Bandsaw stalling out

[Jamie Straw]

Hoping there's a solution to this. I've been processing some Black Locust for turning blanks over the last week. Things weren't going so well Tuesday, so I bought a new bandsaw blade (3/8" 3tpi). Put it on today just to cut a round blank out of a half-log, not very big. I couldn't even get the corners knocked off without it stalling. Here are history details:

• Grizzly 1019Z (yeah, I know, underpowered)
• Saw was cutting fine last week, even when cutting with the grain on 8" tall pieces
• Replacement blade from same company as the last blade
• Only thing different in recent past is an upgraded tension spring. I set the tension using the machine's gauge instead of flutter test.
• Blade is riding smack in the middle of the wheel, cleaned the wheels for new blade.
• I checked belt tension, then decided to move the belt to use higher speed. Did not help.
• Motor pulley and shaft were warm to the touch, motor cool.
• Other odd thing: Periodically, it seems like this wood will slam on the table, even though the base is absolutely flat, with no gaps and no tippiness. Never feels like the wood actually moves, but there's a big slam (or a rapid series of 3 or 4), upper part of saw seems like it jerks.

Anything in your experience like this? Something has changed in the last week.

[Bob Bouis]

I know you said you checked the belt tension, but visually (if possible) verify that the drive belt's not slipping. I bet it is.

[Jamie Straw]

I know you said you checked the belt tension, but visually (if possible) verify that the drive belt's not slipping. I bet it is.

Probably is, but what would cause that? The top tire sqeakes, something I forgot.

[Wayne Lomman]

Jamie, a warm pulley would indicate belt slip. The belt profile could be worn so that even though it may look OK it doesn't fit the pulley correctly. Change the belt and see what happens. Also changing to a higher speed reduces torque. Check your blade specs to make sure you are working in the optimum range. Cheers

[Geoff Crimmins]

Does your saw have glued-on rubber tires or slip-on polyurethane? The jerking and slamming combined with the squeaking tire makes me wonder if one of the tires is slipping on the wheel. Or maybe even the blade slipping on the tire. It would probably be the lower wheel since that's the one powering the blade. I don't know how likely this is, but it's one more thing to check. Does it sound like the motor is bogging down and stalling, or is it just the blade that's stalling? The answer to that question would help determine whether there is a problem with the motor, or if something is slipping between the motor and the blade.
--Geoff

[Gerald Hurst]

Here is a possibility.

I have experienced "slamming" on my band saw with tall resaws of some exotics. Not fun. The wood is probably not moving, it is the entire saw reacting to a lightning quick stoppage of the blade.

See the end of the video in this thread: http://www.sawmillcreek.org/showthre...g-scary-noises

He starts cutting a much taller piece and saw dust is really spewing out. Then it slams. This is caused by a large buildup of saw dust in the cut which heats up, gets "gummy" and binds the blade. This binding of the blade would probably cause the belt to slide on the pulley, thus warming it up.

If the wood and the blade are exactly the same as when it was cutting fine the previous week, then it could just be a variation in the wood moisture or oil content of the new log piece. Feed speed is important too. The resaw environment (bandsaw power, wood type and condition, feed speed, blade gullets, blade cleanliness, etc.) must clear sawdust adequately, or it will bind.

[Eric Schmid]

How does it cut in other material currently? It's Black Locust, so I wouldn't rule that out as a contributing factor. Actually, this wood can reveal weaknesses in tool set ups as it can push some to their limits. I'm sure you'll get plenty of suggestions on bandsaw tuning, so I'll just say it's BL and proceed accordingly

Likely culprits for blade stall and bounce are kerf closing, opposing forces on the blade (e.g. Twisted reference surface rotating in the cut and grain releasing unevenly in the cut). Split some BL and you will see what I mean.

I was cutting some fairly dry BL last night with a friend standing close by. Smoke was coming off the blade at points. The blade was pretty bouncy through a lot of it; catching and releasing. Not enough to stall or bounce, but certainly had my attention. When I took the hand plane to it, my friend said it sounded like I was planing bone.

