Weird Forged Block

[Susquatch]

I'm posting this here because the part in question is a forging. But it's a weird one....

It's a 4x3x2 block that is bolted to the inside of each of the 3-point lift arms at the back of my neighbours Case IH tractor. It's purpose is to limit the sideways travel of the arms when pulling Impliments like plows which generate significant side thrust. It a forging to withstand the wear and tear of a moving arm and the side thrust.

The 3/4" bolt that attaches it broke off flush with the back of the block. He wanted me to remove the stub and make a replacement. The stud has both ends threaded - one end threads into the block and the other end goes through the lift arm and is secured with a nut.

Easy peasy right. Wrong.

Stud puller - NFG.

Drill out bolt and pull out the spring left by the old threads - NFG again. Where do the threads begin? Huh, what threads? No threads! The weirdness begins.

Must be a pressed fit stud. Drill it out completely and pull the remnants. NFG again. Only has remnants for the top 16th.

Below that, no remnant. In fact, I can see a seam at the 16th point.


It would appear that the stub has a huge bottom bigger than the hole. MUCH bigger than the hole. Marked "B" below. How did they do that? Red hot metal pressed in till it bulges out and deforms to fill the cavity?

It gets weirder - at the bottom of the hole there is a really hard plate (item "A" below) that looks a bit like brass. But clearly isn't brass. A drill barely touches it. An end mill just polishes it. How did they get that in there and what is it?

I confess I have never seen anything like it.

Another concern. The part is out of production and it isn't available anymore. So it can not be replaced.

Right now I'm thinking I could epoxy a new stud in there. Epoxy didn't exist when that block was designed. There is no tension on the stud so it might hold. Alternatively, I could drill out and tap the block for a 7/8 stud and turn the top of the stud to make a 3/4 end the same as the old one.

But, I dunno. There isn't a lot of depth and that hard plate has me worried.

Has anybody ever encountered such a beast? How do they make that? Any suggestions on the best way to fix it?

All ideas are welcome.

 

[Chip Maker]

So what depth does it have? Can you fit a couple of grub screws in it and dimple the new shaft. The brass coloured material may be Ampco bronze although I can't comprehend it's purpose. Carbide will cut it if it is Ampco.

 

[Thomas]

The brass looking plate you found sounds like cadmium plated hardened steel, wondering if they used the plate on top of the hot forging and pressed it in with the stud then rolled it over in a forming die.

 

[Dabbler]

The brass looking plate you found sounds like cadmium plated hardened steel, wondering if they used the plate on top of the hot forging and pressed it in with the stud then rolled it over in a forming die.

I was thinking something like that, but my question is: how did they get that cadmium plated washer into the hole at all? -- the only theory i can come up with is that the hole was closed around the stud while the big forging was red hot. wow. that's a lot of trouble to got to for a stud and doesn't make sense.

Here's what I'd do: I'd make a new heat treated stud that is dimensioned as a interference fit and get some liquid nitrogen (The University at Windosr or London will have some) and cold fit it into the hole... There's no way you'd heat the big forging enough if it was something like 50 kilos

 

[Susquatch]

So what depth does it have? Can you fit a couple of grub screws in it and dimple the new shaft.

It is about 3/4" deep and currently plunge milled to the plate. I think your idea to put in a grub screw or two is a good one. Especially combined with epoxy.

The brass coloured material may be Ampco bronze although I can't comprehend it's purpose. Carbide will cut it if it is Ampco.

A carbide end mill (full size 3/4" down to brand new 1/4") doesn't do more than polish the plate.

The brass looking plate you found sounds like cadmium plated hardened steel, wondering if they used the plate on top of the hot forging and pressed it in with the stud then rolled it over in a forming die.

No sign of any rolling operation in a forming die. Looks to me like it was forged in place (maybe that's what you meant). But why? It's an awful lot of trouble to go through with no apparent purpose. If I were still working, I'd take it down to the lab and do an ultrasound on it to see the actual shape and size.

I was thinking something like that, but my question is: how did they get that cadmium plated washer into the hole at all? -- the only theory i can come up with is that the hole was closed around the stud while the big forging was red hot. wow. that's a lot of trouble to got to for a stud and doesn't make sense.

Ya, that's exactly what I am thinking too. My problem is also "it just doesn't make sense". Why go to all that trouble when a regular recessed head through bolt would have worked just fine!

I'm sort of thinking that the part had another use elsewhere and they just used it on the lift arm because it already existed. Who knows, might have even had a minimum order quantity they couldn't use up for the design application.

Here's what I'd do: I'd make a new heat treated stud that is dimensioned as a interference fit and get some liquid nitrogen (The University at Windosr or London will have some) and cold fit it into the hole... There's no way you'd heat the big forging enough if it was something like 50 kilos

The big forging is not so big. It's maybe 3 kilos. Think half a pound of butter in size. Heating it up is no big challenge. We tried to burn out the insert when we thought it was just the remnants of the stud. That didn't work because it turned out to be so much bigger than the hole, but you couldn't touch the block afterward. That was just using a micro-oxy-map torch. OxyAcetylene with a big rosebud heating tip would easily make the whole block red hot. I think cooling the stud and heating the block MIGHT work. But not a tempered stud. It would be better if the stud bent than broke in use. Either way, I'll have to make a new stud (unless we go epoxy) because the hole is now a full 3/4" as a result of trying to get the remnants out.

 

[Susquatch]

I suppose we could also do a helicoil if we can find a good bottoming tap - might have to grind one. Sad to have to do that to good tap though.