Vice Repair (Welding) Advice?

You can't really peen it too much, unless you do it long enough for it to cool off. Be thorough, and basically leave no part of the weld bead unpeened.

I have used a gas bbq grill to get a larger casting up to pretty even heat, then a rosebud to keep the weld area a bit warmer. Vermiculite or sand, or at least back on the grill running wide open for an hour, then down a little at a time works for me. It will run thru a bit of propane though, or if you don't have one, just bury it.
 
G'day Charlie,

I have done a number of cast iron vices and found the quickest and most fool proof way was to braze weld them.Manganese based brazing rod is best suited.They work has to be cleaned and veed out.

Be aware that some angle grinder discs throw off some contaminant that is very difficult to deal with as it embeds in the base material and can make brazing or welding a PITA.

If you do have the rods and flux and a means of maintaining post heat, the very best of all the welding processes is with 100% cast iron filler rod.

Use a big welding nozzle say around .10"orifice diameter with a strictly neutral flame .Acetylene carbon rich flames will render the cooled weld hard enough to ruin grinding wheels. The molten cast iron can be manipulated with the point of the ( neutral ) flame .Molten cast iron the consistency of molasses and as such can be "shoved " around by the flame point to release the embedded gas holes and impurities which will released and float to the top and adsorbed by the flux which floats around the top of the molten weld pool.

The above ensures a very clean welded zone .The cooling down process must ensure that the whole job cools slowly at a consistent rate. Covering the completed work in dry sand is a good way to achieve this. It takes at least 24 hours to cool to ambient temperature.The completed weld will be able to be machined with ease.

Hope this helps you

Ozwelder
 
The advice about preheating and peening is very important and cannot be overemphacized. In fact, with enough of both, you can weld the vise with almost any rod. I have sucessfully repaired a cracked vise with 6011 and there is a video by a welder named ChuckE2009 or something like that who uses 7018. What I did was bury the vise in gravel/sand so that only the V crack was showing. I then gave it the propane torch. I used a large BBO tank torch like a weed burner. When it was nice and hot, almost red, I gave it the stick. Plenty of peening. I hit it hard enough and often enough so that I was afraid that I would break it. When the weld was done, I threw a shovel full of dirt on top and left it until the next day. It worked fine until I sold it on Craigslist when I got a bigger vise.

Be careful about those high nickel rods. You can pile a lot of $$$ into that drack, and if it goes ping, you are going to be sad, but not much smarter. I have seen welds with 10 lbs of expensive rods go ping, and the guy had to air arc it all out. What a pain. Most people on the websites are repairing a low value item, and it is not a good idea to put too much $$$ into the crack.
 
Tony Wells said:
I have used a gas bbq grill to get a larger casting up to pretty even heat, then a rosebud to keep the weld area a bit warmer.
Click to expand...

Funny how a person can have something right under there nose and overlook it, BBQ, what a good idea..!
 
I have been welding cast iron on and off for 46 years and can claim experience and a good knowledge of what works consistently and what does not.
The first two years of my apprenticeship were almost entirely dedicated to the welding of cast iron. Mainly the cast iron welding repairs were carried out on the pre combustion chambers of CAT 4 cylinder diesel engine cylinder heads.

The cylinder heads were always tested after welding for cracks, by filling the water jacket with kerosene. The process used was oxy acetylene flame fusion welding process with a modified water cooled gas nozzle. Standard welding torch nozzles in the confines of a red hot PC chambers tend to crack and then backfire.vBelieve me you don't want a backfire from a nozzle in a semi confined space when pushing around a molten cast iron pool that can be an inch in diameter.

The pre and post heating was achieved by a 2” gas burner, meaning that the work was laid out on the ground and a wall of firebricks built around it and a sheet of iron laid across the top and heated until red hot. We had a couple per week over 10 years and I recall only a few in service failures.

The high success rate was due to :
knowing the type of cast iron
knowing the process to use
Using the most suitable welding technique]
Experience of the welding operator.

The following is intended as constructive criticism not an attack on anyone so please take it the right way OK!
Because a person has welded a cast iron unit with perhaps 6011 electrodes or indeed 7016 does not mean that such electrodes are suitable for all cast welding jobs. It just means he/she have been very very lucky. Yes! I understand that we are only welding a vice here but it is important to understand what you dealing with otherwise the success of your effort is just down to luck and not consistently repeatable. Circumstances sometimes dictate what process and consumables are available and you have to work by necessity from there, but when you have a choice your opportunities for success multiply if a procedure is followed that takes all of the variables into account.

What has not been discussed is the carbon percentage.Steel based electrodes( 6011 or 7016 only have a carbon content of around .03% wheras cast iron carbon content can range from 2% to 7%. No wonder you have to peen the bejesus out of them. The higher the carbon content of a ferrous based metal the more difficult it becomes to weld.Do the math as I have heard you fellows say.The carbon content is not just tens of times greater , it is in he hundreds.

The other thing cautioned against was with the nickel based electrodes.They are great if you get the correct grade of rod suited to the job-ie grade of cast iron and carbon percentage.Some will make your finished hardness so great it can only be ground.Not good at all when you want to drill and tap a hole.

Charlies vice is more than likely made from grey cast iron if it is of a decent quality manufacture. If its not it may be anything. Its not unknown for a run of small CI products to cast from leftovers from another job. Its just another variable which can turn an apparently "easy" job into a difficult one.

I will come back later and discuss this further as I am short for time at this moment.

Oz
 
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I am back,
Another of the welding variables variables to be considered when welding cast iron is the thick and thin sections a casting may have.

It is critical that during the welding and cooling phases that the unit temperature is consistent across all sections .In other words do not allow sections to heat up and cool down at differing rates. To do otherwise invites a crack across the thin section being the weakest area. Take a cast iron pulley wheel. The wheel spokes being of the thinnest cross sectional area,are prone to cracking when cooling

As mentioned first up cast iron is prone to absorbing stuff like oil. Oil consists of hydrocarbons .Remember the carbon, no extra carbon is wanted in cast iron as there is already plenty to go around already.The same goes for,grease, paint and dirt.

If you really must use a grinder disc ,do so and then just knock the ground surface off the prep with a carbide grinder burr.

To recap on welding cast iron

ID Type of cast iron- generally from the application of the casting cylinder head ,lathe body , machine vice ,etc
ID the carbon percentage -this can be looked up from the cast type on the net
Perform an adequate qeld preparation
Select the welding process

Select a suitable heating and cooling procedure.
Its all I can remember at this point.
Oz
 
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