Trunnion ram bearing fix

[ieezitin]

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.

[Chuck in E. TN]

I would make it from O1 drill rod. Drill rod can be hardened with a propane or maps gas torch, and quenched in oil.  If your part is fairly largr, it may take 2 or more torches to get it to cherry red hot to harden. I use old motor oil. Clean a spot with emery cloth and heat again to straw color to temper, and again, quench in oil.
Chuck

[ieezitin]

Chuck

Ok

lets say i turn my diameter down to size and thread my spigot and the plate, this would need to be soft.

Then i harden the spigot what is the going to do to my Fit? This has to be seated perfect because this part takes the full force in one direction of the ram removing the material.

Anthony.

[Chuck in E. TN]

On that question, I'd have to defer to the experts. But, in my opinion, I don't think it would affect the fit.
Chuck

[Lew_Merrick_PE]

Anthony,

First, I would make the part out of A1/A2 or S7 tool steel.  These are air hardening steels that have virtually no deformation induced during a properly applied hardening & tempering process.  They are a bit pricey (about $16/lb here in the U.S.), but very easy to work with for such tasks.

Second, do all the machining (threading, etc.) to the part before hardening it.  Remember that an annealed or normalized steel has a Face Centered Cubic (FCC) nominal crystal structure and a hardened steel has a Body Centered Cubic (BCC) crystal structure and, as such, a hardened part is slightly larger than the unhardened part.  Depending on the steel, the shape of the part, and the quenching processed used, a hardened part may be as much as 0.5% larger than the unhardened part (though 0.2%-0.3% is more common).  Make sure you have allowed for this in your machining.

Third, to check temperature for hardening, use a magnet (AlNiCo is fine) suspended on a fine piece of wire that can be brought close to the part while you are heating it.  Holding the magnet at hardening temperatures will destroy it, so bring it in (close) quickly and remove it from the heated chamber.  When the magnet is no longer attracted to the steel, you have reached your desired temperature.  Maintain it at that temperature as closely as you can for at least 10 minutes (given the size of your part) and quench by hanging it in front of a (room temperature air) fan.  McMaster-Carr's website has fairly good information on this process you can download for free.

Fourth, temper (stress relieve) pretty much as Chuck suggested.  I like to use sand that has been heated to 360°F (180°C) as my thermal blanket for tempering as 360°F is the Martensite Transformation Temperature (low end) and burying the part in such a media leaves me with the greatest surface hardness with the least induced stresses.

You can probably get away with Chuck's approach (02 tool steel), there is just a slight chance it will deform during processing if your temperature changes are not evenly distributed.  If (as you say) this is your first foray into heat treating, then the chances of such an oops are increased.

Also, file down the major diameter of your threads such that the crests are .020 inch (0.5 mm) wide before hardening.  Otherwise you are likely to end up with ultra-hard & brittle areas in your thread.

[ieezitin]

Chuck  / Lew

Great information and certainly in my realm of getting accomplished. a couple more questions for ya.

working in the tolerances for growth (max 0.5% realistic 0.2%-0.3% using aforementioned steels) that would not be a problem, now imagine i made my spigot .030 larger and bored my plate and fit the spigot, i back weld it then i place the plate on the mill and mill all dimensions needed including the spigot (i could put it on the RT) now i have everything flat and square, then do the hardening would the spigot warp and become out of square?

The reason why i say this is if i thread it and lets say i use a Loctite thread lock, over a period of time and being what it does in its life which is rather abusive having it welded would cure it.

Lew

Fantastic explanation on the hardening procedure.

Thank you both.

Anthony