Rod bolt material

[Basil]

I'm at the point where I need to make rod bolts for the Seal Major I'm building. I could go with BS1407. Make the bolts and heat treat or make them out of stainless which of course is softer but quite tough. The valves on this engine are stainless and threaded. It appears the stainless would make a good looking bolt but I am concerned about the strength. Which would you guys recommend? Thanks

 

[Nerd1000]

Austenitic stainless is no better than mild steel for yield strength. I'd go for commercial high tensile bolts, the rolled thread will be stronger than a cut one and it will save you a lot of time.

 

[GailInNM]

All of the 1940'S ETW engine designs that I am familiar with had fasteners that were far stronger than necessary. As ETW assisted David Braid with the 1950 design of the Seal Major I would suspect that the same is true with the Seal Major.
I would not hesitate to use any flavor of steel that you desire for making the bolts.

 

[Jasonb]

Why worry about the looks of the bolts as they will be lost inside the engine, A lot of people just get good quality cap heads but if you want to make them something like EN24T will give a belt and braces job.

 

[Basil]

Thanks for the advice. I could go with standard bolts although they are 5BA which seems to have a limited selection of grades. Because I plan on building more high performance engines I want to try my hand at making some good strong bolts. Thinking of doing some testing with a small torque meter I have.
EN24T, I can not find in 1/4" bar. I see 1/4" is available in EN16T, Also listed as used for making bolts. Not clear what the difference is?

 

[Jasonb]

M-machine list it in 1/4"
http://preview.m-machine.co.uk/CATALOGUES/metals catalogue.pdf

 

[Charles Lamont]

M3 cap heads would be fine, but if you want to make your own high tensile bolts, an easy source of stock material is high tensile bolts.

 

[mrehmus]

I've seen mild screws break in conrod service if you like to rev the engine. The best screws to use are Unbreakos. Unbrako USA

 

[roncohudd]

I'm at the point where I need to make rod bolts for the Seal Major I'm building. I could go with BS1407. Make the bolts and heat treat or make them out of stainless which of course is softer but quite tough. The valves on this engine are stainless and threaded. It appears the stainless would make a good looking bolt but I am concerned about the strength. Which would you guys recommend? Thanks

What stainless are you using. 316 is pretty hard, 17-4 is heat treatable to about C-55.

 

[Rocket Man]

4150 heat treated to 55 Rockwell C is very strong & tough. We had a machine at work that kept breaking 1" bolts I had to experiment with different things until I learned what worked. Above 55 metal starts getting too brittle & below 55 metal looses it toughness. This was a pulling machine designed to pull 30 tons for about 10 seconds over & over 3 shifts 5 days a week.

 

[Peter Murphy]

I'm at the point where I need to make rod bolts for the Seal Major I'm building. I could go with BS1407. Make the bolts and heat treat or make them out of stainless which of course is softer but quite tough. The valves on this engine are stainless and threaded. It appears the stainless would make a good looking bolt but I am concerned about the strength. Which would you guys recommend? Thanks

Hi Basil, where abouts are you? I have 1/4" 4140 if that would work, but I am in Melbourne Australia. Cheers Peter from Oz

 

[L98fiero]

What stainless are you using. 316 is pretty hard, 17-4 is heat treatable to about C-55.

17-4 condition H900 is the hardest at about Rc47, just did parts like that.

 

[roncohudd]

17-4 condition H900 is the hardest at about Rc47, just did parts like that.

We used to heat treat it up to 1100 we in I worked with it in the late 90s making sizemograph parts.

 

[roncohudd]

We used to heat treat it up to 1100 we in I worked with it in the late 90s making sizemograph parts.

Probably wasn't extremely hard, but it seemed hard when I was gundrilling it.

 

[L98fiero]

We used to heat treat it up to 1100 we in I worked with it in the late 90s making sizemograph parts.

17-4 H900 is the hardest condition, higher temperatures are less hard, H1100 is only Rc32-38 17-4 PH Bolts

 

[roncohudd]

17-4 H900 is the hardest condition, higher temperatures are less hard, H1100 is only Rc32-38 17-4 PH Bolts

Yes, but it is so long since I worked with it. I can't remember some of it.

 

[Basil]

Thanks for all the advice guys. Thanks for the offer of the 4140 Peter, Unfortunately not close. Dorset UK. Having used EN24T for the crankshaft and noticing how tough it is I have ordered some from M Machine. Thanks for the contact Jason. As someone noted the bolts are quite large for the rod design and I think the rod would part company before the bolt would give up but this is more of an educational exercise. Get these done and then onto the rest of the pistons.

 

[Weldsol]

Hi Basil
Just read your post re conrod bolts I'm building ETW's Sealion and in the write up out of ME he stated 5BA cap heads I could not locate any in 5BA so ended up machining them from 4BA cap heads (see my post on my engine which describes the sequence)

Paul