Help: odd sized pipe thread needed

[IslandTractor]

Hi folks,

I need to identify a source for a roughly three inch pipe nipple and female/female connector with the following dimensions:

Major OD 0.625 inches
Min OD 0.555 inches
Threads per inch: 16

These are the measurements of a oil breather cap on my Caroni flail mower gearbox. I need to build an extension to keep the oil from oozing out (the gears throw it against the cap and it oozes quite a lot...the extension will hopefully keep that from happening). The gearbox is Caroni built (Italian).

I have found measurements for 3/8 inch NPT (0.675 OD, 18tpi) and for BSP 3/8 pipe (0.625 OD, 19 tpi) and have tried both but neither fit. I cannot figure out what other measuring convention Caroni is using. I have measured the threads directly and also compared them to a thread gauge and it is really 16tpi not 18 or 19. That is pretty darn close to 1.5mm thread pitch and given that the gearbox is made in Italy perhaps there is a metric pipe system that would match. Anyone have experience or suggest a source?

Thanks

 

[randy41]

i would try metric fittings...google it

 

[IslandTractor]

i would try metric fittings...google it

I've been trying. No joy. Perhaps I am using the wrong search terms. I've tried "metric pipe thread 1.5mm" and a few variations. I get a variety of hits but nothing similar to what happens if you put in similar terms for US or Bristish measurement systems. Any thoughts?

 

[davkir]

McMaster-Carr has a lot of this kind of stuff and their catalog (also online) has all sorts of interesting tech. info.

 

[tommu56]

here is a couple of links

British standard
British standard pipe thread - Wikipedia, the free encyclopedia

national pipe

National pipe thread - Wikipedia, the free encyclopedia

cross from national pipe to DIN size
NPS - "Nominal Pipe Size" and DN - "Diametre Nominal"


tommu

 

[Sherweld]

Try this
THREAD IDENTIFICATION CHART -- PART 1

 

[638]

What you have is "11/16-16NS". This is a special thread, and is listed on my thread chart. This thread would be easier cut on a lathe than trying to find a tap and die set. I've worked with odd threads off & on for fifty some years and have never ran across this one. Good luck.

 

[DieselPower]

I'll have to check when I get home. I might have that tap and die size. I have most but not all of the national special tap's and die's under 1 inch. Post back later or tomorrow to let you know if I have it. Would be more than happy to mail it to you to use if I have one.

 

[3RRL]

Island,
Is the number of threads exactly 16tpi? (perfect fit or not)?
If not, I'll bet it's a M16x1.5 Metric thread.
Do you have a Metric thread gauge?

 

[IslandTractor]

Thanks to you all for your suggestions. Here is where I stand after a few hours of internet research and direct measurement: I have looked at the various websites you guys have provided. It makes for some fascinating reading, especially one article I came across that discussed how these American (SAE), British (BSP) and German (DIN) systems came into use. (Believe it or not apparently some of the confusion was intentional on the part of the Brits to make sure the Germans could not easily find substitute parts for captured British weapon systems!!). There is even a "unified" screw thread system designed in the US that seems to be used for bolts but not pipe fittings.

However, back to the practical issue at hand: I think I have narrowed down what I need to one of two thread sizes both of which appear to be practically unobtainable from the big web sources in the USA. The two possibilities are either a British sized 3/8 inch with 16tpi which is called Unified Coarse thread (note different OD and standard 18tpi for SAE). The second possibility is a DIN 10mm pipe with 1.5mm thread pitch. I cannot find any reference that lets me cross check those DIN measurements with the 0.625 Major OD and 0.555 minor OD in inches.

I have used a paper thread gauge and also directly measured the threads of the cap. The 16tpi thread gauge matches perfectly (holding the cap threads directly over the paper print out and sighting down to see the match). The cap threads also line up perfectly with 1/16 inch ruler segments. However, the 1.5mm thread pitch is also extremely close and I could not differentiate which was closer using the thread guage (1/16 inch and 1.5 mm are awfully close as measurements).

