Planing Results with Variable Speed Drive Rollers

[jteneyck]

I recently installed a variable speed drive in my MiniMax FS-35 J/P. I did it primarily so that I could lower the speed to reduce the amp draw on the motor so that I could take deeper passes as well as add a segmented head. A side benefit should be an improved surface finish because of the greater number of cuts/inch as speed is reduced. Today I did some testing to see if it really is a benefit. Calculations show how the cuts/inch will increase as I reduce the speed of the variable speed drive motor.



I found a piece of stock that I had planed before I changed to the variable speed drive, so that represents the "stock" condition on the chart above, approx. 26 fpm.




I don't precisely know the depth of cut that I used on that piece, but I suspect it was 1/32" because that's what I used almost all the time. All of the following photos were done today at 1/32".

With the new variable speed drive set to 100%, the drive speed is 22.5 fpm. This is what the surface looked like on another piece of white oak.




At 50% or about 11 fpm:




And at 25% or about 6 fpm:



It's clear to me that surface quality increased as speed was reduced down to 50%, or 11 fpm, but there was no additional benefit at 6 fpm.

To further evaluate the potential benefit of variable speed feed rate, I found a piece of ash that had some pretty good tear out in one spot. It was done at 26 fpm, before the change:




Here's what it looked like at 22.5 fpm with the same 1/32 depth of cut as used for the other tests:



And at 50% or 11 fpm:




There was not much or any benefit at 22.5 fpm, but if not for that one chip at 11 fpm, I would call it a dramatic improvement. Even with that chip, it's a major improvement over either of the higher speeds.

The improvement in cut quality in difficult wood now has me reconsidering the merits of a segmented head, beyond the obvious of longevity compared to straight knives. I'm going to do more testing when I get a chance to see if the tear out results are consistently better at lower speed.

John

[Maple Leaf]

John,

That's certainly dramatic. Very clever; thanks for the idea.

I don't have any experience with segmented heads, but I'm still really happy with the Tersa head in my Mini Max. It delivers an excellent surface, and there's no faffing around with inserts. A knife change is about 15 minutes, and the old ones get reused for beaters.

dp

[jteneyck]

John,

That's certainly dramatic. Very clever; thanks for the idea.

I don't have any experience with segmented heads, but I'm still really happy with the Tersa head in my Mini Max. It delivers an excellent surface, and there's no faffing around with inserts. A knife change is about 15 minutes, and the old ones get reused for beaters.

dp

My FS-35 is from the 1980's.  I guess that was before they offered Tersa heads.  There's a lot to be said for the Tersa head and it's easy, fast knife changes, fast enough to use a beater set like you mentioned to save the good ones.  

John