Author Topic: Making small Stuart Turner type Drain Cocks  (Read 6261 times)

Offline Chipswitheverything

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Making small Stuart Turner type Drain Cocks
« on: July 05, 2016, 09:56:35 AM »
I needed a couple of the smallest size of drain cocks for the ST Steam Hammer that is now going through the paint shop.
    Also, at a future time, I will need half a dozen similar for the ST Triple expansion engine, and I have a couple of No 10 verticals kicking about that also need drain cocks.  So, 12 of them seemed to be the order.  Now that Stuart want 12.60 ( incl. VAT ) for each of them, I didn't think much of sending off 150 of my dwindling pension for a little plastic envelope of the things!

 I didn't have one to hand, but looking at a catalogue photo I made a rough drawing and determined the basic measurements for a 5/32" by 40TPI threaded d/c.
  I had plenty of 1/4" brass bar, so worked on that basis for the bodies.

Always, except for this time!, I make out a machining schedule, but in my enthusiasm one evening for making up the gauge plate form tool for the body, and looking at the photo in the catalogue, I handed the form tool in what turned out to be an unhelpful way. The nose end is slightly more waisted in than the screw end. Hence, for anyone who wonders why the form tool is mounted at the back of the cross slide, I did it thus to avoid remaking the little tool. I turned the lathe backwards, using the lathe handle. ( I use the handle a good deal, for these small operations it gives excellent control...)

 Before working on the brass bits, I made up the small silver-steel tapered reamer , 6 degrees incl. angle, for forming the tapered through hole for the cocks. The flutes were milled in the dividing head on the mill, after turning the taper.  The backing off was done with a fine file and a lens.  Then it was hardened of course, and gently honed.
 Having turned the taper for the reamer, I left the Myford top-slide set at this angle throughout the rest of the manufacturing, so it would be correct for the brass cocks.
 To be Cont.....

Offline Jo

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Re: Making small Stuart Turner type Drain Cocks
« Reply #1 on: July 05, 2016, 10:58:36 AM »
 8) Well timed Dave.

I have a few of these to make for the triplets  ;)

Jo
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Offline cwelkie

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Re: Making small Stuart Turner type Drain Cocks
« Reply #2 on: July 05, 2016, 02:45:08 PM »
Very nice Dave.  Especially appreciate the extra detail on the nuts and the square hoe in the washer.  With a foreseeable need for 12, perhaps you need to double the in-shop order  :)
Charlie

Offline Chipswitheverything

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Re: Making small Stuart Turner type Drain Cocks
« Reply #3 on: July 05, 2016, 07:09:30 PM »
Thanks for the comments.
 Depending on the brass stock that is available for the job, ( I happened to have the various 7 or 8 inch lengths in the bin ) I'd suggest making the d'cock bodies on each end of a number of bars of a reasonable length: -  it is easier to hold and once parted off, the remaining stock is still useful for other jobs.

 The bars were transferred to the GHT dividing hd., though a vice would do as well, and the cross holes were drilled and followed up by taper reaming. As the tooling was changed in the mill drill chuck for each body, I used a scrap of metal as a gauge ( between the brass body and the top of the flutes )  to take the taper reamer down to similar depth in each case.

  I had some 5/32" stock from which to make the tapered cocks with their handles.  In the first instance, I turned a 6 degree incl. taper on the ends of six bits of the 5/32" bar, giving sufficient turned length to accommodate the square and the 10 BA thread, to be done later on.
 I number stamped the bodies and the infant taper cocks, and worked with them having done that as matched pairs, rather than attempting complete interchangeability.

  The tapered hole in a body was pushed onto its future mate in life, and a fine needle file was used to show where the body met the bottom of the taper, as a guide to positioning the tiny square to be formed.  Also, a scriber point was dotted in at 1/16" above the large end of the hole, to show the lower extent of the handle radius.