I am therefore thinking that either thread pitch would work so I need to match the major and minor OD figures. That is what I have had trouble locating standards for with the DIN and Unified coarse thread. NPT 3/8 is clearly too big. The BSP 3/8 is exactly correct at 0.625 OD but the BSP thread count is 19tpi not 16 so I know it is not a BSP standard.

Again, the other big issue is that I have not been able to locate any US supplier for the DIN or Unified Coarse thread pipe fittings. I tried McMaster Carr and two or three others. I don't have their catalogs so I had to use the websites which can be difficult. Maybe I missed something. I need a 3 inch pipe nipple with threads on both ends and a matching female/female connector. I was thinking of calling McMaster Carr in the morning but this is such an arcane matter that I kinda doubt the guys on the order desk will know...still worth a try.

Again, thanks for your suggestions. I will post a follow up when I have more info.

 

[CurlyDave]

Rather than trying to find what might be the most unusual pipe thread in the world, I might try a couple of alternatives before spending the money on getting that pipe thread.

1. Take your existing breather cap and find a way to pack it with coarse steel wool. The stainless steel pot scrubbers from the grocery store come to mind as a source of coarse steel wool.

2. Think plastic pipe instead of steel. This isn't a pressure application. Get a piece of 3/8" PVC pipe threaded with the closest thread you can easily find, heat it until the threaded end is pretty floppy, and then screw it into the female thread on the gearbox. The threads should deform to a perfect fit. Make up a new breather cap by drilling a few holes in an expander bushing and cap from the plumbing department of a big box store.

 

[Wayne County Hose]

I do have to say, this thread, the fitting and the writing, makes for some humorous reading. Italian made equipment is usually metric. There is French millimetric, GAZ 24 degree cone, JIS metric 30 degree flare, DIN 60 degree cone, and DIN 24 degree cone which in that configuration, may also be metric light-light, light, or heavy thread. Still confused? Well so am I. Rob came the closest, this is a metric thread. M16x1.5 sounds right on. Now they do make M16x1.5mm in light and heavy thread, the difference being the tube size that it connects to. You will want to know how big of a line you want to run. The best thing to do is to remove this fitting and bring it to a good hose shop, not a NAPA or a tractor dealer. The only other 16tpi that may be even close is flush face o-ring, but that is 11/16", and that's not .625". Try getting this info from DHH, Northern, or Harbor freight. Come on Island tractor, you have my phone # .

By the way, there are no odd size threads or fittings. Only shops that don't know what they are. If any shop ever tells you that you have an oddball fitting, they don't know fittings.

 

[DieselPower]

If you need anything and I mean anything in British or Metric and can not find it I suggest you give British Metric's a call. They located a few miles from me in Westminster, MD and I often get hard to find pipe fittings in non-US thread from them. Every time I have needed something they had it on the shelf. They also have a excellent metric and Whitworth bolt and nut sellection.

If you go to their technical link at the top of the page they have some info you might find useful in finding your exact thread. They have data for BSF, BSW, BSPP, BSPT, BA, PG and stock everything in house.


British Metrics

 

[IslandTractor]

OK. Here is my update. It does appear that the fitting is a 16M x 1.5 as a couple of you suggested. Mark at British Metrics identified a coupler they don't have in stock but can get for me that should do the trick. I may need two of them to get the roughly 2 inch vertical clearance I was looking for so I ordered a couple. I'll see how it works and will post back on the Caroni Flail thread with specifics if it does.

For reference, the British Metrics catalog number is 300908. About $11 each.

Thanks to all for the team effort.

 

[3RRL]

Island,
I looked up that catalog number and it is indeed a M16 x 1.5.
I have 2 Chinese tractors and I'm always looking for conversion adapters because all their stuff is Metric too. Another thing is that many valves and even cylinders are of Metric origin so they all need Metric stuff. My Koyker (American made) loader uses an Italian Olfe valve and joystick and it's Metric too. They also use BSP on them. The BSP and NPT can appear very close to each other and can be tricky to identify. They will start into each other but the threads are different. If the valve is Italian or foreign construction, it is most likely Metric and/or BSP for the tapered threads.
I bookmarked that British Metrics site (thanks Diesel Power) and I've also used Discount Hydraulics because they have a good selection too. Surplus Center only has a few.

