Speed reducer

[DavidR8]

This is an interesting thread.
I have an import upright wood/metal bandsaw. At its lowest speed from the factory it runs 650 sfm.
I have a Lenox 12 TPI (could be 14...) bimetal blade on it and it works amazing. I’ve cut up to 3/8 hot rolled plate without any issues.
I would like to swap in some larger amd smaller pulleys to get it into the 300 sfm range but it cuts so well as is that it makes me wonder about speed recommendations.

 

[mickri]

Before I put the speed reducer on the saw the slowest speed that I could get was 1257 fpm. Would cut sheet metal up to around .065. Wouldn't cut anything thicker than that. I am in that indecision spiral. Do I get a 3", 3.5" or 4" pulley.

 

[lis2323]

I think your problem is you cannot feed the workpiece into the blade with enough pressure. Think of its operation if it was a horizontal metal cut bandsaw.

FWIW here is my vertical wood bandsaw converted to metal with a gear reducer.

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[mickri]

If I want to I can apply enough pressure to stop the blade. Right now there seems to be a fine line between too much pressure and just enough for the blade to cut.

Nice looking saw.

 

[lis2323]

Why is the blade stopping ? Drive belt slipping ?


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[rwm]

I have a Jet metal cutting vertical bandsaw. I run a 14 TPI Lennox Diemaster Bimetal blade. I use a 10# weight to feed a homemade sled through. This works perfectly on steel. It should not take a lot of pressure but it should take some time. That is normal. Too much feed pressure with overheat the blade. Incidentally if you have overheated the cutting edges even momentarily. (too fast of a SPFM or too much feed pressure) the teeth are likely shot. This can happen very quickly (i.e 100 milliseconds). For lubrication you can try candle wax. Just hold it against the blade for a second.
If you cut thin sheet metal with a blade that is too course you will tear off teeth. Ask me how I know.
Robert

I have a stick of Lennox bandsaw lubricant but I actually prefer parafin. The Lennox stuff is too gummy and hard to remove.
R

 

[lis2323]

A lube stick like Walter Koolcut or similar works well.


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[Jim F]

I cut a sheet of 1/4" CRS Friday and used 180 ft min. Starrett recommended 230 ft min (on the chart and from memory). I did call Starrett the other day and was put in touch with their local tech rep. He said to slow the speeds some for running dry. He suggested 175 ft. I can't say I had the highest confidence in his advice. I think dry sawing isn't something they deal with much these days.

You answered my question.
I just figured my saws sfm, it is at 176.
I found out the motor was replaced, it is a 3450 rpm motor, factory was 1725.

 

[rbertalotto]

This is a fantastic calculator to figure out bandsaw SFM......

Calculate Band Saw Surface Feet per Minute (SFPM) | VintageMachinery.org

vintagemachinery.org

I've been messing around with my 14" wood to metal conversion. Using a 3/4hp, 1750rpm, 90V DC, variable speed motor with a 50-1 gear reduction right angle drive......I can not stop belt slippage. Plenty of power, and expensive Lenox blades, but any pressure to cut faster slips the belts.

I'm removing the whole belt system and going with #40 chain and sprockets

That should do it!

 

[CluelessNewB]

I'm removing the whole belt system and going with #40 chain and sprockets

Back in the late 1960's my Dad converted a Walker Turner 14" using a gearbox and the final drive was chain from the gearbox. He did use a belt and step pulleys on the input to the gearbox.