help with 440C

[nemat0de]

i have some parts to be made out of 440C SS. They will be machined in the annealed state then heat treated to 60Rc. should I leave the i.d. small and the o.d. big for the material to shrink or the o.d. small and i.d. big for it to grow?

TIA

[HomeCNC]

Would this be 440C by Carpenter Technology? I used to make knife blades from this. I never had to deal with the changes in size after heat treating. Maybe you can go to the company's web site and see if they have any info on that.

[nemat0de]

I already did that. The problem is that I have some +/-.0002 tolerances. I guess I need to figure out how to finish it after heat treat.

[Mortek]

nematOde,

I would think you would like to leave about .002 - .003 for a finish bore and hire someone with an ID grinder to grind the hole to size. Pretty tight tolerance. You could bore them with a boring head but you would definitely have to use a cabide insert and even then the rockwell 60 is going to be very hard to cut. Grinding is your best and most accurate bet. I don't think I would cut them to size before heat treat.
Ken

[hardmill]

First off what type of machine are we talking about?
From the tolerance your talking about (+ -.0002)
the machine needs to be pretty tight.
Let me know then we'll talk.
PEACE

[nemat0de]

the machine is a mori sl-150. It can hold +/-.0001 once it's warmed up. I did convince the engineer to open the i.d. to a total tolerance of .001. Grinding would be a good option but the i.d. is .125dia. X .9 deep. tough to grind, even tougher that I haven't figured out how to get teh centerless to do i.d.'s
It looks like I will have to fire up the 'ol Sunnen.

I am running the i.d. right at the small end of the tolerance and leaving .005 on the o.d. According to our outside shop and the h.t. guy this would be the best approach. btw- I also need to keep .0005TIR from i.d. to o.d.

what do you guys think? I am still on the first op so quick replies would be appreciated.

[Klox]

You can spark erode the holes after heat treatment if you want to play it safe.
I always send parts for Vacume Heat Treatment. You get your parts back nice and clean, distorsion is also less on VHT.

Klox

[dannystooblue]

does the hole go all the way through the part? if it does then you can wire edm the i.d. and the outside shape as well.

[little bubba]

If you can talk to the engineer, see if they can switch it over to 440F, 440C sucks, but 440f cuts like butter. As far as growing or shrinking, I can't tell you, but 440 always looks likes crap when it comes back from heat treat, if its in a vacuum its probably not so bad, but you need to take it up to somewhere around 2000 degrees to achieve full hardness, with a one thou tolerance on the ID, my guess is you would be OK, grind the OD, but don't send the parts to some half ass heat treat where it will come back loaded with scale. If this part needs a passivation, make sure that all the scale is removed first, we lost 4 thou on an OD from passivation after heat treat, it wasn't pretty.

[miljnor]

did you guys look at the post date???

Im thinking your a little late.

[DareBee]

Late or not.
The easiest would be to hone the ID (after hard of course), I like Sunnen's honing machines; then fit it onto a tapered mandrel and OD grind the rest.

[Garage Shop]

You guys are ALLLLL WET!

your talking about a .125 hole... .9 deep. Have you actually cut this material? Im thinking you have not.

440c wont be a problem when heat treating. I cut it all the time. And any part smaller than 1" I make COMPLETE, then send out to heat treat.

When the part comes back all I have to do is beadblast to make it look pretty.

Just like a bunch of engineers over-engineering a job and losing money. LOL

Your talking about a very small part. Im sure when its in the oven the part changes dramaticaly. But when it cools its just how you sent it. Unless its a big prt... Then the theory changes.