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Band saw blade comming off pulley

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Paul Hogarth19/05/2009 17:37:13
3 forum posts
I have a Chester HV 128 band saw which is very useful and usually well behaved but sometimes the blade jumps off the pulley for no apparent reason. After replacing the blade several times and altering the tension etc everything returns to normal for a few more weeks, then off it comes again.  The manual is of little help with advice like 'Adjust tension until it is correct'. Can anybody tell me what I'm doing wrong, or why the blade jumps off the drive wheel.
Richmond19/05/2009 17:41:33
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73 forum posts
632 photos
64 articles
Hi Paul,
 
Have you spoken to the support people at Chester ?
 
I have the Machine Mart version of that saw and I occasionally suffer from the same problem.
 
Mine tendsa to be casued by over pressuring the cut, as well as a slightly out of true pulley .... this is on the to do list .... which is getting longer every day.
 
Rgds
 
Richmond
billy laird19/05/2009 21:52:17
2 forum posts
Hi all ive been having trouble with mine blunting quickly and put it down to driven wheel out of true? ive put some shim steel oppisite the key and this has trued the wheel up. don't know if this would help you but it's worth a try regards billy
jomac20/05/2009 09:07:14
113 forum posts

Make sure the wheels are co-planar ie, in line, parallel and dont wobble.

Tension varies between models and blade thickness so check the manual or ask another bandsaw owner.

My large wood/metal bandsaw (home made) started doing what yours is doeing, so after doeing all of the above I had a new one made up, the problem was, that at some stage the blade had got too hot (cutting  large blocks of wood) and the rear of the blade had stretched minutely,  As a result, no adjustment will fix it. The blade tries to go to the high side of the wheels and because the toothed edge is now smaller in diameter than the rear, the blade jumps  off or can go the other way, hard against the guides, causeing more localised heat.

I cannot use coolants on my bandsaw, so I cut slower with less pressure.

I hope the soution to my problem is some help.

 

 

Paul Hogarth20/05/2009 17:49:07
3 forum posts
Thank you Richmond, Billy and John.
 
I have spoken to Chester who tried to help but basically said it was a matter of trial and error. As far as I can tell the wheels are running truly but I did not think of altering the cutting pressure which I shall try.
 
My usual reaction is to increase the blade tension as much as possible then slacken it slightly and this cures the problem - until the next time it comes off. My manual gives the following instruction for blade tension:
 
Make sure the motor is shut off. Press the blade lightly with the left hand, make the rear blade against the flange of blade wheel and feel the blade tension that the blade does not come off the wheel. Adjust the blade tension adjustable knob with the right hand until the blade obtains the proper tension.
 
If anyone has a better description, preferably with some figures in, I'd be delighted to read it.
 
Thank you again for your help
 
Paul
Robbo20/05/2009 21:27:48
1504 forum posts
142 photos
Hi Paul,  you may be able to adjust the blade tracking, as I can on my old Warco bandsaw.    On the outside of the saw in line with and inboard from the two bolts that hold the idler wheel/blade tensioner is a grub screw buried in the casting. This should adjust the tracking by "tilting" the idler wheel. It's the same principle on all bandsaws,whether wood or metal cutting, though much easier to adjust on a woodcutting saw as it's vertical.  Trial and error is the only way, using small adjustments.  You can stand the saw in its vertical cutting position, open the blade guard and adjust it while turning the saw by hand, when you can see what is happening to the tracking,   Blade must be fully tensioned of course, and stout gloves are essential.
This is how I do the woodcutting saws we have.
Of course, sometimes the blade comes off for no good reason, like mine did today,just because I haven't used the saw for ages!
Regards
Phil Robinson

Edited By Robbo on 20/05/2009 21:30:08

Gareth-Chuk27/05/2009 13:16:27
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1 forum posts
Hi
 
As 'Robbo' says it is trail and error, if you follow his comments you cant go far wrong.  Setting a blade in a bandsaw is one of the things in engineering that can and will drive a person mad, as the blade can just fall off because...... its a wednesday....
 
It can be tension, can be that the blade is worn, can be many a thing im sorry to say, but once a blade is running right it will give you many a hour of good service
 
If your still having no joy, give me a call and I can check a few other things
 
Regards
-Gareth
Steve Sparrow26/06/2009 00:33:02
8 forum posts
I use one of those Clarke vertical/ horizontal jobs, good value for money it is too. I have suffered similar problems and looked for the cause. If the the blade tension and tracking were both initially correct, I thought  it might be worth giving some thought to heat, especially the temperature of the blade (band) itself. I noticed that on warmer days the band was more likely to jump off and took a few temps. with an infra red thermometer. On 'jumping' days the blade was 8-10C warmer, the resulting increased expansion may well be the cause, i.e. the band expands and its tension is not as correct as it was when at room temperature. The same would go for longer cuts I guess. I don't have coolant either so when cutting some huge chunk I switch the machine off and allow things to cool, then resume the cut. I get far less (but not zero!) blade jumping excursions now.
 
And I avoid cutting on Wednesdays.....!
 
