Bandsaw blade problem

[dennisa49]

Good day,
I have a question relating to my small bandsaw. H & F BS-5V, small machine maximum capacity 125mm round stock. Good little machine, extremely reliable.
I was cutting 50mm free machining steel. Nothing difficult.
This morning the blade developed a light “knock”, once per blade revolution.
Sort of 1,2,3,-98,99 bump; 1,2,3-98,99 etc. etc.
As if the blade had material caught on a few teeth. It did not.
The blade then broke.

I replaced the blade, adjusted it until it did not slip. All seemed ok. then a “knock”
developed.
Has this been a problem for others?
Is anyone able to suggest why this may be happening please?
Thanks and regards,
Dennis

 

[bazmak]

A ingle knock per rev indicates a bad joint or small sharp kink

 

[goldstar31]

A ingle knock per rev indicates a bad joint or small sharp kink

A ( s)ingle knock? Could be right but I'm on my second 6 x4 bandsaw and one fault on the old machine was steel bits in the 'enclosed' ball races which gives rise to Brinell-ing.

So maybe a change of bearings is called for.

 

[RM-MN]

With my Woodmizer bandsaw mill that knock was the first indication of a cracked blade followed quickly by a broken blade. Examine your blade carefully and see if you don't have a cracked blade. Too hard of steel being bent on the way around the wheels will do that. You may need to change brands of blades.

 

[Cogsy]

A ( s)ingle knock? Could be right but I'm on my second 6 x4 bandsaw and one fault on the old machine was steel bits in the 'enclosed' ball races which gives rise to Brinell-ing.

So maybe a change of bearings is called for.

Every bearing on a bandsaw spins fast enough that the knocking would be constant rather than what the OP is describing. I'd be looking at the blade based on what is being described.

I'm curious about the blade tension though. They are normally under a fair amount of tension and just adjusting til it doesn't slip sounds like it might be a bit loose. Possibly this is the root cause of the blade fault which is developing? On another note, I have the smaller unit from H&F and had no end of issues with the blades supplied with the unit. I got a bimetal replacement off eBay and it's been perfect - cuts straighter, quieter and faster.

 

[tornitore45]

The OP indicates that the NEW blade exhibited the same problem.
Examine the blade by feeling with fingers (try not to hurt yourself) but consider the possibility that something may be wrong with the path.
It is my experience that if the second fuse blows, there was nothing wrong with fuses.

 

[Cogsy]

It seems very strange that the 'knock' is once per revolution if it's not a blade issue, as everything else on a bandsaw necessarily rotates more than once per blade revolution. I still suspect the low quality H&F blades and possibly a setup issue causing a premature blade failure at a weak point.

Just for a fun example of how back luck can run, I once had an issue with a blown width light on my truck (semi-trailer, not pickup for our US friends) taking out the whole string (wired in series for some stupid reason). I bought a new packet of globes and tracked down the blown one, changed it and...still none of them worked. I checked the fuse, then went round the entire truck removing lenses and checking every single globe with a multi-meter. I finally made it all the way around and they still didn't work. Out of frustration I checked the brand-new globe I just installed and it was faulty! Changed the new one again and they all came back on. 2 hours of my life that I'll never get back...

 

[goldstar31]

Maybe the blade is unsuitable for the material bring cut i.e. wrong teeth per inch or even more interesting- there could be an inclusion like tungsten carbide which will not melt in the normal scrap furnace. It happens.

 

[Arnak]

Hi,

Lift the frame to take the blade out of the cut while the saw is running.
Does the knocking stop?
If it does it is most likely the blade is faulty at some point, check the teeth and the side of the blade especially where it has been joined together.
You could also watch and listen when the blade is cutting and make a note of when the knock happens, stop the saw quickly and examine that area of the blade and teeth.
If it knocks when not cutting take the blade out then run the saw with no blade in it see if the knock is still there, it is unlikely to be.
I would assume that the blade is faulty.

Martin

 

[mfrick]

Well the problem could be several things.

First check the blade where it is welded together, when welding the blade the weld creates a bad spot and has to be ground out to create a tooth that has been filled with weld material, also check to see if the bladed is straight, if the ends are not square when welded together it creates a hump in the blade and it cause it to fail.

Second if the blade tooth pattern is to fine a pitch there is not enough space to carry the chip load and when this happens a tooth will fail and some times it will imbedded the broken tooth into the material or get stuck in the kerf which then causes the next tooth to fail and so on, called snow balling, then when a new blade is introduced into the kerf it fails as well.

Third cutting with coolant or not, dry cutting the blade has zero lubrication and will fail quicker than when using coolant, coolant needs to be mixed richer concentration to provide the needed lubrication.

A simple rule is to have minimum of three teeth cutting at all times so as the thickness of material changes so dose the pitch of the blade. A easy fix is to go to a variable pitch blade, bimetal blade which allows you to cut a larger selection of thickness of material.

best of luck

 

[kvom]

Buy good quality blades.

 

[DJP]

My experience has been a broken tooth on the blade but in one case it was a loose set screw holding a drive pulley from the motor to the saw. The pulley was loose on the shaft.

 

[ignator]

Goldstar I believe has the right idea. Your free machining steel may have a hard embedded particle, that is damaging the blade. The blade weld will have tooth discontinuity, where a partial tooth exists, and this produces a stress point every time it hits the hard material.
Try cutting in a different location on your bar of steel.

 

[dennisa49]

Thank you for the suggestions,
I have a feeling the problem is in the blade or it’s settings. It seems odd that the new blade has developed the same bump. I used the H&F manual’s tension setting method.
I will start from scratch, check the blade condition, alaignment and the blade tension.
It is Starret blade.
Kind regards,
Dennis

 

[mfrick]

When a blade goes bad in the process of cutting I never try to cut in the same kerf with new blade but move over and start new cut when the blade goes bad it leaves galled harden material behind then when you use new blade in old kerf it just destroys it as well.
MF

 

[dennisa49]

Hello MF, thank you,
There is something I was not aware of.
Add to that a lower pitch, wider set, had to fail.
I am seriously cross with myself, after almost 55 years of trade work I forgot the basics.
Thus the new bump, $11 poorer, but a couple of hundred wiser.
Good fortune for the next blade.
Many thanks to all of the kind sirs,
Dennis

 

[bobden72]

[
My band saw has always made a very slight knock and its the joint in the blade as it goes through the roller. This has never caused problems with mine, you say you adjust it till it does not slip, I do mine up as tight as I can, never had an issue in 12 years.

 

[XD351]

I stopped using Starrett blades years ago because they kept breaking at the join , i had one that had a chunk ground out of it on the back where the joint was and this caused the whole arm to jump up and down . I now get my blades from a saw blade manufacturer and have never had a problem since . I get variable pitch bi metal blades and they are not that much more expensive than the standard Starrett units sold by H&F . You should also check the adjustment of the guide rollers as they may be set to tight and when the joint runs through them it can make a noise as well and setting these up correctly i found improved the cut especially the squareness . I also had to play around with the wheels as they were offset and the top wheel was bushed and wobbled a lot so i machined it to accept roller bearings and gave the surface where the blade runs a skim to true it up .
That reminds me - i have to order some more blades !

 

[bob shutt]

Old bandsaw blades make great hacksaw blades. Use cutoff wheel to cut length drill holes using Hss drill. Will dull drill quick. Will need to sharpen after

 

[goldstar31]

Old bandsaw blades make great hacksaw blades. Use cutoff wheel to cut length drill holes using Hss drill. Will dull drill quick. Will need to sharpen after

Please explain as I cannot find a reason. They do make good flat springs however.