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Requesting help from Machinists regarding defective arbor?

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Forum topic by Surfing_Squatch posted 06-02-2018 06:25 AM 473 views 0 times favorited 3 replies Add to Favorites Watch
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Surfing_Squatch

2 posts in 484 days


06-02-2018 06:25 AM

Lumberjocks, I’ve only been doing woodworking for a little over a year (I’m loving it though!) so please excuse my lack of terminology.

I’m refurbishing an old Craftsman 113.29940 table saw. I noticed a lack of power and “whining” noise so I’ve replaced the arbor and bearings. After reassembling the saw I found the runout/wobble of the blade is .012”. I’ve checked the arbor flange on the new arbor and there is less than a .001 difference throughout a full turn. The opposite side flange has no difference as measured with a .001 precision dial indicator. The saw blades are the same and have no significant warping/runout.

I’ve replaced bearings on an arbor of a 315.228310 model before and had great success after the first time.

Some things i noticed that are different with the 113:

For the 315 model I had to seat the bearings with a mallet and homemade wood jig to push the bearings on the arbor.

1). On the 113 I used the same jig setup and it’s a snug fit but I can slide the bearings on and off with my hand. I purchased the new bearing from sears parts and i took the arbor and bearings to a local bearing shop where the clerk informed me the bearing is a standard bearing so they should be the correct size.

2). After many times of disassembly/assembly and still getting the .012” runout after cleaning where the bearings sit in the chassis of the saw I found the flange that is attached to the arbor can be slid of the arbor (see pic). The previous arbor does not do this. Nor did the 315 model. I noticed it because I can hand screw the arbor nut on but when i tried to tighten it with the arbor wrench the blade rotates. This leads me to believe the flange should be “locked” onto the arbor.

Question: Is the flange on the arbor supposed to be able to be slid off or should it be “locked” onto the arbor?

I’ve read the blogs and watched Mathais Wandell’s (sp?) YouTube post that demonstrates how to true a warped arbor flange but i don’t think the flanges are warped. What else could it be?

My guess is the design of the saw is that the flange is locked onto the arbor and the blade is secured with the opposite flange via the arbor nut. Therefore the blade will then rotate when the motor rotates the pulley wheel attached on the opposite side of the arbor. If the flange rotates the bade can then “float” on the arbor while it spins.

Any and all help is appreciated!


3 replies so far

View msinc's profile

msinc

567 posts in 922 days


#1 posted 06-02-2018 12:47 PM

Unless the bearings were tight and getting ready to lock up I doubt they had anything to do with the lack of power and may or may not have been the source of the whining noise. That said, you gotta start somewhere and having some new parts in the saw is never a bad idea.
In terms of run-out, just to make sure I am understanding this…you are checking the arbor flange and getting somewhere around .001” run-out, install the blade and check it up near the teeth and seeing .012”??? If that is the case then yeah, the flange and the arbor have to be zero, as in none because if they are not any run-out you read will be magnified when you check it at a point 5 or 6 inches away.
As far as the flange having to be permanently attached to the arbor, no. It does not as long as it has zero run-out. That said, I agree and I think what you are getting at by having it permanently attached is that it is easier to keep it zero if it is and harder to keep it zero if it floats. This is certainly true.
We are lucky in that with modern machining practices it is pretty much a foregone conclusion that the arbor, flange and blade mounting surfaces will all be true and perfect and have zero run-out as they should. That is sometimes not the case and then you either have to find the bad part and correct it or replace it with one that is right.
I would suggest that you begin by getting rid of the measured .001” run-out you are seeing at the arbor. It is likely that this part is simply not machined true. Having to drive a bearing on with a piece of wood or having it slide snug on the shaft should not matter as to whether or not it will run true once installed if everything else is right. With only .001” run-out you could be looking at a simple little burr on one of the surfaces. You should be able to correct that with some wet or dry 320 grit sandpaper. Your dial indicator will easily tell you where it is high.
Bottom line, yeah, it should all snap together and go with no problems…but when it doesn’t then you might need to make a few adjustments to get it running true. I doubt it is in the bearings. You can check the arbor easy enough by removing it and setting it up to dial indicate in Vee blocks. They should be precision machined blocks, but you could make a pair carefully out of wood for a one shot use. Don’t forget to check and sand the flange area of the blade too, it could be a burr there giving you the trouble. If all else fails send the parts back for replacement, but you can probably get it to work. Removing 1 or 2 thousandths is not really moving a lot of metal. Good luck.
All this said, I don’t know what saw you are working with, but I will say that there is a reason we pay $3000 and up for a fine cabinet saw, but that don’t mean yours can be perfect with zero run-out.

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MrRon

5567 posts in 3662 days


#2 posted 06-02-2018 02:35 PM

I don’t believe the bearings should slide on/off so easily. A sliding fit means there is clearance around the arbor with the bearing and that translates to a “wobble” when there is a force applied at the pulley end perpendicular to the axis of the arbor due to belt tension. How much clearance is ok? I would say a couple -o-ten thousands (.0002”).

View darthford's profile

darthford

612 posts in 2343 days


#3 posted 06-02-2018 03:23 PM

Mark the blade and the arbor where you measure the most run out .012. Now carefully rotate the blade 90 degrees on the arbor and re-measure. Did the .012 run out stay put at your mark on the arbor or did it move and follow the mark on the blade 90 degrees.

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