[Jamie Straw]

Jamie, a warm pulley would indicate belt slip. The belt profile could be worn so that even though it may look OK it doesn't fit the pulley correctly. Change the belt and see what happens. Also changing to a higher speed reduces torque. Check your blade specs to make sure you are working in the optimum range. Cheers

Thanks, Wayne, I went through a whole checklist this afternoon. First up was the belt. Even though it's chronologically old, I could detect no cracks (turning inside-out and folding it to look for tiny ones). My understanding is that the belt should sit against the walls of the pulling and not ride in the bottom of the groove. Not sure how to detect that, but it seems to be riding properly. Speed-wise, I've always used the slower speed. Only changed to the higher one as an experiment yesterday. Made no difference one way or the other.

[Jamie Straw]

Jamie, a warm pulley would indicate belt slip. The belt profile could be worn so that even though it may look OK it doesn't fit the pulley correctly. Change the belt and see what happens. Also changing to a higher speed reduces torque. Check your blade specs to make sure you are working in the optimum range. Cheers

Thanks, Wayne. Seems like if something else is causing the blade to be stressed or bind, that would cause the belt to slip, yes? I will try replacing the belt if I have problems on wood other than the Black Locust, which is beginning to look like a villain, even though I think it's pretty cool wood in its own way. To reiterate, I've only run it at the high speed that one time, it's been at the lower speed for years. Most likely, I'll change out the tires soon -- they do have some subtle signs of age.

[Jamie Straw]

Does your saw have glued-on rubber tires or slip-on polyurethane? The jerking and slamming combined with the squeaking tire makes me wonder if one of the tires is slipping on the wheel. Or maybe even the blade slipping on the tire. It would probably be the lower wheel since that's the one powering the blade. I don't know how likely this is, but it's one more thing to check. Does it sound like the motor is bogging down and stalling, or is it just the blade that's stalling? The answer to that question would help determine whether there is a problem with the motor, or if something is slipping between the motor and the blade.
--Geoff

Geoff, the tires are the original rubber ones (yikes, glued on? guess I'll have to find out how to un-glue them), but I plan to replace with urethane soon. The squeak was in the upper tire, I noticed it when I first installed the new blade, but it seems to have stopped now. I haven't been able to discern whether it's just the blade, or the motor that's slowing down, but the motor is not getting warm. Hope that's a promising sign.

[Jamie Straw]

Here is a possibility.

I have experienced "slamming" on my band saw with tall resaws of some exotics. Not fun. The wood is probably not moving, it is the entire saw reacting to a lightning quick stoppage of the blade.

See the end of the video in this thread: http://www.sawmillcreek.org/showthre...g-scary-noises

He starts cutting a much taller piece and saw dust is really spewing out. Then it slams. This is caused by a large buildup of saw dust in the cut which heats up, gets "gummy" and binds the blade. This binding of the blade would probably cause the belt to slide on the pulley, thus warming it up.

If the wood and the blade are exactly the same as when it was cutting fine the previous week, then it could just be a variation in the wood moisture or oil content of the new log piece. Feed speed is important too. The resaw environment (bandsaw power, wood type and condition, feed speed, blade gullets, blade cleanliness, etc.) must clear sawdust adequately, or it will bind.

Wow, that video was weird -- his saw, even when it's not powered on -- sure doesn't seem very stable. I'm leaning toward my saw's problem being a combination of needing new tires and the wood just being a pain. Am also suspicious the set on the teeth could be a little wider. Will try cutting some maple or walnut (new walnut arriving Tuesday) and see what happens. I re-adjusted the blade tension today, using the flutter test.

[Jamie Straw]

How does it cut in other material currently? It's Black Locust, so I wouldn't rule that out as a contributing factor. Actually, this wood can reveal weaknesses in tool set ups as it can push some to their limits. I'm sure you'll get plenty of suggestions on bandsaw tuning, so I'll just say it's BL and proceed accordingly

Likely culprits for blade stall and bounce are kerf closing, opposing forces on the blade (e.g. Twisted reference surface rotating in the cut and grain releasing unevenly in the cut). Split some BL and you will see what I mean.

