Rolling tailstock

[Jesse Hancock 1Participant @jessehancock1]

Anyone with experience using these?

[Jesse Hancock 1Participant @jessehancock1]

Hi gang, I bought a revolving/rolling tail-stock hoping to ease the job of producing 3mm valve stems in 304 stainless. That is to stop the part deflecting away from the cutting tool by capturing the rotating tail end.

However I get lots of chatter which since I don't get any chatter using a more conventional live center I blame the rolling tail stock which allows the job to resonate within the bearing tolerances leaving striations. Just like dirt road corrugations. If you get my drift.

I'm now wondering about a composite valves using silver steel rods 1/8th " with a stainless heads welded on.

[JasonBModerator @jasonb]

I have done two part valves but mostly on the larger engines typically 3/16-1/4 shafts and 5/8-3/4 heads all in stainless silver soldered together and they seem to work OK. Welding is likely to give you some distortion that will need just as much work to sort out.

You can just see the different colour of the stem material on these

Have you thought about using teh live ctr on the valve syou are making? Just machine teh valve stem a bit longer then hold in a split collet or ER collet to machine the end off the stem to remove the ctr hole. I do it that way most of the time.

[herbert punterParticipant @herbertpunter99795]

JasonB

Can ask about silver soldering stainless? Do you need a different flux?

Thanks Bert

[JasonBModerator @jasonb]

You need Tenacity No 5 or HT5 from Cup Alloys as it contains something that removes the chrome oxide

[Jesse Hancock 1Participant @jessehancock1]

Jason love the valves mate you are the man. Was thinking a coarse thread into head of the valve then locktite the parts together.

Yes I was using the an ordinary live center but I ended up with a couple of scrappers not having judged the depth of the center drilled hole leaving it hollow on a couple and too short on another to trim. Had a few dig in's which bent the stock right at the last moment. I'll try again with what I have left of the stainless.

I like the idea of silver steel for it rigidity and strength. Threading may be a problem though.

[JasonBModerator @jasonb]

Just watch that your exhaust valves don't get too hot and melt the loctite so the head unscrews!

This is another method, not tried it myself.

One thing to remember with built up valves is that you need to be able to accurately hold the stem while you machine the seat angle on the valve head as if its not concentric you may get leaky valves.

[Howard LewisParticipant @howardlewis46836]

May I suggest using a device called a "Roller Box" (when used on a Capstan or Turret lathe)?

Model Engineers tend to call the device a "Running Down Tool" because it is often mounted on the Toolpost of a Centre lathe, rather than on the Turret of a Capstan or Turret lathe. Mounting one on the Tailstock of a Centre lathe will keep it central (which has to be done manually if Toolpost mounted) but may reduce the length of material that can be machined if the Tailstock does not have a through bore, and the Saddle reduces the proximity to the chuck.

A Roller Box carries an adjustable cutting tool, and two supporting rollers, but can be of two types.

It is effectively a travelling steady with a cutting tool mounted on it

One has the rollers leading the cutting tool (riding on the raw material), or the other type has the rollers trailing the cutting tool, (riding on the freshly machined material). The latter type is the only practicable one if the raw material is not truly circular, or is off centre.

The trailing roller type enables the machined diameter to be concentric with an existing smaller diameter.

The leading roller type enables the machined diameter to be concentric with an existing larger diameter.

Since the material is supported close to the cutting tool, it is invaluable for reducing the diameter of slender material, especially over a long length, with minimal taper, or risk of bending.

MUST get round to making one, (or maybe both types) one day! Add to the list of "Tomorrow" jobs!

Howard

[Nigel McBurney 1Participant @nigelmcburney1]

I have made lots of valves for stationary engines,american hit and miss engines (amanco) and some ruston hornsby engines have steel stems and cast iron heads. The stem is reduced by a sixteenth at the head end and threaded,BSF works ok ,the stem is threaded into the head and the steel is peened over to stop the head unscrewing,the valve seating face is is then machined concentric by holding the stem in the lathe chuck. For very small engines silver soldering the head to the stem is ok, Loctite or any type of engineering "glue "will not survive in a working engine.

[Jesse Hancock 1Participant @jessehancock1]

Jason thanks again more food for thought. Point taken on locktite.

Howard L This sounds ok (I understand the concept) but I worry about all the bearing tolerances which might end in something similar to what I have at present. I guess it works like a die with one cutter. I'll make a note and look at it later.

Nigel sounds fair and was thinking on those lines also. I think Ill buy some cheap threaded bar and see what a mess I can make of the method.

Anyone tried threading silver steel?

[Ian S CParticipant @iansc]

These days my steel fabrication is getting done with brass, using borax as a flux.

Ian S C

[Neil WyattModerator @neilwyatt]

Silver steel threads OK with taps and dies, or screwcutting normally, use plenty of lube. Just don't rush.

This is my box tool:

Neil

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