Weird Saw Marks

[Malcolm Wheeler]

I am getting some weird marks when I am doing rip cuts on my table saw and I was hoping some of you would be able to tell me what I am doing wrong

As accurately as I can measure with an electronic caliper and square my blade is square to the table, and parallel to the fence and the miter slot.

I have a Ridgid 3650, with a Shark guard and the standard fence. The blade is a Forrest WWII 3/32 with stiffener. I also have a zero clearance insert from Lee Valley tools (item 46J85.06).

Now first off the problem still happens with the shark guard completely removed - so it isn't that.

What is happening is that the blade is making marks on the wood, but only the portion of the blade rotating up and as well only the bottom 1/8 or 1/4 inch or so. The top portion is almost glass smooth, as is the portion adjacent to the blade (behind the front teeth but in front of the rear of the blade. in other words, the portion cut by the blade rotating down is fine (perfect actually.)

I tried to illustrate this in the attached diagram. In the top diagram I am trying to show the cut surface of the wood - I stopped a cut once before the wood was pushed all the way through and the red portion shows where the scratches appear.

In the bottom diagram the cut surface is to the left and the view is edge on from the front of the saw. The bottom diagram is what happens when the wood is pushed all the way through to the back of the saw past the rear teeth. The last half inch or so of the wood is rounded off as the rear teeth cut into the wood.

How come the front teeth moving down are cutting glass smooth but the rear teeth moving up are hacking at the wood, and then why only the bottom portion - why not hack the whole surface to pieces?

Please help!

[Doug Carpenter]

when you say the blade is square to the table are you checking it in several spots though its rotation?

Could the arbor be poorly machined or loose?

Just guessing.

[Terry Welty]

can you post pictures of the saw marks?

[Joe Scharle]

What happens if you mount a short aux fence? Aux fence that ends just before the arbor.

[Matthew Hills]

How flat is the fence?

What happens if you rip with the fence on the left side of the blade?

Do the marks vary with blade height?
Is your stiffener hitting the wood?

Matt

[glenn bradley]

My first thought is that the material doesn't have a good flat jointed face/edge against the saw table/fence to provide a reliable reference surface. If the board face is well prepared, the description of the mark's location makes me think something along the reference path is deviating.

Things I'd check in no particular order are the thickness of your splitter; if it is the right thickness then the kerf is being held open and we can consider the path. Check your fence to blade relationship to see that it is parallel. Check the table for flatness with a good straight edge and pay particular attention to the area around the blade throat. The marks make it sound like there is a rise near the blade but most of us complain about a dip in the table at that area if anything . . . . is your ZCI flat and flush?

I'll be interested to read how this plays out. Good luck and keep us posted.

[john bateman]

I have a 3650 and got lots of marks and swirls, til I noticed that the whole blade carriage can move when the blade is at zero degrees and the blade height lock is not engaged.

Try just grabbing the dust shroud underneath and see if you can wiggle it...mine moved easily.

Unfortunately, engaging the height lock also pulled the blade to miter slot alignment out of whack.

So I had to repeat that alignment with the lock engaged.

[David Epperson]

My first thought is that the underside of your saw is clogged and you are drawing chips back up and "sand blasting" that corner by pulling dust back up through the insert and your workpiece is being used to knock the chips out of the gullets.

[Terry Beadle]

Have you raised the saw blade so far that the stiffener is touching the bottom of the wood? This would also mean that you are not using a zero clearance insert.

[Howard Acheson]

From your description, the back of the blade is nicking the kerf as the board is being pushed through.

The problem is indicative of your blade not being parallel exactly to the miter slot and/or the fence being slightly off. This leads to a couple of points.

o When using Forrest WW II blades the manufacturer suggests that the fence be slightly "kicked out" in the rear. About 0.003" or slightly more should work.

o Re-check the parallelism of the blade to the miter slot. I don't know how you are doing this but the blade should be adjusted to no greater than 0.001" for the best cut.

[Bill Huber]

The rounding off of the last little bit of the board is from the wood moving into the blade as you finish the cut.

This could come from you or it could come from putting to much side pressure on the blade and it is deforming as you cut. Then as you finish the cut there is less pressure on the blade and it will come back to flat as the last little bit of the board moves by it.

If saw is set up correctly I would bet if you put a normal kerf blade on you would see the problem go away.

[Andrew Hughes]

Throut plate rocking or high on one side.Happens to me on short pieces.

[Malcolm Wheeler]

Doug - arbor is as tight as ever and square according to my lee valley square.

Terry asked me to post some pictures - reflection 1 and 2 are not in focus, but that was done on purpose in high contrast light as it highlights the "clean portion" versus the "scratched" portion. The close up picture has been labeled - hopefully it makes sense...