 Back to the dividing head, and the little square was milled, just nicking beyond the needle file mark on the tapered cock, into where the lower part of the body would extend when the two items went together. ( The square needs to go just a little way into the body globe shape, so that the washer can seat on the lower edge of the globe ). The square is only about 70 thou a/f, a lot of peering with a lens went on....!

 Then, into the chuck on the little Cowell lathe for the lower section of the taper to be turned to 10 BA size, 67 thou (?) , leaving just a short extent of the square, and the thread die-d on.
Phew!, more later...

Offline yogi

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Re: Making small Stuart Turner type Drain Cocks
« Reply #4 on: July 05, 2016, 11:13:39 PM »
Fantastic work! Well done!   :ThumbsUp: :ThumbsUp: :ThumbsUp:

Offline jeff l

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Re: Making small Stuart Turner type Drain Cocks
« Reply #5 on: July 06, 2016, 02:56:11 AM »
Well Done  :ThumbsUp:

Offline toolznthings

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Re: Making small Stuart Turner type Drain Cocks
« Reply #6 on: July 06, 2016, 01:27:02 PM »
Nice ! Better than store  bought and more fun.  :ThumbsUp:

Brian
Thanks for the visit !
Brian

Offline Chipswitheverything

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Re: Making small Stuart Turner type Drain Cocks
« Reply #7 on: July 06, 2016, 10:43:37 PM »
Thanks for your comments Guys.
  With the twiddly bits done on the tapered cocks, back into the Myford with the rods that they were formed on, and the tapered handles are turned, using the same taper as already set on the top-slide.  Use a tool with a decent sized radius on the end, so as to help with resisting the stress of the bending.  The scriber pop previously mentioned will indicate how far towards the cock to take the tool when making the flare of the handle.
  As there is heating to be done on the handles, it's a help to have made the cocks on the end of reasonable length bars, say 7 or 8 inches...

Now for the bending operation, which I was a little concerned about.  I made a few tapered blanks to try a couple of methods, and not wreck the actual threaded and squared cocks.
 Also made a tapered hole in a bit of brass bar to use as a "handle" for the tapered cocks while bending them.

Tried bending while heating to a dull red, with the torch held in the vice meanwhile.  Worked just about OK, but a fair amount of heat was needed because of the heat sink effect of the "handle".  One attempt did break, showing a very coarse grain at the fracture.

So, changed the method, heated just the tapered handle at the bend area to dull red, plunged into water to anneal.  Using the "handle" bar, took the bend about a third of the way, then a reheat and anneal.  Did this three times to achieve the bend angle. Two heats might have got there, but I played safe.

Cut the little handle off to length and round off the end - a bit of filing and twirling with wet + dry...

Now, it's useful to have the washers and nuts done to assist us later.  The tiny square punch shown in a photo above was made, a few thou bigger a/f than the squares on the cocks.  It made a neat job of squaring up a hole drilled to a/f size in the end of a bit of brass bar.  Just pushed in a 1/16" or so by the tailstock... Then chamfer the little washer and part off with a small p' tool. 

Now the bodies in turn can be assembled with the matching cock, washered and nutted up, and the handle of the cock set parallel with the body axis. Do up the nut to hold the assembly firmly for now. Back into the lathe, as per photo, and the through hole can be drilled , through both components of course.   I used 59 thou in the end.

Finally, the funny looking bit on the other end of the form tool that had been made up for the body shape ( see photo above ) was used.  It parts the draincocks off, and leaves a shallow curve on the parted face.  I used the lathe handle again, hence the tailstock support, ( which I removed just for the last few thou of cutting the items free.)





Offline derekwarner

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Re: Making small Stuart Turner type Drain Cocks
« Reply #8 on: July 07, 2016, 02:39:41 AM »
Very interesting result & fine workmanship with the corresponding tapers :ThumbsUp:

With the transfer from the dull RED heat, did it cause any scale or oxidation of the tapered plug surface?

Do you lap [Brasso lap] lap each plug to each body individually?

What type of grease lubricant will you use between the tapers to ensure the steam tight characteristic is maintained?

