Author Topic: Need some good advice on valves  (Read 1162 times)

Offline petertha

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Re: Need some good advice on valves
« Reply #15 on: March 01, 2020, 11:48:09 PM »
Another thing on this topic of valve seal. Once I had some tester valves to act as my standard, I could safely assume the cages were sealing properly. But I was getting inconsistent results on the valves, so I knew there was room for improvement there. No matter how the 45-deg valve face was made on the lathe, I could spot 'record player' tool marks under magnification. The surface looks shiny & true to the naked eye but these undulations are enough to cause seal issues.

So my method was quite simple. For finishing I decided to get the got the valve off the lathe and into a cordless power tool (like a Dremel) on low speed. Blue the face & basically take it down with a series of fine abrasive paper. Despite what looks like sketchy hand work, it's actually a very controlled process. You can see the gradual emergence of machining marks, then flattening to a constant metal surface with no blue remaining, then finish with polish rubbers so you can see a reflection. On the same valve cage I watched the vacuum times increase from horrible 3-5 seconds to 30+secs, and which point I call it good.

Offline petertha

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Re: Need some good advice on valves
« Reply #16 on: March 01, 2020, 11:55:27 PM »
Please tell me more about the tool from Brunell. I would like to see a catalogue showing it and order one.---Brian

This one Brian.
https://www.brownells.com/gunsmith-tools-supplies/barrel-tools/barrel-chamfering-cutters/45-chamfer-cutters-prod41716.aspx

Offline petertha

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Re: Need some good advice on valves
« Reply #17 on: March 02, 2020, 12:08:52 AM »
I'd like to know more details about how you guys made cutters (the Brownells is good, but spendy).

Should I be using A (air) hardening tool steel to minimize quench distortion of oil? Did you make them with common lathe/mill or did you have access to an indexing tool & cutter grinder to dress the facets? I could see some of my lips were cutting & others were dry. When there is so little material to remove, I feel that the teeth need to be precise. Maybe above my pay grade at the time.

Did you leave them fully hardened or quench them? This tool is used for such a fine, finicky operation by hand as opposed to machine, maybe it doesn't warrant quenching for toughness? Now it could be my hand dressing of final edge was more the culprit. I've also read about certain cutters that have non-symmetrical teeth spacing to mitigate what can develop into a crowning effect. (You can create this with the Brownell tool too if you press too hard, the trick is very light touch). A non-symmetrical tooth stagger would be easy enough in home shop environment.

Offline Dave Otto

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Re: Need some good advice on valves
« Reply #18 on: March 02, 2020, 01:17:05 AM »
I made a piloted cutter for the exhaust valve on my Pacific Vapor Engine.
Starting on post 157, http://www.modelenginemaker.com/index.php/topic,1326.150.html

I don't remember if I left it full hard of drew it back a little but it worked very nice.

Dave

Offline petertha

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Re: Need some good advice on valves
« Reply #19 on: March 02, 2020, 03:10:28 AM »
That looks very nice Dave. So using your example, I assume you machine the teeth & basic back relief angles, harden, then only dress the very edge with a stone? I thought my stoning was pretty consistent, I just crept up on the edges & it was progress was visible because the metal was silver against the darker quenched color. But it didn't cut like it was very consistent.

Offline jonesie

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Re: Need some good advice on valves
« Reply #20 on: March 02, 2020, 12:56:44 PM »
i have made cutters for doing the sets from  a drill but i did them in a spin fixture on a surface grinder,and i always have a pilot on the end to just fit into the hole to keep it nice and straight other wise  to cutter could tip a small amount..just the way i do it

Offline Dave Otto

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Re: Need some good advice on valves
« Reply #21 on: March 03, 2020, 01:09:51 AM »
That looks very nice Dave. So using your example, I assume you machine the teeth & basic back relief angles, harden, then only dress the very edge with a stone? I thought my stoning was pretty consistent, I just crept up on the edges & it was progress was visible because the metal was silver against the darker quenched color. But it didn't cut like it was very consistent.

Yes that is pretty much what I did, I did the back relief by hand with a small file leaving a very small land before heat treating. Then carefully stoned the cutting edges after heat treat.
I it is not pretty under the microscope but it did work ok.

Dave

Offline michelko

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Re: Need some good advice on valves
« Reply #22 on: March 03, 2020, 12:02:50 PM »
Have no experiences with making cutters my own but my valveseat cutter work nice without the relief.
Judt turned the 90 Degree angle on the lathe and then milled the flutes.
Then hardene and annealed.
I believe it is sufficient for this Task because it dont cut to aggressive.
I am just happy with the result

Regards Michael