Two piece poppet valves

[jcge]

I put together this order of operations for making two piece soldered poppet valves. Hope it proves useful to others.
Regards
John

[steamer]

Thank you John!

Dave

[CI]

Thanks for the info.
Would that be a press-fit ?

.

[jcge]

No need for a press fit. A successful solder joint relies on clearance and capillary action.
A small chamfer on the narrowed stem where it joins the head leaves a nice ring of solder which marks the transition point from stem to fillet.

[paul gough]

Thanks John, for those of us to whom ‘order of operations’ does not come naturally, this is helpful.

Regards, Paul Gough.

[Vixen]

I put together this order of operations for making two piece soldered poppet valves. Hope it proves useful to others.
Regards
John

Hello John,
Thank you for posting that. As you probably know, I am about to embark on the production of 64 + valves for the two Mercedes engines; so your order of operations is very timely. Your order of operations lends itself to a mass production or a batch production run as it minimises the 'time' involved by your careful forethought. I particularly like the way you have added the centre points to each end of the embryo valve stem, that will provide some much needed support during the machining of the valve head.

Two questions?? What steel did you use? and do you have a link to your valve production run.

We are indebted to you. Thanks again.

Mike

[uuu]

I have some valves to make, too.  And I shall try this order of operations.

I like the idea of having the stem sticking out of both sides during the soldering.  I've found the lower heat conduction of stainless steel (which is what I shall use for the stems) makes it a challenge to get the heat all the the way through the joint.  The head is likely to get hot fairly quickly.  So the extra stub of stainless is bound to help the stem to catch up.

Thank you.

Wilf

[Jasonb]

So what is the advantage of soldering up a two piece valve over making from solid ? I've only done one IC engine that had soldered valves on the drawing and that was likely due to very long stem length and they were also on a large 1/2 scale engine, all others have been turned from stainless bar.

[CI]

One person mentioned to be that you can purchase precision ground round stainless rod, and so that would save a lot of cutting on the lathe, and give a very precise shaft.
This is what I intend to use on the BHM.

I have also seen some insert a stainless shaft into a cast iron head, heat the end of the rod with an oxy-acetylene torch, and peen the shaft to the head.
I will probably use this method too.

.

[crueby]

Over here in the US, I've seen the ground stainless rod at places that cater to the robotics competitions in the schools, like ServoCity and others. Also suppliers for the 3D printers.

[Vixen]

The subject of silver soldered two piece poppet valve is currently being discussed in two separate places; both in this and in the Mercedes Benz W165 topic. You may need to refer to both topics to get the full picture.

Mike

[petertha]

I made a few comments on Mikes Mercedes thread, most of which I'm sure he already knew. But I think neglected some heat & strength conjectures so maybe this is a good place to carry on FWIW.

I ended up making my radial engine valves from solid 303-SS rod in the usual manner. I did not enjoy lapping the stems as part count increases. But I also made a test valve by silver soldering a pin to a disc of 303-SS & managed to machine the tulip & valve face. But the pin was very hard steel, I suspect like a roller bearing pin with some chromium. It was a relatively short length, held in the collet with just enough stick-out to get the machining done. My thinking was even if the blob was not not quite aligned from brazing, it didn't really matter because it was going to be concentric to the stem rod. Where I had problems was naively assuming I could flip it & machine to length & make the 0.6 or 0.8mm? width retaining ring groove. HSS would not touch it & beyond my Nickole carbide. A Dremel or Foredom hand tool type grinder arrangement might do this just fine. So I guess I'm saying if its the real hard stuff, this might be an issue. But could easily be tested beforehand.

Now onto the hardening aspect with another story. My cam plate was made from A2 (air hardening) tool steel & cam followers from 3mm diameter O1 (oil hardening) tool steel. I met a local fellow who was had a niche hardening side business for the knife & blade crowd, complete with proper HT ovens, salt bath, testing gear, you name it. He 'air' quenched my A2 cam between finished aluminum plates to mitigate warpage which is how many similar air steel blades are done. I had already domed my cam followers from 3mm O1 & hardened them myself, torch method. I asked if he could test some because my preference was they be a few points softer than the cam plate. Easy to make more followers, more effort to re-make cam plates if they got scoured. The results were mixed. Like a 5-7+ point hardness variation but at least all softer than the 'controlled' HT of cam plate. I noticed some slight color variations of brown while tempering which I chocked up to my rudimentary kitchen type toaster oven. I confessed my method to him: heat the part to 'red heat' about 4" off the surface of quench oil jar & drop it in. He said he wasn't surprised by that because the mass is so small, its already cooling in the short glide path down. Depends on starting temp, how it enters & rolls the oil bath, temp of oil bath, maybe flame type/duration affecting carbon... If it doesn't go through the proper quench reduction temp/time, it will be semi hard & some variation. Maybe it was my un-trained eye for carrot red. There was no easy way to get a magnet on it & I didn't want to get the torch too close to the oil. Anyway, blah-blah. Raising the temp of a skinny O1 rod by silver brazing might be hot enough, but letting it stand in air is not like the sudden reduction of quench oil. But O1 is (0.9-1.0%) carbon, A2 is (0.95-1.05), remarkably similar. That has always been a mystery to me. I guess the only way for sure is to try or just avoid tool steel altogether?

