reciprocating saw won't cut square

[Bob Glenn]

Many times, especially when cutting thick material, I notice the saw blade on my PorterCable jig saw cuts at an angle through the board, especially when cutting a curve. I've tried new blades to no avail. Is this just the nature of the beast, or is there something else that can help?

[John K Jordan]

Yikes, haven't seen that on my Makita except with a dull or damaged blade.
Is it only with tight radii? (Maybe need narrower blade or different type?)
Same if turning left or right?
Same if you cut fast or slow?

Worn or out of alignment? Do you know someone with a different jig saw so you could compare the cut?

JKJ

[Mike Henderson]

That's the bane of jigsaws. Most of the ones I've used do that - don't cut straight down when cutting a curve through thick wood. Some jigsaws are better than others.

If you can make the cut on a bandsaw, that will solve the problem.

Mike

[Jebediah Eckert]

I have a good quality Bosch (forget the model) and it does the exact same thing. The only think I found that helps is going slow and being careful to keep the blade "pressure" centered in the kerf. Once you start speeding up you tend to drift the blade "pressure" to the right or left of the Kerr bending the blade causing the out of square cut. Almost like your fighting the cut to correct direction.

Bandsaw for sure is better but if I have to use the jigsaw I use a sharp blade and go slow and smooth constantly checking that I'm centered to the kerf.

[glenn bradley]

There can be a tendency to try to steer the saw by pushing on the body in a direction other than the one the blade is cutting. You know, a sort of effort to correct through side pressure or whatever. This will result in poor top-to-bottom alignment on the blade as you cannot force the saw to move in any direction other than that being followed by the teeth.

Do a test by drawing an "S" shaped line on a piece of scrap and follow it with slow, guided pressure leading the teeth through the path. Your only force should be forward with the body pivoting at the leading edge of the teeth. If your problem still exists it is not a technique issue and you can focus on the blade/saw.

Does the PC have any sort of mechanism to assure the blade remains true like the upper end Bosch units? If the blade is free from the chuck to the tip, the tendency to wander under resistance will be pretty high. If the saw accepts T-shank blades, the Bosch Progressive series is pretty stout and can do a little better when no guides are present.

[Lee Schierer]

Try using the Bosch Progressor blades such as the T234X. They cut pretty straight in thick lumber in my Bosch jig saw.
325842
Let the blades cut at their own pace. If you push too hard, the sawdust can't clear out of the teeth and the blade will drift. Since the cut is on the up stroke, the bottom of the blade will wander first as it can't get rid of the sawdust. Basically the same thing happens on a band saw when the TPI is to high for the cut being made.

[Peter Quinn]

Some saws are better than others, like festool, metabo, the newer Bosch models come to mind. Ones with better low blade support. But even the best can only get so close to the wood and none can support the bottom of a cut. It's important to use a good blade sized to the work, i.e. Less teeth for thicker stock, etc. and proceed at a moderate pace. But given the thin blades are only supported on one side....that blade can easily deflect either following a strong grain direction in a curve or through user influence. I use the bandsaw whenever possible.

[Art Mann]

Try using the Bosch Progressor blades such as the T234X. They cut pretty straight in thick lumber in my Bosch jig saw.

That is my experience too. The Bosch jig saw I own has a blade guide mounted right at the foot of the saw which keeps the blade pretty straight. I have tried all kinds of brands of jig saw blades and the only brand I will consider buying any more is Bosch.

[Mike Henderson]

That is my experience too. The Bosch jig saw I own has a blade guide mounted right at the foot of the saw which keeps the blade pretty straight. I have tried all kinds of brands of jig saw blades and the only brand I will consider buying any more is Bosch.
The new DeWalt 20V cordless jig saw has that same type of blade guide. I find the saw cuts pretty straight - not perfect but good.

Mike

[Bill Orbine]

Sometimes it's better to be less aggressive with the saw. Let the saw do the cutting and you slow down a little bit.

[Eric Schmid]

As others have stated, some of it is just the nature of the tool, but the degree in which the saw is cutting out of square can be controlled some with good technique. Not all saws are equal and the right blade will make a huge difference. Putting a Festool scroll blade on my old Dewalt jigsaw certainly makes it cut a lot better, but it does not make it a Carvex. The Dewalt requires quite a lot of care to cut square through a curve. It appears to have the same support for the blade as the Carvex or upper end Bosch, but it does not handle a curve with near the grace.

Try cutting from the underside, so that the blade is pointing up. It might help you see the cause of the blade deflection better (i.e. how your line through the cut effects the blade). You will likely notice that once the blade begins to deflect, its deflection increases as you get further through the curve. With the saw upside down it is easier to see when the blade begins to deflect so you can correct it before continuing.

[Bob Glenn]

All good ideas, thanks. I use Bosch blades and my saw has the bottom blade support. I'll try slowing down a bit to see how it cuts. I'd love to have a band saw, but don't have the room. So I'm mostly a hand tool guy as a consequence, but I don't get crazy with it.

[Howard Acheson]

>>>> The only think I found that helps is going slow and being careful to keep the blade "pressure" centered in the kerf.

You got it. The kerf centering is the key factor for cutting when you want a straight sided cut. The tendency for many when cutting a curve is to apply pressure on the side of a kerf. That will lead to a tapered cut every time.

It's best not to rely on a jig saw or reciprocating saw when you want a straight cut. Use a different tool that uses a stiff blade supported on both ends.

[Art Mann]

By the way, the "reciprocating saw" you mentioned in the thread title usually refers to a type of saw that Milwaukee makes and others copy called a "Sawzall".