Stuart 10v valve rod

[Nick WelburnParticipant @nickwelburn]

I’m struggling with this it’s reducing a length of 1/8 rod down to 3.3mm. It’s a length of about 2” or so.
I’ve had two issues, the cross slide being drawn in and making the piece narrower. I’ve sorted this today by shimming the cross slide to remove 0.3mm of slack.
I’m struggling with the piece bending away under the cut. I’ve tried with a travelling steady but it’s still deflecting and popping up onto the cutter.
I'm also getting a very chewy cut. I think this is probably chatter.
I have a choice of tool posts so I could put the cutter between the steady and the Chuck, or in front of the steady.

Thoughts welcome!

[Nick WelburnParticipant @nickwelburn]

How can something so simple go so wrong?

[Former MemberParticipant @formermember12892]

[This posting has been removed]

[Nick WelburnParticipant @nickwelburn]

Apologies it must be 1/4 about 6mm or so.

[Anonymous]

Posted by Nick Welburn on 08/06/2021 20:50:08:

I’m struggling with this it’s reducing a length of 1/8 rod down to 3.3mm. It’s a length of about 2” or so.
…………….
I'm also getting a very chewy cut. I think this is probably chatter

Errr, 1/8" is 3.175mm so reducing it to 3.3mm is going to be tough, unless you've got a magic "put on" tool.

Why does it need reducing? Given what you've got it'll be easier to make any mating holes slightly bigger. If there are threads at the end a short length only can be turned down for the thread.

Chatter tends to produce a regular pattern. A chewy finish sounds more like the material, or the cutting conditions are wrong, such as a blunt or poorly ground tool, tool not on centre height or wrong speeds and feeds.

I'd use a roller box, but I'd guess you don't have one available?

Andrew

[Nigel Graham 2Participant @nigelgraham2]

Is the diameter constant for the component's full length? If so, you will be better off buying free-cutting stainless-steel of the right diameter already – 1/8". (You may be able to use 3mm or 4mm with small adjustments to the mating components.)

[Nick WelburnParticipant @nickwelburn]

Posted by Nigel Graham 2 on 08/06/2021 21:53:15:

Is the diameter constant for the component's full length? If so, you will be better off buying free-cutting stainless-steel of the right diameter already – 1/8". (You may be able to use 3mm or 4mm with small adjustments to the mating components.)

It’s mostly constant, the tip is taken down to 3/32 but only for maybe 1/2” that would be easier to manufacture as it wouldn’t need much stick out from the Chuck

[JasonBModerator @jasonb]

You are supplied with 1/8" Stainless Steel material in the kit so it should not need reducing except for the short 3/32" length at the end which should not be a problem with a sharp tool correctly set on ctr height. It may not be obvious from teh drawings but the square block that the fork is made from is a separate piece and should be tapped 5BA to accept the end of the valve rod that is threaded 5BA, don't try and make it all from 1/4" square material.

Or are you trying to turn down the piston rod material in error?

Sone details of making the valve rod throughout this page

 

 

Edited By JasonB on 09/06/2021 07:46:33

[Former MemberParticipant @formermember12892]

[This posting has been removed]

[Paul LousickParticipant @paullousick59116]

I have been making spindles for some small valves from 8mm dia 316 S/S rod. (316 is not an easy material to machine). The end is turned down for a M2 thread. The overhang from the chuck was too much and the rod flexed at the end when trying to turn the full length. The 2mm dia at the end was too small for a centre and the part too small for a travelling steady.

Made the part by extending each section from the chuck and turning to finished size, then extend a bit further to finish the next section of the rod. Procedure works if the concentricity of each section is not super critical.  For llengths that are turned in 2+ cuts and dia. not critical, blend joins by smoothing with emery.  (I used an ER collet chuck – MT3 taper in the lathe spindle which is more accurate than my 3-jaw chuck).

Paul

Edited By Paul Lousick on 09/06/2021 10:17:25

[Nick WelburnParticipant @nickwelburn]

Lots to go at here. I think my tool is a touch below centre. It’s shimmed up with bits of .8mm mild steel. This may need addressing. I’ll dial it in with the quick change tool post. Jason’s point that it only needs machining at one end is very valid. But I’ve clearly made something else on the engine with that material… I think it’s the piston rod.

im going to try and get a good cut on the remaining part with the tool better centred. Clearly what leaves a tiny pip is enough to give a vertical force and bend the rod.

learning more with every mistake

[Anonymous]

Posted by Nick Welburn on 09/06/2021 10:07:42:

Clearly what leaves a tiny pip is enough to give a vertical force and bend the rod.

