Bandsaw problem - stalling out

[Jamie Straw]

I'm pretty desperate for help with this, so pardon if you noticed cross-posting with SMC. I've been processing the 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.🙁 Could it have anything to do with the squeaky tire?

 

[Odie]

Hi Jamie......Yes, I've had the exact same problem with a grabby blade. It's a combination of the number of teeth per inch, the MC, and the specific pieces of wood you're working with. The solution for me, has been to install a B/S blade with more teeth per inch.....this helps to overcome the grabby cutting on the wood you are experiencing with this. I'd have to go out and check, but I think the blade I've been using is around 8tpi......slower cutting, but much smoother a go of it......

 

[Bill Boehme]

The tension gauge on any bandsaw is worthless ... use the flutter test.

When did you last replace the drive belt(s)? If the saw is stalling, but the motor continues to turn one of the belts may be worn out. A belt usually squeals when it slips on the pulley, but not necessarily if the belt is worn out. A belt runs on its side walls. If it is worn to the point where it bottoms out in the sheave, it will slip and the pulley will run hot. A belt is also worn out if it is hard. The most obvious sign is ozone cracking. Turn the belt wrong side out and pinch the back of the belt together as as tight a bend as you can. If any visible hairline cracks can be seen then the belt is hard from ozone cracking ... toss it and get a new one.

Check for stiffness when turning either wheel by hand. Do this with the blade installed and tensioned. The drive belt should be in the low speed range. The wheels should turn very easily. If it seems to be too much drag then it is time to do fault isolation. First remove the upper and lower blade guides to see if that changes anything. If yes, check the guides to isolate to bad bearing. If no, remove the blade and check if upper or lower wheel is stiff. If upper wheel is stiff, it's probably the wheel bearings. Check the tension mechanism to make sure it was installed correctly. If the lower wheel is stiff, remove the drive belt and check it again. If it's still stff then it's the wheel bearings. If not, check the idler pulley for stiffness. If that's OK, check the motor shaft to see If it turns freely. You should be able to spin the pulley on the motor shaft and the motor should coast down a couple turns or more. If it feels stiff then the motor bearings probably needs to be replaced.

Your saw will have the most torque when the belt is in the lowest speed setting. That is the speed that I would recommend.

Wood slamming on the table could be The result of something binding and then breaking loose momentarily.

Why was the tensioning mechanism replaced?

Are you forcing the cut?

Are the guides set correctly?

It's a Grizzly.

 

[john lucas]

Not sure about the stalling other than if you have more than one pulley and have it on the high speed it simply may not have enough power on that pulley. A slower speed should have more power. The snapping is usually caused by the blade grabbing or the wood not sitting flat. It doesn't take much. I've had it happen with when resawing small pieces and noticed that the insert in my table isn't perfectly flat so the wood is being pulled down into it. It's not very much but the force of the blade can pull it down and makes the blade grab. Never happens when the wood is on both sides of the plastic insert. Happens on bowl blanks that are pretty flat but not perfect.
On side note I've always heard the blade tension guides weren't accurate. There was a test done in one magazine (fine woodworking I think). They tested a bunch of bandsaws and found out to their surprise that the tension guides on almost all of them were right on. I've always used the flutter test my self and arrived at that by doing a test with a gauge I built from a another magazine article that actually measured blade stretch so you knew when you had the right tension. However that particular test was done using numbers they gave for a particular blade and may or may not have valid for the blades I use.

 

[Douglas Ladendorf]

Black Locust is a pretty hard wood. If there is any twist in the blade, easy when freehanding a curved cut, that could bind especially with wet wood. You might want to try dressing the back of the blade gently with a stone, and running a bit of paraffin on both sides of the blade for some lubrication.

 

[Mark Wollschlager]

Like Doug says, Black Locust is hard stringy wood. Slow feed speed, allowing the saw dust to clear the cut, making sure the turn radius is not too tight. And tune the blade.
Also make sure that the wheels are clean. A long time ago I bought a bunch of accessories from Iturra, I think the products might still be around.
Anyhow one of them was a stiff brush that ran against the bottom wheel to knock dust and shavings away.

