Chain and Sprocket strength ???? Bandsaw conversion to metal cutting

A few years ago I converted my 14" wood bandsaw to cut metal. I used a 3/4hp, 1750rpm, 90V DC motor to slow down the blade SFM. It has worked well on aluminum and thin steel up to about an 1/8". But the blade speed of about 500 SFM is too fast for anything thicker and wears out blade very quickly

I decided to upgrade it with a gear reducer

From Surplus Center I bought a right angle 50-1 gear reducer

Using a 5" pulley on the reducer and a 3" pully on the bandsaws 14" wheel I get my SFM down to 238 which should be right where I need it.

Problem is I now get belt slipping. No problem with torque. but the 3" pully slips badly. I do not have room to increase the size of the pulleys.

Therefore I want to go with chain drive and be done with it.

A #40 chain has strength of 3700 pounds. Would this be strong enough for my application or is this overkill? I have zero experience with chain drive other than motorcycles and bicycles.

Any help or advise is appreciated

rbertalotto said:

A few years ago I converted my 14" wood bandsaw to cut metal. I used a 3/4hp, 1750rpm, 90V DC motor to slow down the blade SFM. It has worked well on aluminum and thin steel up to about an 1/8". But the blade speed of about 500 SFM is too fast for anything thicker and wears out blade very quickly

I decided to upgrade it with a gear reducer

From Surplus Center I bought a right angle 50-1 gear reducer

Using a 5" pulley on the reducer and a 3" pully on the bandsaws 14" wheel I get my SFM down to 238 which should be right where I need it.

Problem is I now get belt slipping. No problem with torque. but the 3" pully slips badly. I do not have room to increase the size of the pulleys.

Therefore I want to go with chain drive and be done with it.

A #40 chain has strength of 3700 pounds. Would this be strong enough for my application or is this overkill? I have zero experience with chain drive other than motorcycles and bicycles.

Any help or advise is appreciated

Click to expand...

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You are still to fast for cutting steel. Make the 3" the driver, not the driven. #40 chain should work fine. It will need oil every now and then.

From everything I've read, for mild steel you want 200-250 SFM with a BiMatal blade. No?

Band Saw Blade Speed And Feed Chart



This calculator for SFM is fantastic.....
Calculate Band Saw Surface Feet per Minute (SFPM) | VintageMachinery.org

rbertalotto said:

From everything I've read, for mild steel you want 200-250 SFM with a BiMatal blade. No?

Band Saw Blade Speed And Feed Chart



This calculator for SFM is fantastic.....
Calculate Band Saw Surface Feet per Minute (SFPM) | VintageMachinery.org

Click to expand...

Sure, if you're using a real saw like this: PA10/3 Horizontal Scissor Style Saw | Marvel Saws

If you're using a converted wood saw, I wouldn't expect to run 250SFM in steel.

Are you varying the speed of your DC motor? The only reason I asked is that you probably would not have used a DC motor unless you were. I have used 3/4 and 1 hp DC motors and varied the field voltage to reduce the speed. They can still have very good torque at low speed even when running crazy slow.

Yes, I can vary the speed and maintain torque, especially with a 50-1 gear reduction. I figured if I started with 238 SFM I can turn it down for harder steels. Sorry I didn't mention this previously.

ive tried to convert one over, totally not worth the hassle. as most are direct drive units so you have no slip.

In my opinion a chain drive would be somewhat overkill. I would think a cogged belt would suffice and need no maintenance and be cheaper. Think motorcycle drive train on some modern bikes for the amount of torque they can transfer. You might look into a junkyard timing belt and pulleys. That way you can replace it if needed at NAPA.

cogged belt would be great, but expensive and at such slow RPMs and infrequent use the maintenance of a chain would be near zero

If I went direct drive from the gear reducer my SFM would be 143...And the DC motor would allow me to turn the SFM down to around 50...Maybe that would be my best solution. I could easily turn an adapter at at a turning speed of 39rpm it wouldn't need to be balanced.

Rather then change the physical location of your reducer (which could be a problem maybe not), if you want to go direct then install two sprockets of equal size and use the chain. In other words use two 3" chain sprockets. It sure as heck isn't going to slip and it will be plenty durable.

