Anyone know what an acceptable tolerance is on planer/jointer knives? I just sharpened 2 sets of each(dewalt 12" planer, and Jet 6" jointer) and I weighed them just to see. There is 1.8 grams difference from heavest to lightest on one set of jointer knives. Every thing else is closer. Just got me to wondering...How close do they need to be? Don't need me no bearing probs if I can help it.
Thanks for your knowledge
jack
On Sat, 27 Sep 2003 00:13:18 -0500 (CDT), snipped-for-privacy@webtv.net (Jack Gray) Crawled out of the shop and said. . .:
i would say, don't sweat it. that little of a difference in weight wont hurt anything.
I'm going to guess that these are from a 3-knife head in which case they should be the same weight (balance). With a
4-knife head you could load unequal weights as long as the knives opposite each other were identical in weight and balance, i.e., 1-2-1-2 in the revolution of the head.If you would like there is a 167 page knife grinding manual from C.G. Schmidt you can get. I suspect it would/could also substitute for Nytol in a pinch as it goes into all knife grinding applications.
You are right about the premature bearing wear. It is best to do these things right the first time.
Oh, and try and realize this is all free advice (advise to some) and worth every penny.
UA100
Went out to the shop this morn to see what is "1.8 grams" It is basicly a 1 1/4" #8 self drilling wood screw W/nibs. I thought that was just a little to much. I ground the back corners off the heavy knives into a curved radius about the same on both sides. Was surprised how much I had to grind to get them real close. The knives came from Jet about that far out of balance cause I haven't sharpened them but twice and ground them evenly when I did it.( on tormec) It was probably not a problem but I feel better now that they are real close.
So the lesson is...just because your knives are new doesn't mean they weigh the same.
Damn boards will probably joint themselves now!!
jack
Also, it never hurts to ask a question but you may want to re-consider (disregard) some of the advice (advise) given.
What! And have it take away all the fun?
UA100, who enjoys an afternoon/day of prepping for panel glue up...
On Sat, 27 Sep 2003 11:10:21 GMT, Unisaw A100 Crawled out of the shop and said. . .:
Well i'll be danmed,,learn something new every day. guess i gotta go and check on mine,,, sorry for posting bad information to the OP, and thanks Keith.
T
If one was to get real teknikul about this, a bunch-o-factors could get involved. If'n you grind off the back corners, the center of gravity ain't in the center, making things possibly unbalanced when the blade edges are all at exaktly the right height. In fact, a difference in thickness could move the center of gravity on the knives even though they are aligned properly, and even though they all weigh the same. It all gets so confusing...
Probably need a 'puter app to really screw it up ;-)
-Doug
Yeah they might. I remember a plastic surgeon who hung himself. Hank
I suppose getting REAL technicle about the balance would be a little "over the top". I weighed the knives on a reloading powder scale. (real accurate) The weights weren't even close. What was balanced on one knife would bottom out hard on another. I wasn't trying to get to some zen perfection on the knives, but it looked like "balanced" on one knife should be close to balanced on the others. Hell, the beam on the scale hit the top so hard on the heavy knife, I checked to see if it broke! It was like the knife was 1/2 " longer or something. Me and my bench grinder fixed that lard assed knife good though.
Life is good.
Happy Jack
You check the balance of the cutterhead?
No, I'm gonna have to hope Jet did that for me. I just checked the knives after sharpening cause I think that comes under user responsibility. Thats something that will change with every sharpening. The cutter head should be balanced from the fact. just like the knives "should" be. I ain't gonna take the damn thing apart, just gonna make the knives weigh the same , within reason.
jack
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