My table saw’s arbor has a gap between the “shelf” that the normal blade rides on and the beginning of the screw threads. This gap is just wide enough for a dado chipper to “fall” into, thus cutting deeper than the rest of the dado. (Otherwise, the arbor is uniform thickness.)
I hear that you have studied this problem. Other than replacing the arbor, have you found a DIY solution?
It has been suggested that I shim between the fixed flange and the inside dado blade, thus putting the full dado on the screw portion of the arbor. Would this be a safe solution? What about just enough shim to allow the outside blade & the first chipper to bridge the gap?.
Edited 3/19/2007 11:55 pm ET by MsCut
Replies
Can you give me the make and model of the saw? I'm betting it is a Ridgid.
John White.
Delta 36-979. Like I said, the arbor has uniform thickness. It's just that the threads don't start soon enough after the flat spot for the single blade.The saw is new & Delta would replace the arbor, but replacement would involve a whole lot of hassle. I'm not near a service center.
Your problem sounds similar to the problems that a batch of Ridgid table saws had a few years ago. Ridgid offered to replace the arbors but I posted the fix below as a much simpler solution:
The saw has a shoulder machined into its fixed flange that properly centers a single saw blade, but the saw's arbor narrows down slightly right next to this shoulder which will cause the second blade in a dado set to run slightly out or true, creating a dado with an uneven bottom. Additional dado blades will center up properly because the shaft comes back up to full size after the gap, which is about 1/8 inch wide.
I have been in touch with Ridgid's engineers and expect that they will be correcting the problem and repairing saws already sold at no charge, but this will take time. When I hear back from Ridgid I will post their response here on Knots.
In the mean time, I've come up with a simple fix that will get the saw to work properly with a dado set. Basically, I filled the necked down area of the arbor with epoxy and then used a file to dress down the epoxy as the arbor was spun by the saw's motor.
Start out by thoroughly cleaning the area to be filled. I used naphtha and a small brass brush followed by a second wipe down with naphtha on a paper towel. If you didn't get all the grease and oil off of the shaft it will show up on the towel and you'll know you need to keep cleaning. I used naphtha because it evaporates in just a minute or two and doesn't attack plastics or paint, alcohol would also work.
For epoxy, I used J-B Kwik Weld which sets up in just a few minutes and achieves full strength in four hours. J-B weld is available in most hardware stores and at least some Home Depots. If you can't find J-B brand, any epoxy meant for use on metal will probably work, as long as it isn't too thin when mixed. J-B has just the right consistency, about like tooth paste. It is liquid enough to work into the rough spots on the arbor, but thick enough not to drip.
I applied the epoxy with a tooth pick, filling up the low area of the arbor and working the epoxy just slightly into the start of the threaded section of the arbor. Use the epoxy to build up the low area until it is slightly higher than the threaded part of the arbor. Once the epoxy is in place, let it harden for at least a few hours before filing it down.
To smooth the epoxy, I used a moderately coarse flat file to remove the bulk of the material and a fine file for the final touch up. The epoxy will clog the teeth of a file so you'll need a small metal brush to clean out the file's teeth. To protect the flange's face as you work, the files will need what are called safe edges. If you don't have a file with safe edges you can take an ordinary file and grind the teeth off of its edges to make it into a safe edge version.
To file down the epoxy, start the saw and gently hold the coarse file against both the shaft and the face of the flange. Move the file with a forward stroking motion to prevent the rapid clogging that would occur if you held the file still. After a couple of forward strokes, stop the saw to check your progress and to clean out the file's teeth. After a minute or two, and a dozen or so passes, you should have the epoxy down almost to the level of the shaft all of way around. Now switch to the fine file to finish the job. You'll only need to use very light pressure on the files, so there is no risk of cutting into the shaft and reducing its diameter.
After repairing the saw we have here, I used a dado set to cut 10 feet of grooves into a maple plank. When I removed the dado blades after completing the cut, the epoxy was, as I expected, still solid and unmarked. I don't think there will be a problem with the epoxy wearing out, so this will work as a permanent fix if you don't want to hassle with getting the saw fixed under warranty.
John White, Shop Manager, Fine Woodworking Magazine
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