Regards
 
Steve
Jim K29/06/2009 04:31:37
44 forum posts
I had a problem with my blade coming off on a regular basis, the reason was i went to the saw centre and bought a Bi metal blade unfortunatly it was wider than the standard used on these machines.
Due to this it would not stay on the wheels.
I then found another supplier who made me a bi metal blade with staggered teeth sizes (on his recommendations) it was the correct dimensions and i have never had problem since.
I have the address on email of this supplier maybe his phone No. these blades are about 3 times the price of the standard ones but cut like butter and last forever.
Jim
Steve Sparrow06/07/2009 18:10:13
8 forum posts
Hi Jim,
 
Cut better, no jumping off and last forever.....Sounds like the Holy Grail applied to bandsaw blades! I want one!
 
Regards
 
Steve
Jim K06/07/2009 18:29:49
44 forum posts
Steve,
I had your email and sent you his email etc. anyone else wanting it contact me as i dont want to put his email address on forum.
Jim
Steve Sparrow26/07/2009 10:51:54
8 forum posts
Thanks for the info Jim.
 
In return, and hopefully to save others the problem I had with my bandsaw (not related to blade jumping) I wrote this snippet last week.  I hope it saves damage and / or injury!
 
Regards
 
Steve
Mick "h"07/09/2009 13:11:30
5 forum posts
Hi Folks,
 
    My bandsaw is a home made 3 pullied type,my pulleys are made of 3/4 plywood ,8" dia running on plain bronze bearings,its fair to say that they are not perfectly in line however I rarely have a blade dismount-the idler wheel that is adjustable to centralise the blade can be fitted with a rubber band on it's circumference in fact fit them on all the pulleys(an old car tyre inner tube is good )
& the pulleys should be domed on their circumference. I always turn blade over by hand before starting
Mick "h"
Vince Bashford08/09/2009 09:51:23
1 forum posts
Hi Guys,
 
   Just a few thoughts on bandsaws. Some ideas have already been discussed in particular feed rates and buying good quality blades. Also look at the speeds you are cutting at and thickness of material etc. A trick I was taught many years ago is slack off the tension on the blade at the end of each day after use. When fitting a new blade move the guides back out of the way and check the running of the blade manually (without the isolator on) and see how it tracks. Be carefull you do not take off the very tips of your fingers, easily done, then set the guides up once you are happy. The side guides  should almost be touching and give the back guide 40 thous/1 mm clearance. If you cut a lot of metal fit a simple coolant system. I hope this all helps, Regards Vince
Eric Lougheed06/11/2009 20:36:08
23 forum posts
Please accept a comment from a very novice engineer:
I think wheel alignment is always a problem - but my experience is with wood-cutting only.
I have a very useful book on bandsawing which suggests a 'test-frame' (you need a large surface plate to set it up, perhaps) of a straight-edge long enough to bridge both wheels - or all three if you have a deep-throat machine - and subsidiary straight-edges (as long as wheel diameter) so that your main edge can bridge the gubbins that is always in the way. This reveals whether the wheels are co-planar, i.e. not just parallel but also with their faces on a common plane; but what to do if neither wheel can be tilted, I know not.
When that is sorted you can enjoy the other problems of 'square' to table and fence(s)!
 
Eric L
Jim K07/11/2009 03:08:21
44 forum posts
Hi
Try this yahoo group there is a lot of info on setting up these bandsaws, i followed them and i am having good results.
JimK
Jim K17/11/2009 12:44:13
44 forum posts
Hi does anyone know where Dragon Saws has gone, Steve Sparrow did you get in contact with him way back. If not can anyone give me the name of a good and not so pricy supplier of Bandsaw Blades.
JimK
chris stephens17/11/2009 17:41:13
1049 forum posts
1 photos
Hi JimK,
It depends where abouts you are in this great nation of ours, if for instance you are near Windsor you could go to Bandsaw Services. If not and you want to collect then go to the yellow pages, if you want to order over the phone you could try MSC/J&L Industrial supply. They do a range of blades, but I would recommend , wherever you get it, an HSS blade they do last longer. One down side to buying from J&L is that the blade might have the teeth facing the wrong way, this is a matter of seconds to fix, so should not put you off.
chriStephens
Chris Gabel17/11/2009 17:52:30
2 forum posts
The price on the imported bandsaws is always  tempting but past experience with bandsaws in school and college workshops has always made me reluctant to  part with my money.
 
Does anyone have any experience with the Evolution/Rage TCT cut-off saws?   Their  sales  video on their website looks impressive,  and the saws are close to the same price as the cheap  bandsaws.
Jim K17/11/2009 18:04:46
44 forum posts
Chris Stephens
I am in Scotland but I had found Dragon saws from wales good and cheap they were HSS and were as I say very good I am curious in what you say about the teeth facing the wrong way being easy to rectify can you explain.

Chris Gabel
I have bought a vertical band saw for cutting wood so this is why I need new blades, So it is not the metal cutting horizontal one which are fine if set up properly  they all have their good and bad points.  I have one for sale if anyone is interested. 
On your Evolution range those tools really impress me on the videos but I would like to try them myself I don't know how they would do on solid bar I will go search youtube now to see if they are doing that.
JimK

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