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?
Thanks
Ray
Replies
You have aligned you blade to the slots, but have you aligned your fence and miter gauge too? You also need to align your splitter and riving knife. They need to be coplanar to the right side of your blade teeth.
Finally, depending on the length of the pieces you are ripping, .010 isn't too bad. You can correct that with a couple of swipes with a plane.
Could be too much side-pressure on the fence. Clamp a block to the rail or table at the rear of the saw to prevent deflection. If it turns out to be the issue you just have to alter your methods a bit.
Featherboards can provide less agressive holding power so you are just feeding stock without the heavy side-pressure.
>>>>I have Aligned the saw top to the blade and the blade to the fence – running right ~ .001″ for both.......... I end up with ~.010 of taper, which I can't figure out.<<<<<
I was puzzled by same problem a few years ago with my Unisaw. Turns out my fence rail had a tiny bend - like maybe .010 inches.
When I used a dial indicator to align the fence to the right-hand miter slot, I did it with the fence up close to the slot. I adjusted it to perfection.
Then I would slide the fence out (past the bend in the rail) for a 24" cut and get burning!
Since I have an aluminum fence rail (Unifence), the solution was to add shims between the right-side table and the rail until it was dead straight.
Now I can cut with the fence anywhere between zero and 52 inches and always get burn free and taper free cuts.
In the drawing I attached to this post, imagine how the fence rail bent when I bolted it to the side table.
I'm not saying yours has the same problem, but it's something to check.
For what it's worth, I'd like to share my experience.
I've been woodworking since about 1980. For around 20 years, my primary power tool was a Craftsman radial arm saw. For the last 20 years or so, it has been a Ridgid 10 inch contractors table saw. It has a stock fence, and always has a good quality, sharp, combination blade.
I don't know what the arbor run out is, or have anything with which to check it. It's probably not as good as 1,000th of an inch. I've never used feeler gauges to check the flatness of the fence or table. Every once in a while it becomes obvious the back of the fence is binding, causing a little burn on workpieces. A few light taps with a mallet, and it rips just fine again.
If someone told me my rips were only .01 off, I would say "fantastic." Every surface that comes off the table saw, except for glue joints, get handplaned, scraped, or sanded. After which .01 of tolerance is long gone.
If folks are happy measuring stuff with micrometers, that's great. But you can do fantastic work without giving any of that a second thought.
I'm not trying to be critical. I just want new folks to understand they can make beautiful woodwork with mediocre tools. If they are worried they aren't capable of the sort of precision a NASA engineer is seeking, they needn't worry. Practice and skill will take them farther than micrometers.
Hi All,
Thanks for the replies!
John: I understand your point, put this translates to a visible error when I am cutting tenons.
Mike: The saw has a Biesemeyer fence, nothing to bend
MJ: Very little side pressure, not at all aggressive
Robbie: I aligned the blade and the fence to the T-slot. Both the blade and the fence are perpendicular to the table. Everything has been checked with a dial indicator or a good square.
Ray
My Beisemeyer fence faces had up to .007" of deviation along their length. As you have observed, very minor deviations can accumulate and no one wants a .01" gap in their tenons, box joints or dovetails.
I rigged a dial indicator to ride along the miter slot and against the fence. I was quite surprised by the amount of wiggle along the fence face. Working the fence, face and all, against some fine sandpaper stuck to a reference surface cured that and my irregular rip widths. The amount of impact these deviations had depended on the stock length but, at best I got excessive saw tooth marks in places prior to giving the fence faces a little attention.
That being said, it is rare that a furniture part gets used right off a machine. Final fitting and surfacing are done with hand tools in my shop. I am a machine tool lover and the speed and efficiency they supply, I would not want to be without. That is, I am not a dyed in the wool galoot who only uses hand tools. I do however use hand tools to finalize many tasks.
Unless you are running really high end automated machines, you need to set your expectations to what the machine at hand is designed to do. I try to get my machines as accurate as I can with .001" being the normal target. This at least gives me the best starting point I can reasonably achieve.
There are times that material characteristics can cause blade flutter or other feed path or cutter motion deviations that will reach the level you are measuring. The point being, adjust and align to the best that the machine will do. Then add technique and experience to achieve your end goal.
Oh, and I should have asked right off the bat; are you using feather boards?
I am not using feather boards. I agree that there is a fair amount of 'post-processing' :-) but the errors are visible when making the cheeks of long tenons ~6". My fence seems good to ~.003 over the length. I have been using a lot of hand tools lately, but I am building a large door and was hoping to save time - should have known better. BTW I have the tools to easily measure to this degree of accuracy, and saw these errors and just measured EVERYTHING to try and figure out why I was getting what I saw.
Ray
The Wood Whisperer has a good video on this, check it out if you can, I found it helpful. Cheers!
It might not be the saw, it could be the wood. Wood has natural tension in it that ripping releases. Long rips (+20 inches, roughly) should always get a final pass over the jointer after the rip.
Hey,
I've been doing this a long time & can say if you're focused on .01" maybe you could quit worrying about it. Woodworking is supposed to be fun.
Best to you,
Mikaol
I do agree that is seems silly, but what happened is that I was making some tenons for a door and ripped a piece of mahogany to with - with a little left over to finish. Then I cut the cheeks on my TS, cut one side, flipped the wood, and cut the other side - these were 4-6" wide. What I saw was that on either narrow side, one side was visibly higher than the other. So I started trying to figure out how I screwed up. Started measuring everything and eventually found that the long edges of the wood were not parallel and this is why the ends of the cheeks did no line up. Started making small test cuts after measuring everything and found that the trailing edge of the wood ended up wider than the leading edge. The problem did not go away when I flipped the wood end over end. It just left me with a lot more clean up that I wanted to do and being an engineer (gave it away with the .01 nonsense :-) ) wanted to figure out what is wrong. The wood is all mostly straight grained - I have had wood really move after cutting, but this does not seem to be the case. I STILL don't understand why this happened
Ray, first I have to say we are woodworkers not machinists I understand the issue here, but I wanted to say I see machinists/turned ww'ers often have difficulty!!
The fence/blade distance should be 3-6 thou wider at the back of the blade. Be sure you are using a riving knife or splitter. I believe this is the problem.
Thanks, been woodworking far longer than a machinest.
The 3-6 thou in the back (had forgotten that) may be my issue! Thanks
I do need to add a knife or splitter...
Thanks
Ray
The wider at the back thing only works if you NEVER cut from the other side of the blade. Move your fence over and everything changes. With a riving knife in place the stock will be pulled away from the fence. With the blade angled you can have uplift or squeezing.
Having the fence coplanar with the blade is safest.
Good point, currently the fence is coplaner - I still don't understand what (or why) the result is happening.
Reading all the above their is not to much left to check? Bearings in the arbor maybe. Sometimes this kind of thing will not show itself because it is gradual. The 66 model has been around a long time. If your saw was made near the beginning of production and has a lot of use its ready for it.
Just to add credence to an alternate view on the toe-out fence thing, I'm with _MJ_. I set the fence dead-on. If I have a situation where I need that feature I just put a short sac-fence on. As _MJ_ mentions, the toe-out fence thing can have drastic consequences if you use the fence on the other side of the blade. Not as uncommon as you may think.
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