Not so; cutting forces are primarily a vertical force that is opposed by the torque from the spindle, whether the tool is on centre height or not. Having the tool on centre height will not stop the work deflecting.

In the absence of fancy equipment the simplest way to turn a slender section is in short lengths, moving the work further out of the chuck at each cut.

The 1/8" diameter spigot on the stainless steel valve rod bottom left was done using the above method:

Andrew

[John OlsenParticipant @johnolsen79199]

From what I recall of the 10V and Double 10 that I have built, the main length of the valve rod should not need turning down. Only the short length on the end that goes into the guide hole in the end of the steam chest. If the rod is only a little oversize I would look at making the holes to suit. If it is much too big, order some the right size.

If you do have to turn down a long slender piece, there is a way of doing it with a combined steady and cutting tool. This needs a piece of steel held in the tool post, with a hole drilled in it on centre height that matches the starting size of the rod. A piece of tool steel is then attached on the right hand side that takes off the desired cut. The hole guides the rod so it can't deflect. A bit fiddly to set up, and possibly too much trouble unless you have a lot of work to do.

The moving out from the chuck idea works better if you have a collet chuck.

John

[JasonBModerator @jasonb]

If your tool is set tool low that may explain why it was being drawn in as the work will want to climb up over it. You will also loose the top rake if the tool is low which may be a factor in your rough finish as the tool will be scraping not cutting.

[Dr_GMJNParticipant @dr_gmjn]

I think I centre-drilled mine, and used a tailstock centre to stop it flapping about. I think I also had cutting issues, until I used Jason's suggestion of a DCGT insert. In the end (after two failed attempts) it was very easy to do.

Someone mentioned not turning the end down at all, and enlarging the hole in the valve chest to suit (I think that's what they meant), but you can't really do this because the middle of the rod needs threading, and so the turned end needs to be just a bit smaller diameter than the die that you'll use to do the threading (ie the turned diameter has to be equal or less than the root diameter of the thread). I made this mistake first or second time, and had to start again – again. If you didn't turn the end down, you'd end up with a threaded rod going into the valve chest guide hole.

I think someone also mentioned when I was having issues with this, that another way around it is not to turn down or thread the rod at all, but drill and tap the side of the square brass valve plate so that you can slide it along the rod and lock it precisely where you need it with a grub screw. It makes adjustment much quicker and easier. Using that method I guess you can use the same diameter holes in the gland and and the dome end of the chest.

Only reason I didn't use this method was because I wanted to build to plan, and didn't want it to defeat me!

[mechman48Participant @mechman48]

..'Why does it need reducing? Given what you've got it'll be easier to make any mating holes slightly bigger. If there are threads at the end a short length only can be turned down for the thread.

That's what I did with my S10V, a lot easier.

George.

[JasonBModerator @jasonb]

Well if it is the 1/4" that the OP says it is then it's going to need more work than just opening up some holes if the OD is to remain untouched.

New valve nut will be needed and a new redesigned valve if it can even be fitted, new valve gland and the gland boss on the valve chest will need a bigger thread but that is likely to be bigger than the cast boss so new or modified valve chest needed. All new materials needed to be purchased rather than use the supplied items.

[Nick WelburnParticipant @nickwelburn]

Ok – progress has been made. Kinda! I’ve used the other tool post and really carefully set the tool height. I was probably 0.25mm or so down.
I then chucked up about 8cm of 6mm aluminium and drilled the set tight on the live centre it came very close to working. The final cut for the reduction from 2.5mm to 2.4mm dug it and bent the piece.

Hunting about I found a steel bolt. The same process reduced to 3.30mm along the length and down to 2.5mm at the end then on the last pass dug in and bent.

I reckon with a bit of luck, oil and finesse I might get this.

Thanks as ever for all the suggestions. I’m very much a newby but I am going to make this engine. Possible called the Jason B! In respect to Jason’s constant answers to my daft questions

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nick Welburn on 09/06/2021 21:04:42:

Ok – progress has been made. Kinda! I’ve used the other tool post and really carefully set the tool height. I was probably 0.25mm or so down. […]

.

I would say that’s at least 0.24mm too much

… dead-on, or just a touch high, would be preferable.

MichaelG.

[Author]

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