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In depth questions regarding Table Saw blade wobble and calibration

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Forum topic by TheWoodenOyster posted 12-05-2014 01:43 PM 771429 views 0 times favorited 21 replies Add to Favorites Watch
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TheWoodenOyster

1275 posts in 1399 days


12-05-2014 01:43 PM

Topic tags/keywords: tablesaw

I recently posted regarding my inability to make a decent crosscut sled. I realized that one of the culprits was no doubt the fact that my tablesaw blade was out of alignment with my miter slot. Idiot… Anyway I decided I had better fix that, so I went to HF and got a dial indicator and a magnetic base. Upon testing the blade I found about a .020 misalignment between the miter slot and the blade, enough to mess things up. I have started working on aligning them but I am not finished yet. One concern I have is that when I put the dial indicator on the body of the blade (not the teeth) right above the arbor, I get about a .005 fluctuation. This is a high quality blade and I will test another to see what the comparison is. To describe the occurrence:

1. I set the dial indicator on the body of the blade about 1” or so above the level of the saw top. The saw blade is at 90 degrees.
2. I turn the blade using my arbor wrench so that my hands won’t be pushing the blade around side to side.
3. As I turn the arbor, I get some resistance for about 3/4 of the turn, then it gets easy and almost turns itself for about 1/4 turn. This is where the blade wobbles about .005. Then the blade resumes giving me a little bit of resistance and the process starts over.

I have no idea what this could be, but I guess it could be an arbor issue. I know it could also be a blade issue, and I’ll check another blade today. What worries me is the resistance I get for the majority of the turning of the blade, then it gets easy for a minute. The resistance isn’t really much and by no means is difficult to turn, it just pushes back a little bit.

The saw is a direct drive early 90’s 3 HP unisaw that I bought used in very good condition. I know this is a pretty in depth issue, so I may not get many answers, but I thought I would throw it out there. Any tips would be appreciated in diagnosing this problem (if it is a problem) and any tips in calibrating a tablesaw in general would be appreciated.

Thanks

-- The Wood Is Your Oyster


21 replies so far

View DocSavage45's profile

DocSavage45

7703 posts in 2307 days


#1 posted 12-05-2014 06:03 PM

I’ve not had to deal with this. Just thinking out loud? Was this resistance present before? Has the blade been dinged in any way? Vibration in a blade can be reduced with a saw blade stabilizer.

When were the bearings last lubed?

Good luck!

-- Cau Haus Designs, Thomas J. Tieffenbacher

View dozer57's profile

dozer57

92 posts in 964 days


#2 posted 12-05-2014 06:32 PM

I would guess you have a bearing issue here. One of the balls on the bearing possibly has a flat spot. If the motor is not total inclosed style it may just be saw dust inside of it. try blowing it out first and if this doesn’t fix it then replace the bearings with high quality bearings.

View Bill White's profile

Bill White

4454 posts in 3425 days


#3 posted 12-05-2014 06:46 PM

My comment/question does not address the resistance issue, but are the blade washers/flanges clean and true?

If so, then the issue is within the motor arbor or bearings.

Bill

-- bill@magraphics.us

View waho6o9's profile (online now)

waho6o9

7174 posts in 2041 days


#4 posted 12-05-2014 06:52 PM

See if you can use the dial indicator on the arbor and

check for run out.

View runswithscissors's profile

runswithscissors

2189 posts in 1489 days


#5 posted 12-06-2014 12:26 AM

A direct drive Unisaw? That’s a new one on me. The only ones I’m familiar with have the motor mounted in the cabinet, quite close to the arbor, with 3 short belts driving the arbor. Resistance to turning may just be that the belts have developed a “set.”

And, of course, as others have mentioned, bearings could be the culprit.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View bigblockyeti's profile

bigblockyeti

3668 posts in 1185 days


#6 posted 12-06-2014 12:58 PM

Take the belts off the arbor/motor to eliminate them as a possibility for generating the resistance you speak of. Remove the arbor nut, washer and blade and put the dial indicator directly on the clean arbor flange to eliminate any discrepancies that could be generated by any blade. Grab the spindle and see if you can move up and down or front to back by hand, any radial movement at all that you could feel by hand would be too much and would need to be corrected.

