Material for Small Pins, Heat Treat Concerns

Rick Finsta · Aug 19, 2021

So I have these small pins that go into one of the tools in my product line. They are made from 13/64" drill rod, are about 1.5" long, and have a taper to a 1mm radius end, and the other end has a 2mm radius with a small inverse radius transition to it. I just grabbed A2 from McMaster to prove out the program, and this will be the cheapest to get processed through heat treating (they just need to be above about 40HRc so they don't wear in contact with automotive connecting rod bolts).

Is this going to turn into a banana during heat treating? Would O1, W1, or M2 be a better choice? Maybe I get something like 17-4PH in TG&P?

I am open to ideas. First few are going to heat treat this week so we will see what happens but I want to have a backup plan in place.

TDegenhart · Aug 19, 2021

None of those would be my choice, particularly not W1 or M2. I am not familiar with 17-4.

How are you planning on making the blanks, Swiss or grinding? Closed die header? Does the material need to be through hardened or would carburizing work? How straight is "straight" Can these be made from preharded spring steel, 17-7 or music wire? Volumes? Ductility?

Tom

EmGo · Aug 19, 2021

Rick Finsta said:
So I have these small pins that go into one of the tools in my product line. They are made from 13/64" drill rod, are about 1.5" long ...

Is this going to turn into a banana during heat treating?

Usually, for long skinny stuff you have to quench, you try to drop it in end-on. They still like to bend, often, and have to be straightened.

If possible, this looks like a case for hard turning, to me. Or semi-hard, 40 is not that hard.

If you can't get something you like in 40, how about heat treating a rod first, then machining it ?

dgfoster · Aug 19, 2021

If they bend a “little” with heat treat, does it matter? If these are used as retaining taper pins driven into tapered holes, they will straighten when driven. O1 should deform minimally. I’d buy some O1 and give it a try. Not much to lose and I’d bet it will be ok for the purpose.

Denis

plastikdreams · Aug 19, 2021

17-4 move very little if any during heat treat. A2 supposedly doesn't move much but I don't have any experience with it.

You can also get 17-4 h900 which is already about 45rc, it machines well.

Garwood · Aug 19, 2021

I would try making them from 1018 or 1045 with a very light carburizing. Maybe go wild and use 8620 (can you get it that small?)

Overkill is neat and all, but all the stuff that's actually inside the engine rubbing, sliding, clacking and whizzing around and absolutely none of it is toolsteel or anything close.

The tricky bit with thin crossection parts is keeping the case light enough so you don't lose core strength.

For a product my advice would be to take the money you save on material cost and put it into a fancy cosmetic process that makes it look neat. That's all people care about.

hvnlymachining · Aug 19, 2021

I recently spoke with a heat treat shop owner, he told me D2 was very stable.

jscpm · Aug 19, 2021

Why would you need to harden a non-moving part?

A taper pin should never be performance-critical. It should be wide enough that there is no chance of it shearing no matter what it is made of. Also, normally you want a more ductile steel for a taper pin, because a hardened steel will be more likely to fracture.

You probably can use 4130 just fine. Some people use stainless steel, like 410.

If you actually REALLY need a highly engineered pin, then look into H11. H11 is very tough and shock resistant, and can be hardened to very specific fracture tolerances. Using this material will be much more expensive and complicated than just a plain turning out of 4130, so I would advise going down this path unless you have good reason to do so.

plastikdreams · Aug 19, 2021

The product is some kind of tool for automotive applications, we don't know the application or type of tool so this just may be something that moves or is in contact with something...or whatever.

rogertoolmaker · Aug 19, 2021

Rick Finsta said:
So I have these small pins that go into one of the tools in my product line. They are made from 13/64" drill rod, are about 1.5" long, and have a taper to a 1mm radius end, and the other end has a 2mm radius with a small inverse radius transition to it. I just grabbed A2 from McMaster to prove out the program, and this will be the cheapest to get processed through heat treating (they just need to be above about 40HRc so they don't wear in contact with automotive connecting rod bolts).

Is this going to turn into a banana during heat treating? Would O1, W1, or M2 be a better choice? Maybe I get something like 17-4PH in TG&P?

I am open to ideas. First few are going to heat treat this week so we will see what happens but I want to have a backup plan in place.

Why a tool steel for 40Rc? A hard surface and a soft timbre will do. This can be accomplished with a low carbon steel and carbonized.

Roger

BoxcarPete · Aug 20, 2021

A big question is, "How many?"

A lot of these answers will make sense for a quantity < 100 per year, those people who say that's stupid are suggesting options that make sense at quantities > 1000 per year.

