Repairing destroyed vise

"What about oxy acet brazing? That's all I have aside from the multiprocess welder. (no Tig)"

Oxyacetylene welding/brazing heats up relatively wide areas although admittedly brazing occurs at a lower temp. The advantage of Tig is that it's focused heat. I'm not sure whether Tig would or would not warp the cast iron which is why I posed the question of whether anyone has done a repair with Tig. I don't honestly know the answer. I was hoping to hear from someone who tried it. Filling holes with metal is a more durable repair, and probably more cosmetic.
 
I worked with epoxy composites for six years with a good deal of time spent studying cure rates.

When an epoxy has hardened to the touch, it has only cured about 10%. A full cure can take years for epoxies that take a day to harden. Epoxies also continue to shrink with curing. Heat will hasten the cure with the cure rate doubling for every 10ºC increase in temperature. A higher temperature will also result in a harder and more heat resistant product. Epoxy also has a property called the glass transition point which is the temperature at which the cured epoxy changes from a rigid to a plastic solid. This temperature increases as the cure becomes more complete

If I were repairing the vise with an epoxy composite, I would fill the recesses generously and allow to cure at room temperature until hard. Then I would slowly increase the temperature until it reached between 110ºC and 130ºC. This process would take place over several days and the epoxy should be close to fully cured.

As to the composite, I would use a slow curing epoxy and mix in iron powder to make a thick paste. Not having the powder, saw dust from cutting iron with my horizontal band saw or filings from filing with a fine tooth file would work.

Fully cured epoxy is fairly immune to most solvents. I would expect good resistance to the chemicals that would be used in machining.
 
The vise I repaired with JB weld has held up fine for the past 4yrs. And is still going strong. I did let it harden for almost a week to make sure it was hard all the way through.. This vise was my main vise for milling.
 
In South Africa we have a product called Pratley Putty which is a two part epoxy putty - you kneed parts A and B together and it softens as you work it, but then cures rock hard and can be filed or machined. I have used it on my mill table to fill the worst scares, and it avoids the problems with liquid type epoxy running out of where you actually want them to be.

It's a bit of a South African legend it was used by NASA in 1960's on Ranger landing craft, so has the distinction of being the only South Africa product ever to go to the moon.
 
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Epoxies seem to share some characteristics with concrete as far as curing
 
markba633csi said:
Epoxies seem to share some characteristics with concrete as far as curing
Click to expand...
Exactly, and for much the same reason.
Concrete's curing depends upon water and carbon dioxide molecules finding their way to the uncombined calcium oxide to form hydrated calcium carbonate. Once the mixture solidifies, the only mechanism for this reaction to occur is for previously combined molecules to uncombine, passing the CO2 and H2O along and recombining with fresh CO2 and H2O, in effect passing the molecules along like a bucket brigade. This process will continue as long as there are uncombined sites but will necessarily slow down as the number of uncombined sites is available.

The University of Wisconsin began a study of concrete over a hundred years ago. Every year, a sample was removed and tested for compressive strength. The study was to have ended after fifty years but their testing showed that the samples were still increasing in strength so they elected to carry the study for another fifty years. As I recall, the strength continued to increase throughout that part with the study ended because they ran out of samples.

The epoxy reactants are an epoxide and an amine. The amine has multiple reaction site on each molecule which permits the cross linking that gives epoxy its rigidity. Like concrete, in a liquid form the molecules are free to move around to find active sites but once solidified, the bucket brigade mechanism is the process by which unreacted molecules find partners. And like concrete, as fewer and fewer active sites are available, the curing rate becomes slower and slower.

Fortunately, with both concrete and epoxy, the products reach an acceptable state of usability long before the reaction is complete. In my particular case with the epoxy composite, we were trying to make a product with extremely tight density tolerances so curing shrinkage was of great concern. I would think that shrinkage, hardness, and possibly temperature resistance would be issues of concern when trying to build a precision surface such as the floor of a milling vise. To that end, I would error in the direction of overcuring rather than under-curing.
 
I had a canadian customer that brought me a product called Metalset A4 made by the company Smooth-On.
It was so much better than JB weld it was unbelievable.
I found the website. smooth-on.com
It says to store and use it at room temp...funny he told me to keep it in the fridge.. It also says it has a limited shelf life....maybe that's why the fridge...have had these two tubes for 20 years and everytime I use some it works great.
 
Interesting. Smooth-On moved for Easton, PA west so now about 40 min drive. I have been to the new location a few times to purchase other epoxies for wood working.

The Metalset A4 product is not cheap, $20 for 11oz. I may have to pick up the 11oz size to give this a try next time I visit the store.
 
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