Problem with Jigsaw Blades Bending

[Mark Maleski]

:confused: Before I put in a call to the Bosch service center, thought I'd float my issue here to see if there are any suggestions. I'm using a Bosch 1591 EVSK to make cuts in 1/2" plywood. I need the cuts to be parallel to the edge, so tried to guide the cut by clamping another piece of plywood to the project piece, with the factory edge of the clamped piece guiding the shoe of the jigsaw in a straight line. Whenever I do this, the jigsaw blade deflects under the board I'm cutting and the cut is drawn off parallel. When I try cutting from the other direction it deflects in the same manner (always to the same side, relative to the jigsaw). If I remove the guide and cut freehand, I don't have the deflection problem (but don't have an acceptable cut - need this to be straight). I'm using quality Progressor blades (and have encountered the same issue with multiple blades), the blade guides are locked, the issue occurs at all orbit settings, and it occurs no matter how slowly I cut. The only thing I can think of is that perhaps the jigsaw shoe and the blade mechanism are not coplanar (but seems they'd have to be pretty far out of whack for this issue, and they don't appear to be). Anyone think that could be the problem, or any other ideas of what else could be wrong?

Thanks,
Mark

[Andrew Nemeth]

Are you using an upcut blade? I have had some issues with wandering in some situations using downcut blades.

[johnny means]

I usually see this happen when guys ae cutting to aggressively. Maybe the use of the guide is making you cut faster than he blade allows. i use a pulsing action during cuts to avoid this. the blade will straighten itself out each time I stop pushing forward.

[Rich Engelhardt]

If I remove the guide and cut freehand, I don't have the deflection problem (but don't have an acceptable cut - need this to be straight).
Prior to getting a Festool track saw, I used to cut to the outside of the line, then come back and use a router/straight edge/bearing bit to dress the cut.

I figured in the long run, I'd use the tracksaw for enough things to justify the cost. YMMV.

In all honesty though, the only workable solution to cutting a perfect straight line in sheet goods is either a track saw or a sliding table saw.

W/the router method, while it works perfectly, you trade time for $$.

[Joe Scharle]

My first guess is that the blade is not parallel to the shoe edge. When not using an edge, you may be compensating for the 'drift'. One of mine is a scroller and will give similar problems if the blade is not locked exactly N/S.

[Chris Harry]

Interesting, I had this same issue with the same saw when trying to cut down a door slab. Granted its thicker than 1/2" plywood, but I was using a straight edge, not going too fast, etc. Progressor blade that wasnt quite brand new but wasnt old either. It curled right under the slab and I didnt even notice. All of a sudden I was getting sparks from the "precision control" guide wheels because the blade had bent so much it was catching on them.

Two things: I hope I didnt hurt the saw! And, I have no idea why it happened. I had attributed it to the thickness of the door, and never attempted it again. I was using a straight edge like yourself. Now that I hear it happened to you, it makes me wonder if maybe our straightedges werent perpendicular to the material we were cutting. Also, Ive noticed that I have a tendency to "tip" the saw over when trying to keep it tucked against a straightedge while cutting. That could lead the blade to be out of 90 with the material and could lead to the blade "rolling".

[David Helm]

I think maybe you're using the wrong tool for the job. I've been using the Bosch jigsaw for many years and have often had blade deflection, usually by different densities in the grain of the wood. This will happen to all jigsaws. To get a straight cut in plywood (emphasis on straight, not a jigsaw's forte) you would be better off using a circular saw.

[Andrew Pitonyak]

Let me see if I can summarize what you said:



Cut free hand, no deflection.
Cut with a straight edge, always deflection in the same direction.


So, something changes when you use a straight edge, but what?

I will use the acronym YAPATSE for "You are pressing against the straight edge".

Here are a few ideas off the top of my head:



YAPATSE, which may cause a specific vibration in the saw.
The blade cuts a specific path, but, YAPATSE, which keeps the saw pushed over. If the cut is a bit over to one side and you keep pushing the saw back, this may cause the blade to bend.
As YAPATSE, you may be slightly tilting the saw.

