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Table Saw Blade Alignment help

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Forum topic by bbasiaga posted 03-13-2016 10:35 PM 866 views 1 time favorited 26 replies Add to Favorites Watch
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bbasiaga

754 posts in 1455 days


03-13-2016 10:35 PM

I need a little help understanding what I am seeing on my table saw. I have a dial indicator set up in the miter slot, and am testing the parallelism of the blade to the slot. My blade has four relieve holes/slots in it, and I used those as reference to test four chords across the blade. The blade is the brand new blade that came with the saw (Sawstop PCS, and the blade is their brand).

As you can see from the illustration below, I put the four holes in turn at the top of the arc, and measured the chord below. The first two measured zero difference front to back, then the next one .004”, then the final one .007”. I repeated these measurements about 6 times each, and got spot on the same results each time, so I don’t think my set up on the indicator is the problem.

What I think is going on here is that my slot and blade are aligned, but this blade has a warp in it. All of the drift in the measurements are in the same direction (to the right). Trying to decide if I am interpreting this correctly, or if there is another problem and I may need to make an alignment adjustment to the table to get it parallel to the blade. Any thoughts would be appreciated.

Thanks,
Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.


26 replies so far

View MadMark's profile

MadMark

976 posts in 913 days


#1 posted 03-13-2016 10:55 PM

Ive never seen that particular test. How does it cut? Is it clean and square? Yes, it matters not.

M

-- Madmark - Madmark2150@yahoo.com Wiretreefarm.com

View teejk02's profile

teejk02

423 posts in 585 days


#2 posted 03-13-2016 10:59 PM

I think your signature pretty much says it all but that’s just me. You work with wood. .003” (which I guess translates to .006 on run-out which might equate to 1/128th”? I think most people would be happy with that.

View Paul's profile

Paul

721 posts in 1025 days


#3 posted 03-13-2016 11:10 PM

The smarter we get, the dumber we get /sigh.

Paul

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OhioMike

73 posts in 1622 days


#4 posted 03-13-2016 11:49 PM

7 thousandths seems a little bit too much. John White, author of CARE AND REPAIR OF SHOP MACHINES says for best results the blade should be within 5 thousandths of parallel to the miter slot. I agree that the problem is likely the blade and the best way to check is to put another (good quality) blade on the saw and test again.

Also, you could test the runout at the arbor flange like this:

If the flange tests within a thou or two, then you can assume the blade is the culprit.

Mike

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teejk02

423 posts in 585 days


#5 posted 03-14-2016 12:05 AM



The smarter we get, the dumber we get /sigh.

Paul

- Paul

I think I’ll put that in my “quotes to remember” book. Personally I think I’d be afraid to perform his test on my table saw or any other table saw I know of…figure as long everything comes together “life is good”...

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bbasiaga

754 posts in 1455 days


#6 posted 03-14-2016 12:29 AM

Thanks Ohio Mike. I think I will try that test next time I am back out in the shop. I’ve got to get a new power cord for it, as I need a longer one and with a different plug, so I haven’t fired it up yet. May not even be a problem in application. Runout is expected, and what I was really testing for here is parallelism. Just have a slight confound in the results that I don’t know what to make of. If I average the readings, that’s a little less than 0.003” out of parallel, which is well within acceptable. Just don’t know what to make of that one big one. I don’t have another high quality blade on hand right now either.

Paul,

I’m just some modern idiot following the instructions in the owner’s manual. Society is doomed.

For the rest of you wondering about this test, the owner’s manual says to find a spot on the blade, and measure it front to back. Rotate 1/4 turn and try again, looking for the spot with the most consistent shift (i.e. gradual front to back, not bouncing around which may indicate surface imperfection). Well, there is not a lot of jumping on any of the 4, so that’s what confused me.

-Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View hotbyte's profile

hotbyte

841 posts in 2435 days


#7 posted 03-14-2016 12:45 AM

Test I’ve always seen/used…put a dot right under tooth with sharpie and measure there at front of saw, rotate blade so spot can be measured at back. Spin blade, mark another spot and repeat if you want.