 

[kennyd]

If you need anything and I mean anything in British or Metric and can not find it I suggest you give British Metric's a call. They located a few miles from me in Westminster, MD and I often get hard to find pipe fittings in non-US thread from them. Every time I have needed something they had it on the shelf. They also have a excellent metric and Whitworth bolt and nut sellection.

If you go to their technical link at the top of the page they have some info you might find useful in finding your exact thread. They have data for BSF, BSW, BSPP, BSPT, BA, PG and stock everything in house.


British Metrics

I live about 2 miles from them...but have never been there. But when I was flying model helicopters I did go the Maryland Metric a few times for oddball fasteners.

 

[DieselPower]

I live about 2 miles from them...but have never been there. But when I was flying model helicopters I did go the Maryland Metric a few times for oddball fasteners.

Never been to the Maryland Metrics. There just down the road a little further in Owings Mills. Might have to stop by the next time I'm down there on sales calls.

If you stop in British Metrics make sure you get one of their catalogs. Their catalog is about the size of a Baltimore yellow pages phone book. Packed with all kinds of hard to find fittings, gadgets and gizmo's. When you walk in the front door they have a small waiting area with a coffee table full of catalogs.

Next time your in the Airport complex do some window shopping. You might be surprised how many specialty businesses there are in there and all the ones I have dealt with have been more than happy to help out the little guy that only needs a handful of items.

 

[kennyd]

Never been to the Maryland Metrics. There just down the road a little further in Owings Mills. Might have to stop by the next time I'm down there on sales calls.

If you stop in British Metrics make sure you get one of their catalogs. Their catalog is about the size of a Baltimore yellow pages phone book. Packed with all kinds of hard to find fittings, gadgets and gizmo's. When you walk in the front door they have a small waiting area with a coffee table full of catalogs.

Next time your in the Airport complex do some window shopping. You might be surprised how many specialty businesses there are in there and all the ones I have dealt with have been more than happy to help out the little guy that only needs a handful of items.

Thanks for the info, I will check them out...I have been to the Airport complex a few times-I got all my stuff from Northeast plumbing when I built my house. I also have a friend with an RV-4 plane that flies into the airport and gives me rides occasionally

MM is further south than Owings Mills by about 10 miles in the "bad part of town" (It's inside Baltimore City)

 

[IslandTractor]

Just thought I'd give a follow up on this thread. All's well that ends well.

I contacted British Metrics and they had a 16mm extender with 1.5mm threads in their catalog. They had to order it from somewhere in Houston of all places (British??) but the bottom line is that it fits and works perfectly. Problem solved. Also, the extension has a shoulder on it so it is a very solid mount, much different than trying to cram a 3/8 inch NPT fitting into the hole.

To remind you what it was needed for, the Caroni flail mower gear box has a vented oil dipstick cap directly above the gears. The gears fling oil at it when operating and the oil leaks out in considerable quantity (maybe an ounce every hour or two. Makes a mess on the mower and leaves you wondering about gearbox oil all the time. The extender actually has a narrow passage (about 3/8 inch) and there is no leakage once the extender is installed in place of the oil cap and the cap screwed into the extender. Luckily the range of proper oil level is about what the length of the extension is so I now just keep the oil high enough that it hits the tip of the dipstick.

Photos below. Invoice from British Metrics shows exact part number. I think it was about $10 plus shipping. Last photo shows the oil leakage with the standard cap. No leakage at all now.

I'll add a few nonsense terms to help people find this post in the future: oil leak gearbox caroni flail tm1900 dipstick vent extension 16mm x 1.5mm thread

Thanks again team.

 

[toddler]

British Metric is now asking over $20 for that piece. Odd since the two sizes that flank it are under $7.
$20 doesn't seem outrageous, but it seems like they realized there was a small market and decided to raise their price in response to guys here buying these.
Are there any other sources?