"Hydraulic Thread" Can Someone Identify This?

npalen · Dec 14, 2016

I was hoping that the term "hydraulic thread" would catch your attention and you can help me out here.

I'm wanting to check the relief valve setting on the 3PH (three point hitch) on my Kubota B9200 HST-D. I need to make a bolt similar to that shown in the photo in order to perform step 2 shown in the print. The bolt shown attaches the banjo fitting to what I believe is the return port on the 3PH valve. The new bolt for testing would be similar except no cross drilling and a 1/4" NPT port on the end to attach the pressure gauge.

I had planned to lathe the single point thread that I thought was a metric pitch but it appears to be a really odd pitch. Here are the measurements I come up with: The pitch appears to be about 1.38mm or .054" or 18.5 TPI and the diameter measures 0.645" (16.4mm)

Using thread pitch gauges it shows between 18 and 20 TPI (threads per inch) and about .054" pitch and about 1.38mm pitch. Weird! The note in figure 3 (screw size PS 3/8") throws me also. Is that some kind of 3/8" pipe thread for attaching the test hose with gauge?

I'm guessing that Kubota makes this odd thread so that a dealer has to buy their special fitting. Maybe someone with inside knowledge can hopefully shed some light on this.

k0ua · Dec 14, 2016

You got my attention, and wish I could help... but sadly I cannot..

4570Man · Dec 14, 2016

Is there any other location to check it? How much is a new piece? It might be easier to buy another one and modify it.

npalen · Dec 14, 2016

I'm thinking perhaps plugging the cross hole with a piece of pressed in brass rod. Then drilling from the head end thru at about 1/8" diameter, then drilling and tapping a 1/4" NPT thread for the pressure gauge rather than making a new bolt. Then the brass plug could be punched out after getting the pressure readings.

IceStationZebra · Dec 14, 2016

As you probably already know metric uses mm/thread to designate pitch. 1.5 mm/thread is common for fittings.

Older Japanese equipment turns up with BSPP sometimes. 3/8-19 turns out to have a 0.656" OD and 19 TPI. Sounds like what you have.

ISZ

npalen · Dec 14, 2016

British Standard Pipe Thread Chart
I'll bet you're right. I found this chart which shows a 3/8"-19. My Bota is a 1987. Seems strange that Japan used British thread standards rather than metric but I'm sure there is a logical explanation.

My lathe will cut 18 or 20 pitch but not 19.

LD1 · Dec 14, 2016

9035-06-04

Type that into the search box at discounthydraulic hose.com

Or 9035-06-02 if your gauge is 1/8npt instead of 1/4

npalen · Dec 14, 2016

LD1 said:
9035-06-04

Type that into the search box at discounthydraulic hose.com

Or 9035-06-02 if your gauge is 1/8npt instead of 1/4

How does the BSPP thread seal?

LD1 · Dec 14, 2016

With a flat copper washer, bonded sealing ring, or o-ring

npalen · Dec 14, 2016

Thanks! Great information!

Xfaxman · Dec 14, 2016

Can you put a tee with the gauge in the pressure line somewhere ahead of the 3 point valve?

Does it have a loader with quick disconnects?

TractorGuy · Dec 14, 2016

Here is a banjo bolt with 12mm x 1.25/1/8 in. NPT for testing if that might help.

MinnesotaEric · Dec 14, 2016

npalen said:
I was hoping that the term "hydraulic thread" would catch your attention and you can help me out here.

I'm wanting to check the relief valve setting on the 3PH (three point hitch) on my Kubota B9200 HST-D. I need to make a bolt similar to that shown in the photo in order to perform step 2 shown in the print. The bolt shown attaches the banjo fitting to what I believe is the return port on the 3PH valve. The new bolt for testing would be similar except no cross drilling and a 1/4" NPT port on the end to attach the pressure gauge.

I had planned to lathe the single point thread that I thought was a metric pitch but it appears to be a really odd pitch. Here are the measurements I come up with: The pitch appears to be about 1.38mm or .054" or 18.5 TPI and the diameter measures 0.645" (16.4mm)

Using thread pitch gauges it shows between 18 and 20 TPI (threads per inch) and about .054" pitch and about 1.38mm pitch. Weird! The note in figure 3 (screw size PS 3/8") throws me also. Is that some kind of 3/8" pipe thread for attaching the test hose with gauge?

I'm guessing that Kubota makes this odd thread so that a dealer has to buy their special fitting. Maybe someone with inside knowledge can hopefully shed some light on this.

It May be German metric or british standard pipe perpetual. The threads on my Kioti loader are German metric while others are JIC or BSPP and what not.

Have you a hydraulic gauge kit?

Thread Identification Kit | Parker NA

BukitCase · Dec 14, 2016

"british standard pipe perpetual" - Hey Eric, is autocorrect messin' with ya like it does me, or is this an inside joke? BSPP stands for British Standard Pipe Parallel (as in "threads") - There's also a BSPT (as in "Tapered" threads)

Now, if I can just find somebody that knows what my old AC 160 has for threads (into the 3ph block) I'd be happy - tried a BSPP, it makes it about a half turn then gets stubborn - the tubing there is metric, so I ended up getting some 12mm to JIC swage fittings and will probly just cut the tubing, bend it off to the side and tie into it there for the 4 stack remote valve I'll eventually get to... Steve

MinnesotaEric · Dec 14, 2016

BukitCase said:
"british standard pipe perpetual" - Hey Eric, is autocorrect messin' with ya like it does me, or is this an inside joke? BSPP stands for British Standard Pipe Parallel (as in "threads") - There's also a BSPT (as in "Tapered" threads)

Now, if I can just find somebody that knows what my old AC 160 has for threads (into the 3ph block) I'd be happy - tried a BSPP, it makes it about a half turn then gets stubborn - the tubing there is metric, so I ended up getting some 12mm to JIC swage fittings and will probly just cut the tubing, bend it off to the side and tie into it there for the 4 stack remote valve I'll eventually get to... Steve

Brain fade, I'm afraid.

PILOON · Dec 14, 2016

Well I know that machine bolt that you show is actually for a 'banjo fitting', if that helps. As such could be metric or SAE, but probably metric.

npalen · Dec 14, 2016

Xfaxman said:
Can you put a tee with the gauge in the pressure line somewhere ahead of the 3 point valve?

Does it have a loader with quick disconnects?

The lines feeding the 3PH are all steel tube with banjo ends so would have to cut into a line for a tee.
I'm wondering if I could tee into the PB (power beyond) coming out of the added rear remote valves since that is what should be feeding the 3PH? Will check into that.

Xfaxman · Dec 14, 2016

That would be easier, Then run a chain down from a box blade or other heavy implement, to a tree and raise the three point. You will hear the relief open and look at the pressure on the gauge.

npalen · Dec 14, 2016

npalen said:
I'm thinking perhaps plugging the cross hole with a piece of pressed in brass rod. Then drilling from the head end thru at about 1/8" diameter, then drilling and tapping a 1/4" NPT thread for the pressure gauge rather than making a new bolt. Then the brass plug could be punched out after getting the pressure readings.

I tried this without success. There was enough leakage past the bolt threads that was showing only 500 PSI on the gauge. Took me a little while to figure out what was going on. The leakage, of course, was going into the return line.