Back to brazing a 'hard' rod. My valve diameter is 9.5mm relative to 3mm stem. Where things get interesting is the radius or tulip shape. That was done with a 6mm diameter carbide radius tool. Its coming back to me now that I managed to bend a regular steel rod with a bit over-zealous feed & of course increased tool edge contact area. That's why I went to the hardened dowel. But I also learned my lesson & reduced DOC considerably so probably both helped. So just speculating that a relatively 'big' valve diameter relative to skinny stem might magnify these same issues. This would be no problem on a CNC but I have manual lathe. And if the FS valve has any undercut features like this sketch, then its the same cutting hard stuff challenge, so might have to be simplified with a flush fillet?

Well, I look forward to seeing how these different valve fabrication methods get on. My SS valves have taken on a tan brown color after rather limited running. Not sure if that's fuel induced but I know its pretty darn hot in there.

[Dave Otto]

I have done two piece valves, both in full size and model size. These are not silver soldered but peened in place after pressing the head on. Cast iron head on a steel stem, which is typical of how many of the early engine valves were made. Probably not a good choice for a high speed racing engines though.

Dave

[Kim]

Just to touch back on the issue of hardening 303 when you silver solder:

303 stainless doesn't respond to the standard heat-treating methods, so I don't think silver soldering should cause SS to be hardened.

Here's a quote from the Speedy Metals site:

HEAT TREATING
303 is not hardenable by heat treatment. Cold working increases tensile strength and hardness. Annealing range is between 1850° and 2050°F. Cool rapidly. Water should be used for heavier sections; air for lighter sections. The stress relieving range is between 400° and 750°F.

Kim

[crueby]

Just to touch back on the issue of hardening 303 when you silver solder:

303 stainless doesn't respond to the standard heat-treating methods, so I don't think silver soldering should cause SS to be hardened.

Here's a quote from the Speedy Metals site:

HEAT TREATING
303 is not hardenable by heat treatment. Cold working increases tensile strength and hardness. Annealing range is between 1850° and 2050°F. Cool rapidly. Water should be used for heavier sections; air for lighter sections. The stress relieving range is between 400° and 750°F.

Kim

Correct. I've  silver soldered lots of 303, never any hardening issues, I  do let it air cool just because it's  simpler.

[steamer]

300 series stainless steel is Austenitic Stainless steel, and does not harden by quenching.   The only way to harden it is to work harden it.    Red heat will anneal it.   303L machines nice as it's got more carbon in it    304 and 316 are miserable to machine, but are more corrosion resistant.

400 series is a martensitic steel that will respond well to heat treating....Made some great Ultra precision machine spindles from 440C...

I like the 2 piece idea here.....getting small diameters really consistent is no small task!, but centerless ground pins are everywhere.

Dave
 

[CI]

I am told that using a material like Class 40 gray iron for the valve head and a corrosion-resistant ground stainless for the rod gives the best of both worlds, ie: strength and corrosion resistance where it was needed, and an excellent wear and impact resistant material at the seat.

I don't have experience with making valves yet, but it won't be long, and I will be trying the two piece method.

I have seen a video of someone using a stainless rod, and a cast iron head, and they heat the top of the rod with an oxy-acet torch, and then peen the top of the rod. (can't find the video now).
It is a quick process, and does not significantly heat the head or the lower end of the rod.
I don't think you would want to try and siver solder a cast iron head to a steel rod, since cast iron is prone to cracking unless preheated and then cooled very slowly.

.

[Dave Otto]

I have seen a video of someone using a stainless rod, and a cast iron head, and they heat the top of the rod with an oxy-acet torch, and then peen the top of the rod. (can't find the video now).
It is a quick process, and does not significantly heat the head or the lower end of the rod.
I don't think you would want to try and siver solder a cast iron head to a steel rod, since cast iron is prone to cracking unless preheated and then cooled very slowly.

Did you not see the photos that I posted above? Not necessarily SS stems but the process is the same.

Dave

[CI]

I did indeed miss that.
Thanks for the pointer.
 

[stevenz]

New to the forum and noticed a question about the fit or clearance for soldering as well as the response that clearance is required. I recalled that Harris published some info on clearances and their alloy catalog includes clearance recommendations for their various products. No idea if there are well understood clearances but this might be a place to start.

[CI]

My understanding is that less is more when it comes to silver solder clearances, ie: a thin silver solder joint is much stronger than a thicker one.
And of course if the fit is too tight, there is no place for the silver solder to flow, so it just sits on top outside the joint.
I have done some silver soldering, and it is a viable high-strength method to connect metal, but boy does it require a lot of heat.

.

[petertha]

I found this to be a useful guide for stainless, well, the more common N-Am designations

https://nickelinstitute.org/media/1814/stainlesssteelsformachining_9011_.pdf