South Bend Shaper Cutting Speeds

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Mister Ed

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I have had a SB shaper for a couple years now. I only use it once in a while when I need to make something flat. I want to change that, so recently I have been doing a bunch of reading through some old literature. I had always wondered about the cutting speeds on the shaper and really had an "aha moment" with the relationship of strokes/min and stroke length ... as they relate to cutting speed.

So, I made up the following chart and laminated it to keep at the shaper. The center section should be avg surface feet per minute, left section are the 4 different SB belt settings, and the top is stroke length in inches.
Capture.JPG


Hopefully this helps someone else. Its funny that they really do not talk much about this in their literature.
 
Nice - I
I'm mathematically challenged ;-) How did you calculate the SFPM? I'd like to make one for my 7" AMMCO.
 
Not knocking your idea. I like it and I think I will print 1 up for my shaper too. But I would be interested in the math formula used because I am coming up with a different set of numbers :confused:

Cheers Phil
 
Well, I think I have it correct, maybe not. I also rounded. I will try and dig up the couple items I was reading when the light bulb came on in my noggin. What I was not getting before was that for every revolution of the crank arm you have both a cutting stroke and a return stroke ... easy enough. But since the return stroke is faster than the cutting stroke, things get complicated. The documentation that I was reading stated that as a general rule (for a crank shaper) 3/5 of the revolution was the cutting stroke and the other 2/5 would be the return stroke. So, in the formula below the 7 (or .14=1/7) is really 3/5 x 12. The 12 is simply converting inches to feet.

I used this formula:
SFPM= (stroke per min) x (stroke in inches) x .14 [ This is the same as (stroke per min) x (stroke in inches)/7]

Or to get stroke/min for a particular SFPM:
stroke per min = (SFPM x 7) / stroke length
 
Here is the one publication that I used. This is from the New York Education Dept and over on the NEME site:
http://www.neme-s.org/Shaper Books/Shaper Work/Section 18 Description of Speeds and Feeds.pdf

This section starts on page 293. Take a look at page 295 and the top of 296. Then page 299 to page 303.

I wondered about the 3/5 - 2/5 rule on the strokes and if this was brand specific. But I did see this used in a couple more places as well ... so I figure it must be close enough. It is at least better than what I had before ... nothing, LOL.
 
Thanks a lot Mr. Ed. I made one using your formula (and rounding) for my AMMCO 7" shaper.

AMMCO%20SFPM_zpsstj8j2pr.jpg
 
There you go! If you get a chance read those pages of the link I posted (that is where the formula came from). Even if you skip the gory details, the overall topic helped me with the understanding.

I have made it a goal this year to pay more attention to speeds on all my machines.
 
M.E.
I just went out and cranked my shaper by hand, and (without resorting to an indicator or protractor for testing), I get, (on the bull wheel), cut stroke starting at 270° to 100° (about 53%) of a revolution, dwell time 100° to 120°, return stroke starting at 120° to 260° (about 39% of a revolution, or close enough to 2/5 :encourage:) and dwell time again 260° to 270°.
But to go back to the math, (and just for simplicity) if we used an RPM of 12 and a stroke length of 1" I calculate that to be 12"/minute, or 1'/min. If we up the speed to, (your slowest), 42 RPM, that is 3.5 times faster than 12 RPM, so now are we cutting at 3 1/2 ' per min??? Even if we factor in a fudge amount for 53% of the revolution, you might get to 4SFM. Or am I just oversimplifying the math? Happy to be wrong

Cheers Phil
 
FWIW the 1967 South Bend Catalog (available here on H-M) says the range is 3 to 114 fpm.

SB7_Specs.PNG
 
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