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Webster I.C. Project.

Started working on making some valves yesterday. I made 3. Each one had major flaws. Trying to use stainless something, most of the metal I have is a mystery. I will keep trying. That’s what this project is for. So I can learn how to be more accurate.
 
I used 303 for my valves which machined pretty well. This past week I tried a new 'stainless' DCMT insert from Ali that was very good on my 304 that usually causes grief. It was really quite amazing, 0.0005" DOC passes & it just peeled it off, nice finish & no work hardening. I think this pic was a 0.002 - 0.003" DOC pass just messing around.

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Anyway back to valves. Mine start ~ post #128

Ohrndorf 5 Cylinder Radial

The heads at this stage were cleaned & the valve cages installed using Loctite 680 HT retainer. Permanent installation is required at this point because the next step is to cross drill the port passages through the aluminum head & into the bronze cage. As you can see, the valve seats are cut. I...
www.homemodelenginemachinist.com www.homemodelenginemachinist.com
 
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Hi Peter. I ran in to those exact issues. Cutting nice then it hardened each time. I have tried a couple different cutting fluids as well. One even grabbed and bent. I will try another set of inserts I have. Maybe I will switch to some of my HSS bits that I have. I don't have a very big amount of cutting bits. But I do have some options. I might switch to cutting some of the aluminum and steel pieces. I wanted to start with the valves as I think they require the highest level of precision.
 
What I would recommend is get a handle on the hole that the valve stem will be sliding in. Very likely drill & ream job because you want the size & finish. Lets say that's 0.1250". That will become your reference to make the valve stem, meaning both OD & finish. You can probably get away with sanding sticks to work it down the last say 0.002-0.003" as long as lathe turning is good. Lapping is better but another kind of rabbit hole. Anyway just saying hole first, valve second. If you reverse it, not only are you chasing reamer size ($$) but your own batch of valves may vary enough that they don't fit as well. Also make spares while you are in the groove. They may be otherwise perfect except when you get to seat seal & then you wish you had another.

You may want to make that cheapo vacuum tester I copied from another fellow. Then valve seal becomes a very precise yes/no/maybe diagnostic before the engine is ran.
 
Thanks Peter. My logic was not correct. I was looking at valve first then seat and guide. I have a 3mm reamer so that’s what I’m aiming for. I’ll see if I can get the seats and guide made.
 
It has been a bit since my last update. I’ve been busy working on some other parts of the building. I kind of gave up on the valves. Broke my Amazon reamer in my one seat. I seem to be learning by breaking on this project. I might have to admit it and buy some decent tooling.
 
Do you mean a tapered reamer to cut the valve seat itself or reaming the main hole for the valve stem? What kind of material are we talking?
 
Reaming the the valve stem hole. I think I did not have the speed right. I should have maybe pecked it better or added more oil.
 
The usual reaming recommendation is reduced speed & increased feed based on a similar size hole drilling. You want the pilot hole to be undersized enough so the flutes are cutting but not so small that the reamer is struggling or chips are packing. Different materials ream differently so just takes some familiarity. It helps if your hole entry is a bit chamfered (usually just a leftover of spot drill preceding the hole). And if you have any doubt about your tailstock not being centered to the lathe axis, now is the time to correct it. Brass & bronze can be interesting because they can be grabby materials. If you have an inferior drill or didn't spot, that makes the hole not-so-good & just causes more problems for the reamer following the hole. Good luck!
 
PeterT said:
The usual reaming recommendation is reduced speed & increased feed based on a similar size hole drilling. You want the pilot hole to be undersized enough so the flutes are cutting but not so small that the reamer is struggling or chips are packing. Different materials ream differently so just takes some familiarity. It helps if your hole entry is a bit chamfered (usually just a leftover of spot drill preceding the hole). And if you have any doubt about your tailstock not being centered to the lathe axis, now is the time to correct it. Brass & bronze can be interesting because they can be grabby materials. If you have an inferior drill or didn't spot, that makes the hole not-so-good & just causes more problems for the reamer following the hole. Good luck!
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I will have a better look at it. I may have had a to small of a hole. It cut ok and then snapped off. I'm just using the drills I have on hand and the reamers are from amazon. Nothing matching just eye balling them. I will do some more diligence. I'm trying to bore the seat first then make the valve to fit. I have actually made about 12 valves at this time. I think 1 is good, 2 decent the rest bent, broke or gouged. I will have a look at making sure the tail stock is dead on. I think I'm learning, which is what the project is about.
 
I made 18+ good valves for my radial project, 0.093" diameter stem. (and about as many bad ones). I struggled to get a good finish on them. The tips that helped me get a good surface finish:
1. use a very sharp tool (positive rake) with a small nose radius - I used a DCGT carbide insert intended for aluminum but a ground HSS is just as good or better.
2. up the speed probably as fast as your lathe will spin for ~3mm diameter stem. I used 2300 rpm for mine as that was the max speed it would go without screaming.
3. I followed up with a bit of scotch brite pad to polish the last little bit.
As Peter says, make the hole first and then make the valve stem to fit, I did the other way round and ended up with a few too loose valves and a few too tight, so I just had to go make more valves rather than remake the valve guides.
I also changed my material - stainless isn't needed on an engine like this so I switched to 1144 "stress proof" as it machines very nicely (and I had used up all my 303 SS)
Below shows the improvements the changes helped achieve.

Good luck and keep going.
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