Tom
fully equipped rock polisher
My dad Tom suddenly passed away yesterday, Just wanted his "rock" family to know.
Member since January 2013
Posts: 1,557
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Post by Tom on Nov 20, 2013 8:23:26 GMT -5
Morning all, if you have been following the water based lube oil thread you may have read that my new blade has a bit of a dish to it. So how much is too much? I am afraid I know the answer:( Anyway my 12 inch blade has a dish in it. If you lay a straight edge from edge to edge straight across the center it has an edge gap between straight edge and blade of less than 1/2 mm. Still not good I know, but??
My last blade is dished more, its a 303 as well, I actually used it for a couple months at least cutting small rocks with no problems (although I believe that lead to premature inboard bearing wear.
I really hate to buy another blade until I get everything working on this saw again.
Thanks
Tom
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,487
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Post by Sabre52 on Nov 20, 2013 9:23:18 GMT -5
Tom,
I know someone more mechanical than I will chime in but, in my experience it kind of works this way. The larger the diameter of the blade being used and the larger the rock workpiece being cut the more effect the dishing seems to have. Those big blades need to be dead straight to saw large, hard rocks. On my old 20" saw I used to run, that 1/2 mm you're talking about would definitely have an effect when cutting a large rock with a lot of surface. Often the blade would bind in the cut. On the other hand, I could cut small rocks all day with the same blade with no binding in the cut due to the small rocks having a smaller surface area.
My ten inch saw blades, being used with smaller rocks anyway, seem to show much less effect if slightly or even pretty badly dished, probably simply because there is less surface area to bind against the blade in the cut. I've actually had ten inch blades with big ole dings in the edge that I've simply pounded out as straight as possible and they still cut fine though they did leave a lot of deeper scratches.
Hopefully, someone will have a more scientific explanation for you, with more specific measurements and tolerances....Mel
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Post by catmandewe on Nov 20, 2013 9:52:59 GMT -5
If you have the equipment (Hydraulic press and a set of elevated round rings of different sizes) you can press the dish back out. If it is just starting to dish, which yours sounds like it is, just turn the blade around and continue using it. It will push the dish back in the opposite direction, soon you will be straight again and then soon after that you will start dishing again at which point you need to turn it around again.
I have several blades I have continued using like this. One is an 18" on it's 5th year and still cutting everday. I turn it around every couple of months when I notice that it is starting to pull away from the stone when it finishes it's cut.
Tony
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Post by johnjsgems on Nov 20, 2013 11:39:25 GMT -5
Is it dished when laying on a flat surface or when installed on the saw? If only on the saw you may be over tightening the blade nut. Snug enough to prevent blade slipping is all you need. More and you can dish the blade. 303's have a pretty tough core. They are also single directional so reversing may straighten but you likely won't get good cutting performance.
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Post by catmandewe on Nov 20, 2013 15:35:27 GMT -5
Good point John, I forgot to mention that some blades are directional and only should be run in one direction. Most of those have an arrow stamped into the blade showing which direction it needs to be run.
Tony
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Tom
fully equipped rock polisher
My dad Tom suddenly passed away yesterday, Just wanted his "rock" family to know.
Member since January 2013
Posts: 1,557
|
Post by Tom on Nov 21, 2013 19:26:04 GMT -5
Hi guys, thanks for the advise, The blade is dished both on the saw and off. Its a small dish and I did manage to get most of the dish out. I have changed the bearings (IMO there was nothing wrong with the other ones) The blade is on the correct way, although I ran my old 303 backwards for dozens of cuts with no problem. I have made one tiny cut in a hard jasper, I mean tiny, going to work my way bigger and bigger until I have to clamp the split nut so it won't slip. I used my other blade with a much worse dish for tons of cuts, not on super big (for a 12 inch saw) but decent sized and the cuts were smooth and straight. My split nut from Lortone has not shipped yet, they are busy for Xmas LOL. we shall see what happens now, I think I hate slab saws now Very interested in the other peoples water lube tests as I really don't think it was the water that was screwing up my cuts
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Post by DirtCleaner on Nov 22, 2013 20:35:18 GMT -5
A long-gone great uncle of mine worked in a blacksmith shop. When I was young he was showing us a large wood cutting blade and explained that they would tune them be hammering a dish or cup to the blade. When it spun then it would straighten out and cut true. Now, to answer the question about how much….all I know is that it is RPM, weight and diameter dependent. Possibly different compositions of blade material matters too. Sure wish he was around to ask.
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