With respect to the brittleness of the brass when bent, would repeated heating to bright RED hot and hammering the bar stock prior to machining not have a similar effect to rolling or forging where the granular structure is layered & hence reduce the brittleness?

Derek  :cheers:
« Last Edit: July 07, 2016, 03:00:08 AM by derekwarner_decoy »
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Offline Jasonb

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Re: Making small Stuart Turner type Drain Cocks
« Reply #9 on: July 07, 2016, 07:38:07 AM »
I opted for 303 stainless which bent easily as is when I had to make some earlier this year which bent very easily, Nickle silver is another option. I did look into the avalability of one of the softer brass alloys at the time but they mostly come in sheet & tube not bar.

Nice looking collection of valves and a good write up of the process.

Offline Chipswitheverything

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Re: Making small Stuart Turner type Drain Cocks
« Reply #10 on: July 07, 2016, 07:56:02 AM »
Pleased to have your comments, Derek and Jason.

  Yes, the brass did scale a little from the annealing / heating.  Cosmetically, I just gave the items a superfine wet and dry going over to brighten up..  I will have a go at lapping the tapers in with a bit of Brasso.  The tapers do fit snugly as machined, but the extra smoothing would be beneficial.  ( If they ever see any steam, which I do wonder about...!!)
 Though I need a couple of the d'cocks soon for the Stuart steam hammer, ( quite well on the way with the painting now ), most of these items will be sitting in a tin for however long it takes to build / sort the other engines. So a final titivation can wait until I need them: -  I need to trim a few 10 BA threads, and so on.
 The Stuart Turner d'cocks seemed to be supplied with a rather waxy, greenish coloured grease applied. Does anyone know what this product was, or is?

Dave

Offline JR72

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Re: Making small Stuart Turner type Drain Cocks
« Reply #11 on: July 08, 2016, 08:10:48 AM »
Hi David
Having seen these drain cocks in real life I am amazed as usual at the lovely job you have made of them, very monotonous making so many of the same thing, but what an achievement, would the ones bought from Stuarts be of the same fine quality? I doubt it. Having the satisfaction of making the yourself is a real bonus even though most people would not appreciate the work involved, saving the money is an extra bonus.  I look forward to seeing the form tools.
 Well done David, a real professional job.

John

ps. even the drawing is a work of art

Offline Chipswitheverything

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Re: Making small Stuart Turner type Drain Cocks
« Reply #12 on: July 08, 2016, 12:35:08 PM »
Thank you, John, appreciate your kindly comments.   In fairness, the Stuart ones are perfectly decent bits of kit, but the price is off-putting when more than a few are wanted.  Whether making them oneself is cost effective, only the individual can decide according to time and means, but it made quite an interesting mini project, and does mean that I can say I made them along with the other engine bits...

Cheers, Dave

Offline scc

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Re: Making small Stuart Turner type Drain Cocks
« Reply #13 on: August 07, 2016, 09:51:34 PM »
Well done Dave,  I plan to have a go at a small engine when I have finished my current big lumps, After looking at your thread and your fine work, (as well as others on this forum) I begin to doubt my ability to cope with the tiny components. However, your set-ups, photos and descriptions hopefully will inspire me to try.  Thank you...........Terry

Offline Chipswitheverything

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Re: Making small Stuart Turner type Drain Cocks
« Reply #14 on: August 08, 2016, 11:29:58 AM »
Hi Terry, thanks for your kind comment.  I've just been looking through some pictures of your mighty Burrell build ( there is a lot to catch up with on this forum, I've only been looking for a few months...), and I really can't see a man who can contend with that having any worries with knocking up a few drain cocks!  On the other hand, I might struggle more than somewhat with the huge road loco lumps...       ( A friend has got a big box of 3" scale Fowler road loco castings salted away, which I have looked at with interest, but I've had to admit that trying to machine even those castings would probably bring my relatively small machines to their knees, along with me...)

Cheers, Dave