Welding a Cracked Trunnion PM66

[Jim Yielding]

Hello all,
Long time lurker, first time poster.
As I was disassembling my PM66 to free up the blade elevation and tilt the other day I noticed the trunnion had a crack in it. I purchased the saw used a few months ago and hadn't gotten around to cleaning it up til this past weekend. Needless to say I was gutted when I discovered the crack.
I called Powermatic and the gentleman I spoke to suggested I have the support welded. This sounded all well and good, but after scrounging the internet all weekend I ran across story after story of failed attempts at welding cast iron.
I've got a few feelers out on a new or used support, but it's looking like that will be cost prohibitive.
So since I've got really one shot at it, I need a suggestion from a fellow Phoenix woodworker on who would be best at fixing this. I've called a couple people, but they've been leery of doing it when they find out what it's for. I've attached pictures to give you an idea of the area I'm talking about.
Thanks
JY

[Erik Loza]

100% serious: What about some JB Weld?

Erik Loza
Minimax USA

[Jim Yielding]

That was my first thought too, but given the weight of the motor and the vibration stress in that area. I'm thinking no on the JB Weld. If this were a non-stressed area I'd be all for it, the consequences of a failure are just too great for me to use it with confidence.

[Erik Loza]

Yea, I hear that. The vibration definitely could be an issue.

Why couldn't it be welded, I wonder? Just build up around that area as needed? It's not like one of the ways is cracked and I don't see any moving parts that could collide with it. Just curious.

Erik Loza
Minimax USA

[Bill Huber]

I have welded CR many times, you have to do a good deep V in it and weld it a little at a time and let it cool, then weld some more in.
I have always used my little Lincoln welder to do it and got the rod form a welding supply company that was for cast iron.

I am sure if you went to a good welding shop they could do it.

Good luck.

[Judson Green]

I think your looking to have it brazed or possible stitched.

[John C Bush]

A good welding shop can do it. CI needs to be pre-heated and brazed. Should work just fine. I had old CI trestle table legs repaired --less than $100.

[John TenEyck]

I'm sure it can be welded by a competent shop, but I'd first look for a good trunnion from someone who's parting out a used saw. The cost will likely be no higher than getting yours repaired. You can always go ahead with the repair on yours if you can't find a good one in whatever time frame you decide on.

John

[Jeff Heath]

I'm an OWWM guy, and I've got a shop filled with OWWM machines. I also, for my business, do a lot of welding and fabrication, and have a lot of experience welding cast iron.

A couple thoughts:

The best way to repair this is by either grinding/milling a deep V groove out of the crack, an using the appropriate nickel alloy (I use Ni55, but there are others available) to weld in short bursts, so as not to overheat the part. All problems come into play when the part is overheated with a long welding bead, which causes the carbon in the cast iron alloy to be drawn in to the welded area, thus making it brittle. When it cools, it shrinks, and cracks. Short bursts of an inch, or shorter, will not overheat the part.

I have repaired trunnions for PM 66's, just the same as yours, in this manner, as well as trunnions for other machines (Unisaw, Yates American Y20 bandsaw, etc...and many others) and have never had one fail after the repair.

Another 2nd option would be to have the part brazed. Either procedure will get you what you need as long as it's done by a competent welder/metal guy.

If I were you, I'd get it repaired, all the while looking for an affordable replacement part used. There are enough PM 66's being restored these days, and enough that are just toast, so that parts are available, albeit not in abundance. I paid $300 for my entire saw, and restored it myself. I've got less than $1000 invested, which includes new bearings in motor and saw, new belts, new paint, and a brand new Biesemeyer fence.

Hope this helps....

PS If welded, it needs to be done with an arc welder that has DC + welding capabilities. Regular AC will NOT be adequate.

[Doug Ladendorf]

What Jeff said. Sounds like you just need to find the right guy in your area. That part isn't toast, just a little extra trouble for you.

[ian maybury]

The trick is probably to take it to a suitable specialist, and not a general welding service. Welding cast iron is quite complex - quite apart from the basic underlying difficulty caused by the high carbon content there can be quite a bit of variability in composition/type, and when part shape, choice of welding process and filler material, pre-treatment, technique, equipment, risk of distortion, post treatment etc are factored in as well there's lots of scope to get it wrong. There's quite a bit out there on the web which describes some of the various processes and what can go wrong.

The guys that get really good at that sort of work tend to offer a highly specialised single/few person(s) based specialist repair service, and will sometimes warranty the work. Best to look for a proven performer. Some may be inclined to try opportunist pricing, but it shouldn't be that big deal done right. The big risk is letting a guy at it that is 'having a go' - who doesn't really realise what he's getting into...

[Don Jarvie]

Poke around on the bay and see if you can get one. It doesn't have to be the same year just within 20 years. PM didnt change the design much on the 66.

[Brad Adams]

I don't think I'd v out and weld that small crack. Brazing that would easily be a permanent fix, If you know some one experienced at it.

[Phil Thien]

Consult your local technical school, speak to a welding instructor.

[Jim Yielding]

I agree about the brazing, and a welding instructor is a great idea.
Thanks gentlemen, you've given me a great place to start.
JY