If you want to make a handful, I'd suggest buying a pre-hard something or other and machining it. If you have tons of the things to do, it would be more worthwhile to look into a carburizing process on a milder steel, with all the extra pains taken to get it dialed in to something consistent and stable.

The other consideration is strength. You said you more-or-less grabbed WLA tool steel (for what it's worth I believe A2 is quite stable in heat treat so it's a good choice) for the prototypes. Be careful swapping over to a case hardened steel with lower strength unless you know just how much overkill the tool steel is.

MrWhoopee · Aug 20, 2021

17-4PH H900 is commercially available. Rc40-48 as received.

17-4PH H900 - Penn Stainless

Rick Finsta · Aug 20, 2021

I appreciate all the replies. I meant to post a picture for size and use reference and got a customer call so just hit "post."

Here you can see it just needs to be straight enough to be coaxial with the dial indicator. It would have to really banana to cause issues, I think.

Quantities to start off with are projected at a few hundred a year. I am cutting them to length (plus facing stock) and then sticking them in a collet, machining the first side, M00, manually flip it, then machining the second end. I originally intended to hard turn material, but I do have concerns about the machine being capable (this is on my archaic Takahashi gang lathe).

Why hardened? Partly because "that is the way the old owner did it" but also because I don't want the anvil to distort against the thumb screw over time, and I don't want the radii to wear on rod bolts over time. Making them hard removes the concern.

The heat treater is picking up some to test today. He doesn't expect problems due to the short length. Biggest issue is they will have scale on them afterwards, and I'll have to try tumbling them and maybe polishing as well.

If I can't get pretty parts this way, I will look into the 17-4 prehardened. I don't have the SFM to run CBN but the Sandvik rep got me a few inserts to try out in up to 60HRc at the speeds I can run.

Again, I appreciate all the information.

plastikdreams · Aug 20, 2021

Rick Finsta said:
I appreciate all the replies. I meant to post a picture for size and use reference and got a customer call so just hit "post."

Here you can see it just needs to be straight enough to be coaxial with the dial indicator. It would have to really banana to cause issues, I think.

Quantities to start off with are projected at a few hundred a year. I am cutting them to length (plus facing stock) and then sticking them in a collet, machining the first side, M00, manually flip it, then machining the second end. I originally intended to hard turn material, but I do have concerns about the machine being capable (this is on my archaic Takahashi gang lathe).

Why hardened? Partly because "that is the way the old owner did it" but also because I don't want the anvil to distort against the thumb screw over time, and I don't want the radii to wear on rod bolts over time. Making them hard removes the concern.

The heat treater is picking up some to test today. He doesn't expect problems due to the short length. Biggest issue is they will have scale on them afterwards, and I'll have to try tumbling them and maybe polishing as well.

If I can't get pretty parts this way, I will look into the 17-4 prehardened. I don't have the SFM to run CBN but the Sandvik rep got me a few inserts to try out in up to 60HRc at the speeds I can run.

Again, I appreciate all the information.

You don't need anything special to machine 17-4, hardened it machines like tool steel.

MrWhoopee · Aug 20, 2021

plastikdreams said:
You don't need anything special to machine 17-4, hardened it machines like tool steel.

Maybe a little better.

EmGo · Aug 20, 2021

Rick Finsta said:
... I do have concerns about the machine being capable (this is on my archaic Takahashi gang lathe).

I wouldn't worry about your archaic Takahashi. Ancient machines tend to be beefier, because the old way of machining was to take off as much as possible in few big cuts. (A 10" Cinturn was 20,000 lbs) Newer stuff tends to be lighter and want higher speeds with small cuts, but your Tak is probably happy with hefty and hard.

BoxcarPete · Aug 20, 2021

MrWhoopee said:
Maybe a little better.

Yep, IME it's significantly easier to work than A2. My lathe is a 1968 LeBlond Regal, I ran a 17-4 ph pin about that diameter yesterday at 1100 RPM, bog standard carbide insert, came out just fine.

4GSR · Aug 20, 2021

If it was me, I would make them out of 1018-1215 and have them Nitrided. Just need a very shallow surface harden surface. And if they need to polished tumble them in a tumbler or polish by hand with Scotch Brite wheel. Another process would be to have them ION Nitrided. Both very low distortion after treatment.

EmGo · Aug 20, 2021

I don't know if there's anyone left near you who can do this ? But a centerless could knock these out lickety-split. Maybe your volume is too low tho .. but might be worth looking into ?

beege · Aug 20, 2021

An idea...
We used to make tiny pins at my old company. Stuffed them into pipes with a filler wire to make them snug, then heat treat. Knock them out when done. Pretty straight.

Material for Small Pins, Heat Treat Concerns

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