shermlock
has rocks in the head
Member since August 2011
Posts: 612
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Post by shermlock on Apr 21, 2012 20:49:22 GMT -5
I went to my scrap metal shop today and asked for a used 1/3hp 1750 rpm motor. The owner looked and came back with a brand new GE 1/3 hp 3500 rpm motor that he sold me for the scrap price of $25. It was still in the factory wrapper! Even if the motor doesnt't work out for my saw, I'll find a use for it!
Now comes the pulley question: If I put a 2" pulley on the motor and want the driven pulley to spin at 1700 rpms, than I need to use a 4" pulley on the driven saw blade to get close to the 1700 rpms correct?
Extra credit question: Is 1700 rpms about right for a 12" 303c blade?
Thanks, Scott
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Post by Rockoonz on Apr 21, 2012 21:50:45 GMT -5
What size saw and what kind of blade? If your goal is ~800RPM 1 1/2 inch to 6 1/2 inch is a better choice, a 1 inch pulley will wear out a belt in a hurry.
Lee
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Post by deb193redux on Apr 22, 2012 1:21:52 GMT -5
Yes, if the driven pulley is twice as big as the drive pulley, the RPM is reduced by 1/2
should work good for 12" 303c
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Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Apr 22, 2012 10:26:45 GMT -5
If I am reading this right you want to run the blade at 1700 rpm, the same as what I run by 12" Lortone. In that case you need to run it one to one which would be two 4" pulleys which is what I have on my saw. I can not afford the 303 blade so I can not say what they recommend but my cheaper blade cuts smooth as silk at 1700 and they last a long time. I cut mostly nephrite/jade, agate and jasper. I have never had to sharpen my blade and I have a bad habit of letting my oil get pretty damn dirty before I clean up because it is difficult to clean it in a Lortone saw.
deb 193 says that the 303 works good at 850 is good for a 303 and he knows more about that blade than I. In that case you would need a 1 1/2" and a 3" to get the speed of 850.
I am far from an expert but deep in my heart I think I am correct. lol Then again I have a 3/4 horse on my 12" so I can probably cut the planet in half without overheating. Jim
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shermlock
has rocks in the head
Member since August 2011
Posts: 612
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Post by shermlock on Apr 22, 2012 11:13:37 GMT -5
My motor's rpm is 3500. I want to roughly cut that in half to get to 1700. I will put a 2" on the motor and a 4" on the blade. That cuts the rpms in half from the motor to 1700 at the blade, correct? I am sorry for the confusion due to my wording. Thanks everybody for trying to figure it out for me. Scott
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Post by deb193redux on Apr 22, 2012 12:11:58 GMT -5
I never said anything about running at 850. I saw he got a 3400rpm for cheap even though he wanted a 1750rpm. the necessary correction is to cur the speed in half with a larger driven pulley.
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Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Apr 22, 2012 13:35:40 GMT -5
Sorry, I somehow missed the 3400 motor. duh Jim
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Post by Rockoonz on Apr 22, 2012 18:16:59 GMT -5
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Post by deb193redux on Apr 23, 2012 12:05:44 GMT -5
As Lee's chart links show, bigger driven pulleys reduce RPM, and for a 303C blade, 1700 RPM is right in the middle of the recommended range for 12".
You can also see that the generic Covington RPM recommendation for 12" is way way slower than the 303c recommendation. I think the generic is based on older blade technologies. The new strong stainless cores and sintered diamond construction (like 303c) really can run at higher speeds.
I thought I understood that 301 and 303 now had same speed recommendations since they now use the same core (since factory changes a few years back).
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Post by johnjsgems on Apr 23, 2012 16:42:53 GMT -5
Daniel, you are correct. The 301 on the BD/MK chart is the old style 301 mild steel core notched rim. The 303C and current 301 use same high carbon tool steel core and both work better at faster speeds than the old style blades did.
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unclestu
Cave Dweller
WINNER OF THE FIRST RTH KILLER CAB CONTEST UNCLESTU'S AGUA NUEVA AGATE
Member since April 2011
Posts: 2,298
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Post by unclestu on Apr 23, 2012 18:33:59 GMT -5
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shermlock
has rocks in the head
Member since August 2011
Posts: 612
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Post by shermlock on Apr 23, 2012 19:27:50 GMT -5
Thanks everybody!
Unclestu: that is the calculator that I used before asking for help...it seemed too easy!
Scott
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