I was cutting some fairly dry BL last night with a friend standing close by. Smoke was coming off the blade at points. The blade was pretty bouncy through a lot of it; catching and releasing. Not enough to stall or bounce, but certainly had my attention. When I took the hand plane to it, my friend said it sounded like I was planing bone.

I suspect you're on the right track, at least as part of the problem. The moisture content of the 3 bowls I've turned varied by a fair amount, and of course if it's over 30% Delmhorst can't tell any details. I can see that Black Locust is an independent thinker, does its own thing.

[Jamie Straw]

Have ordered urethane tires for the saw. Black rubber tires are probably 20 years old, odd thing though -- doesn't look like they were glued on. What's with that? I can find zero residue under the tire when I peek under. How many of you have changed tires without taking the wheel(s) off? Am really hoping to do it that way.

[John K Jordan]

...I'm leaning toward my saw's problem being a combination of needing new tires and the wood just being a pain. Am also suspicious the set on the teeth could be a little wider....

I would have a hard time blaming the wood, mostly since I've cut a boatload of black locust and don't remember any difference between it and other wood. Or maybe I'm spoiled by my saw - an 18" Rikon. I stick to 1/2"x3tpi blades made from Lennox stock for all my green wood. Do you have a local place that can make up such a blade to try?

When it stalls does the motor actually stall? Most of my cuts are straight, up to 12". Does it do this with straight cuts too or only curved? If only curved, are guides too tight or gummed up?

I've never seen the tension gauge on a bandsaw be correct even after replacing the tension spring on my 14" Delta. (I check the tension with a standalone Starrett tension gauge.) Maybe try higher tension?

I've also never experienced the slamming sound. Perhaps something is gumming up then releasing suddenly? After it stalls, are the gullets jammed with sawdust. Any junk on the sides of the blade? I did cut some problem wood once (can't remember what) that was helped by waxing the sides of the blade with a big Lennox bandsaw blade lube stick.

Last time I removed a glued bandsaw tire I just pried it up with a screwdriver.

Maybe you could measure the set of the teeth on this blade and compare it to the set on another blade.

JKJ

[Jamie Straw]

I would have a hard time blaming the wood, mostly since I've cut a boatload of black locust and don't remember any difference between it and other wood. Or maybe I'm spoiled by my saw - an 18" Rikon. I stick to 1/2"x3tpi blades made from Lennox stock for all my green wood. Do you have a local place that can make up such a blade to try?

I've been using 3/8" 3tpi blades from local saw company. As mentioned (way back when), things were fine through the first several cuts I made, some with the grain in relatively tall pieces (I have a riser block, so max height is a little over 10", but I didn't max it out). Yes, an 18" saw with a much stronger motor would make a difference.

When it stalls does the motor actually stall? Most of my cuts are straight, up to 12". Does it do this with straight cuts too or only curved? If only curved, are guides too tight or gummed up?

I don't think the motor itself stalls, the blade stops moving, both straight cuts and curves. Guides are Cool Blocks, don't gum up and have always worked fine for the type of cutting I do.

I've never seen the tension gauge on a bandsaw be correct even after replacing the tension spring on my 14" Delta. (I check the tension with a standalone Starrett tension gauge.) Maybe try higher tension?

Tried that, no joy. I use the "flutter test" to tension, then if I'm having trouble I'll add a little to experiment.

I've also never experienced the slamming sound. Perhaps something is gumming up then releasing suddenly? After it stalls, are the gullets jammed with sawdust. Any junk on the sides of the blade? I did cut some problem wood once (can't remember what) that was helped by waxing the sides of the blade with a big Lennox bandsaw blade lube stick.

I've conversed with others who've had this happen (slamming for no apparent reason). It's not like with maple where the blade gets really gunked up and the blade just can't clear fast enough. This BL, surprisingly, had very little in the way of long strings cutting with the grain. Things went fine at first.

Last time I removed a glued bandsaw tire I just pried it up with a screwdriver. Maybe you could measure the set of the teeth on this blade and compare it to the set on another blade.

JKJ

I think these will be pretty easy to get off. I could measure, but a friend gave me a couple of Timberwolf blades (which is what I used to use regularly), so I think I'll just thrown one of them on an do an empirical study.

Thanks.