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.

[Edward Weber]

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


That was my interpretation too. A little over 1/32" over the length of his cut. You would think an error like that would show itself in other ways, like blade or burn marks as Kevin Janness mentioned.
Personally I would remove the fence toe out and try again. (maybe on something less expensive)

[David Utterback]

I started having problems with this same setup last time I used the saw several months ago (before knee replacement). When looking along the face of the fence, light reflection showed a wavy pattern in the fence face. The fence has the Jessum fixture mounted by previous owner whose skill level appears to be quite high. The saw came with an extra fence which I will try the next time I use the saw.

[Alan Schwabacher]

If the width varies, could it be that you are pushing hard enough on the fence to deflect it? Try putting a magnetic base from a dial indicator or something on the opposite side of the end of the fence. If that fixes the problem you have an answer.

[glenn bradley]

The JessEm setup and Board Buddies are fine but do not offer the control of a firm feather board. It may be worth making a run with a feather board just to be sure you aren't chasing the wrong thing. On thinner cuts I will sometimes place one feather board behind the other in the feed path ahead of the blade to assure the material is under control before being cut.

[Keith Outten]

Four thousandths is the diameter of the average human hair. Wood will vary more than that if the temperature in your shop increases or decreases just a few degrees.
I would be very happy with the quality of the cut your getting. I suspect the majority of the woodworkers here have never seen a rip cut to your current tolerance :)

[Brian Holcombe]

.040” not .004” as I read it.

[Alex Zeller]

I think part of the confusion is that the OP said his fence is out by .004" but the piece he cut was out by .040".

[Warren Lake]

these posts go all over the map. .040 is huge on that cut.

If i saw someone in front of me cut and how they stand and work and feed material, had a straight edge to check the fence. Id make a cut into the blade from the front then remove the offcut portion then still with the saw running id go into the heal of the blade tight on the fence and Id know what the blade is doing. Ive measured blades but dont trust that compared to the saw running.

Im not suggesting you do that cause I have no clue what your experience is and it could be a nightmare if you dont understand and cause an accident. If i told the old guys or Joe id have no worry suggesting that.

Usually there is not enough info to answer these posts, we dont see a person working or know their gear, its guessing at that point.

In "up in smoke" the police chief asks how much weed the cops think is built into the van and they all make guesses. Like Dr Evils ransom money amount. Reminds me of these posts :)

[tim walker]

Here is a pic of front of fence using a master gauge dial reader. As you can see there is little deflection over the 27" of the miter slot to fence deflection.44606310630

I am thinking it is definitely user error vs an alignment issue. Will do more test cutting on scraps and report back.

[tim walker]

So I just cut a thinner piece of Ply and the cut measure 2.610" and 2.611" on opposite end. I am ood with that so definitely apparently user error on the feed. The piece I was feeding was 47" wide and 36" long and I was feeding with the 36" side parallel to the fence.

[Warren Lake]

if the piece is 48 x 96 as long as stuff is right and the edge is straight and you stand in the right place and move and have the feel then that can be bang on or close as well.

If you want to make it easier and again how I work wont likely be the same but for the times ive had to be bang on put a wood insert in the saw. RIp a piece past the heal of the blade say 3" shut off the saw and hammer in a finishing nail tight to the wood Then snip the head off. You now have a riving knife that will work better than a riving knife because it will keep constant pressure to the fence. I have the feel from cutting lots but even so mess up from time to time. The finishing nail will keep constant pressure to the fence provided you are not doing a larger heavier sheet then its less effective as you can flex it. One of many things an old guys showed me.

[Kevin Jenness]

One of the many reasons I would never go back from a sliding table saw to a cabinet saw.

[Stephen White]

I have the same saw and do 30-40ish rips at a time and they need to be right. If I am reading you right you want to be able to slide fence into place, lock it down and get a perfectly square cut?

When I move that fence into place it sure seems to me there is no way its ever going to be perfectly straight, there is just a little play from end to end, close but it seems to me no matter how you slide it into place its going to be a little off. Because of this I always measured top and bottom distance from blade and tap into square. Just don't see any other way for it to work but admittedly have not tried anything as that has always been part of my routine to setup a cut.

I have only used inexpensive table saws over the years and the fences were all of much less quality than the one on my SS and only for general construction cuts have I ever not squared my fence after sliding into place and sitting it. When I got the SS I did a few cuts without the tap square part of my routine and it was awfully close with the better fence but still have to tap square to really nail it every single time and to me I want what I'm doing to be as dead on as I can make it on a one after the other basis.

It also doesn't bother me to have a tap to square routine because I really don't try to hurry up on the table saw so the extra 10-15 seconds is of no consequence. I set every rip up with the tap square and a few moments to just look over the cut. I have also started using a feather board for safer and more consistent width feeds.

[Warren Lake]

hes ripping material nothing more

old guys did this for 6o years on cabinet saws and had no issues.

I want to cut material as i have using a fence for the most part. Big sliders have poor access ive seen guys twisted sideways on the net trying to use a rip fence.

[Derek Arita]

Only advice I have is to make sure your workpiece is against the fence all the way until it loses contact with the blade. The blade continues to cut as it enters and exits from the blade. I've had boards veer away from the fence as they exit the blade.

[Doug Dawson]

If this was real wood (as opposed to plywood) you could just kiss it with a plane.

Or even if not, maybe. (Choose your battles.)

[Edward Weber]

hes ripping material nothing more

old guys did this for 6o years on cabinet saws and had no issues.



Either poor machine setup, human error or a combination of both.
It should be a simple task, don't over complicate it.
Make one adjustment at a time and check results, repeat until satisfied.

[Kevin Jenness]

Before we had a long stroke sliding table saw at my old shop we ripped all the sheet stock on a Powermatic 66. My colleague Ron described using an "athletic stance" to get good results- using balance and power and attention to keep the stock riding smoothly against the fence all the way through the cut. You can't rely on board buddies to make it happen. Proper setup is important, then keep an eye on the contact between the fence and the material.

[glenn bradley]

You stock being wider than long is working against you. The blank is pure ballast. Lop off a more usable size and see if your accuracy goes up maybe.

[Warren Lake]

doesnt matter. you either get the feel or you dont, either taught or figure it out. The more you do the better you get. Where you stand, how you feed, how you move and change position as you go down the fence. Sometimes foot over foot as you walk in.

Its no different than anything in life. You play guitar you have hand position, you polish cars you have positions, you play golf you have stance and and, you race cars you have a proper seat and all set up correct placement etc.