I have an old Toledo power hack saw that I bought many years ago at a salvage yard. The basic saw function works well but the mechanism that lifts the saw blade during the return stroke was subjected to severe stress (prior to my purchase) and has three 2 inch fractures along the shaft that transfers the lifting power from the cam to the saw arm. The broken piece itself weights about 20 pounds and is roughly 6 inches square. The casting is complete (no missing pieces). I can push the fractures back together with a pair of pliers. I was quoted a $75 per hour (4 hour minimum) from a commercial welder to make the fix. Since the saw itself cost less than that total, I was not interested. But I would STILL like the repair done. Are YOU interested in the job? Gary

Sure, bring it by my shop next week; I'll only charge you for as long as it takes, but $75 hour seems reasonable. And it might take more than 4 hours to do it correctly. When comparing the price of the saw to the price of repair, you might consider that aside from being an obsolete item (a power hacksaw) it was also pre-broken, further lowering its value. A similar discount does not apply to the skills required to fix it. The prior owner evidently concluded that the repair was not worth doing and sent it off to salvage, where you bought it.If you want to do it yourself, an arc welder via craigslist is often under $200 with leads and sometimes a shield as well, and cast iron repair rod is not too expensive. Search for "cold weld", "cast iron", etc. You will find two divergent methods - one with preheat/postheat, one with no preheat/postheat - I suggest (and have posted details on at least twice in the past) the one with no preheat, and I also suggest practicing.

In a used machine part casting, the crack will be full of grunk, won't wick in like it will in a perfectly prepared joint. The brazing material is as strong as the base material and more more ductile to boot. Jordan wrote:

Cast iron repair anyone?

Feb 26, 2007 24 Replies

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RoyJ 19 years ago

I'm partial to bazing, mostly because that is what I've done in the past. The braze material is usually the 50kpsi range, about the strength of the original cast iron. A 6" square piece would preheat nicely to

600F to 800F, just pour the braze material into a prepared groved crack, let it all cool slowy in a pile of vermiculite.

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Tom Gardner 19 years ago

Whodathunk?

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Jordan 19 years ago

What's the purpose of the groove? When bicycles and motorcycle frames used cast lugs, the joints had no "vee" to help. Capillary action draws in the molten brazing metal.

Jordan

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Steven E. Eyrse 19 years ago

Take it out to one of the Special Effect Shops in the valley. There are some around the Burbank Airport. Talk to them. To stick cast back together you need to A) heat it in a oven to about 400 deg to push all of the junk out. then while still HOT B) Arc weld it with a nickel rod. Did this on the sterring box for the '29 hot rod and have put well over 100,000 miles of hard road one it.

Steve E.

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RoyJ 19 years ago

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