheel, has started to deviate to the left. After about 10" I stopped the cut, by when the blade had deviated by about 1/8" off course and was visibly no longer vertical. You can see the resulting cut in final attached image.

Before I chuck this saw in the rubbish bin, can anyone suggest what I'm doing wrong? I don't expect miracles from a jigsaw, but I thought I could expect a straight cut in such thin material and under the conditions I've described .

Thanks for any ideas.
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Last edited by baldpate; 12-16-2009 at 01:47 PM.
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post #2 of 10 Old 12-16-2009, 03:10 PM
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In my experience a jig saw isn't the best for cutting straight lines. Is there any play in your jig? Looks like a long jig, might need a clamp in the middle to stiffen it up. Also do you run the jig saw tight against one side of your jig or do you push down the middle? Might be a little play if your not just using one side.

Thanks for your help
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post #3 of 10 Old 12-16-2009, 03:53 PM
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I never considered trying to make that kind of straight cut with a jigsaw. Most jigsaws have a little rotational play in the blade holder and also since the blade is unsupported is subject to deflection from anything including heat buildup in the blade. I use a scrollsaw with tension on the blade and still experience some blade deflection when cutting in harder woods. For my uses I always used the jigsaw to cut slightly larger than the line and sanded to a smooth edge. I would use a small circular saw for the type cut you are attempting.
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post #4 of 10 Old 12-16-2009, 08:32 PM
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BP,
I have to agree with the other two said. I have a porter cable that has adjustable side guides in the foot plate and cuts pretty true. But I don't think I have ever used it in a cut against a guide. I do cut a lot of cabinet openings out for fitting ovens and such, but I draw a line and follow it freehand. I don't think I would pitch the bosch yet. Try it on some freehand cuts and see how close you can get it to stay on the line. If you can't get it to work then for you, then pitch it.
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post #5 of 10 Old 12-16-2009, 11:29 PM
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The first question I would ask is are the roller guides contacting the blade. While not familiar with your particular model (Bosch doesn't sell the "green line" in the US), that would be the likely culprit. Otherwise, I think you need to adjust your expectations of accuracy, or ditch the saw.

Save the now long discontinued Bayonet saw from PC, Bosch is the premier jigsaw manufacturer. I have a 1584 and 1591, and they are both are excellent machines. The Festool Trion saws have less blade deflection in thicker stock, but aren't worth the price difference for me(my one Festool purchase that I somewhat regret). The PC 7549 (I think that is the right model number) was also a really good saw. Makita also makes some good saws. I can't remember the model number, but I have a 20+ year old Makita that still does a great job. I am sure there are other great options out there, but these are the models with which I have experience.
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post #6 of 10 Old 12-17-2009, 04:38 AM Thread Starter
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Thanks for all your input.

Judging from your answers, it seems I simply had too high an expectation of a jigsaw. Ho-hum, live and learn!

I guess I need to think of it simply as a powered keyhole saw (pretty obvious, I suppose, when you think about it).

Rather than chuck it, I'll put it on the shelf and reserve it for freehand work or awkward 'internal' cuts.

I think I foresee a Circular Saw under the Christmas Tree this year!

Thanks again.
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post #7 of 10 Old 12-17-2009, 12:27 PM
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I have had better luck geting straight cuts with my jigsaw with short blades. That blade looks long to me for what you are cutting.
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post #8 of 10 Old 12-17-2009, 01:16 PM
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Cicular saws are good for straight cuts. You can also buy or make a nice edge guide you can clamp to your work peice and I have had great results cutting straight.

One thing no one mentioned which I have found makes a huge difference in cut quality is a good blade, this is for any saw. It looks like you were using a bosch blade which I've had good results with in my jig saw. Bosch does make a bunch of different blades for wood, smooth cut, rough cut, curves, etc. Maybe try a different blade and you might get better results. Blades can get expensive real quick but they truly make a difference in results.

Is that laminate flooring you are trying to cut? I can't tell from the picture but it kind of looks like it. If it is, I have put in a bunch and I usually use a jig saw for the notches and the cuts besides my miter saw. Usually those cuts don't have to be perfectly straight because you cover it with some kind of trim or quarter round.

Thanks for your help
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post #9 of 10 Old 12-17-2009, 01:30 PM
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I have had high end and cheap jig saws and can't tell a nickles
difference in them. The big thing I found is, that the slower you
go the more accurate they cut. And the blades have a short life
if you want a fine cut.

It is the least used tool in my shop.

One thing, The high end Makita broke a drive gear both times I tried to
cut 1 1/2" ply, two 3/4" laminated with epoxy. The $9.95 Skil is still
running twenty five years later and has cut miles of 1 1/2" ply.

I make boat rudders and center boards from the lamination's.

Makita took care of the problem both times. No problem but the
wait.


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post #10 of 10 Old 12-17-2009, 01:39 PM
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I can't explain why the saw goes off line when your useing a straight edge to cut by. In my case with my new Bosch, when I try to cut with a straight edge as a guide, I always get off for some reason. I get a better (straighter cut) when I free hand it.

Again, I don't know why, it just happens that way with mine

RLH
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