1"-18 Straight Thread for fluids 1

[iainuts]

I have an old pump (1980's) I'm redesigning and found a very strange threaded part on it. The pump has an oil sight glass and another port which adapts to a pipe thread. Both are 1"-18 (straight thread). Both ports are wrapped with Teflon tape and pipe dope even though they are not tapered. I've never seen anything with this thread before, and after looking through all my fittings catalogs, I've come up empty handed.

Do you know of any pipe fittings, pipe plugs especially, that are designed for a 1"-18 straight thread?

 

[Philrock]

Can't help on the 1"-18 threads.

As for the dope and tape, I wouldn't make any assumptions - I've seen a lot of dope and tape where there should be none.

 

[MintJulep]

There is a 26 x 1.5 metric parallel thread.

This would be very close to 1"-18, and could be easily misgauged if you are using a simple comb gauge.

Straight pipe threads are generally intended to be used with o-rings, gaskets, or crush washers of some sort, and should not rely on thread interferance for a seal.

Good adapter site:

http://www.adaptall.com

 

[iainuts]

Hi MintJ. I don't think it's metric. If it is, it's the only metric thread on the pump, and it was built in the US. Seems strange to have just one metric thread on it when there are pipe threads and straight threads all over. Also, inspection of the part seems to rule out the 26 x 1.5 metric size.

Regarding the lack of O-rings or other types of gaskets, I thought that was pretty funny myself. Seems like some farmer must have put this one in. Maybe it matched something on his John Deere tractor. <sigh>

 

[FACS]

We used to have to put straight threads in our pump designs at the request of the customer. It's been done. We used ORings and crush seals.

It's possible to have come mixed ports from the pump mfg.

Looks like it's up to you to make it right, and get rid of the pipe dope.

Charlie

http://www.facsco.com

 

[CorBlimeyLimey]

Is the guy into flying?

http://www.airsuppliers.com/aircraftparts/S1000.asp

 

[lbmakem]

you could have a 1"-18 uns thread to american standard B1-1-1960

 

[CorBlimeyLimey]

iainuts ...
Is the 1"-18 the actual thread size (1" O/D) or a pipe thread size (approx 1.327" O/D)?

 

[lbmakem]

its the actual thread size, a 2A fit has a o/d of .9986/.9899

 

[iainuts]

Hi CorBlimey. OD of fiting is 0.998" I don't think he enjoyed flying though. Corn shucking machines are just too heavy.

Hey lbmakem, Is there anyone that makes fittings with that size thread? In particular, I need a couple of plugs. Also, does that fitting use some kind of gasket? I'm thinking there should be.

 

[eromlignod]

Are you sure it isn't a port for an electrical conduit fitting? 18 tpi is common for them at that dia. But then I guess if it had Teflon tape, it must be sealing something. Also, elecrical threads would be obvious if you were using a sawtooth thread gauge, since they'd have an angle of 80 deg.

It could be a unified special thread (UNS), but then you can make any diameter or pitch thread you want and call it UNS as long as you follow the thread profile and tolerance standards. It's certainly not a "standard" unified thread, like UN, UNC, UNF, or UNEF.

If they were true "pipe threads", then they would be made with a major diameter that is equal to a standard pipe size. The closest pipe to this is 3/4" which has an OD of 1.05, but the tpi is still way off (14).

I once came across some really bizarre threads on an Italian hydraulic four-slide machine, years ago. As I recall, the diameter was metric and the pitch was in threads-per-inch. What really distinguished them was the fact that they were of Whitworth form! Can you look with a magnifier and see whether the teeth have rounded crests?

Don
Kansas City

 

[CorBlimeyLimey]

http://www.efunda.com/DesignStandards/screws/unified.cfm?start=228&finish=301

http://www.parker.com/quickcouplings/QCD/3800_G_03_02.pdf

http://www.parker.com/brassprod/cat/3501E/3501-D.pdf

 

[eromlignod]

I'm not sure I understand your post. Lots of specialty fittings have screw threads on them. Screw threads aren't pipe threads. Pipe threads mate with pipes.

If you have ever specified a non-standard thread, you know that UNS is a catch-all for any size combination you might desire that doesn't fit under the standard sizes (UN, UNC, UNF, UNEF). That's what the "S" is for: "special", as opposed to "standardized".

I used to design large reprographic imaging cameras that had large, high-grade lenses with all sorts of bizarre diameters. You simply pick a nominal diameter and tpi, list the critical dimensions and tolerances in your call-out and call it a UNS thread. This covers the unified profile.

Another good example is the threads used for AFBMA bearing lockwashers. A 25 mm bore bearing, for example, calls for an N-05 locknut, which requires that you thread your shaft with 31/32"-32 UNS-3A threads.

Don
Kansas City

 

[unclesyd]

I have seen 1" straight threads on some low pressure oil site windows that use a gasket in a recess under the hex nut part of the window. The gasket seals on the boss created for the window. I don't know what the thread pitch was.
They also make these windows with BSPP threads, but at 18 the pitch is off.

 

[iainuts]

Thanks for all the feedback folks. Looks like a plug for this isn't going to be easy to find. I'll just drill and tap the port for a conventional pipe thread and be done with it.

Thanks again.

 

[dimjim]

It is only a sight port. The teflon tape was
only to keep any moisture out would be my guess.
You might be able to find the glass port from
one of the lube fitting manufacturers. It must
be a standard somewhere for those who make these
sight glasses or ports.

 

[dimjim]

These people might have what you want.

http://www.donaldson.com/en/ih/support/datalibrary/033984.pdf

 

[unclesyd]

Here are two suppliers that I've used.

http://www.jwwinco.com/products/section12/index.html

http://www.ernstflow.com/eindex.html