Repair Question

I'm working yet again on my aging fleet of farm equipment and have a few metalworking questions for the group.

The machine is a 60's vintage OMC mower conditioner and the parts are of the sickle drive area. Specifically a couple of 7/8" grade 8 bolts that have wear on them. Maybe 1/32 deep X 1" long on one side. I want to build up with arc welding and turn down on lathe for a precision fit on bearing. Any reason not to do this? What rod will give max wear and still be machinable?

7018? Is the HAZ zone a issue on *8 bolts if welded? I suppose spray arc would be best but not an options for me. Durability is desireable. It will get new bearings. I replaced these bolts maybe 20 years ago and can't complain about the service , just enjoy utilizing the shop and usually can improve upon the factory design in the process.. I still have the origional bolts to play with. The bolt/bearing fit is not real precise to begin with, needs to be dissasembled regularly for servicing the cutters.

This is a recipocating drive and get hammered @600 strokes/min. I know I should just replace em but would rather spend the money on shop tooling of course.....

Interested in any thoughts...

DE

Reply to
DE
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Grade 8 bolts are listed as "Medium Carbon Alloy Steel, Quenched and Tempered" with a proof load of 120,000psi and a minimum tensile of

150,000psi. Weld>
Reply to
RoyJ

Bad idea. Only under very controlled conditions should one weld on heat treated items. What are the risks if you have a failure? If none, give it a go, but I think you'll find it's a false economy. Anything you save in material you'll spend in labor tearing it down more frequently. You'll either anneal the bolts by welding on them, or create fracture zones so they fail if they are still heat treated when you're finished. Being carbon steel, I think they'll be annealed instead, so you'll have lost all the advantages of grade 8 bolts, and introduced stress areas.

It will be interesting to hear how this goes.

Harold

Reply to
Harold and Susan Vordos

Harold knows exactly how to cut through the BS, doesn't he?

Harold, Harold - he'll true you true If he don't know it, Nobody do.

Bob Swinney

Reply to
Robert Swinney

As others said, don't weld!

But if you are seeking for new shop equipment that solves the job: Get a "metal sprayer". It is basicaly a OA torch with a (gravity operated) spray gun like feeder. This feeder puts some metal powder into the flame's blast where the metal melts and is blasted onto your surface. You get quite a big selection of powder to use. Among them is wear resistant bronce. The process is quite simple, so you might also be able to build one by yourself. Also, it doesn't heat up the base material too much. After spraying the metal on, you can use your lathe to get the part back to size.

Nick

Reply to
Nick Müller

After posting I did a search and found bolts online for much less than the local guy. Story over.

But said machine has a rod end bearing holder that need some attention. The stresses on the insert bearing are rated at around

1400 lbs dynamic and half that static. So the 7/8" grade 8 bolt is way over that. The grade 8 bolt must be for wear purposes.

The bearing holder insert is a self centering type bearing . Have a bunch that I picked up new surpluss. The holder is a Fafnir proprietary item @ $120. I use 4. Only one is loose presently and it looks like a forged piece with a 7/8 14 male threaded end. Looks like one of these but is fitted with different type bearing

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Maybe drill/tap a setscrew/jamnut to hold bearing tighter?

The failure risk is of non injury type only money.... I can hear when things are coming apart and can get shut down before total failure.

The machine has some design shortcomings that I manage to find workarounds and I enjoy the challange of keeping it running. I paid $350 for it back in 74 and it paid for it self the first couple of day I ran it...It is stout as hell and could go another 50 years easy the way I run it.

Tnks for the input

DE

Reply to
DE

Reply to
carl mciver

I think I'd buy a couple of new bolts..

John

Reply to
JohnM

I've been thinking exactly what you describe. High speed recipocating movement tends to tear itself apart. When I refurbish that drive it sounds like a sewing machine, but after some wear is starts to chatter and the wear accelerates. The unit is built around weldments, not real precise. I'm thinking along the lines of using locking sleeves that lock the inner race to the shaft. Or somehow make the bolt into an expanding mandrel sort of a thing.

Newer drives that solve this problem are expensive by several orders of magnitude.

DE

Reply to
DE

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