What if you create a straight edge on both sides? This is likely only practical for a test cut, but it may be informative.

[Rob Woodman]

If all else that has been suggested fails, try a Festool S75/4FSG/S blade they are thicker than the standard blades and less prone to wander.
http://www.festool.co.uk/Products/Accessories/Pages/Detail.aspx?pid=486551&name=Jigsaw-blades-S-75-4-FSG-5

This from the uk site but are available in the USA.
Failing that get a Festool PSB300 Jigsaw, I have cut straight and square with mine through 4" Iroko cills ( it was that blades longer version).
Rob.

[Don Jarvie]

I run into the same problem with my Bosch jigsaw. The problem is the strenth of the steel in the blades. As long as they are made with some flex in them they will deflect somewhat.

If its too much bother to use a router to clean it up. Try to cut a smidge or two before the line and then make the final pass. By only having to cut a 1/16th or so of wood it might not cause the blade to deflect at all.

[David Thompson 27577]

:confused: ..............I'm using a Bosch 1591 EVSK to make cuts in 1/2" plywood. I need the cuts to be parallel to the edge, ............................

In general, jigsaws are used (and meant to be used) for cuts that are not planned to be straight.

If you want to make a straight cut, you should be using a circular saw. The added length (diameter?) of the blade helps to keep you on-the-line, and blade deflection is almost unheard of.

[Kyle Iwamoto]

+1 on using even a cheapo circular saw for breaking down plywood. It's much faster, much cleaner and if you invest in even a cheap Freud blade, the cut will be much much nicer than the stock blade most saws come with.

[Lee Schierer]

I have a Bosch Barrel grip jig saw and on several occassions I've cut 3/4" plywood with the setup like you describe with no problems. I use the Progressor T-234X blade http://ecx.images-amazon.com/images/I/61XKWMM551L._SL500_AA300_PIbundle-5,TopRight,0,0_AA300_SH20_.gifand the zero orbit setting. My edge cuts are all 90 degrees and as smooth as a TS cut. I think I use a 4 or 5 speed setting.

[David Cefai]

I once had this problem and it drove me nuts until I discovered that the blades I was using were thinner than most. When mounted in the jigsaw they would be off the line by one or two degrees.

Instant cure: use thicker blades - you will need to experiment or take calipers to the store, if the blade packs are not sealed.

I can now cut a 2' width of 19mm plywood, against a straight edge, with a jigsaw and not have the blade bend.

FWIIW the worst blades were Blackspur cheapies. Middling were B&D, best are Wolfcraft.

[Mark Maleski]

Thanks all for your suggestions. In the interest of time, I followed Rich's proposed method - cleaned the edges up with router w/ bearing bit and moved onto the next part of the project. I do realize the jigsaw isn't the optimal tool for making straight cuts, but dang it, they do sell fences for these things and I have seen others do it successfully. I think perhaps the stars just need to align for it to work. Through this thread, I've settled on 3 things that I think might help me with this next time:

1) Careful with putting pressure against the guide. Think I might've been twisting ever so slightly by either putting too much or applying uneven pressure. Johnny's suggestion for a pulsing action could also help with this - back up and re-establish the straight kerf.

2) Use a different blade that has more set to the teeth (wider kerf relative to the blade) and shorter depth (from tooth edge to back of blade) to have less metal to bind.

3) Throw in the towel and use a different tool.:D

I almost wrote "better tool" above, but I do love this Bosch - at least in curve cuts.

Mark

[Luther Oswalt]

I was having the same problem with my Bosch Jig Saw until I read a article several years ago about speed of cut and holding the saw more toward the rear. This little change in the way I was working the saw made a world of improvement to the cut.

[Jim Becker]

If this is one of the Bosch models that has the blade guides (they support the blade on the sides) then your guides may need adjustment. The one time that I found the blade on my Festool jig saw wandering as you describe, I found that something had knocked the guides out of alignment.

Otherwise, using a heavier blade and cutting slowing should help. Many folks tend to force the speed of the cut beyond what the blade can actually accomplish comfortably and that adds both stress and frictional heat; both can contribute to blade deformation.