I have lots of 525 motorcycle chain and many same size sprockets. I think I might go this route. Talk about overkill on chain size!

But Direct Drive wouldn't be too difficult and I'd remove some loss and minor cogging of the chain. I think direct drive would be a smoother cut.

I know you don't want to hear this, but I am correct. It is uneconomical to convert a high speed wood band saw to cut metal. There are several reasons why this is so. Many wood band saws only have a blade guide above the table. All metal band saws have guides both below and above the table. In order to saw metal, the band saw must be able to run at many different speeds, so metal band saws not only have a mechanical multi speed gearbox, they also employ a variable speed drive to feed the gearbox. My DoAll has a speed range of 50 to 5000 sfpm. It is much less expensive to sell your high speed saw and replace it with a proper metal saw. I tried this years ago, that's why I know. It does not work out well. Your end product is never good enough and the effort and cost is truly a waste.

TeachMePlease said:

Sure, if you're using a real saw like this: PA10/3 Horizontal Scissor Style Saw | Marvel Saws

If you're using a converted wood saw, I wouldn't expect to run 250SFM in steel.

Click to expand...

'Teach me' - please: Seems to me that the blade is the primary factor determining appropriate speed. So why wouldn't a wood saw with a metal blade run the same speed as a 'metal' saw with the same blade?

How about a tensioner that increases pulley wrap

So you understand, and I love to hear comments that might help.

My bandsaw has both upper and lower guides and they have been updated with full ball bearing guides from Carter Products. Top quality products and a huge upgrade in bandsaw performance.

Band Saw Guides - Guidall & Micro-Precision Band Saw Guide | Carter Products

The saw now runs with a 3/4hp, 90V DC motor with infinite speed control and a voltage tachometer to continuously monitor RPM and apply voltage as needed to maintain torque. The motor can not be stalled like a conventional AC motor can. Nothing like DC motors for these types of applications. I used the same motor on my lathe with fantastic results.

I would love to have a Do-All. Fantastic saws. I don't have the room, weight carrying floor in my shop or pocketbook to have one......And I'm a Hobbiest. I use my vertical bandsaw about 25 times a year. I have a hydraulic horizontal bandsaw and recently bought an amazing Cold Cut saw from Evolution Saws(One of the best metal working tools I ever bought and used!)

Hundreds of folks have converted various wood cutting bandsaws to more than serviceable metal cutting saws.

I only use the vertical saw to cut long strips of metal. Usually 3/16 and thinner.....Anything thicker and the plasma cutter is called upon. The bandsaw is just more convenient as it is always set up and ready to go.

But as I'm sure you are aware, 80% of the fun we have in our shops is playing and modifying the tools! I laugh at myself sometimes as I spend so much time and effort on the tools that I could simply farm out the work for much better economics....But what fun is that!

Check out my website for more nonesense!

RVB Precision | Welcome to the world of ultra precision

How about a tensioner that increases pulley wrap

Click to expand...

I tried that, but still had unacceptable slip when pushing hard on a cut.

I ordered the chain and sprockets from Surplus Central a few minutes ago......Stay tuned for full report!

Never start out assessing the usage any piece of equipment with the words 'just' and 'only'. It shows that you've already given up on having something that isn't a POS. If you are going to spend time and money on a saw, plan from the onset to have one that kicks ass at all sorts of tasks.

so....here's what I suggest, and I suggest it as the most economical solution. Ignore or even throw out the 14" saw and buy a good used DoAll or Grob that is a "real man's" saw. They're still available and cheap, and offer no-compromise performance and durability. Then, get on with life.

for less then $500 I bought a large vertical band saw, my wood one I had I sold for $300. I couldn't ever build or modify one for less then $1000, plus it has a variable speed pulley that you can adjust while running. just a motor and gear box reducer I had bought was $500. then you still need pulleys if you want more then 1 speed.

Gordon Heaton said:

'Teach me' - please: Seems to me that the blade is the primary factor determining appropriate speed. So why wouldn't a wood saw with a metal blade run the same speed as a 'metal' saw with the same blade?

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Rigidity. Blade tension. Coolant.

If the saw is janky and shaky (compared to a real metal bandsaw) the blade life will suffer.