short use custom cutter

[brunneng]

Hey all-

I'm working on a benchtop plastic injector. I'm making a mold for a model railroading part which is basically two washers connected by a bar. It's 1/16" thick by 1/4" widest and 1" long.
To make the washer shapes in the mold (6061 alum) I was going to make a cutter out of drill rod - 1/4" dia with a 1/8" center bore(reamed). It only needs to cut 1/16" deep with a flat bottom (smooth finish desirable).

My question is I don't have any grinder set-up for "fixing" the cutter if I harden it (torch and water dip). It only needs to cut 10 cores in the alum and thats it. Will it last through that without hardening it? Or will it distort so little if I'm careful with the heating and dip that it's not a problem. It won't matter if it's off 0.010" but it should fit tight to the pins on the railcars.

Suggestions? cheap suggestions - I ain't sending it out.

Thanks-
Kevin

[JCHannum]

Go ahead and make your cutter. You will only need a couple of flutes, cut them with a file, relieve them with file.
Harden, and draw.
Heating and quenching is best done with cutter slowly revolving in drill press.
Touch up the edges with a very fine stone and you will be in business.

[snorman]

Yep, drill rod will work fine. There won't be enough distortion from heat treat to worry about. O-1 is good that way. It should cut all the aluminum you want also.

But: If I understand right, you just want a 1/4" depression by 1/16 deep with an 1/8" reamed hole in the center? Why not just use a 1/4" end mill for the counterbore? The end should be flat enough for this surely.

Or perhaps I misunderstand what you're after. I know very little about molds I'm afraid.

[Thrud]

You could do it with a single flute - and you should not have to harden it for just two cuts in Aluminum.

[brunneng]

Thats what I was thinking guys, thanks for the confirmation.

I did get a find on Ebay for a termocouple based digital controller for the injector. Can't wait for that to come in.

Snorman- Close, but the reamed hole is in the cutter which leaves a raised pin in the center of the depression which forms a hole in the injected part. Like a core in a sand mold.

[SGW]

O-1 ought to work fine for what you're proposing. To help preserve the cutting edges through the hardening process, get some "Keep-Brite anti-scale compound." A one-pound can ought to last you several lifetimes. I find if I use that, sharp edges survive heat treating quite well. You can always touch them up with an oilstone, if need be, but I doubt you'll need to.

[lynnl]

SGW, what're some good sources for that "Keep-Brite"? In some of the tool catalogs (MSC, etc.) I see stainless steel sheet/foil intended as an outer wrap for heat treating. (very expensive stuff) Does the Keep-Brite serve the same function?

[SGW]

Pretty much. You heat the part up slightly, dip it in the powder to coat it, then proceed as usual. I think I got my can of the stuff through Brownell's (www.brownells.com) but don't MSC, Travers, etc. sell it as well? Seems as though I've seen it around....

Brownell's repackages it under their own brand name, or at least they did when I bought mine, but I'm sure it's the same stuff.

P.S. Yes, both MSC and Travers carry it. Look under "KeepBryte" or "anti-scale" in the index. Travers is a little cheaper.

[This message has been edited by SGW (edited 01-08-2003).]