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

[Erik Manchester]

Jim,

Your saw looks like it was never used, and it really sucks to find a crack in it. If that saw had any amount of use you would be unable to see the crack under all the dust.

You could look around a long time to find the right person to do that weld, but if it were me I would send the trunnion to someone I trust to get it right the first time.

Padded well you could ship it cheaply by Greyhound Bus and it would travel across the country in a few days.

Put your feelers out but don't be afraid to send it to the right person.

[Jim Yielding]

Eric,
I really was a great find. The gentleman I got it from bought it new and really didn't use it much in the ten + years he had it(a dozen picture frames and a couple chairs) before his health declined and he couldn't use it anymore. It sat for about two years before he decided to sell it. None of his children were interested in woodworking so he dropped on CL. I snatched it up for what I thought was a pretty great price for a low mileage saw.
Had it not been for the stiffness in the elevation and tilt, I would never have seen it. The original lube had hardened and mixed with saw dust and made the adjustment wheels very hard to turn.
I had originally just planned to loosen the crud and relube, but then I saw the crack. I was half tempted to leave it and press on. Who knows how many saws have a crack like that and run for years with no incident. But knowing it's there would always bug me.
I'm still leaning toward shipping it to Lock-n-stitch. I've seen some of their work and they do a great job. So far they're the only ones that have come back with a reasonable plan (furnace braze, with a slow normalization). I think it's going to all depend on how much the thing weighs when I get it out. I won't have time until the weekend to get it apart and do a thorough inspection for more cracks.
JY

[fRED mCnEILL]

I am a backyard mechanic/hobiest and have brazed CI. I'm sure any competent welder would understand what to do. Call a machine shop and tell them what you have. Its not really a big deal.Stuff like that is what they do.

[Doug Ladendorf]

Jim, for lube on the gears I use a dry moly with graphite spray that dries on and works great. Won't attract sawdust either. I know some folks that use paraffin (Gulf) wax with success.

[Bruce Wrenn]

Check with an automotive machine shop. I bet they would know someone who can weld cast iron. That's the way we used to have cracked heads fixed

[george newbury]

One of the first things I'd do would be look at school auctions. PM 66's are showing up all the time.
One nearby just went for $162.00
Powermatic Table Saw Model# 66 - Serial# 8166953 - Working When Taken Out Of Service In routine Rotation -
http://www.publicsurplus.com/sms/auction/view?auc=1266272

http://www.publicsurplus.com/sms/docviewer/aucdoc/141203_002.jpg?auc=1266272&docid=11755804

As I posted elsewhere I got a school haul of a PM66, PM160, PM60, PM81, Delta 31-710, and another spare table saw for about $950. At least around my area the school stuff is well maintained and lightly used but often replaced because "wood shops" are being downsized or equipment routinely rotated..

[Erik Manchester]

Good luck with the repair Jim, I agree that once you know about it it needs to be fixed or it would be forever on your mind.

[Trevor Remster]

Once upon a time I bought a new unisaw in the late 80's. Didn't strap it down in the bed of my truck on the way home from the woodworking store. Someone pulled out in front of me and I had to swerve to avoid the accident. You can guess what happened next. My trunion was cracked like yours and I thought it was wasted. I headed down to a local machine shop that I knew. They told me the quality of the cast iron was very poor, but they would give it a shot. The saw has been working without a hitch since. I would agree with the others who say to start with a machine shop experienced in engine block and cylinder head repairs.

[Jim Yielding]

Well, I got the trunnion out and I got a better look at the crack.
Now that its out and I can see it up close, it looks like it was cracked at the foundry and they repaired it before it was painted. I can see a few spots along the crack where it looks like it was brazed then ground flat. I sprayed a bit of brake cleaner along the crack and it doesn't seem to soak in, so I'm thinking it's closed
I think at this point I'm going to leave it as it is and not mess with it. I'm glad I got it all the way down, as the elevation and tilt shafts were pretty gummed up, as were the teeth on the trunnion and arbor.
Tomorrow, I'm going to wire wheel them clean and rinse them off real well.
I've got some dry graphite lube on the way and I should have it back up and running by next weekend!
I appreciate all the helpful insight.
JY