How do you know if a band saw's too fast for metal cutting?

*******SOLVED*******I have a Delta with a 93"(?) blade. I was told it's for metal, and have been using it as such for about 3 years. But, it sure looks faster than the one at a friend's shop. Is there a way to tell? I put a piece of masking tape on my and the friends blade to see how long it took to come back around. Mine's faster, but is it too fast, and how do I know? It's on the slowest of 3 settings

 

If your friend's saw has a different length blade to compare blade speeds you'd need to divide blade length by the time. That would give you actual inches per second blade speed. good luck

 

how has it been cutting for the last 3 years?

 

The guy I apprenticed under said that steel likes to cut at 60 feet per minute. That's pretty slow, and with coolant you can get away with lots higher speeds. I suppose that you could use a stop watch and do some math to arrive at some semblance of a speed, but you actually might be able to tell by the sound of the cut. A pulley change may be an easy and rewarding experiment.

 

this might help you out

http://www.jalopyjournal.com/forum/showthread.php?t=296328

 

If you have been using it for three years, you most likely have a metal cutting bandsaw. A metal blade on a wood cutting bandsaw lasts about three minutes. D.

 

These are the cutting speeds on my metal cutting saw. They are in feet per minute.
59fpm for high speed alloys, stainless.
96fpm for tool, stainless and bronze.
155fpm for cast iron, mild steel, hard br*** and bronze.
170fpm for aluminum, plastic and wood.
This should give you a idea what speed u need.

 

Same 93"

 

Fine, but it seems my friend's blades last MUCH longer

 

If your friend's saw has a different length blade to compare blade speeds you'd need to divide blade length by the time. That would give you actual inches per second blade speed. good luck

Feet Per Second. 2 blades of different lengths can have the same speed depending on the wheels and motor speed.

 

The metalcutting Delta bandsaw has a transmission in the power part of the saw frame and it has 3 pullies.
One on the lower wheel shaft, one on the motor and one on the transmission.

If I didn't just describe your saw, it isn't a Delta metalcutting bandsaw.

 

different size wheels , different size pulleys , different speed motors

93 inches is 7-3/4 feet. put that small piece of tape back on the blade and count how many times it comes around in one minute.

simple math: how many times X 7-3/4.....then compare that to JC Sparks suggestions

 

If you have access to a mechanical shaft tach measure the rpm of the drive pulley. multiply the diameter of the pulley ( in inches and thousandths i.e. 12.500 not 12 1/2) by 3.14 x rpm. This will give you the surface speed in inches. Divide by 12 to get surface feet per minute. This figure should be between 60-80 fpm for general use. Quality blades will more than pay for the extra cost in extended use.

 

It has these 2, and a 4 groove on the motor down below

 

I put a piece of tape on the blade and count about 30 revs in 15 seconds (120 revs per minute). That's over 900 feet per minute, isn't it? What did I do wrong?

 

if you get a ragged lip on the bottom of the piece on either side of the kerf, it's too fast. normally, you get enough to barely feel, but beyond that. like 1/16" is excessive.

 

That means you are running at 930 fpm. I cant imagine you can cut anything metallic no matter what kind of blade you are using with out killing it within seconds.
Do you think someone has changed the pulleys on this machine to make it cut wood instead of metal? But...... if it has pulleys on it you can make it do anything you want by changing them.

 

According to post #7, I did something wrong in my figuring. At SEVERAL times the speed he mentions for plastic/wood, I'd get no life at all out of my blades. Such is not the case. Where would I find pulleys?

 

Old rule of thumb ! If ya can't see them dar TEETH it's going to darn fast fer metal !!

 

Lets see a pic of the motor and transmission that drives the belt that we see in your first pic.1. See what the electric motor rpm is, 2. what ratio the transmission is, 3. what the diameters of the pulleys are that have the belts on them now including the large one that we see in your pic, 4. the diameter of the wheels that the blade turns on.

 

I've got a 12" Delta band saw, it's got the 3 shive pullys +a 2 speed gear box. I use it to cut steel , alum. &stainless,on the low speed and wood ,plastic and thin alum. at high speed. I have never had any issues with blade life in the 10 years I've had it. I think the
slowest speed is about 40' per min. ,that works well on 2" steel. It all depends on blade TPI and blade speed,just remember "speed kills".

............Jack

 

For steel.....slow speed, fine teeth
For aluminum, plastic, wood, rubber.....fast speed, co**** teeth

 

AAARGH!!!!!!!!!!!!!!
What's slow?
What's fast?

And, how can you tell?

 

Generally a wood cutting band saw won't go slow enough to just put a steel cutting blade on and work well. Next time you are in a shop with either setup have them switch it on and see how the speeds compare to yours. Once you see them operate you will figure out what is slow and what is fast.

 

You're killin me (not enough info)

 

Slow goes.....WHRRRRRRR, fast goes ....WHEEEEEEEE

 

COOL! That really clears it up!

 

Sorry Groucho, I shouldn't have joined in, this **** is way too technical for me. I'm not too good with numbers.

 

Blades come with the RPM rating on them. Just paint a white stripe on the blade, get a 6 pack and turn the saw on, now count the rpm to the second hand on your watch. Every time you loose track of the count open another beer. You might need a 12 pack >>>.

 

If the chips are purple or blue, your going too fast. They make a tool that "wheels" along the blade side to measure your blade speed in FPM, for calibrating saws. Maybe Grainger or MSC or some other tool co. has one? Tooth pitch will dictate how fast you can go, too (clogging). Regardless, if you're cutting steel a bit of coolant or atleast water in a spray bottle is better than nothing. TPI is teeth per inch BTW.