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Gadgets, Gizmos, and Dohickeys => Fixing, Modifying and Refurbishing your Lapidary Equipment => Topic started by: Ranger_Dave on July 03, 2016, 01:49:59 PM

Title: Which motor?
Post by: Ranger_Dave on July 03, 2016, 01:49:59 PM

I recently acquired a 12 inch, gravity feed, saw. It's now in 15 pieces on my workbench. That's an improvement since it was in about 25 pieces at one time. It's old. The bearings I replaced were from the 1950's.

The motor it came with, probably just as old, is 3/4 HP with 3450 RPM. That motor works just fine and I figure a 1 inch pulley on the motor and a 2 inch pulley on the shaft would give me the right speed.

I have a newer 1/3 HP two speed, 1725 and 1140 RPM.

Should I stick with the old motor? Would the two speed motor be of any advantage even though it has less power?

Title: Re: Which motor?
Post by: jakesrocks on July 03, 2016, 02:31:09 PM

On a 12" saw, a 1/3 hp motor would be pushing the limits. 1/2 hp would be better.

Title: Re: Which motor?
Post by: Ranger_Dave on July 03, 2016, 02:59:34 PM

That's pretty much what I thought. I just wanted some better informed opinions.

I can always vary the cutting rate with different amounts of weight.

Title: Re: Which motor?
Post by: jakesrocks on July 03, 2016, 03:51:07 PM

Check with the maker of your blade for recommended RPM's too, and adjust blade speed with pulleys.

Title: Re: Which motor?
Post by: Ranger_Dave on July 03, 2016, 05:10:04 PM

I don't have a blade  yet, but most seem to be at 1325 to 1750 rpm.

I've used this; http://www.blocklayer.com/pulley-belteng.aspx  , to figure out pulley sizes.

Title: Re: Which motor?
Post by: johnjsgems on July 05, 2016, 10:59:56 AM

Easy formula is motor rpm X motor pulley diameter divided by Driven pulley diameter.  Or look at charts in Diamond Pacific or Covington catalogs. 

Title: Re: Which motor?
Post by: Ranger_Dave on July 05, 2016, 06:36:23 PM

I'm no good at math, that's why I like that site I linked to. Just put in the pulley diameters, the RPMs, and it figures it all out for you. You can even play with some of the parameters with some sliders.