 

[Jamie Straw]

Why was the tensioning mechanism replaced?

Are you forcing the cut?

Are the guides set correctly?

This saw still had the original, probably sub-standard, spring from the mid-1990's, my pockets were heavy, so I spent a bit on a Carter replacement spring. Nope, definitely not forcing the cut. The coup-de-gras was when I was cutting a half-"log" into round shape, said piece of wood being barely 5" tall. Nicely flat on the face side, bark side up (sans bark). Any pressure at all stalls the saw. Guides are set in my usual fashion -- not fancy guides. A bearing in back of the blade that contacts with pressure on the blade, Cool Blocks on either side. Been using this set-up for a long time. Thanks to you and all for the suggestions, I'm starting diagnosis now, will see how it goes. Have had a few people pointing the finger at the Black Locust.😀 I'm reading everything, just not responding piece-by-piece. Will let y'all know what I find. Thanks!

 

[robo hippy]

Some times they grab because the blade is dull. Another reason is not good set to the blades, meaning how far sideways the teeth are tweaked to give the blade room to wiggle as you cut and to clear the dust/chips. Both are reasons why I prefer the Lennox Diemaster Bimetal blades.....

 

[Jamie Straw]

Hi Jamie......Yes, I've had the exact same problem with a grabby blade. It's a combination of the number of teeth per inch, the MC, and the specific pieces of wood you're working with. The solution for me, has been to install a B/S blade with more teeth per inch.....this helps to overcome the grabby cutting on the wood you are experiencing with this. I'd have to go out and check, but I think the blade I've been using is around 8tpi......slower cutting, but much smoother a go of it......

I have a few blades of different tpi, all are wider than the 3/8" I'm using lately, but will test 'em out if they're not rusty -- most are left over from the flat-work days. Thanks.

 

[Bill Boehme]

If you apply any twist to a blade while cutting a curve it will make the cut pull to one side at the top and the opposite at the bottom. This can mean a big increase in friction because the cut is no longer vertical. With very much twist, the wood may actually rise up from the table in order to align the kerf with the blade.

Binding of rhe blade can also lead to a slightly different tooth set on one aide versus the other. This can lead to other problems such as not cutting straight in thick pieces of wood.

All of the above means that the motor has to work harder. It's possible that the motor doesn't have the oomph that it once did ... or maybe it never did.

 

[Jamie Straw]

Some times they grab because the blade is dull. Another reason is not good set to the blades, meaning how far sideways the teeth are tweaked to give the blade room to wiggle as you cut and to clear the dust/chips. Both are reasons why I prefer the Lennox Diemaster Bimetal blades.....

I'm a bit suspicious of the set on these last two blades. May have to re-evaluate how cheap I want to go on blades.😀

 

[Jamie Straw]

The tension gauge on any bandsaw is worthless ... use the flutter test.

OK, OK,🙂 I did. The magical mark is just above the 3/8" on the gauge. Not sure what "zero flutter" looks like, but can definitely see super-flutter.

A belt runs on its side walls. If it is worn to the point where it bottoms out in the sheave, it will slip and the pulley will run hot. A belt is also worn out if it is hard. The most obvious sign is ozone cracking.

No sign of cracking (kinda surprising, yes?) but I did what you said, saw no cracking. Far as I can tell, the belt is not bottoming out. Adjusting drive-belt tension is a challenge. Supposed to get a half-inch deflection with "moderate pressure." Is there an age/sex conversion chart for what is "moderate"??😛 It's pretty close. What are the consequences when too loose? Too tight?

Check for stiffness when turning either wheel by hand. Do this with the blade installed and tensioned. The drive belt should be in the low speed range. The wheels should turn very easily. If it seems to be too much drag then it is time to do fault isolation. First remove the upper and lower blade guides to see if that changes anything. If yes, check the guides to isolate to bad bearing. If no, remove the blade and check if upper or lower wheel is stiff. If upper wheel is stiff, it's probably the wheel bearings. Check the tension mechanism to make sure it was installed correctly. If the lower wheel is stiff, remove the drive belt and check it again. If it's still still then it's the wheel bearings. If no, check the idler pulley for stiffness. If that's OK, check the motor shaft to see. If it turns freely. You should be able to spin the pulley on the motor shaft and the motor should coast down a couple turns or more. If it feels stiff then the motor bearings probably needs to be replaced.

