I need a new perspective on this problem, before I break something. My 7 year old Unisaw has started making rough rips. I’ve done all the usual stuff. Blade is aligned to the miter slot to .001. Fence is aligned to about the same. Actually, the biesemeyer fence has greater variability across it’s length, but only about .003. I’ve tried three blades. 1/8″ Forrest, TK Forrest, and a 24 tooth Freud rip. I’ve ripped with and without the splitter (which I religiously use otherwise). The ripped edge looks like the rear of the blade is heeling because all the marks are “upward”. I’ve opened up the rear of the fence a few thousanths, but no change. I used to get nearly flawless ripped edges….didn’t need to joint the edges before glue-ups. What am I missing?
Mike
Replies
Mike
Assuming that you have sharp blades, using the same woods and feed rates as always when you got the smoother cuts. You have covered the normal alignment of dado grooves, blade and fence. You have attempted with and without the splitter, so that eliminates splitter mis-alignment.
Have you tested for arbor run-out. A nine year old saw! If you do a lot of cutting, those bearing won't last forever. I would check for any wobble in the blade, arbor an pulleys an go from there.
Luck...
sarge..jt
Sarge,
Thanks for the tip on arbor run-out. Whats the best way to check that? I have a dial caliper and one of those mostly worthless magnetic bases, but it might have a use here. Should I check the arbor (threaded portion) or the flange? What's acceptable run-out on a Unisaw?
Mike
Mike
My BIL (machinist) does my tools with a dial caliper with a bar attached. I've seen him use several gadgets when doing various checks. I'm too cheap to buy the high dollar calipers when he already has them. ha... I am not sure of the correct procedure. Hopefully, someone will respond on that. If they don't, I will give him a call.
I am not sure what acceptable run-out on a Uni-saw is. My saw has about .002, but the guts were customized. I would call Delta customer service and tell them what you have done. See if they have had the problem occur and what solution they suggest. I would definitely check to make sure a bolt underneath has not backed out. Sounds like some kind of slip on the rear of trunnion if you get the problem from the rear of the blade.
Again, check all the obvious underneath and then call Delta C/S if you do not find an obvious answer.. I have a feeling they have seen the problem.
Good Luck...
sarge..jt
You can check to see if the arbor is out by using your magnetic base and dial indicator right against the blade. Just set the magnetic base on the saw and place the tip against the side of the blade. Slowly rotate the blade and watch the indicator. If you see the indicator needle jump then your blade is wobbling. I would try a second blade on the saw to confirm this. Your first blade might be out of wack also. If you see the same thing then if you want to know how much it's out then set the dial indicator against the arbor, just behind the threads and rotate the shaft slowly.
One thing comes to mind. Have you checked the tension on your belts?
Hope this helps,
Len
Len,
Thanks for the tip. I checked runout with a Forrest blade installed. It was amazingly true. I got almost .001 deviations. As far as I can tell the belts are tight. I stood a nickel on edge while the saw was running, so I don't think there are any flat spots on the belts. I rechecked the blade to mitre slot and there is no way I can get it any better than it is (.001) and I've fiddled with the fence to dead on to the same mitre slot. Then I opend it up .002 - no change. I guess I'm stuck with jointing edges 1/64 or so before glue-up. Not that big a deal, but it bugs me that I never had to do that before. I guess it's possible I could have three damaged blades (at the tips, not the plates) but I find that hard to believe. Maybe it's a good excuse to buy some new exotic blade. I'm stumped...a bit embarrassed to have asked for help. Oh well, life is still quite good. Thanks to all for the suggestions.
Mike
Just a wild thoughts here.
1. Have you checked the table for flatness?
2. Has the saw been moved?
3. Has the floor under the saw moved? Such as:
A. Cracked concrete.
B. Shifted or compressed shimms.
C. If on wood floor, could be a variety of things.
4. Any substantial humidity changes if on a wood floor?
Just a though.
Good Luck!
John
John,
Thanks for the ideas. I haven't moved the saw for 7 years...guess I don't really need that mobile base it sits on! It sits on a concrete floor that doesn't appear to have moved and has no cracks. I leveled the throat plate, but haven't checked the table for flatness. I doubt that's it because it occures on rips of even narrow boards. I'll check it though.
