any difference -wood or metal???

[Downunder Bob]

You don't need excessive blade tension to cut metal well. Properly set up, it doesn't take any extra tension at all.

I find that the blade jumps off the pullys if not very tight.

 

[C-Bag]

What blew my mind in the Carter vid was he addressed EVERY notion I had about what I thought I knew about how band saw's work and how to adjust them! I don't even know where I got those ideas. Once I went through all the steps he lays out tracking was absolutely not an issue anymore. My HF saw had gone through several hands with each new owner compounding the problems of the previous owner until the tensioner/tracker was trashed and the tires were worn out. Now it takes very little tension to track. And I would bet for the first time in the saw's life it cuts straight.

I personally do mostly metal on mine so my reduction setup has proved to be excellent for what I do because it never bogs down. If I ever get to it I'd like to find a DIY design for a saw blade quick release. The Carter is nice, but kinda pricey for I don't change blades but once in a great while. Hard to justify just being lazy.

 

[Dabbler]

I find that the blade jumps off the pulleys if not very tight.

What I mean is that blade tension is solely related to blade width and thickness. A 3/4" .030 blade for wood or the same dimension blade bimetal metal cutting blade need the same tension. There is no difference at all. If you are making the metal blade much tighter, then either your wood blades aren't tight enough or you are overstressing the metal blades leading to breakage.

I've been using a metal/wood 18" bandsaw for 30+ years using blades from as little as 1/8" to as much as 1.5" on the same saw. I haven't
broken a blade in probably 20 years. I've never had a blade 'jump off the pulleys'.

How do I set the tension? sound. I adjust until I hear resonance in the blade and then tighten a little bit. If the pitch changes suddenly, it is too tight, so I back off a bit. The scale on my machine is way off! When I first got my machine, I broke blades because I went with the scale.

 

[Downunder Bob]

What I mean is that blade tension is solely related to blade width and thickness. A 3/4" .030 blade for wood or the same dimension blade bimetal metal cutting blade need the same tension. There is no difference at all. If you are making the metal blade much tighter, then either your wood blades aren't tight enough or you are overstressing the metal blades leading to breakage.

I've been using a metal/wood 18" bandsaw for 30+ years using blades from as little as 1/8" to as much as 1.5" on the same saw. I haven't
broken a blade in probably 20 years. I've never had a blade 'jump off the pulleys'.

How do I set the tension? sound. I adjust until I hear resonance in the blade and then tighten a little bit. If the pitch changes suddenly, it is too tight, so I back off a bit. The scale on my machine is way off! When I first got my machine, I broke blades because I went with the scale.

I get that the blade tightness is related to the blade thickness and width, and while I have never broken a blade, I think that my blade tension is higher than it should need to be, basically I have to tighten my blades as tight as I can get them or they jump off the pulleys. My machine has metal wheels without rubber or urethane tyres. There is no crowning on the wheels, the blade runs with the back edge of the blade against a small shoulder or flange on the wheel. Sometimes it will run for hours then all of a sudden it will just jump off the wheels, This happens more often when cutting wood than with steel.

 

[C-Bag]

I get that the blade tightness is related to the blade thickness and width, and while I have never broken a blade, I think that my blade tension is higher than it should need to be, basically I have to tighten my blades as tight as I can get them or they jump off the pulleys. My machine has metal wheels without rubber or urethane tyres. There is no crowning on the wheels, the blade runs with the back edge of the blade against a small shoulder or flange on the wheel. Sometimes it will run for hours then all of a sudden it will just jump off the wheels, This happens more often when cutting wood than with steel.

I got that with 4x6's with bad bearings. Either the drive wheel or takeup. When I replaced the bearings or bushings it went away. The only other time is when the blade was wearing out. It would also quit cutting square. On saw with tires it's different.

 

[Dabbler]

Really good points. One thing I would check is that your wheel faces (that the blade runs on) is exactly perpendicular to the rotation. If there is a small wobble, or if the wheels were faced wrong, there would be a tendency to have the blade jump.

