Odd thread

[Kludge]

I have a Northwest Short Line model railroad press (nice for itty bitty pressing service) that has a threaded plug in it. I originally planned to remove the plug and make adapters to scre into the same hole but I've come up with a problem. Absolutely none of the tables, charts, guides or other referecnes indicate what it is. The major diameter is .420" (10.66mm) and it's threaded at 20tpi.

My first choice would be to find a die to match this but I may wind up drilling and tapping it for a smaller thread (1/4-20?) for the adapters. Keeping the original hole unmolested will allow me to use other NWSL accessories later on, a path I would prefer not closing off.

Has anyone seen this thread before and know where I can get a die for it?

BEst regards,

Kludge

 

[lenscad]

Could it be 7/16-20 UNF that is just a bit undersize?

Len

 

[Bluechip]

Hi Kludge

Any unlikely chance it is 55deg ?? / worn 7/16" [ .437 ] altho' more likely UNF.

20tpi was a 'constant pitch' thread used in UK.

http://www.watchman.dsl.pipex.com/thread.html

Some UK Motor bikes used it.

Together with a 20tpi 60 deg thread, to make life easy. Also constant pitch.
Litte wonder the UK bike industry went belly-up :

I have heard it referred to as 'Whitworth Fine Series' which is not another way of saying BSF !

Shufti the link

Regards

Dave

 

[Maryak]

Hi Kludge,

Went through my Machinerys Handbook and:

7/16" UNF Class 1A has a major diameter tolerance of 0.436" - 0.424" and 20 tpi. Closest I could find.

Best Regards
Bob ;D

 

[GailInNM]

Kludge,
Like the others I would guess on the 7/16-20, but if it is really a smaller major diameter, you could probably close up a 7/16-20 split die enough to cut the thread. Take it a small step at a time however as the die will get unhappy and eventually break if it is closed up too much.

On another note, you and I discussed special taps and having them made a long time ago. Here is a company that has a large stocklist of special taps and dies that they make and will make specials also. They don't have the 17/32-40 that we were looking for as a stock item. They also have small taps going down to 1mm as stock items. Minimum order of $25, but nobody is perfect. New York, USA based.

http://www.victornet.com/cgi-bin/vi...departments=Special+Thread+Taps:618,1170,1171

I will add them to the suppliers section on this board.
Gail in NM,USA

 

[Kludge]

Hi, folks,

The 7/16-20 is the closest I've found as well. I've only removed the plug a couple of times (to measure and recheck when I couldn't find it the first time) and it's pretty insistant about being .420. I have a 7/16" UNF die around here somewhere* and I can turn down some rod to size to try it out - if I have some appropriate rod to turn down. I haven't yet built up the stock & recycle bins you gentlemen have so it's likely I don't. This isn't a worry; I'm sure I can find something.

Bluechip - Way back in my questionable youth, I got to ride a few BSAs. Lovely bikes, to be sure.

Gail - That's my thinking as well for the above trial. The die I'm thinking about is a split die so I can play with the major diameter some that way as well as turning down the rod.

Also, way cool about the tap & die maker. A $25 minimum (which I doubt I'll get down to!) is a minor detail if a special order solves a problem. Being able to solve problems is of far greater interest.

BEst regards,

Kludge

*Actually, I have a complete tap & die set and I know precisely where it is. The phrase "around here somewhere" fits my apparent modus operandi a lot better.

 

[John S]

More that likely a fitting made by Enotts.
They specialised in pipe fittings and standardised on 20 tpi thru their range of fittings.

They are now part of IMI Norgen and still make fitting but modern push in ones.
They used to supply workshop kits at one time, a box with assorted fittings, nuts and olives for maintainance crews, I may still have the odd set kicking about.

They used to be a pain as nothing fitted their fittings because of this special pitch.

.

 

[tel]

... sounds a bit like Hardi, who make their stuff deliberately off size so you have to buy their replacement parts

 

[macona]

They used to supply workshop kits at one time, a box with assorted fittings, nuts and olives for maintainance crews,
.

Olives? It that slang for Ferrule?

 

[Peter Neill]

Yes, I suppose that ferrule is the correct technical term, but we've always called them pipe olives over here for as long as I can remember.
Just to be clear, it refers to the brass compression ring around a pipe that clamps it in a fitting by the use of a nut that compresses the olive as it is tightened.

Peter

 

[tel]

Yep, always been called olives here in Oz as well

http://www.choiceful.com/choiceful-id-20342-22mm-Brass-Olive-Compression-Fitting.html

Never heard 'em called ferrules before, tho' I've run across a couple of pretty feral ones.