# Jointer rpm?



## ctwistedpair (Jan 6, 2015)

Hey all, I purchased a small jointer, circa 1960's, 4 inch 3 blades. The motor that came with it is a 3/4 hp 1725 rpm. The pulleys gave a final rpm of 2800. The cut looks scalloped, even with the slowest feed rate and removing less than 1/32. The commercial bench top planers run at 9 to 10k rpm. Question is, how high can I or should I go? I can get 6900 rpm with a pulley change. 8 inch drive and 2 inch driven. Any thoughts?
Thanks for your comments.


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## Steve Neul (Sep 2, 2011)

I don't know for sure but I think 6900 is too fast. I have one jointer the cutterhead turns at 3450 rpm and another that is direct drive and runs at 3600 rpm.


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## woodnthings (Jan 24, 2009)

*cuts per minute vs RPMs*

This 6" jointer has a 14,000 cuts per minute spec. with a 3 knife head at 4800 RPM.
http://www.grizzly.com/products/6-x-46-Jointer-with-Mobile-Base-Polar-Bear-Series/G0452P

You should get close to that if yours is similar. A 3 to 1 ratio should get you close. A 2" machine pulley with a 6" motor pulley would be about right. for 5175 RPM. 

You can use this calculator for your specific pulley sizes:
http://culvermotor.com/Engineering-Formulas/Pulley-and-RPM-Calculator.html


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## FrankC (Aug 24, 2012)

Another factor that comes in is the feet per minute (FPM) speed of the cutter head.

Cuts Per Minute (CPM) is a constant compared to RPM and depends on number of blades, Feet Per Minute determines how fast blade cuts through the material and depends on diameter of cutter head.


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## TimPa (Jan 27, 2010)

if that is the original motor and pulley set-up, you may evaluate the blade installation for equal height. if a slow feed still scallops, i would blame unequal blades.


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## GeorgeC (Jul 30, 2008)

ctwistedpair said:


> Hey all, I purchased a small jointer, circa 1960's, 4 inch 3 blades. The motor that came with it is a 3/4 hp 1725 rpm. The pulleys gave a final rpm of 2800. The cut looks scalloped, even with the slowest feed rate and removing less than 1/32. The commercial bench top planers run at 9 to 10k rpm. Question is, how high can I or should I go? I can get 6900 rpm with a pulley change. 8 inch drive and 2 inch driven. Any thoughts?
> Thanks for your comments.


At 2,800 rpm that is 46.66 rev per second. With a 2 blade cutter head that is about 93 cuts per second. Unless you are pushing the board through very fast any scalloping because of cutter head speed is going to be very difficult to see.

Have you tried varying the downward pressure you are putting on the board and where you are putting it?

How much bite are you taking at each pass?

George


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## ctwistedpair (Jan 6, 2015)

*rpms*

I picked up a 7 inch drive pulley from grainger, brings the rpm to 4025. Much smoother finish. The blades were all running true. This seems to have done it. The bearings might not last so long, but I have extras. Thanks for all of your help.


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