Heat Treating O1 - Post Heat Treat Dimensional Changes

JC in SC

JC in SC

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Feb 28, 2009
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I'm going to be using some precision ground O1 bar stock to make some knife making related tools such as a file guide and a bushing lap. Assuming the parts are machined to size prior to heat treat, how much dimensional change I should expect on the parts following heat treat. I know that we see changes on the order of a few thousandths on many of the heat treated parts we use at work. Sometimes those changes aren't consistent batch-to-batch. Those parts aren't O1 though, so I'm looking for a little guidance. Should I drill and ream holes to size prior to heat treat and expect to lap to finished size afterwards? Or should the parts retain preheat treat dimensions following heat treat?
 
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You must drill and ream all holes prior to HT, its too tough to get a good hole after HT. I have not noticed any significant dimension change in O1, but I am not measuring to 0.001.
 
In rereading my original post, I realize that it isn't perfectly clear what I'm asking. To rephrase my question, if I machine, drill and ream the parts to size prior to heat treat, how much change can I expect after heat treat? I think I have good numbers on what size the dowel pin holes (for the file guide) need to be for both the press fit side (0.1557/0.1562) and the tight slip fit side (can't remember this off the top of my head, but will edit to add tomorrow). I'm just curious how much change I should anticipate, if any, following heat treat.

Another thought I had was to maybe fill these holes (and the threaded holes) with some sort of clay (similar to that used to differentially harden a blade) such that the holes themselves wouldn't be hardened and maybe retain the original dimensions.
 
Check the data sheets from a steel manufacturer. That type of info is listed on the specific steel data sheets. Places like Admiral and other online steel suppliers may have it too. Crucible's web page is full of info on nearly any steel they make.
 
O-1 was designed to be dimensionally stable and to move around a lot. You shouldn't have any problems as long as you follow the manufacturers specs on heat treat. Do not fill the holes with aything, you may cause the very problem you are trying to avoid.
Thanks,
Del
 
Why not just make a few samples after taking precise measurements first and then finding if any dimensional changes have taken place?
 
me2 said:
Check the data sheets from a steel manufacturer. That type of info is listed on the specific steel data sheets. Places like Admiral and other online steel suppliers may have it too. Crucible's web page is full of info on nearly any steel they make.
Click to expand...

Good point. I bought it through McMaster-Carr, so I checked their website for this information. Nothing is available that I can find. I'll see what other sources have.

delbert ealy said:
O-1 was designed to be dimensionally stable and to move around a lot. You shouldn't have any problems as long as you follow the manufacturers specs on heat treat. Do not fill the holes with aything, you may cause the very problem you are trying to avoid.
Thanks,
Del
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That is good news and makes sense. Logically, you'd want dies, punches, etc. made from tool steel to be dimensionally stable. The packaging has heat treat information including temperature and temper times and temperatures, but no specific time for heat treat. McMaster-Carr has more detailed information on their site though.

Karl B. Andersen said:
Why not just make a few samples after taking precise measurements first and then finding if any dimensional changes have taken place?
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To be honest, I'm not sure how precisely I can measure a bore this small. We have laser measurement instruments for very precisely checking ODs, but I'm not sure what our capabilities are for IDs. For the time being, this is the plan I'll go with, hoping that Del is right and I have nothing to worry about.

Thanks for the responses.
 
The O-1 I got from McMaster-Carr is Starrett. Their(starrett) website has technical specs for O-1
 
Are we talking reamed holes, tapped holes.... slip fit, press fit... what tolerances are you working with? Is it an OA dimension concern (dovetail, keyways...) If it is simple drilled and c'bored mounting holes or taps, you will be fine. PF/SF/LSF dowels might be an issue, but I doubt it. As long as you aren't overheating, you'll be fine. I worked with O1, 4140, A2, D2, P20.... for 14yrs in T&D and never came across a problem with dimensional distortion aside from warpage.



Rick
 
Steinerj said:
The O-1 I got from McMaster-Carr is Starrett. Their(starrett) website has technical specs for O-1
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Until you mentioned this, I hadn't even paid any attention. A quick check of my steel reveals that mine is as well. Per teh Starrett website: "Stock is dimensionally stable – use it for the most intricate work" and "The Starrett Company uses its own ground flat stock and die stock for many of its fine precision tool parts". Looks like I should be good to go:thumbup: I'll do my best to post an update once I've got the parts finished up.
 
Magnussen said:
Are we talking reamed holes, tapped holes.... slip fit, press fit... what tolerances are you working with? Is it an OA dimension concern (dovetail, keyways...) If it is simple drilled and c'bored mounting holes or taps, you will be fine. PF/SF/LSF dowels might be an issue, but I doubt it. As long as you aren't overheating, you'll be fine. I worked with O1, 4140, A2, D2, P20.... for 14yrs in T&D and never came across a problem with dimensional distortion aside from warpage.



