Band Mill Blade Speed
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Determining the feet per minute that a band should run at on a home-built mill. May 11, 2005
Question
I'm looking for information on building a band mill. I need to know what the band blade speed in feet per minute should be. Is there an actual set number? I need this information to figure the pulley sizes from the output shaft to the input shaft of the band wheel. I'm using a 14hp Kohler, 20 inch band wheels, 158" standard 1 1/4" band blade. The band wheels I'm using are rated for 1240 rpm. They are Browning pulleys. That would be 5.236 feet per revolution x 1240 = 6492 feet at the max RPM of the pulleys. The max blade feet per minute would be 6492 BFPM. If I'm doing this wrong, please let me know. One guy told me that 42 blade feet per second is minimum speed.
Forum Responses
(Sawing and Drying Forum)
From contributor G:
I have a 20hp, 18" wheels at 5000fpm and would not want anything less. Max log is 30". I read on this site a long time ago that Wood-Mizer runs at 4500fpm. With 14hp you will want to stay at the lower end because you will find you lack hp. Nothing wrong with that, you just feed slower. Your math looks correct.
From contributor D:
There's a bandspeed calculator at the link below. There's also a pulley calc partway down the index at this link, under "Machinery".
http://www.ls.net/~windyhill/Calcs/CalculatorIndex.htm
From the original questioner:
Thank you, contributor G, this will help me out a lot. I can work the pulley sizes from here.
From contributor A:
What is important to know is the rpm of the motor shaft at full (cruise) speed. The 1240 rpm rating for the band wheels is only an approximate figure. And the length of the blade is not a factor here, I think.
From contributor M:
I run a 10 hp 3 phase with 24" wheels at 4800 fpm. I used to be higher, but in large oak - 24" - I would have problems. On some advice from Tim Cook at Cook's Saw, I slowed it up. I was at 5600. It runs a lot better at 4800.
From the original questioner:
Is it better to run slower (FPM) on hardwoods and faster on softwoods? Or reverse? Does the hardwood heat up the blade faster than softwood? I'm thinking the softwood might tend to heat the blade up faster because of it having more sap, creating friction. Or does it just take more torque/HP to cut the hardwood versus soft? It would be better in the long run if I set the mill up so that I can vary the speed, instead of having to change sheaves for soft or hardwood.
From contributor M:
I don't know of a mill that changes speeds for hard or softwood. Usually that's more changing the blade set and hook angle. Suffolk Machinery (they make blades) really gets into that in depth. Not being on any production schedule or time clock, I buy Simmond's Red Streak blades from Cook's, 10 degree hook, and use them right out of the box. I send them back usually twice to get resharpened. There is a new Munkforsager blade out I've heard is good, but I haven't tried it yet. I don't know how you can easily vary the blade speed. I can't without changing sheaves. With an engine, I'm pretty sure you want it at maximum rpm so the governor works depending on the load. If I remember what Tim told me, the 10 degree hook is trying to pull the blade into the log. With 10 hp there isn't enough power there to run 5600 fpm on large logs. This was almost 10 years ago, so it's a little fuzzy. I just know it runs a lot better at 4800 fpm.
