30" bar very slightly bent. (1mm or less in the middle over the full 30) How to fix?

[cjdg]

I must have been a muppet on dealing with a particularly large 5 stemmed sycamore and bent the bar which, unsurprisingly, now wanders on the cut.  When I first measured the deformation it was about 2.5 mm and by judicious use of boot and a flat surface I have reduced this to "almost" straight BUT I am somewhat concerned as to how to get it fully straight and not overdo it and bend it the other way!  To exceed Young's modulus by just the right amount I am thinking of using two plates of steel  at each end about 2mm thick and pressing down on the centre with about 100 mm wide load eg a 4 x 2" timber and a lump hammer and see if that works.  If not go up in 1 mm increments until it does

 

Is there a professional way to do this in a better precision engineered way?  Who would provide such a service?  I am near Oxford

See also the other post on sticky links

 

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[Haironyourchest]

Lump hammer is too brutal. Build a jig involving a bottle jack, for controlled, incremental pressure. 

[Stubby]

If you know of a workshop that has a fly press, ask them if you can use it . " blocks of wood at each end and 1 on top of the bend and gently push down using the press . Slightly over bend a little each time until  it returns to strait .  Might be better to lift the weights off the press as well for this .

Edited Thursday at 05:13 by Stubby

[ostosix]

A hydraulic press. I have one and probably use it to do as much bending back and straightening as I do bearings on it. 

 

But you'd probably be able to do that by hand carefully levering on a hardpoint of your choice. Obviously need to bend it further to allow for spring back. Key here is little and often. 

[Stubby]

3 hours ago, ostosix said:

A hydraulic press. I have one and probably use it to do as much bending back and straightening as I do bearings on it. 

 

But you'd probably be able to do that by hand carefully levering on a hardpoint of your choice. Obviously need to bend it further to allow for spring back. Key here is little and often. 

A fly press with the weights taken off would be better as you get much more feel . IMHO .

[outinthewood]

I've been using Tsu bars for a long time and first thing I do is cut the tail of the bar to release all the tension or on a daily used bar it will crack. So now the tension is gone you should be able to use as suggested by others get it back to pretty true ? Although the way Tsu and Sugi bars are tempered and finished I would't bet on it 

[AHPP]

38 minutes ago, outinthewood said:

I've been using Tsu bars for a long time and first thing I do is cut the tail of the bar to release all the tension or on a daily used bar it will crack. So now the tension is gone you should be able to use as suggested by others get it back to pretty true ? Although the way Tsu and Sugi bars are tempered and finished I would't bet on it 

 

Could you post a photo showing what you mean please.  

[outinthewood]

Using the thinnest cutting disc you have, I use a dremel, put a slice at the back of the bar slot at the tail of the bar. It can have a fair bit of tension so mind your eyes as it can break a small disc 

[AHPP]

All the way through I assume?

[AHPP]

I can’t find one now but there’s at least one horrifying video out there of someone cutting an I beam (or H beam) lengthways. Lot of internal stress. Big twang. Bloke with an oxy torch gets batted into the next postcode.