Mike
The symptoms tell me that the saw is hitting the wood on both the inside and outside edges (teeth coming up out of the table out outside and going into the table are inside in my terminology). If you've opened up the fence .002, that tells me that the blade should be missing the wood on the outside, but it's not.
Try a test with a short piece of hardwood, say 16 inches long and not too wide (4 inches). Rip it and see if you see the problem. Then unplug the saw and put the wood back between the fence and the blade, and rotate the blade by hand. See if the teeth are hitting the wood on the outside and inside edges, and see if it is consistent as you rotate the blade a full 360 degrees. That might give you a clue as to what is happening. But be sure to unplug the saw before you do this ...
John
have you cleaned the blade of pitch and caked on saw dust? That stuff causes friction and therefore rough cuts.
I had the same symptoms on my Unisaw. I checked the arbor and it looked good. Lacking any other option, I replaced the belts and bearings. The problem was solved.
It is not a big job to change them, nor does it cost a lot.
One of the earlier post said to check flatness of the table
I think the table is ok but would check the insert around the blade - make sure it flat with the table. The insert can get beat down from cutting warped twisted boards that don't lay flat - as they go through the saw the blade will jerk it down and hammer a hollow in the insert.
I don't know how much you use the saw but I don't really think in a home shop it would get that much use even in 7 years .The unisaw is farilly rugged built saw and really doubt it out of alignment un less you had one hell of a kick back .
How rough an edge are you talking about?
With a dry fit of the ripped edges does joint look bad?
Are you letting it get away from the fence as you cut?It does not take much , maybe you need to slow down your cut and try to keep the stock moving.
How high do you have the blade above the stock? Are the gullets of the blade clearing the stock?
Have you tried a freshly sharpened blade?
I bet the saw is ok I would slow down and look at Technique and the insert.
Mike,
There are a few things that may be causing your ripping dilemma. Start with the arbor - unplug the saw and take the blade off. Grab the (non-removable) flange on the arbor and rotate it two or three full revolutions. If you hear any grit or grinding noises, or if the arbor seems to stick at some point in its rotation a bearing has worn out and needs replacing. Try and move the arbor around as you rotate it (up/down, front/back). If there is any play at all you'll know a bearing has failed.
I'd say the chances that a bearing has gone bad are fairly low (Good news!). Assuming that all of the saw's parts are adjusted perfectly (e.g. fence, miter slot, splitter), there are two things that are most likely causing the problem. The first would be the pulleys - rotate each pulley by hand, and give it the same push/pull test as above. You may find that a pulley has come loose and possibly shifted on the shaft. If one is loose, make sure it is aligned properly, and tighten the set screw. This would be a good time to check all of the saw's set screws. The second cause would be from a worn out belt. Even if the belt looks alright, it should be replaced if it is more than a few years old - the loss of resiliency isn't always visually apparent. (Link belt time!) When you replace the belts, clean off all of the pulley's surfaces with denatured alcohol to remove any debris or glazing.
This would be an excellent time to do a thorough clean up of your saw's internal mechanisms, as well as removing old grease/lube and reapplying a new coat of lubrication. In a home shop (i.e. not a pro shop where the saw is running day in and day out) a table saw should be completely cleaned and lubricated a minimum of two times per year - more if you do large amounts of work or cut a great deal of MDF or other man made materials.
Break out the respirator and glasses and use a shop vac' to remove as much dust as possible. Use a small stiff bristle brush to sweep out dust from all of the small crevasses. If you've got one, us a compressor to blast out any tenacious debris. Resist the urge to use lithium grease, WD40, or 3 in 1 oil (and anything similar) to lubricate the saw. These are dust magnets! You will see all of your hard work vanish is a sticky, lumpy, saw dust encrusted mess if you do. Instead use a dry stick lube over all of the necessary parts.
If you have any additional questions, please feel free to ask!
Dan Kornfeld, Owner/President - Odyssey Wood Design, Inc.
Edited 7/10/2003 1:40:04 AM ET by Jackie Chan
Emerckx,
I can't help but wonder if its the fense...I have been suspicious of mine for sometime. Mine is a Bies knockoff (shop fox) and I have measured the same variances you indicated. I have been thinking of taking my aluminun straight edge and clamping it to the table but having its length go only to the half way (the midpoint) point of the blade....thereby elminating any possibility that the fense is pushing the stock back against the blade.
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