Piston Pin matterial

[borna]

Hello all,
I got this Chinese multi-cylinder engine, and during the assembly, I noticed that I am missing one piston pin. This is a picture of one set of piston, pin, and connecting rod. Since I decided not to wait for them to send me a piston pin, I’m planning to make my own. That said, the piston is aluminum, and the connecting rod is most likely brass or bronze. So, my question is: What material is best for making the piston pin? Can I use HSS? Should it be hardened or not? If HSS is not a good metal for it, please let me know what to use?

Thanks

 

[kuhncw]

You could use either a piece cut from a drill blank (HSS) or you could use drill rod or silver steel depending on what it is called in your area. Either water or oil hardening are ok and no need to harden the drill rod in this application.

Please let us know how this turns out and post a picture of your engine.

Regards.

Chuck

 

[borna]

You could use either a piece cut from a drill blank (HSS) or you could use drill rod or silver steel depending on what it is called in your area. Either water or oil hardening are ok and no need to harden the drill rod in this application.

Please let us know how this turns out and post a picture of your engine.

Regards.

Chuck

Thanks for the info. Since the diameter of the pin is 4mm exactly, this should work?
https://www.amazon.com/dp/B07SYYDTVZ/ref=ox_ya_os_product?th=1

 

[kuhncw]

That should work. A drill blank would cost less.

Chuck

 

[abby]

Quick question , why would you not harden the piston pin made from drill rod?

 

[kuhncw]

It is ok to harden the piston pin and necessary in full scale engines. Loads are light in our model engines and the engines usually don't run hundreds of hours. Again, either method is ok. Builder's choice.

Chuck

 

[rleete]

Even plain CRS is harder than the rod, so hardening would not be necessary.

 

[petertha]

Hardened dowel type pin should be fine, just check the tolerances. Some are +/- either side of nominal dimension depending on the application, some are plus & some are minus. Presumably the ends are 'plain' meaning no end features like a hole for softer scuff pads? If so, then if the stock has to be machined, hardened would present a few more challenges.

 

[Steamchick]

Even regular Mild steel is adequate for this application. Steel and Bronze are similar densities so balance should not be a significant problem.
BUT if you can get some hard brass or bronze that should be exactly the same mass as the Chinese pin.
However, (1) why not ask the supplier for a piston pin? (2) If that fails, "shout" at the supplier, saying you will give them a bad report on the web unless they finish the contract of delivering ALL the parts? - I have only had to do that once, but bad reports on the internet can really upset the Orientals, so they are quick to resolve issues in that case.
On models, some people are not concerned if the model shakes a bit. But this engine should be relatively smooth, and may be spoiled by using a steel pin instead of a Bronze pin. - You can only try that and see?
K2

 

[stevehuckss396]

I agree with Chuck. Hardened drill blanks work great.

 

[abby]

The original question was " can I use HSS , should it be hardened or not ?"
Answers then went on to refer to drill rod and drill blanks.
For us in the UK, what are drill rods and what are drill blanks ?
From past experience I believe that US drill rod is what in the UK we call silver steel , a carbon steel which can be easily hardened and tempered to whatever requirement.
However drill blank ? I presume this to mean use the shank (chuck end) of a HSS drill , as I am sure we all know , the shank of HSS twist drills and end mills are not hardened , infact larger sizes often have welded steel shanks.
So , having worked in the Clarkson International factory , I ask how do you harden HSS ?
Although I did not work in the hardening shop I know it was a complicated process involving molten salts of sodium cyanide and Barium at very high temperatures and probably not the sort of thing to do at home.
Dan.

 

[Richard Hed]

The original question was " can I use HSS , should it be hardened or not ?"
Answers then went on to refer to drill rod and drill blanks.
For us in the UK, what are drill rods and what are drill blanks ?
From past experience I believe that US drill rod is what in the UK we call silver steel , a carbon steel which can be easily hardened and tempered to whatever requirement.
However drill blank ? I presume this to mean use the shank (chuck end) of a HSS drill , as I am sure we all know , the shank of HSS twist drills and end mills are not hardened , infact larger sizes often have welded steel shanks.
So , having worked in the Clarkson International factory , I ask how do you harden HSS ?
Although I did not work in the hardening shop I know it was a complicated process involving molten salts of sodium cyanide and Barium at very high temperatures and probably not the sort of thing to do at home.
Dan.

You can buy silver steel (drill rod--You Brits really need to learn English!) that has not been made into drills--it is "blank" thus drill blanks. I use it for different things. You should be able to get it cheaply.

Me thimpfks it would be a mistake to use HSS for your purpose.

 

[Jasonb]

As Said silver steel is drill rod a carbon steel that is accurate on size and what I use

A bit of 4mm mild steel is likely to come in undersize so not good for this application unless you like a knocking engine though you could turn down a larger diameter

Drill blanks are just lengths of HSS rod much like buying a round HSS toolbit. Fully hardened and ground all over Also they ar eonsize whereas the shank of a drill bit is often a little undersize.

https://www.cromwell.co.uk/shop/cut...ss-hardened-groun-d-drill-blank/p/SHR0242424J

 

[Bentwings]

Even plain CRS is harder than the rod, so hardening would not be necessary.

Have to disagree . Top fuel wrist bins are super hard. They have even gotten thicker over the years. Unless you run a lot of nitro model engines don’t need to go much beyond dowel pins unless you have something a standard dowel pin won’t fit. If you run a bejillion rpm standard dowel pins work fine rods pistons and crank will fail first.

 

[Steamchick]

Agree. Piston pins are often a very high quality steel, but in "everyday" cars can be cheap steel, precision ground and surface hardened.
While I audited piston and ring manufacturing, piston pins (gudgeon pins in PROPER English) were not audited by me. They were weighed individually to within 1mg, as we're all piston sub components, and the set of parts coded for weigh and fits, and graded for matching balance and fit to each bore, small con-rod end, and Piston to pin. As were crank journals bearing shells and housings. Assembly to graded parts was only possible with very high production volumes, but permitted clearances to be maintained to tolerances that were a fraction of the machining capability.
Piston pins were forged, then ground and induction hardened. Not a parallel bore but tapering in to the middle. Not seen on models?
K2