"Hydraulic Thread" Can Someone Identify This?

[npalen]

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]

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

 

[4570Man]

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]

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]

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]

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]

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]

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]

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

 

[npalen]

Thanks! Great information!