did 30 seconds cutting steel at standard speed ruin by band saw blade?

[dansawyer]

The band saw is a 30 year old Craftsman 12 inch. Life time use is less that 10 hours. I had forgotten about steel requiring a speed reducer. I purchased a 80" (6' 8") x 1/2" x 14tpi Imachinist Metal Cutting Bi-metal M42 blade. I proceeded to cut a single 3/8 inch diameter steel rod. The cut went smoothly and quickly. I was satisfied I had solved by steel cutting problem.
I then was distracted by another project and moved on. To get to the point the next project with the band saw was to cut a 3/8 by 3 inch piece of 6061 aluminum. This was a disaster. The saw cut very slowly; less than an inch per minute. The aluminum became very hot.
Did I ruin the blade with the single steel cut? Is this the wrong blade?
The blade still eels sharp. I have been cutting steel with bi-metal reciprocating saw. Those blades seem to last for about 1 square inch before they noticeably feel dull. The band saw blade feels more like the unused end of the cut off blade then the worn cutting area.
Videos show band saws ripping through aluminum like it was wood.

 

[kb58]

For steel, it's typically 150-200 fpm, while aluminum is up around 1000-2000 fpm - note the huge difference in speed.

Also, a fabricator told me that with most mild steels (depending upon source and quality) it's a gamble what's in it. They melt down all sorts of steel, including ball bearings buried in donor material. If one of those isn't completely melted, and you try sawing through it, yeah, it can get ugly. I've run into something like that myself, where it was cutting just fine, then just stopped. Cut in the other way and it stopped at nearly the same point. Just sayin'

Oh, and don't overlook tooth type and count. The rule of thumb is 2-3 teeth on the material at all times, so if you're cutting sheet, that needs 14-18 tpi, but for 3/8"-thick material, it's only 8 tpi. Admittedly, using the wrong count doesn't hurt, but very much affects cutting speed and whether the blade tends to load up (remember, add wax when cutting aluminum).

 

[Cobra]

If you had the blade speed set for wood, then yes, likely the blade is toast.

 

[projectnut]

Blade speeds for cutting metals generally much slower than wood. My horizontal metal saw has speeds of 60, 100, and 160 feet per minute. The harder the metal the slower the speed. If the bandsaw you are referring to is a wood saw the blade speed is an all likelihood too fast. Standard wood saws have a blade speed between 1,500 and 3,000 ft. per minute. At the very minimum you knocked the set off the teeth, but if you are running at the speed required to cut wood you probably ruined the blade.
As for the tooth count. The rule of thumb is a minimum of 2-3 teeth in contact with the material and a maximum of 24 teeth. With less than than minimum number of teeth are engaged you're likely to knock a tooth off the blade. With more than the maximum number of teeth engaged you're likely to fill the gullets and cause the blade to slip on the wheel, pop off the wheels, or break.

Here's a link to a Lenox Guide to Band Sawing:

https://www.lenoxtools.com/Guides/LENOX_20Guide_20to_20Band_20Sawing.pdf

 

[Latinrascalrg1]

Did you attempt to cut the steel again to see if the blade is actually dull or if its the different material thats the problem?

 

[Asm109]

Slow cut and hot Aluminum are two sure signs of a dull blade. Yeah, one steel cut toasted the blade.

 

[rgray]

I had forgotten about steel requiring a speed reducer.

So your bandsaw is still at wood cutting speeds?

I purchased a 80" (6' 8") x 1/2" x 14tpi Imachinist Metal Cutting Bi-metal M42 blade.

14 tpi is very slow in aluminum, and the teeth like to plug up making things hot.

Videos show band saws ripping through aluminum like it was wood.

Cutting your aluminum on a wood bandsaw works well. Speed is up and teeth are open and don't plug up.
Have to be carefull starting a cut as there will likely be only one tooth contact at first.
The cutoff piece will be cool enough to hold in your hand when done.

 

[pacifica]

The band saw is a 30 year old Craftsman 12 inch. Life time use is less that 10 hours. I had forgotten about steel requiring a speed reducer. I purchased a 80" (6' 8") x 1/2" x 14tpi Imachinist Metal Cutting Bi-metal M42 blade. I proceeded to cut a single 3/8 inch diameter steel rod. The cut went smoothly and quickly. I was satisfied I had solved by steel cutting problem.
I then was distracted by another project and moved on. To get to the point the next project with the band saw was to cut a 3/8 by 3 inch piece of 6061 aluminum. This was a disaster. The saw cut very slowly; less than an inch per minute. The aluminum became very hot.
Did I ruin the blade with the single steel cut? Is this the wrong blade?
The blade still eels sharp. I have been cutting steel with bi-metal reciprocating saw. Those blades seem to last for about 1 square inch before they noticeably feel dull. The band saw blade feels more like the unused end of the cut off blade then the worn cutting area.
Videos show band saws ripping through aluminum like it was wood.

A dremel with an alum oxide bit, 1/8" diameter and you can resharpen the blade. Leave it on the saw while you sharpen. Might take 30 minutes

 

[projectnut]

You must have far more patience and skill with a Dremel than I do. On my Startrite saw the blade is a little under 8 1/2' long. That translates to 1350+ teeth @14tpi. Even if you did manage to stay conscious and sharpen all the teeth I doubt there would be enough set left in the teeth for them to clear the chips through the kerf. At $26.00 per blade I'll just go over to the Ellis factory about 10 miles away and have them make me a new blade.

Just a heads up, I usually get about 2 years use from one of their bimetal blades if I run it at the right speed.

 

[rwm]

I have done this by forgetting to change the transmission. The blade is probably toast. $50 lesson. At least that is what I pay for Bimetal Diemaster.
Robert

For the record, my usual technique to ruin a blade it to cut thin stainless and rip off a group of teeth.
R