Cast iron repair anyone?

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
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snipped-for-privacy@panamsat.com wrote:

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 sci.engr.joining.welding 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.
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wrote:

I suspect that your shop isn't nearby. But the piece is small enough to send to you in the mail.

Yup. And since I only have the one piece to experiment on (and about 3 hours total of arc welding experience dated 30 years ago), I've elected to have someone else with more experience than me do the work this time - IF it isn't too expensive. Remember that I already have a quote for $300 that I felt was too high.
Gary
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On 26 Feb 2007 14:33:35 -0800, snipped-for-privacy@panamsat.com wrote:

Either braze it or weld it with stainless steel wire. I'd grind back the edges to form a "V", clamp it in position, pre-heat it with a torch and tig weld it with stainless wire. No tig? then oxy acetelene weld or arc weld with Ni-Rod
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On 26 Feb 2007 14:33:35 -0800, snipped-for-privacy@panamsat.com wrote:

if you can..drill and install long pins as well as having it welded.
Gunner
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Are YOU interested in the job? ^^^^^^^^^^^^^^^^^^^^ I have welded cast iron successfully, but I am by no means an skilled welder. Where are you located? If I think I can do it, I will do it for the fun of it--you take the risk if I spoil it. So, don't come to me unless you are about to give up anyway.
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Or braze it? I once snapped a leg off a cast iron seat. The cross section was about one square inch. I'm no expert, but have an oxy-acet kit. I got the fluxed pieces together and the joint to high temperature, introduced bronze filler rod which soaked right in. It worked first time, for invisible repair when painted. Been sitting on it this way for many years.
Jordan
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I've done quite a bit of oxy-acet welding and a little brazing so I feel comfortable with the technique. My only concern with brazing is the ultimate strength of the repair.
I don't know what happened to the saw that caused the failure but it was obviously something VERY bad. What is the relative strength differences of welding vs. brazing?
Gary
PS I live in the Los Angeles area but am willing to send the part via USPS to anyplace they deliver.
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The finished repair strength will depend upon several factors.. the type of damage, the stress that the part endures in use, repair material/process (electric or gas, and steel, nickel or bronze filler), heating pre/post, and extra filler build-up where possible (determined by proximity of mating parts).
As suggested, if you could post a couple of pictures, others could recommend and estimate an effective repair. Assuming you have a digital camera (or know someone who does), if your internet service provider reserves web/drive space for your own personal use, check to see if they have instructions for sharing or posting pics on their server. If not, there are numerous free photo sharing websites where you can send the pics to, or use the metalworking dropbox for posting pics of the part. http://www.metalworking.com/dropbox.html
Brazing can provide a very good repair of cast iron parts. I don't have the actual numbers (although I've seen tensile comparison numbers), but a brazed joint isn't much weaker than a welded one. With brazing, more filler rod can sometimes be applied over a wider area to add overall thickness to the repair area (the build-up aspect).
If the original part appears to be too difficult to repair, or susceptable to early failure, you might consider fabrication of a new replacement part made from steel. There's no time machine to turn labor rates back to the time when the machine was built, but talented and generous folks do exist.
It seems to me that the 4 hour minimum quote you were given, was intended to send you out the door.
WB metalworking projects http://www.kwagmire.com/metal_proj.html ...........
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I'll take some pictures and post them. It will take a few days to set everything up (web site, uploads, pics with acceptable lighting, etc.).
I'll post the link when I have everything in place.
Gary
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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.
On thing that concerns me is that the OP mentioned that the crack flexes, can be closed up with a vice grip. I've never seen a cast iron part with that much flex that was still in one piece.
Wild Bill wrote:

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RoyJ wrote:

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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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:

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On 27 Feb 2007 08:57:19 -0800, snipped-for-privacy@panamsat.com wrote:

A good braze beats a mediocre weld every time, particularly on cast.
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On Feb 27, 8:57 am, snipped-for-privacy@panamsat.com wrote:

I'll flame spray it for $110 subject to seeing the part. Similar to brazing but the deposit is a nickle alloy that has the strength of the original cast. The cast-iron will break before the repair will. There will be less distorsion than if it was arc welded. Probably take me an hour. The filler is expensive though thats why I would have to charge you. I live about 350 miles north of you. USPS is fine for getting it here. I would be sending it back via UPS. If for some reason I decide I can't do the repair you'll be getting it back UPS collect.
Send an email to: starbolins at: sbcglobal.net
Bud
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snipped-for-privacy@panamsat.com wrote:

Brazing can be very strong. Where I used to work, we had a Sheridan 350 ton mechanical die cut press that worked on a toggle action. One of the toggles (cast iron) was shattered when a stop block was left in the machine.
My boss found a company that basically put all the pieces together in some kind of sand mold with flux and brazing metal and took it up to brazing temperature in an oven. A bit of machining to get some center distances back in tolerance and that machine ran for years.
Wes
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On 27 Feb 2007 08:57:19 -0800, snipped-for-privacy@panamsat.com wrote:

Properly brazed cast iron will be plenty strong enough for your job. ERS
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wrote:

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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On 26 Feb 2007 13:31:08 -0800, snipped-for-privacy@panamsat.com wrote:

Gary-If you have a good torch setup I would strongly suggest that you braze it. It's pretty easy to braze, pretty easy to see if it's working while still hot, and if you try just one end of one crack it won't ruin the piece for welding if brazing doesn't work. I will, for free, even tell you how to braze it. ERS
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On 26 Feb 2007 13:31:08 -0800, snipped-for-privacy@panamsat.com wrote:

Welded my 5" cast iron vice twice. ( flux core wire feed Lincoln) Second time was because I was a bonehead the first time & didn't do it right.
Depending on the weight/angle of the part, is it possible to drill/tap & install a long bolt or 2, THEN weld it? ( thinking structural strength here)
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