Saskrock
fully equipped rock polisher
Member since October 2007
Posts: 1,852
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Post by Saskrock on Jun 8, 2008 22:44:14 GMT -5
I saw somewhere the other day that a workforce THD550 (7") runs at about 3500 rpm. The homebuilt saw I have that I had been looking to replace was running at 1725 rpm. I figured for the price of a pulley ($5) I would try speeding up my saw before replacing it. I have been using the cheapest diamond blades you can possibly buy ($2 each 7") so I thought that was probably half my problem. It was not (or at least not half). What a unbelievable differance the rpm makes!!!.
Anyhow I am now cutting agate at least 3 times as fast as before. One of my cheap blades that before would be wore out after one day is now showing very little wear after a day cutting.
Just shows the importance of RPM. Guess I'll keep my saw.
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Post by akansan on Jun 9, 2008 9:07:26 GMT -5
The 3500RPM is basically construction RPM. Lapidary saws cut at 1725RPM...but the blade actually runs slower that that. You sacrifice delicacy in exchange for speed, resulting in chips if you're not careful.
It's interesting that your blades run better at a higher RPM. Makes me wonder how a "typical" WF blade would handle slower RPMs...
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Saskrock
fully equipped rock polisher
Member since October 2007
Posts: 1,852
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Post by Saskrock on Jun 9, 2008 9:58:29 GMT -5
I knew I had found that 1725rpm somewhere before I built the saw. Maybe the differance is all in the blade. Maybe its a lapidary vs tile blade differance in design speed? I know the blades I have say max rpm of 5000. The workforce blade should be a tile blade as that is what the saw is sold as. I'm also wondering now how it would cut at lower rpm. Might need a WF owner to do a experiment for us.
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Post by deb193redux on Jun 9, 2008 10:11:50 GMT -5
I suspect the 1725RPM would be a little different with today's slintered stainless steel blades. It also varies with the diameter because the real number is the feet per second at the rim. ANother factor is the amount of heat generated because some non-slintered blades lose diamond at very high heat, and some rocks fracture.
I get fuzzy on the engineering, but the ideal speed for any blade and material has to do with the wear of the metal vs the breakage/loss of the diamond. YOu want to expose fresh diamond fast enough for hard materials, so that often means softer metal.
Not sure why the cheap blade lasts longer at faster RPM, unless it has to do with how hard you were pushing, and the blade keeps up with the pressure better now.
Glad you got good results.
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Saskrock
fully equipped rock polisher
Member since October 2007
Posts: 1,852
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Post by Saskrock on Jun 9, 2008 10:28:12 GMT -5
I was definantly pushing harder before. It didn't cut well at all otherwise. I just got off the phone with a gentleman from MK diamonds he tells me that the lapidary and tile blades are designed for different RPM's. He said a lapidary blade will glaze over more at 3500 rpm and require more frequent dressing but would work fine. I didn't want to admit I was using a $2 tile blade on a lapidary saw so no professional opinion but I'm thinking the result that way is it works terrible. In any case lapidary blades are designed for 1725 rpm, tile blades for 3500 rpm.
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terrastomp
starting to shine!
Member since May 2008
Posts: 30
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Post by terrastomp on Jun 10, 2008 15:11:06 GMT -5
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Post by deb193redux on Jul 1, 2008 0:20:40 GMT -5
But if you have autofeed, use enough RPM so the blade does not bind and die a lot sooner
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drjo
fully equipped rock polisher
Honduran Opal & DIY Nut
Member since May 2008
Posts: 1,581
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Post by drjo on Jul 1, 2008 13:43:50 GMT -5
All this is well and good but now I need to know...Where do you get a $2 blade??!?!? Dr Joe .
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drjo
fully equipped rock polisher
Honduran Opal & DIY Nut
Member since May 2008
Posts: 1,581
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Post by drjo on Jul 2, 2008 20:48:10 GMT -5
Names...places!!!! ;D
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Saskrock
fully equipped rock polisher
Member since October 2007
Posts: 1,852
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Post by Saskrock on Jul 3, 2008 1:47:51 GMT -5
I got the $2 blades at "bianca amor's liquidation supercentre" but after more cutting the blade I had on kind of got ate away. Must have had more diamond then usual on the outside. I'm actualy looking at getting a blade from rocklady1.com/Products.html that rockitman mentioned. I have one of their 8"premounted flat lap disks and it seems really good.
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