Bending stainless bar

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prv

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EDIT: Problem now solved, please move along :)

I have a scheme, involving small highfield levers (no, it's not a rigging project). However, the ones I've found for reasonable prices have ring ends, where I need hooks. The levers are like this:

http://www.ebay.co.uk/itm/2-LOCKABL...ailers_Transporters_Parts&hash=item53f2f649dc

except slightly bigger, I assume the same size as these:

http://www.ebay.co.uk/itm/2-LOCKABL...ailers_Transporters_Parts&hash=item53f33a1097

(from the same seller but zinc plated; she says she can get the same ones in stainless).

How would I best go about re-bending that loop into a hook? I have normal home workshop tools, including a vise (albeit not as sturdily mounted as I might like) and a plumbing-type blowtorch. I guess all I really need to do is cut it off just before the third bend and then straighten out the first.

Apparently the material is 316 stainless, and trying to measure the "large" zinc-plated one on my screen it looks like the bar is about 6mm.

Feasible, or should I just buy the right thing in the first place? :)

Pete
 
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I'm sure some experienced metal worker will correct me here, but I've never needed to heat stainless to bend it. Stick it in the vice and shock it in to shape with a hammer. Plumbing type blow torch won't get it hot enough anyway.

Either that, or looking at the pic, it seems taking a wee bit off with a grinder would be enough to create a hook?
 
nathanlee said:
Either that, or looking at the pic, it seems taking a wee bit off with a grinder would be enough to create a hook?
Click to expand...

It would create a hook of sorts, but one that's just asking to be opened up by any load. Doing the same cut and then straightening out the first bend would make a stronger shape.

Pete
 
Pete,

I must say I'm more in favour of the ' buy the right kit ' approach, stainless is quite difficult to work with without a serious workshop and gear.

' Protex fasteners ' do lovely examples of the catches you mention, not cheap but you only fit them once. No connection.
 
6mm stainless bends very easily after heating to orange/red with a gas torch.
It blackens the surface but this is easily polished off.
It has to be done quickly as it cools fast when in the vice.
Make a rough jig so that it can be bent around quickly.

Plank
 
316 stainless steel in its as-cast form has a surprisingly low yield point and is easily bent. Wire used for the sort of fittings that you are looking at may be in the normalised (= as cast, almost) or it may have been cold drawn to increase its strength, in which case its yield point will be higher. The main problem for you might be that making the bends in the original wire might have work hardened it, in which case it will be more difficult to straighten the bends, whereas the straights will be softer. Trying to persuade all of it to form a nice smooth curve wil pose problems.

Heating it to above about 750C will remove any work-hardening effects but of course this will return it to the as-cast condition, where it will be weaker. Your subsequent shaping will restore the strength to some extent but nowhere near as much as was there originally.

I think that for your small section 6 mm wire I would try to bend it straight first, cold, then re-shape it. You just might develop cracks in the previous bends, in which case heat it. I have bent several shackles and other fittings in the past, all of which survived being bent back into shape. Rigging wire is cold drawn and seems to accept bending several times without fracturing, but of course the strands are a lot thinner than 6 mm.
 
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