Welding Broken Vice ?

[GordonC]

Just looking for some advice, I broke my vice (I know thats what I get for using cheater pole) and I'm going to have a go at welding it. If it doesnt hold or breaks then Im not bothered I just want to give it a shot and it gets me some more practice with the arc. So I've got some cast iron welding rods and I've v'ed both pieces but what I'm not sure of is the pre-heating of it. I havnt got an oxy torch or powerfull propane torch or that, All I've got is my standard oven (Goes to about 230?) Or I've got a small gas blowtorch ? How should I go about it ?
Thanks,

 

[MattF]

I broke my vice (I know thats what I get for using cheater pole)

Can I ask why? I've never, ever come across an occasion where I've even considered, let alone needed, to get that much grunt behind a vice handle, so just curious as to why people do that. Not trying to be obnoxious or owt, but it honestly is one of those little things I hear of on occasion of which the answer has constantly eluded me, hence my curiousity as to when it's considered necessary.

Regarding the heating, any method should work fine, from what I gather. Not a welder personally, but the information I've seen on the subject of welding cast merely indicates that you want to warm it to a point which makes it less likely to suffer thermal shock and heat stress, so I'd guess that notably hot but not glowing is the type of temperature you want to achieve. The slower the cooling process the better too, apparently, so a gradual heat reduction after welding is best.

Conversely, there was someone mentioned on here the other day that they've never bothered heating before welding, so mileage varies. Cast can be a fickle beast at the best of times, and all cast iron is most definitely not equal. It will be suck it and see to some degree with even the best of preparation.

 

[GordonC]

Can I ask why? I've never, ever come across an occasion where I've even considered, let alone needed, to get that much grunt behind a vice handle, so just curious as to why people do that. Not trying to be obnoxious or owt, but it honestly is one of those little things I hear of on occasion of which the answer has constantly eluded me, hence my curiousity as to when it's considered necessary.

Stupidly I was trying to straighten a bent bit of 5mm flat bar and I thought if I got a bit more force on it then it would be bang on straight but the vice went bang instead.

 

[GordonC]

I will stick it in the oven for a while and just try it. If it doesnt work then I'll just buy a new one.
Thanks

 

[jonjoe]

Heat it until it is near red, then weld it, and as soon as you are finished welding it cover it in sand to allow for it to cool slowly.

 

[Paul.]

Unless you can heat it evenly to around 500 deg C and weld it hot then there is little point in pre heating, you would be better to weld it using a nickel based electrode and keep it relatively cool around 50 C, keep the runs short and peen each weld before the next run, some cheap cast vices are of very poor quality material and not worth bothering with, I have fixed quite a few over the years, one I can think of has been in regular use for some 20 years, others haven't made it off the bench without cracking, the cost of nickel electrodes may just make you decide to buy a new one.

 

[MrFluffy]

I repaired a large machine vice and it cracked post cooling and is on the todo list to have another go at, but a previous bronze weld repair had lasted several years. So maybe if you know someone who can bronze weld that would be a better option.

 

[MattF]

Stupidly I was trying to straighten a bent bit of 5mm flat bar and I thought if I got a bit more force on it then it would be bang on straight but the vice went bang instead.

Aah. If you need to do something like that in the future, try three pieces of rod or suchlike in the vice. Two pieces behind the bend/kink, one each just either side of it, and then the third piece on the other side pressing against the proud/raised section of the bend/kink.

If you just press it flat, it will spring back to some degree. Using the above method is a basic and cheap variation based on the principle of how a straightening press works. You need to bend the kink/bend slightly beyond the point of flat in the opposite direction to the existing kink/bend to straighten it. It tends to be quite effective in most cases, when only a vice is to hand.

 

[MattF]

I repaired a large machine vice and it cracked post cooling and is on the todo list to have another go at, but a previous bronze weld repair had lasted several years. So maybe if you know someone who can bronze weld that would be a better option.

Isn't that brazing?

 

[BrokenBiker]

guy on youtube called chuckee2009 or something similar has a series of vids about welding up a broken vice