Can't cut straight with Jigsaw

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Building a deck and using Trex. Had to use a jigsaw for notching around posts. I don't use the jig saw often but I can't cut straight with it. Looks straight, I follow my line but the bottom portion of the blade seems to ride in. So I follow my line but looking down the bottom 1/3 bows out. Like the blade is not strong enough.

Am I doing it incorrectly?
or
Is there a better blade? I got a craftsman wood blade.
 
Originally Posted By: coopns
So I follow my line but looking down the bottom 1/3 bows out.

How thick is the Trex?

If the bottom is skewed from the top, then you're likely still on an angle at the top but dragging the blade through the material against the angle. If going slower doesn't help, then angle is the problem.

A blade's natural path is dependent on the "set" of the teeth. Rare is the blade that is "set" perfectly straight from the factory; most blades require that the saw be held on a bit of a bias one way or the other to cut a truly perfect path. We used to hand-set the teeth of all factory-new blades with a drift and hammer prior to sharpening with a hand-file (lasers replaced our old jigsaws long ago).

A thicker blade may help, but would only correct for what I think is a a technique and "set" problem. Jigsaws do take considerable experience to operate well.
 
I've built hundreds f decks, some using Trexx. I always use a circ saw to notch out. I only use a jig saw to clean out the edge of the cut.
 
Does trex cut well with a handsaw? I just use that and try to take advantage of knowing which part of the cut is going to be seen.
 
Guessing your looking for perfect and dealing with decks there is room for "comfort." I swear, I'd rather build s whole house than the deck I had to deal with.

Not sure what cutter you are using, I used a Dewalt. If you are hitting Trex you better have the right bit. Start there. Mine is about 600sq foot and has lots of obstructions so I feel your pain. Just go slow and make sure you mark it with a square. If you find it hard to cut straight by eye just use the square to line up the shoe of the cutter. If you can't do that -- practice until you can, or hire it out!
 
If the blade gets hot it can warp.
Perhaps the blade you are using is blunt, you are running it too fast or the cut is too fine.

Try another blade, or another type of blade.
 
Originally Posted By: Tegger
Originally Posted By: coopns
So I follow my line but looking down the bottom 1/3 bows out.

How thick is the Trex?

If the bottom is skewed from the top, then you're likely still on an angle at the top but dragging the blade through the material against the angle. If going slower doesn't help, then angle is the problem.

A blade's natural path is dependent on the "set" of the teeth. Rare is the blade that is "set" perfectly straight from the factory; most blades require that the saw be held on a bit of a bias one way or the other to cut a truly perfect path. We used to hand-set the teeth of all factory-new blades with a drift and hammer prior to sharpening with a hand-file (lasers replaced our old jigsaws long ago).

A thicker blade may help, but would only correct for what I think is a a technique and "set" problem. Jigsaws do take considerable experience to operate well.


This is honestly the most absurd post I've ever read about anything to do with carpentry.
Op. you must be referring to the blade not cutting straight as in up and down,so the cut is curved in respect to the top of the lumber to the bottom.
First off what kind of jigsaw and does it have a switch to adjust the blades travel.as in the blade cutting a level stroke or a rounded stroke. Either or you are simply pushing too hard. Try holding the jigsaw back,and letting the blades stroke do the cutting.
As far as the comment above I've built easily a couple million sq/ft of residential and easily 1/2 million sq/ft decks,and I cannot even fathom trying to make sense of that comment.
3:39 am, and this is what's presented. Baffling
 
I've always found a jigsaws blade to bend slightly inwards when making curves; slowing down helps.
for notching for a deck, I would use a sawzall or a circular saw.
 
If you're using an older Craftsman jigsaw...with the skinny, thin blades..no wonder. Been there. Done that.

I replaced it with a Bosch jigsaw 15 years ago, with thick blades, very sharp, with a roller support behind the blade: Problem solved.

Cheap thin blades will easily warp with heat.
 
Trex has a lot of plastic / glue in it, and it will likely dull steel tools quickly. It may also be "gummy" and clog the teeth of the jig saw with dust.

As another poster stated, best to use a circular saw with carbide teeth to make most of the cut and use the jig saw to finish.
 
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