Replies

1. 
   Ricky_Yu | Dec 02, 2003 02:55pm | #1

   I think a variance of .010" or .020" is not inconsiderable. For example, most "fine woodworking" shoot for a tolerance of 1/64" or less. That's already .016". Taken another way, if you were making just one part, the difference may not be too great. But since most projects comprise a number of parts, and often these parts rely on the accuracy of their neighbor to ensure a nice tight fit, then just a couple of these differences can easily add up to 1/32" or more. Anybody who works with plywood knows that 1/32" is definitely considerable.

   Also, besides accuracy, the quality of your cuts may suffer. And not to mention that runout will put undue stress on the arbor and/or motor. The greater the runout, the greater the stress. Safety, as you point out, could also be an issue in that runout might increase the chance of kickback. I'm not qualified to say at what point does runout pose an unacceptable risk to your safety or your machine's well-being, but common sense tells me that the less, the better, and the manufacturer's tolerances is a good guideline.

1. 
   HenryVIII | Dec 03, 2003 07:49am | #4

   "... a couple of these differences can add up to 1/32 inch."

   In the electronics racket, where I spent a lot of my life, we called this phenomenon "tolerance stack".  Every semiconductor had a spec of +/- 5% or whatever.  We knew, deep in our hearts, that if we had ten parts in an assembly, that half of them would NOT be + 5% and the other half -5%, because the tolerances would then cancel each other out, and the net result would be close to 0%.

   What happened, against all odds, for more than thirty years, was that they would ALL be either + 5% or -5%, and in the end we'd have a + (or -) 50%.

   I've found the same thing is true of woodworking.  ;-))

   Keep things as straight as you can, and hope for the best.  Don't worry about a tolerance which is less than the expected movement of the wood throughout the course of a year's climate changes.

   Hope this helped.

   Enery

2. 
   USANigel | Dec 02, 2003 03:30pm | #2

   Runout could be just like a wobble blade and the worse problem is a wider cut than you expected (5/64" as expected 1/8") The final cut will tend to be rough with the saw cuts showing big time. Bigger problem is loss of clearance for the teeth as they cut through the wood. They will rub and this causes drag so you push harder and harder you push the less control you have, now that effects safety. Add to this vibration due the runout. ( bit like driving with out of balance wheels) And the saw feels poor and unfriendly to use.

3. 
   Mackwood | Dec 02, 2003 08:04pm | #3

   JR

   If you're cutting rafters, no big deal.  If you're making an exotic jewelry box, then you've got a problem.  On a wobble dado, you've got to measure from the fence to a particular tooth to get your cut right.  Same would apply to the blade.  How are you going to tell, time after time, which tooth to measure from.  That said, I certainly don't see a safety issue from the runout alone.  Tune your saw, get a good blade, get runout as minimal as practical for you and then go for it.

   Enjoy!

   Mack