Injector Exercise

[Jack Foreman 1Participant @jackforeman1]

Following the posts in my '4 Jaw Work' thread, and having suggested that I may try to make an injector,

I've started on making an injector ~ again, out of a billet of aluminium, for no other reason than this is what I have a stock of, in appropriate sizes. I started by doing a sketch from the *LINK* information which several of you kindly provided; to ensure that I had a steam inlet, a water inlet, an overflow & a safety valve which incorporates the outlet to the boiler. That done I put some dimensions to it, which would enable me to access all of the internal parts to fit the pressure cone. (one cone will do for the purpose of the exercise)
So – the body is machined ~ I don't yet have a mill, so some of the drilling was done in the pillar drill and some done on the lathe in the 4 jaw chuck. All of the openings line up and are where I anticipated they would be [internally] and I have bored out the two ends to take the cover caps which I have also made. These will bolt onto two BA studs each. (I do appreciate that the real injector would have more than two fixings, but two on each end is sufficient for this exercise purpose)
My next task is to machine the four spigots for steam in, water in, overflow and high pressurized steam out. I intend to make the cone and the external connections with brass and use 1/4" copper pipework.

Can you please advise on the thread type and pitch for brass gland and compression nuts ?

Thanks
Jack

[Jack Foreman 1Participant @jackforeman1]

[JasonBModerator @jasonb]

Something like 3/8" x 32tpi ME would be the usual size thread.

On most steam models in the UK the nut is not quite like a plumbing compression fitting which compresses an olive around the pipe. Instead a Nipple or Ferrule to use the PC term is soldered onto the pipe, this nipple has a shoulder that the nut bears on and the other end a 60deg included angle taper which is pulled into a matching tapered hole in the fitting. The hole can be done with a large centre drill and if making your own nipples set teh topslid eover to teh required angle , couple of pics and the sizes whan you click on the nuts here

[Jack Foreman 1Participant @jackforeman1]

Thank you Jason.
Now that I've looked at the fittings on your link I understand what you have explained. I'll check that my spigots are greater than 3/8" (I'm sure they are because I had no idea what size or type of thread to use – so I'm sure that I've left them larger than anticipated)

For this first occasion I will buy a pack of nuts & ferrules – to see exactly what they look like and from which I can procure dimensions ~ plus a 3/8" x 32TPI ME tap and die, so that I can subsequently make them myself.

At the moment, because I need to learn and gain experience, I am resistant to buying 'kits to machine' and simply assembling.

OK – all the pieces ordered from Steam Fittings

Edited By Jack Foreman 1 on 24/10/2014 22:07:35

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