6×4 bandsaw

[Steve PaveyParticipant @stevepavey65865]

I have a 6×4 bandsaw which has been cutting well for a long time, but has just started chucking the blade off within a couple of seconds of starting a cut. It tracks fine without a load on it. I have read the John Pitkin guide **LINK** , I’ve adjusted the tracking and the blade guides, cleaned the bearings on the guides, but no luck. I have no idea why it has suddenly started misbehaving with no apparent reason, so if anyone has any ideas perhaps you can make some suggestions.

If your suggestion is to buy a cut-off saw or a mechanical hacksaw, then you’ll be preaching to the converted, but I daren’t risk buying another workshop item for some time!

[Steve PaveyParticipant @stevepavey65865]

Blade comes off when cut starts

[john fletcher 1Participant @johnfletcher1]

Years ago i had a similar problem and was discussing it with a friend in the queue at Harrogate show, another person also in the queue, said change the blade, which i did, and all as been well ever since. i also recently made the simple vertical blade alignment tool as shown in recent MEW magazine. I Silver Solder/repair the blades utilising an alignment jig (a bit of angle iron) from an article in ME many years ago, a worthwhile tool. Once you get the idea of the Silver Soldering a blade, an old damaged one can be resurrected by using another damaged blade John

[Simon Williams 3Participant @simonwilliams3]

+ 1 from me for change the blade.

What seems to happen is the set gets lop sided on the teeth, and/or unsymmetrically blunt, and the blade won't cut straight for love nor money. There is nothing you can do to keep the blade on the drive wheels|!

I've gone over to HSS blades, they're expensive but they're worth it.

HTH Simon

[EmgeeParticipant @emgee]

Hi Steve

A few months ago I experienced the same problem, the blade running off at the non-driven end, so much it cut through the tin shield below the frame.
When checking all screws for tightness the 2 screws securing the non-drive bearing block were loose by about 2 turns, took the tension off and tightened the screws and the blade has remained in the correct position, still cutting almost square after many years of use.

Emgee

[Steve PaveyParticipant @stevepavey65865]

I should have mentioned in my post above that I’ve already changed the blade this morning – a new Starret from Tuffsaws. I also should have mentioned that I cleaned the wheels and I don’t use any sort of oil or cutting fluid.

[not done it yetParticipant @notdoneityet]

As Emgee, or a dead or dying bearing, only affecting the blade when under load.

[Simon Williams 3Participant @simonwilliams3]

Posted by Steve Pavey on 25/08/2020 13:05:18:

I should have mentioned in my post above that I’ve already changed the blade this morning – a new Starret from Tuffsaws. I also should have mentioned that I cleaned the wheels and I don’t use any sort of oil or cutting fluid.

So has this cured the problem, or are you still suffering the same difficulty after fitting a new blade? Or perhaps (perish the thought) things were going just fine until you changed the blade??

Either way, check the blade isn't riding on the step flange on the wheels. It should be running adjacent to the step in the wheels' flange, but not on it. But you'd knno if it were, it puts a shoulder down the length of the blade.

Now why do I know that?,

[Howard LewisParticipant @howardlewis46836]

It sounds as if your saw would benefit from a detailed check of all adjustments, to ensure that the guide rollers are correctly set, and that the tracking is correct; once you are sure that there are no fixings loos that should be tight.

Don't forget that the pins on which the guide rollers run are eccentric to provide adjustment

If the bearings for the Idler wheel are worn, that needs to be rectified before starting on further adjustments.

Worn Driver wheel bearings will be evident by oil leaking through the lower seal. Remedy, new bearings and seal, plus making a substantial replacement for the thin tube masquerading as a bearing spacer. Whilst the wormbox is apart, it may be worth taking a few thou off the back of the wormwheel to prevent the teeth rubbing on the casting.

HTH

Howard

[Steve PaveyParticipant @stevepavey65865]

@Simon – it was running fine the other day, then it shed the blade this morning cutting a piece of ms strip. Refitted, check it was ok by manually turning it and it was ok until I lowered the blade onto the work. That’s when I changed the blade for a new one. When it did exactly the same with the new blade I checked the alignment and cleaned the bearing guides.

i gave up in disgust (at myself for not being able to sort it out!) but just about to steel myself for a second go, following the procedure in the guide I linked above to the letter. If all else fails I’ll get the angle grinder out.

[Steve PaveyParticipant @stevepavey65865]

An update..

Dismantled the carrier for the top/front (idler) wheel – it slides between two plates which locate in grooves in the carrier. I filed the bolt holes so that the two plates can be pushed well home into the grooves – this reduced the play in the top wheel – some play is inevitable given the geometry of the whole arrangement. Then another realignment of the two wheels after reassembling. I rebuilt the saw completely when I got it a few years ago, with new bushes, spacers, washers etc, so there should be nothing that is overly worn in that time.

A test cut with 25×3 ms was more successful this time. I noticed that the blade slipped on the drive wheel a couple of times so added a bit more tension. As far as I can work out, this might have been the root cause of the problem – the blade may have been snagging slightly in the cut (the first blade always had a slight jiggle at the welded joint, and the second was obviously new and therefore had a good bite to it). I guess it was also slightly out of adjustment too, so the combined effect was to throw the blade off the wheels. A few more bits to cut this evening will show whether it is really sorted out.

Thanks for all the suggestions – always useful to hear of other folks experience.

[john fletcher 1Participant @johnfletcher1]

Back again, i remember there is an adjustment to the the pulley wheel at the no motor end using an Allen key. I helped a friend years ago when his kept flipping the blade off. I think the pulley has a thin shoulder to guide the blade, the adjustment slightly tilts the pulley and therefore blade..John

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