It will happen more in wood becasue the metal works as a secondary guide if there's a wobble, but the wood won't.

 

[C-Bag]

Really good points. One thing I would check is that your wheel faces (that the blade runs on) is exactly perpendicular to the rotation. If there is a small wobble, or if the wheels were faced wrong, there would be a tendency to have the blade jump.

It will happen more in wood becasue the metal works as a secondary guide if there's a wobble, but the wood won't.

I don't cut wood with my 4x6 so I wouldn't know. But usually when the saw was getting marginal it would jump whenever the blade would catch. Either on a kink in the blade or where there was some missing teeth. Cranking down the blade tension helped a little but it usually sped the deterioration of the bearings or bushings that we're going out. Some metal cutting saw's have a takeup wheel tracking tilt adjustment to help compensate for bearing wear. Usually you can look at the wheels under tension and see if they are tilting.

 

[woodchucker]

x

I don't cut wood with my 4x6 so I wouldn't know. But usually when the saw was getting marginal it would jump whenever the blade would catch. Either on a kink in the blade or where there was some missing teeth. Cranking down the blade tension helped a little but it usually sped the deterioration of the bearings or bushings that we're going out. Some metal cutting saw's have a takeup wheel tracking tilt adjustment to help compensate for bearing wear. Usually you can look at the wheels under tension and see if they are tilting.

Those tilt tracking are not for bearing wear. They are for getting the blade to ride on the crown of the wheel if they don't. Bearing wear is something that should be addressed wen it happens. Like any other machine, a worn bearing is not working efficiently. 2 things can happen, you can have a heat build up and ruin the shaft, or you can have a catastrophic failure where the race is ruined and the wheel blows off (rare). A well adjusted saw is one that has the blade riding on the crown of the wheel.

 

[Downunder Bob]

Really good points. One thing I would check is that your wheel faces (that the blade runs on) is exactly perpendicular to the rotation. If there is a small wobble, or if the wheels were faced wrong, there would be a tendency to have the blade jump.

It will happen more in wood becasue the metal works as a secondary guide if there's a wobble, but the wood won't.

Really good points. One thing I would check is that your wheel faces (that the blade runs on) is exactly perpendicular to the rotation. If there is a small wobble, or if the wheels were faced wrong, there would be a tendency to have the blade jump.

It will happen more in wood becasue the metal works as a secondary guide if there's a wobble, but the wood won't.

Thanks guys, some good info here. the wheel faces are a square as I can measure, The bearings appear to be good, no wobble and spin freely. The blade guide rollers apppear to quite good also and correctly adjusted, The machine is quite new and has probably not done more than 4 hours run time. I have noticed that the problem only happens at certain times. Such as when cutting metal, the blade breaks free at the end of a cut, or sudden transition from thick to thin section, going from thin to thick doesn't seem to matter.

When cutting wood, solid square or rectangular sections, soft or hardwood, no problem, but round wood as in tree branches the blade suddenly grabs the wood and rotates it then twang the blade is off the pulleys.

Another thing I have noticed is that when cutting wood I get a build up of small wood particals on the wheels, perhaps this is changing the trueness of the wheels and contributing to the problem, possibly allowing the blade to ramp up on the wheel flange and then jump off.

 

[Downunder Bob]

Regarding blade speed 100 - 120 fpm is ok for m/s but if you want to cut s/s or any other hard steel you will need to go even slower. Gear it down with gearbox or belts doesn't really matter as long as you get it slow enough. If you can gear it down to about 150 fpm at full speed on the motor then slow the motor down from there is probably the easiest, just be wary of slowing the motor too much or you will lose torque.

It would be interesting to adapt an old small motorbike gearbox to give you a final range of speeds, with quick easy selection. Similarly I once saw a planer driven by a 15 hp electric motor via an old model T ford gearbox, it worked extremely well. They used the reverse for cutting and 2nd or top gear for the table return, so the table return took about only half the time of the cut. much like a shaper does.