Joe - I will give that a try

Matt - I will try those suggestions

Glenn - the fence seems to be parallel using a caliper, and I am not using a splitter.

John - the height wheel is locked down (I assume you mean the small wheel at the center of the height wheel?)

David - I have two dust extractors running - no dust clogs.

Terry - stiffener is below the ZCI

Howard - will try the slight non parallel approach

Bill - I agree - which could point to the fence right?

Andrew - the ZCI is not moving...

[Howard Acheson]

I have never used a caliper for determining the parallelism of a saw blade. But having used calipers quite a bit, I would not ascribe great accuracy to them. Here is an inexpensive way to very accurately set your blade and fence.

Here is the low tech, low cost way to align a tablesaw that I learned maybe forty years ago and use to teach to my students.

Make 3/4 x 3/4 x 12" hardwood stick. Drill a hole somewhat centered in one end and insert a brass #8 x 1" round head fine thread machine screw about half way. UNPLUG THE SAW. Raise the blade completely up. Clamp this board in your miter gauge (if you determine that there is some slop in your slot to miter gauge, use a playing card to take up the slop) so the screw head just about touches the blade at the front. Now rotate the blade by hand and determine which tooth is the closest. Adjust the screw in or out until it just touches this tooth. Mark this tooth. Rotate the blade so the tooth is now at the back of the table and move the miter gauge/stick assembly to the back and see if it touches the marked tooth to the same extent. If it doesn't, adjust the trunnion (if a contractor saw) or the tabletop (if a cabinet saw) until it does.

For a contractor saw, first use a small c-clamp on the rear trunnion and cradle to keep the assembly from moving. Then loosen the two rear trunnion bolts and one front trunnion bolt. Slightly loosen the other front trunnion bolt and use a stick to tap the trunnion until the blade and screw lightly touch. The blade does not move directly around the center so you will need to repeatedly go back to the front of the blade, readjust the screw, and then again measure the back. Be sure to check after tightening the trunnion as the trunnion frequently moves when being tightened.

For cabinet saws, loosen the bolts that hold the tabletop and tap one corner until things come into alignment.

The same adjustment gauge can be used to set the fence parallel to the miter slot. Slide the miter gauge to the front of the table and move the fence over to the screw head and insert a playing card between the screw head and the fence just so you can move the card as it touches both the fence and the screw head. Now move the miter gauge to the back of the table and see if you have the same feel when you insert the card. I like my fence absolutely parallel--if you want to have a slight opening to the fence, you can easily estimate the opening by adding a thickness of paper to the card.

I always show my students with a dial gauge that their adjustments are within .001 - .002.

You can also use the same gauge to measure blade runout by using a $5.00 feeler gauge.

Finally, after you are satisfied with the above adjustments, check the position of the splitter to make sure it is exactly in line with the blade.

Bottom line, there is no need to spend more than the $0.05 for the brass screw.

[Bob Wingard]

Is your table top flat ?? Especially in the area of the throat plate. It almost looks like you're getting a clean cut, and then it is chewed up by the teeth rising from beneath the table, but only on the lower part of the cut. This could be accomplished if there were a pretty significant hump in the table right around the arbor. It would explain how you could get a clean cut .. then the hump would twist the board slightly.. then the rising teeth would yield the "heeling" marks at the lower edge of the cut.

With your calipers, measure the WIDTH of a fresh cut at the very top, and again at the scuffed up bottom .. .. see if there isn't at least a few thou. difference between the two.

Oh .. if you DO take the advice to go through the entire alignment procedure .. make sure to carefully inspect your trunnions .. .. I "THINK" your saw has 5 bolts instead of 4 holding the trunnions to the bottom of the table.

Where are you located ?? I have a specially ground plate that I mount in my saws to do the alignment routine. It is a 1" thick flat aluminum bar that is about 18" on length, giving a much longer reference surface and better resolution. If you are nearby, I can let you borrow it to diagnose your problem.


You really only have three things that come into play .. .. ..

1) Table top : is it flat with no obstructions ?? For this ripping operation, the miter slots have absolutely no concern, although they should be considered during a typical alignment procedure.

2) Arbor assembly : is it holding the blade such that it (blade) is square to the table along it's entire length .. NOT twisted in any way .. no bearing runout or endshake ??

3) Fence : is it straight along it's entire length and square to the table top, again, along it's entire length ?? AND .. is it properly aligned to the blade ?? "PROPERLY" is the operative word here .. .. some guys use the outward splay .. some strive for perfectly parallel. I like the splay, but I never measure to quantify the amount. I install a new blade and set the fence for zero splay. Then, I make a few test cuts, "opening" up the back just till the upward swirl marks (if any) disappear. It is largely blade dependent .. some blades require the offset .. some not at all .. at least on my particular saw.

good luck .. .. ..