Problem with table saw

[Ray Bahr]

Hi All,The saw is a Powermatic 66 – gold color, saw blade is a Forrest WW II, wood is Mahogany.I have Aligned the saw top to the blade and the blade to the fence – running right ~ .001″ for both.The blade has <.001 of lateral runout, the arbor has < .001 of runout, yet when I rip the mahogany I end up with ~.010 of taper, which I cant figure out. and since the 2 edges are not parallel, the tenons I was cutting are off…I am out of answers here, does anyone have some suggestions?ThanksRay

[Frank DiSessa]

Hi All,The saw is a Powermatic 66 – gold color, saw blade is a Forrest WW II, wood is Mahogany.I have Aligned the saw top to the blade and the blade to the fence – running right ~ .001″ for both.The blade has <.001 of lateral runout, the arbor has < .001 of runout, yet when I rip the mahogany I end up with ~.010 of taper, which I cant figure out. and since the 2 edges are not parallel, the tenons I was cutting are off…I am out of answers here, does anyone have some suggestions?ThanksRay

It could be your fence is deflecting a little when you put pressure on it with the stock. Try tightening your fence a little and repeat the process. Another thing to try is to lessen your stock pressure on the fence at the beginning of the cut. 10mils is such a small difference that it will take some trial and error to fix.

Regards,
Frank

[David Buchhauser]

Are you sure you're keeping the stock tight against the fence as you push it thru the saw?
David

[Bob Jones 5443]

I feel your pain: I'd hate my tenons to be off that much!

First, a probably stupid question, which I could figure out if I thought more about it: Which end of the board is narrower, the part you feed in first or the back end?

Could the wood be releasing tension and thereby warping as you rip? How much are you taking off and how wide is the board to start?

Are you feeding the board in edge down or face down? Which part of the tenons are off, the cheeks or the shoulders? It sounds like the cheeks and you're feeding the board in on its edge. If that's the case, do you have a thickness planer?

Is the board perfectly foursquare before the rip?

Are you using a featherboard and a splitter just shy of the kerf width?

[Jim Andrew]

Have you thought about getting a rip blade? No need to go to the expense of a forrest, I have been getting CMT blade packs on sale occasionally at menards. Is the stock tightening up on your blade as you rip it? I have been experiencing some tension in boards lately.

[Lee Schierer]

Hi All,2 edges are not parallel, the tenons I was cutting are off…I am out of answers here, does anyone have some suggestions?ThanksRay

I found through experience that using a crosscut or combination blade when cutting tenon cheeks resulted in tapered cheeks. When I switched to a dedicated rip blade things got noticeably better.

[Eugene Dixon]

Is your rip fence straight/flat down it's length?

[Rod Sheridan]

I would suggest using a rip blade and a short fence that ends just beyond the start of the blade.

You could probably just clamp a piece of something like MF to the fence as a test run....Rod

[Ray Bahr]

Hi All,

Thanks for the comments. I know that this seems like a small error, but I was cutting some pretty wide tenons, and I could see the error when done...

Jim - this is a rip blade. I like the Forrest blades - these are 15-20 years old - I just get them sharpened and cleaned up when needed

Bob: The cheeks are indeed where I see the error. The back of the wood is wider, no feather board or splitter, the board was prepped - surface planed, edged. The board COULD be releasing tension, but it is fairly straight grained, so not so much, and it is not obvious. The error is on the long side of the cheeks (~6" long)

Dave: I was taught that when ripping to keep light pressure on the left rear of the wood being cut - up to where it gets dangerous, and use the right hand or a push stick depending to also apply forward pressure. So, yes there is pressure, and it is light.

Frank: Since the fence is a Biesemeyer, there is no rear connection, but it still takes a fair amount of force to cause deflection - tried it with a dial indicator

Ray

[Sanford Imhoff]

Just to be clear...are you standing the board on end and cutting the cheeks? What jig/procedure are you to cut the tenon?

[Donald G. Burns]

Try using a rip jig vs. pushing through by hand. You could be allowing the wood to shift as you push. See if the jig solves the problem. If not, then look for a problem with the fence or alignment.

[Peter Kuhlman]

Need to attack this one step at a time.
Try clamping the back of the fence down to eliminate one possibility.
Try a different blade.
Try using some scrap of a different species.