Rick
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Hey Rick,

I'm talking two reamed holes, two drilled holes and two tapped holes.

Thanks,
JC
 
Making one of these?

fb4084a6c5ecf63aba8ec2964e137bd5.image.750x514.jpg
 
Exactly. If they aren't too problematic, I hope to make extras to sell.
 
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Well, I wasn't able to precisely measure the preheat treat dimensions on the holes; however, I was able to confirm that the pins were a silky smooth slip-fit in the intended slip-fit holes and couldn't be inserted, by hand, into the others. I think the preheat treat dimensions were spot on.

Moving on to the heat treat, I might have screwed up:( I won't know if or how bad until tomorrow, but here is what happened. I borrowed a hot plate to heat my quench oil from another department at work. I was excited because it had temperatures labeled on the dial, so I wouldn't have to deal with getting a TC and all that. I set it at about 130 degrees and put my O1 into the furnace to heat up. I let it ramp up to 1450F at which point I started timing the 15 minute soak, though my set point was 1475F. When I pulled the O1 out of the furnace and put into the quench, I noticed that it didn't smoke as badly as I expected. I happened to check the dial and noticed that it is in degrees C instead of F. That is right, instead of having my quench oil preheated to ~130F, it was preheated to ~130C:eek: The dial isn't very precise, so this could actually have been has high as 280F! My department typically deals in F, so I didn't even think to check the scale on this one. In hindsight, I should have known, because the other department typically deals in C:o

I was planning to draw these back to around 61 Rc, but now I'm not even sure if the pieces will be that hard to begin with. I'll find out for sure tomorrow, but tonight the suspense is killing me. Any thoughts on whether or not I screwed up and if so, how bad?
 
Hmmm...well, I don't know about the overheated oil.... How much oil did you heat up and what kind of oil? It can take a little while for a couple of gallons of oil to heat up, so are you sure it was up to that temp? As for the lack of smoke, flash point is flash point, so warmer oil shouldn't necessarily smoke any less than cold oil. I'd tend to think that you would be fine, but test the hardness if you're able for sure. Heck, if they're meant to be file guides, put em together and clamp the to some scrap and file away. See if they work as intended :)

Oh, and here's a data sheet I have hosted on my site for O1 with the info you were looking for initially:

http://www.burgessknives.com/media/O-1.pdf

It should be around 0.06% or 0.07% change with oil hardening on average.

Check out my resources page for a collection of data sheets I've found for various steels.

Let us know how that guide turns out!

--nathan
 
I don't think you screwed anything up, JC. The quenchant's main goal is to get the steel from 1475F to 900 in less than a second. I would be more worried if your temperature was too low. On the other hand, you could have had one hell of a flash fire kick up. Now, did you remove the pieces from the tank to let them air cool? they need to get down to 130 or so within about 15mins. Don't temper them before they drop to that point. (Basically, if you can hold them in your hand without doing a dance, they are ready to temper.)

I think it will work out fine. How big was the tank and how much quenchant was in it?

****Edit to add****

See Nathan's post for what I meant to say..... lol.


Rick
 
My quench tank is a small (~4" x 7" x 4" deep) deep drawn aluminum enclosure from the scrap bin here at work. It probably had a quart maybe a quart and a half of generic quench oil in it.

I did remove the pieces from the quench oil after a few minutes and put them on top of a 1" thick copper plate to continue cooling. We do have several hardness testers, so I plan to do that some time this morning:thumbup:
 
The Good News: Per our Rc tester, it is between 60.x and 62.x depending where it is tested. I took four samples on the file guide faces and since these are of equivalent hardness to where I originally planned to temper, I think I'm good to go as-is. I don't think this is overly critical as I plan to bond some solid Carbide strips to the surface anyway:eek:

The Not-so-Good News: My silky smooth slip fits are still nice and smooth, though they seem to be perhaps just a slight bit looser than they were prior to HT. The press fits seem to have shifted a little as well, at least one of them anyway. One of these is not a slip fit and the other will still be a press fit, but perhaps not as tight as it should be. I'm planning to put some sort of Loctite in and call it good:thumbup: I'll try to get some pics up this afternoon:cool:
 
Carbide!!! You could have used aluminium for the blocks! No need to heat treat at all.

60-62HRC will still get eaten by new files so if you don't use carbide, file easy, brutha.


Rick
 
Well, the plan was to have one side for files and the other side (Carbide) for belts. I was concerned that the carbide might be hard on the edges of files, but don't really have any factual basis for that concern.

I'm a little surprised to hear that 60-62 Rc isn't sufficient for files though. The ones that I've seen available elsewhere are advertised as 61 Rc.

I made a "magnum" sized guide to cover all my perceived needs. Using it during lunch on a slip joint blade, I can tell that it is overkill for that. In fact, it is sort of clumsy for that size blade, so I'll eventually make one more appropriately sized for <1" blades.
 
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