Width Inaccuracies driving me crazy

[tim walker]

Cutting on a SawStop PCS. Fence is out by 0.004". I am running a 47" wide piece of 18mm ply for a cut that is 3-1/2" wide. When I mic it one end is 3.52" and the other end is 3.48". I am sure it is some user error but for the life of me I cannot figure it out. The outside tooth (nearest the fence) at front of blade measures exactly 3.5" from blade and so does the rear tooth. Any suggestion or recommendations? Ply is too expensive to make screwed up cuts these days. Sorry the piece of ply is 36" x 47" And I have JessUm fence rollers.

[Brice Rogers]

I'm wondering if your fence isn't perfectly flat?

[Jamie Buxton]

Or the plywood edge you're putting against the fence is not straight.

[Jebediah Eckert]

Is your fence square to the blade?

Is the leading edge narrower or wider?

[Curt Putnam]

Too lazy and tired to do the arithmetic - but your fence is out by .004" over a distance of what? Divide your fence measurement length and multiply nu .oo4. That should account for ,ost of the error. Are the rollers properly adjusted? Try measuring the fence from the front edge to the back edge if you have not already dones so.

[Mel Fulks]

It’s plywood…not platinum. Probably moving as it’s cut. Try cutting it a little wider ,then cutting it again.

[Mark Hennebury]

What kind of accuracy ae you looking for? You can rip oversize. joint one edge and trim the other on a shaper or router with an offset fence (So like a thickness planer)

[Lee Schierer]

If you are measuring blade alignment off a tooth, bear in mind that the sides of teeth are ground on an angle. Measure blade alignment from the flat part of the blade. For the accuracy you appear to be chasing, you should purchase a flat set up blank. Your blade should be aligned to the miter slot and the fence gets aligned to the same miter slot. Your cutting error appears to be 0.040" over the 47" length of the cut, which indicates your setup is wrong.

[Edward Weber]

If you are measuring blade alignment off a tooth, bear in mind that the sides of teeth are ground on an angle. Measure blade alignment from the flat part of the blade. For the accuracy you appear to be chasing, you should purchase a flat set up blank. Your blade should be aligned to the miter slot and the fence gets aligned to the same miter slot. Your cutting error appears to be 0.040" over the 47" length of the cut, which indicates your setup is wrong.

Took the words right out of my mouth.

[tim walker]

So maybe I am missing something, I Tht a variance on the fence if 0.004” was totally acceptable. The fence is 27 “ long from edge of table to back edge

[Brian Holcombe]

I use a set of feed rollers when the work is critical. You’re probably pushing off of the fence and don’t realize it.

[Kevin Jenness]

Assuming a rigid fence aligned with the blade, a difference of over 1/32" has to be caused by not holding the workpiece to the fence consistently. Perhaps it is too large for you to control- are you trying to take 3 1/2" off a 48" x 96" sheet? If so, cut it smaller first. Are you using feed rollers or a power feed? If so, adjust the tracking.

Have you checked that the fence is aligned with the blade? A misalignment could lead to the workpiece drifting away from the fence. You state that the "fence is out by .004"- what exactly do you mean by that? If the fence is toed out by .004" over the length of the exposed blade that could be causing your problem, especially if cutting an over-large workpiece. Align the blade and fence to the miter gauge grooves . Check for the blade heeling by looking at the tooth scratch pattern on the sides of the cut and looking for the fibers torn upwards from the surface by the blade at the back of the cut. If there is misalignment you will see downward tracks on one side of the kerf and upward tracks on the other and tearout at the top surface.

[Michael Dean]

If I read this correctly, you are trying to correct an error of .004" over a 47" rip cut. What kind of tolerance are you expecting to achieve?

[Brian Holcombe]

Looks like .040” from his original description. The fence is off according to his measurements .004”.

[Lee Schierer]

If I read this correctly, you are trying to correct an error of .004" over a 47" rip cut. What kind of tolerance are you expecting to achieve?

According to the numbers he posted (3.52 to 3.48) it is a 4 hundredths or 40 thousandths error.