[TheForge] rpm/horsepower

[David E. Smucker]

As Ries notes -- woodworkers like slower grinders and softer wheels to keep 
tools cool.

Klingsport for example sells a 3/4 horse 1720 rpm 8 inch grinder (import) 
with white friable grinding wheels of 60 and 120 grit for $ 120  -- at 
www.woodworkingshop.com.    I have not seen it and have no connection with 
Klingsport.

They also sell the TORMEK grinding system with its large wheel running wet 
at just 90 rpm.  It cost a bit -- $ 399 plus up to $ 459 for all of the 
"accessory kit"

Dave Smucker
----- Original Message ----- 
From: "Ries Niemi" <rniemi at fidalgo.net>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Wednesday, October 06, 2004 5:16 PM
Subject: Re: [TheForge] rpm/horsepower


>
> On Wednesday, October 6, 2004, at 10:33 AM, Schade wrote:
>
>>
>> I need a new bench grinder. The one I have is 1/2 HP 1750 RPM.
>> It seems like everything I have seen is higher horsepower and 3600
>> RPM. Is this marketing? Is a 1/2 HP 1750 RPM the same (torque)
>> as a 1 HP 3600 RPM?
>>
>> Bob
>>
>>
>
> Where the heck did you get a 1750 rpm bench grinder?
> Grinding wheels are designed and rated in surface feet per minute, with 
> the average stones wanting to run around 5000sfpm.  A 6" grinding wheel on 
> a 1750rpm grinder is running at about half that- too slow, in other words.
> Commercially, almost all bench grinders are 3450 rpm until you get up to 
> the big dogs- say 12" or 14", at which point they drop down to 1750.
> Now if you are gonna use this for buffing, or wire brushing, that might be 
> different. But for grinding, in a 6" or 8" size, you want 3450, and thats 
> what they make.
> As far as torque goes, yes, its true that a slower motor has more torque 
> for the same horsepower. But you need the speed, so you do need a bigger 
> motor. I have a 1 1/2hp Jet that I am quite happy with- cant seem to slow 
> it down.
>
> If you are wet grinding woodworking tools, of course, throw all this out 
> the window, and buy a special machine for that. But for general purpose 
> sharpening and grinding, 3450 is right.
>
> ries
>
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