bandsawing steel stock - what am I doing wrong?

250 FPM is still pretty fast. If you EVER cut tool steel,you have to get the speed down to 75 FPM,or you will quickly ruin another blade. In fact,even at a low speed,01 tool steel can suddenly harden just from the heat of cutting. This hardening is only a few thou. deep,but it is quite enough to strip the teeth off your blade. You need to go 75 FPM,and KEEP the tool steel moving. If you hesitate,it may allow heat from friction to build up and surface harden the steel.
 
I mentioned earlier that I slowed down my 14" floor standing wood band saw for efficiently cutting metals. It's slower than needed for aluminum and softer metals, but great for steel. I still use it for wood as well, although it's a little slower than needed. I'm not in a hurry and so I don't care. I used an electronic tachometer to measure the actual wheel speed to be sure the numbers are correct. Of course, the best thing is a variable speed if you can afford it or need it.

Here is the formula and the sizes that I used. I think it cost me about $150 for the parts from McMaster-Carr. I don't have room for another saw, and I already have a horizontal 4X6" for cutting thicker stock, so this mod fit my needs.

IMG_0807.JPG IMG_0808.JPG Bandsaw Speed Formula.jpg
 
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I have a shopsmith bandsaw. And I honestly considered running it off of the chuck on my lathe. Don't think it would be slow enough though.


Jamie
 
DC motor is a great solution!
I am confused about the DC motor and the VFD? I thought VFDs were for AC motors of various phases? I though DC motors were controlled by PWM's? Can someone school me on this?
I have the 18" jet that has high and low gears so I can cut wood or metal. I just leave a 10-14 tpi blade on it.
R
 
I have been following this thread and it got me to thinking about working on my Powermatic 14" wood cutting bandsaw (Model 141). I have been looking for a while for a stand alone vertical metal cutting bandsaw and nothing ever seems to become available. I then thought of trying to find a drive system for a Powermatic Model 143, metal cutting bandsaw. Now this idea of using a 90volt DC 1725 RPM motor with SCR speed controller really seems like the smart and economical way be able to lower the blade speed for metal (changing the blade, of course) while still being able to increase to the max for cutting wood.
I did a bit of math to calculate how slow I would need to turn the drive pulley to get the saw blade to be moving at 75 FPM. (This would me the slowest I would expect to have to turn for cutting steel.) I found that the motor would have to be turning at 40 RPM. Here is how I figured this.
Motor speed =X
Drive pulley dia.= 3"
Driven pulley dia.= 6"
Dia. of bandsaw wheels= 14"
Driven wheel speed= Y RPM
Speed of blade = 75 Feet per minute(FPM)
75=Y*circumference of band saw wheels / 12
75=Y* 43.9/12
Y= 20 RPM
20 RPM= X * Drive pulley dia./driven pulley dia.
20 =X * 3"/6"
X= 40 RPM
Now if this correct what I am wondering is would the motor have sufficient torque at this reduced speed to be able to be effective at cutting steel. Assuming correct blade and appropriate feed pressure?
Thanks for all your help,
David
 
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