All of the above seem fine. I think I do need to replace the upper bearing that backs the blade (what's that called? Keep wanting to say "thrust bearing".) It doesn't spin as freely as the one on the bottom.

Your saw will have the most torque when the belt is in the lowest speed setting. That is the speed that I would recommend.

The lower of the two (1750, 2650) is what I've always run it at. Just took it up yesterday for giggles. "You never can tell" being the guiding principle.

It's a Grizzly

Yeah, and it's a 1019Z. Not a bad saw for $375 (at the time), but they make a darned good 17" saw, have watched it in action (not sure exactly which of their "Extreme Saws" it was) when one of our members took down a near-century-old maple and had a cutting party with everyone invited. Grrrrrr!

Thanks, Bill!!

 

[Jamie Straw]

Like Doug says, Black Locust is hard stringy wood. Slow feed speed, allowing the saw dust to clear the cut, making sure the turn radius is not too tight. And tune the blade.
Also make sure that the wheels are clean. A long time ago I bought a bunch of accessories from Iturra, I think the products might still be around.
Anyhow one of them was a stiff brush that ran against the bottom wheel to knock dust and shavings away.

Thanks, Mark. I was doing the right things, as described -- something in the saw changed methinks, since I'd done all the hard cutting already. Or, something in the wood changed. I was amazed at how not-stringy it was. We were told the tree had been down for a month, but I suspect it was more like 3. With-grain cutting on fairly tall pieces went very smoothly. I'll check out Iturra's lower-wheel brush. The one I have on there now is too flexible and soft to be of much use. I clean the wheel with Kirkland surface wipes, with the blade off, let the tire dry and re-install. Sometimes, if I don't want to take the blade off, I'll use a brass brush with the wheel running, touching the empty space between in the middle of the wheel.

 

[Jamie Straw]

If you apply any twist to a blade while cutting a curve it will make the cut pull to one side at the top and the opposite at the bottom. This can mean a big increase in friction because the cut is no longer vertical. With very much twist, the wood may actually rise up from the table in order to align the kerf with the blade.

Oy! That is interesting! Have to ponder that one. All done for today, dinnertime. Will cut something nice and tame tomorrow, see how it goes, and order new tires. Hey guys! I haven't gotten much in the way of replies to my "urethane bandsaw tires" thread. What's with that?!? Surely you have opinions based on purchasing experience, eh?😀

 

[Bill Boehme]

I don't recall if you said that the motor also stalls when the blade stalls, but that would be important to know.

Pulley and shaft warm could possibly mean belt slipping, but depends on how long it was running. Slipping could mean that the belts aren't as good as you think. If they're as old as the saw maybe time to get new belts just because they're old. Any sign of glazing on the sidewalls? Any sign of wear on the bottom of the groove in the sheave? If it looks polished like the sidewalls then the belt is worn out.

Instead of flutter test, use procedure where you pluck the band like a guitar string and slowly increase tension until it makes a clear tone rather than a dull thud. This is the procedure that Mark Duginski describes in his book.

While a high blade speed might normally be a good idea, it isn't for this underpowered saw.

Try a different blade.

Try different wood.

Try different bandsaw. 😀

 

[Bill Weaver]

Jamie,
I think I read in your 1st description that the shaft and pulley would feel warm and motor cool. Does your motor drive have small oiler cups on housing to pulley and on back side of motor. I have a really old band saw that I use sparingly now that has those on the motor. Just a thought.

 

[Jamie Straw]

Jamie,
I think I read in your 1st description that the shaft and pulley would feel warm and motor cool. Does your motor drive have small oiler cups on housing to pulley and on back side of motor. I have a really old band saw that I use sparingly now that has those on the motor. Just a thought.

Thanks, Bill, I'll take a look tomorrow. That side of the band saw is cuddled up to the left side of the miter saw cabinet, so I don't look at it in idle moments.😀