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Trunnion ram bearing fix - Printable Version

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Trunnion ram bearing fix - ieezitin - 01-20-2013

Gentlemen

I have never hardened anything. I have a outside camp fire, I have fire bricks, I have propane lances and also at my disposal is the wife’s oven.

Here in the attachment is a very simple sketch of a plate with a spigot poking up, this spigot needs to be hard, it fits through a phosphor bronze block that is connected to my ram trunnion in my shaper. This also has to be exactly perpendicular to the plate x and y and the base plate needs to be square and flat.

I have my own ideas but I would relish someone else’s perspective. How would you make it?

Anthony.

RE: Trunnion ram bearing fix - Sunset Machine - 01-20-2013

Half-hard, turned, ground and polished 4140 (goes by 4140 HT TGP PH and other names). It's called "machinable", it's pretty hard but softer than a chisel. Store-bought, saw off a bit and press it in the hole. .001" undersized.

http://www.speedymetals.com/information/Material63.html

Small part like that could be made of O1, red-hot with just a propane torch & oil quench. Shine it up a bit with emery cloth and re-heat to, say, purple and quench again. It'll be hard enough to cut metal and hit with a hammer, like a chisel. Instead of purple, go light yellow and it'll be as hard and brittle as a lathe bit.

edit: Just a thought, but that might be a standard pin you could find at Enco, MSC, McMasters, etc.

RE: Trunnion ram bearing fix - f350ca - 01-20-2013

How about a dowel pin pressed into the plate. They come ground and I think they're hard. Are they?

RE: Trunnion ram bearing fix - EdK - 01-20-2013

Here's what McMaster says about the dowel pins they sell.

"Alloy Steel—Our strongest dowel pins. Made from hardened steel. Diameter tolerance is +0.0001" to +0.0003" (unless noted). Meet ASME B18.8.2 (unless noted)."

Hope this helps.

Ed

RE: Trunnion ram bearing fix - ieezitin - 01-21-2013

Well what I have in my mind is this, the pin has to be hard as it sits in a phosphor bronze bearing, if it wares fast it will transmit the wobble through the machined spur-gear and bearing carriers on that, like the old one did.

It’s the one piece on this machine that takes the full force of the reciprocating action of the ram, I don’t know the forces but they must be considerable to slice off .050 material over 6”. The original plate and pin was constructed that the pin looked like it was probably pressed fitted in and from the back they had a flaring tool mushroom over the last 1/16 of the pin, they may have left the last part of the end soft.

If anyone owns a shaper they will know what I am talking about. What I was fishing for was does hardening warp or change dimensions, obviously I cant machine a hard surface so this is either made first then hardened or hardened and affixed to the plate. Either or any ideas would be welcome, as we all know there are ten ways to skin a cat.

Anthony.


F350
I just re-read your post. A dowel pin perpendicular to the spigot buried in the plate and bored through the pin sounds quite a good idea, then the question is the hole pre-bored through the pin before it was hardened is it still true to size? Although saying that slapping allot of locktite thread locker on the pin-hole and pin may hold it.

Anthony.

RE: Trunnion ram bearing fix - f350ca - 01-21-2013

I was thinking more of using a 1 inch dowel pin as the spigot that way its already hardened and ground . Could you bore the hole then slit the plate to the short end and put a bolt through to clamp the pin? doubt if locktite would take the forces involved here.
Hardening the pin is going to ruin the surface finish, it would need to be ground after hardening.
Does this plate slide to change the stroke length? My little shaper has a T slot in the bull gear, the shaft is hollow and a trough bolt locks the pin from the outside.

RE: Trunnion ram bearing fix - stevec - 01-22-2013

Spaenaur offers 1" dowel pins with on end tapped 5/16-18x3/4" deep. They come in lengths of 2",3",3.5",4" and5". Case hardened to58-62 Rockwell C . They come in unit pkgs of 5, split pkgs. are available but at a greater cost.
They can be found on page E88. Dowell Pins,Pull

http://www.spaenaur.com/

RE: Trunnion ram bearing fix - ieezitin - 01-22-2013

F350. / Stevec

i like your idea. slitting the bore and clamping would without a doubt apply allot of clamping force coupled with stevec recommendations on pins that can be purchased commercially would work, all so having the pin threaded and clamped would stop the pin walking out.

I agree the Loctite would be suspect for strength.

This plate and pin is used to lengthen / shorten the stroke of the ram but my action is with a Acme screw coming from a bronze bush/block connected to the top of the plate, the block is recessed into the plate.

See, brain storming pays dividends, so far i like this idea if nothing else turns up i probably will go with this.

Thank you

Anthony.

RE: Trunnion ram bearing fix - TomG - 01-23-2013

I would use a 1" dowel pin and shrink fit that sucker into the plate. A 1" hole in steel will expand .00065" per 100º so you can easily get a .003"-.004" interference fit. Heat the plate up to 1000ºF with a torch and the pin will drop right in and essentially become one piece forever. You could even throw the pin in the freezer and get a little extra assembly insurance. You'll need to quench it as soon as it's assembled though to keep from drawing the hardness out of the pin.

Tom

RE: Trunnion ram bearing fix - ieezitin - 01-23-2013

Tom

thank you for the little math on heating and expansion rates, one worry would be to me that it may distort the plate it has three machined surfaces.

here are a couple of shots of the old one that i have tried to repair but failed.

This shot shows i placed the old pin back in the plate and held the plate square to the pin then i back welded it.


[Image: rockerarmplate4.jpg]


this shot shows what it looks like from the front, this whole plate is buried in the spur-gear hub which has a milled channel to receive this plate. The hole you see at the top is for the bronze bush threaded to an acme rod for ram forward advanced motion



[Image: rockerarmplate5.jpg]


This shot shows the milled ledge, the outer one fits into the spur-gear channel the perpendicular one on the 90* is there to accept a plate the is bolted to the gear face this plate holds it in place and stops it from walking forward, the fit on the plate was in my opinion was designed for a clearance fit but the spigot was probably a close running fit.

well this repair failed due to the spigot being out in one direction by about .002, when i intalled it back on the machine it squealed and the plate got hot.



[Image: rockerarmplate3.jpg]


Thanks for all of everyone's input.

Anthony