View Bogeyguy's profile

Bogeyguy

548 posts in 1532 days


#7 posted 12-06-2014 01:33 PM

Yep, what bigblockyeti says.

-- Art, Pittsburgh.

View TheWoodenOyster's profile

TheWoodenOyster

1275 posts in 1399 days


#8 posted 12-06-2014 04:18 PM

First off, I’m a doofus. You are correct about the three belts. They’re so short and deep in there that I never see them and forgot they were down in there.

Second, I did more testing yesterday and the actual arbor has no runout to speak of, maybe .0005, so negligible. I tested a different blade as well and it was a little more flat, I suppose. Both blades had a little bit crook to them. About .005 for both of them. They are the free world made Delta blades that KnotScott always recommends on ebay. Either German or American, I can’t remember. I don’t know if that .005 is normal for tablesaw blades or not…

I could see what you are talking about with the belts getting a memory and that is what it feels like when I turn them by hand. It isn’t a grinding resistance or necessarily a “bad-feeling” resistance, just a smooth push back. I was thinking it could be the belts. Saw runs smoothly when on though. I might take the belts off to get a better idea.

I am learning that calibrating tools is just as much of a skill as dovetailing and sharpening. Takes a while to learn how to work on these machines.

-- The Wood Is Your Oyster

View unbob's profile

unbob

718 posts in 1368 days


#9 posted 12-06-2014 07:17 PM

This may be hard for me to explain, but I will try.
Most blades I have run-out .002” or a bit more. But, you can still use a blade with run-out and accurately align the miter slots. Make a mark “dot” near the edge of the blade with a sharpey. When testing with a dial indicator, place the indicator on the dot when moving to and fro. This will align the miter slots to the radial motion of the arbor…....Not to any mis-alignment of the blade or arbor flange.
The photo, there using a single dado blade-to hopefully show the point of what I stated above. Well….I tried.

The above photo, I am testing arbor to miter slot alignment with the blade tilted.
After, the miter slots were aligned with the arbor at 90, testing at 45 showed mis-alignment of .017”....contractors saw!

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TheWoodenOyster

1275 posts in 1399 days


#10 posted 12-07-2014 02:18 PM

Unbob, I think I get what you are saying. You did a good job describing the process. I went ahead and aligned my blade to my slot using your method and I think I got it pretty close. I guess with the little bit of warp or bend in the blade, you just end up cutting a .130 kerf instead of a .125 kerf, correct?

-- The Wood Is Your Oyster

View wbrisett's profile

wbrisett

201 posts in 1813 days


#11 posted 12-08-2014 10:08 AM

I absolutely hate trying align tablesaws using a blade, as mentioned they have a runout in themselves. I’m currently having an issue with a a blade in my saw, so I documented the whole process here: http://lumberjocks.com/topics/65848

If you notice, I’ve spent the $40 on a MasterPlate. It really makes setting up blades and saws a piece of cake compared to using a blade.

Before you go all crazy and tear your saw apart thinking it’s bearings or something else, you might want to consider spending $40 and getting a masterplate.

View TheWoodenOyster's profile

TheWoodenOyster

1275 posts in 1399 days


#12 posted 12-08-2014 02:44 PM

Cool accessory wbrisett. I might grab one of those next time I need to calibrate, which will be in 6 months when I move.

-- The Wood Is Your Oyster

View TheFridge's profile

TheFridge

5765 posts in 950 days


#13 posted 12-08-2014 02:59 PM

Really sounds like your belts have a set to them now. Had same prob with my unisaw. I Just shifted the belts to fix it.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View TheWoodenOyster's profile

TheWoodenOyster

1275 posts in 1399 days


#14 posted 12-08-2014 03:56 PM

Cool. I’ll take a look at those belts. I’ve never looked at them since I bought the saw about 2 years ago.

-- The Wood Is Your Oyster

View Sylvain's profile

Sylvain

639 posts in 1964 days


#15 posted 12-08-2014 04:25 PM

Have a look at Matthias Wandel site:

wobble

and alignment

someone said he had forgotten to remove the label on the blade:
Put a brand new 7.25” blade in there, and make a cut. It’s garbage. ??? I forgot to remove the sticker from the blade before I mounted it. Cleaned that off, polish with steel wool and presto – almost perfect cut, can barely tell it was cut with a saw as opposed to on the jointer.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

showing 1 through 15 of 21 replies

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