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sasquatch
09-20-2013, 09:34 PM
Converting a bandsaw over to cut metal/aluminum, and the pulleys i have to do this appear to give me a 14 inch wheel speed of 72 RPM.
Could someone tell me what surface feet per minute this would be for the blade please?
(I,m not sure is this too slow or too fast?)

Thanks much.

Don Young
09-20-2013, 09:43 PM
Fourteen inch wheels have a circumference of 14 X 3.14 or about 44 inches. If they go around 72 times in a minute that is 44 X 72 = 3168 inches per minute. Divide that by 12 inches per foot to get 264 feet per minute. (Unless I have messed up, which is entirely possible.)

dp
09-20-2013, 09:46 PM
Feet per minute can be between 80 and 250 for metal cutting. Your wheel is 14" diameter so that is a circumference of
pi * 14 = 44"
Divide that by 12 to get feet and you have a diameter of about 3.6 feet.

To get rpm, divide fpm by the diameter.
80 / 3.6 = 21 rpm
250 / 3.6 = 68 rpm

So find pulleys that will give you that 21 to 68 rpm range and you can cut steel (21 rpm) and Aluminum (68 rpm).

To get fpm for your current configuration you multiply 3.6 * RPM.

3.6 * 72 = 260 fpm which is close enough for a home shop.

Errol Groff
09-20-2013, 09:52 PM
Pi x 14 = 43.98 inch circumference. Times 72 RPM = 3166 inches per minute divided by 12 in/ft = 263 ft/min. OK for aluminum but a tad too fast for some steels. Check this chart for further guidance:

http://freetechnicalcharts.com/Band_Saw_Speed_Chart_for_Metal.php

Errol Groff

sasquatch
09-21-2013, 01:42 AM
Thanks guys, much appreciated. I should have stated it will be cutting aluminum up to 1 inch thick, and sheet metal, such as body metal thickness.

Lew Hartswick
09-21-2013, 09:10 AM
Don't forget that for that 1" stuff you should be using a blade with 3 or 4 teeth per inch, for thinner
material more and more teeth per inch. Sheet metal ( 1/16") lots more teeth, even as high as 18 or 20.
...lew...

Dr Stan
09-21-2013, 10:42 AM
Don't forget that for that 1" stuff you should be using a blade with 3 or 4 teeth per inch, for thinner
material more and more teeth per inch. Sheet metal ( 1/16") lots more teeth, even as high as 18 or 20.
...lew...

Use the "three teeth rule". In other words there should be a minimum of three teeth in contact with the cutting surface at all times otherwise you run the risk of hanging up on the blade and ripping off teeth. Three to four teeth in contact will also give you the most efficient cutting action by giving you the largest gullets which can carry off the chips.

You would need a blade with around 100TPI to properly cut the sheet metal. Consequently you should be using something else to cut your sheet metal such as a metal shear, nibbler, or snips.

sasquatch
09-21-2013, 02:41 PM
Thanks again, if you have any other tips/advice fire away.

Tilaran
09-21-2013, 03:10 PM
Aluminum isn't an issue. You can gut it with anything using the right blade. Thin steel is also a non issue at that thickness.
Just get a good blade. Starrett die 24 tooth oughta do it. Thin stuff will cut quick without generating heat. If you'r going to cut thick (1/8+) you'd have to re-group. Portabands with stands work good for small pieces up to 3/8".. 1/2" if you have serious patience and lube. Geez. Sounds like Doctor Ruth:p ( I'm old)

brian Rupnow
09-21-2013, 07:43 PM
Sasquatch--180 foot per minute is a good speed to cut aluminum or mild steel over 1/8" thick. With a 14" wheel, that equates to about 50 rpm of the wheel. If you are driving it with a 1750 RPM motor, which is standard, then you need an overall speed reduction of 35:1 Use bi-metal blades, they last longest, and try to get one with about 12 teeth per inch. Cutting sheet metal thinner than 1/8 becomes a whole different thing--That will rip teeth off the blade I just mentioned. I think the speed will still be okay, but you will want a blade with teeth in the 24 tooth per inch range.

sasquatch
09-21-2013, 09:04 PM
Thanks Brian, much appreciated.