View JBrow's profile

JBrow

814 posts in 380 days


#8 posted 03-14-2016 01:14 AM

bbasiaga,

It seems to me that it is pretty difficult for any blade manufacturer to produce a blade from 1/8” thick stock that is dead flat. A little warping is inherent in the metal. But I doubt the deviations you are seeing are much of a concern.

When checking that the blade is aligned parallel to the mitre slot, a single point on the blade is generally recommended for making the measurement. The reason, I suspect, is that blades in their static state are not dead flat. Using different points on a blade, like you are seeing, can therefore result in false readings.

When wood is cut, the blade is spinning at more than 3250 rpm. This imparts a good deal of outward directed centrifugal force to the blade and this force can cause the blade to flatten and run in a more or less, perhaps perfect, geometric plane. It is this geometric plane defined by the spinning saw blade that actually must be parallel to the mitre slot. Obviously the dynamically generated plane in which the spinning blade travels is too dangerous to measure. Therefore marking a single reference point on the blade is the recommended method for truing up the table saw, even though this point on the blade may not lie in the plane of the spinning blade.

View builtinbkyn's profile

builtinbkyn

651 posts in 400 days


#9 posted 03-14-2016 01:37 AM

Am I wrong to assume that if the blade is slightly warped, the kerf will just be a bit wider? If so, that should not effect the alignment of the cut, but it will effect the final dimension of the cut and be slightly less than intended.

-- Bill, Yo!......in Brooklyn :)

View runswithscissors's profile

runswithscissors

2176 posts in 1485 days


#10 posted 03-14-2016 01:41 AM

I had a crappy Crapsman jobsite saw that had such bad runout you could see it on startup. Flattened right out when the blade got up to speed. Of course feeding wood into it slowed the blade, and the wobble became visible again.

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

View TheFridge's profile

TheFridge

5764 posts in 946 days


#11 posted 03-14-2016 01:51 AM

Blades are tensioned to prevent warping. They are pretty flat. I’d check the arbor. Easy to fix.

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

View bbasiaga's profile

bbasiaga

754 posts in 1455 days


#12 posted 03-14-2016 02:02 AM



bbasiaga,

When checking that the blade is aligned parallel to the mitre slot, a single point on the blade is generally recommended for making the measurement. The reason, I suspect, is that blades in their static state are not dead flat. Using different points on a blade, like you are seeing, can therefore result in false readings.

- JBrow

Thanks JBrow and Hotbyte. I was just thinking that myself. The next few pages of the owner’s manual gave an alternate method like you suggest – mark a point, use your carpenter’s square to measure, move that point to the back of the saw, measure again. This is impossible to do accurately of course, but I decided to try that method with the dial indicator. Got an average of about 0.0025”, testing a spot in each quadrant, and all the measurements were either .002 or .003. Close enough for me. That method at least eliminates the variability of the blade.

I did check the arbor as pictured above too. Less than 0.001” runout. Next test will be to run it once I get a power cord.

-Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View hotbyte's profile

hotbyte

841 posts in 2435 days


#13 posted 03-14-2016 02:34 AM

You can use a combo square and feeler gauge. Lock combo square close when measuring at front of blade and check with feeler gauge. When checking at rear, leave combo square locked and use feeler gauge to determine the difference.

View rwe2156's profile

rwe2156

2187 posts in 940 days


#14 posted 03-14-2016 11:40 AM

They also make machined set up disks to substitute for the blade if you want to be that accurate.
But I’ve always used the same tooth method always worked for me.

I’m surprised a saw that expensive is that far off.

-- Everything is a prototype thats why its one of a kind!!

View dbw's profile

dbw

143 posts in 1096 days


#15 posted 03-14-2016 11:51 AM

We can think about this all day. The bottom line is: how does it cut and are there any issues with the work piece after it is cut.

-- measure 3 times, cut once

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