Bending ali bandsaw frame back to normal

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Mel769

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I have a bandsaw with a cast aluminium frame (Inca 205) thats quite badly out of alignment. Today I stripped all the parts off and using various straight edges and clamps, now have it clamped up and all square. I suspect when I remove the clamps it will spring back to its twisted form. If I heat the frame with a heat gun while its cramped do you think this might help retain its new shape ? If I left it cramped for longer than overnight would this help ? Any ideas ?
 
Aluminium work & age hardens so will tend to spring back if forced into a different shape, If its twisted as a result of being dropped , falling over or similar it will need annealing to soften it.
Aluminium anneals very differently to steel. With steel you heat it to red heat & let it cool slowly leaving it soft.
With Aluminium the procedure is paint a stripe of ordinary soft soap on the part, heat the part until the soap turns brown, at this point quench the part with water, this leaves the aluminium soft & malleable & it can then be worked or twisted/bent into position, Sometimes this will have to be repeated several times.
Last time i did this was with a set of Volvo Duoprop boat propellors that had been driven across a concrete causeway at 30 knots, Basically they resembled an aeroplane crash all bent & curled over. A local marine engineer said they couldnt be straightened but i did it in an afternoon of blowtorch & anvil work. Took about 5 anneals to get them straight. They came out pretty well!
 
Sounds like there may be other ways to me.
You could give us a clue as to whether or not carriage adjustment might be possible,
and you could try doing some alignment tests, like this for example...
The test is done with blade under tension, as top wheel needs to stay put and not tilt.
SAM_6752.JPG

SAM_6763.JPG
SAM_6775.JPG

Visible pencil effective .jpg


Tom
 
it'd be a major job to tweak the frame back even in an engineering shop with decent kit.....
basically it needs bending back past the flat stage...then see how much more u need to tweak it.....
Knowing how much is the skill....it's so easy to go to far.....
I reg do it with steel and the odd cast iron frame.....
Ttree's is right
I think Id spend my time relocating the wheels to a flat plane sooner than using a press.......
depends how far out it is of course.....
or u could make a perm fixed steel frame that hold the B/S frame in tension.......
 
I see you are using a straight edge to check the alignment of the upper and lower wheels - Ionly make this point because they don't have to be co-planar !

Are you able to adjust the tracking to position the blade gullets correctly on the centre of the upper wheel with the blade still within the confines of the tyre on the lower wheel - if you can, all is well ...
 
After attempting to set the wheels coplanar last weekend with straightedges and through all ranges of adjustment it was not possible, the frame is too far gone. So, right now the frame is stripped and its clamped up flat and trueish since last night. Ive yet to remove the clamps but im fairly sure it will spring back when I do. I was toying with the idea of heating it up with the clamps in situ so it deforms to a new shape, is that possible ? I cannot make a frame as it will need to span the throat so thats out. Looks like i will have to over bend with the clamps and hope It dont break ! If it does break I will have some spares for sale !
 
There is a law in physics called youngs modulus, this states that upto a given point of applying a load to any solid material you have elastic deformation which is reversable. Exceed this point, ie over tensioned blade and you go into permeant deformation where when the load is removed the material no longer returns to its pre load condition. I think you have a problem that will require a lot more effort to force it back to original and the risk of it wanting to return or spring back to the twisted condition. So how would I approach this, well I would want to cut and weld to release any stresses rather than trying to heat various areas up to get it back to being right but is this cost effective ? Being aluminium you would need to TIG weld and not induce further problems so again higher cost, then can you achieve an end result that will work and handle the tension of the blade which is the bottom line for a bandsaw blade. How much is the saw actually worth, you can get a new small bandsaw for less than £300 so would that deliver the same results as your Inca.
 
Yep its looking like it wont be cost effective to repair, shame really as its a nice saw just the right size and weight.
 
Inca bandsaws frames are injection moulded with a ton of cross braces / webs included as part of the moulding, yes ? Consider me defeatist but a design like that isn't made to flex. It's meant to be as stiff as possible with minimal materials. Once gone, I think you'd need great skill or a minor miracle to recover it.
Shame, they are a classic, well made and if a saw of that quality were still available new these days I'd bet they would be priced near to £1,500
 
Could you pack out the bearing blocks if theyexist with washers to bring into like or are they mounted into the casting?
 
Could there be flat tires on this Inca, I guess so...
Is those flat tires giving you the impression of the machine warping......
i.e for flat tires, tensioning will have an effect like tracking!
- the more tension,
the further the blade's teeth will overhang off of the wheel.

Failing that, and there is something clearly evident...
Could it be that it was intentionally bent?

As far as I'm concerned, impossible to know anything without doing this test above
and as you can see, my motor has now got an adjustable mounting plate to match
the top wheel, seeing as it's only the lower wheel on most modern machines which is adjustable
in regards to east/west.

I guess the Inca is a bit different though in regards to what's adjustable/or can be made as such.


Trial and error finding shims, draw another line and check again.
The right shim.jpg


And as Jameshow mentioned, one could shim the wheels if they needed to.

To do so, one could use fishing line or other string,
The lesson being these magnetic or taped blocks are necessary for the use of plumblines, no question about that.

SAM_4964.JPG

That's so the wheel protrusion check can be done
SAM_4977.JPG


And it's the bolt heads in this case which steadies the line, just like the blocks do.
SAM_4997.JPG


Beam and rule check for east/west alignment with blade under tension and allowed track on the wheels...
before the lines of the holy bandsaw trinity are drawn.

Beam & rule .png
SAM_4595.JPG


Hope that helps some,
Tom
 
I would measure the amount of "twist". Then I would clamp it with shims to over correct at least 100%. Then release and see if the over bending helped and by how much. Now you know how much to over bend the frame and can do it once more with more shims, hopefully getting the frame right and nothing cracking. I wouldn't heat it unless as a last resort.

Pete
 
I would measure the amount of "twist". Then I would clamp it with shims to over correct at least 100%. Then release and see if the over bending helped and by how much. Now you know how much to over bend the frame and can do it once more with more shims, hopefully getting the frame right and nothing cracking. I wouldn't heat it unless as a last resort.

Pete
Thats my only option. The frame is definitely twisted/bent which is effecting the coplanarity of the wheels. There is some movement in/out on the lower wheel but too far and the blade rubs on the enclosure housing the blade height mechanic. Thanks for the reply's
 
Unless you follow mr snodgrasses video and that is how my bandsaw is set, wheels co planar and no more problems.
Roy ...
Just to make sure we're beating the same drum regarding Alex Snodgrass's view on wheel alignment, take a look around 5:58 in his 'Bandsaw Clinic video - where he talks about the co-planar myth and basically says don't dick around with wheel alignment on your bandsaw.
I've helped numerous people get their saws back into trim after they've tried to adjust the bottom wheel (especially on Record and Charnwood machines where there's a big boss with 4 bolts in quadrature that scream out "adjust me !").
 
Incas don't run on the center of the wheel anyway they have the teeth just off the edge, states so in the manual
 
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