Help with oil plug B&S 31P777

StarTech

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No
I use BSPT taps & dies or NPT taps & dies
They are different thread pitch.
3/8BSPT190.5709"
3/8NPT180.5625"

And the Briggs is 3/8-18 NPT. If you use a 9/16 drill bit you can confirm this.
Okay, being NPT, I already saw that the thread tooth angle is 60 ° and the taper can be 2 °.
But I also saw that every NPT / BSP female is parallel, so the male can be at standard NPT angle (1 ° 45 ' to 2 °) or parallel.
I believe that the fact that bertsmobile1 uses both NPT and BSP in "taps & dies", is due to aluminum fluff in the housing, as it will be compliant for both 55 ° (BSP) and 60 ° (NPT) teeth.
I also saw that all thread material in tubes, for the 3/8 tube, the thread has 18 wires per inch ... if confirmed, this information is enough for me to make the thread in an aluminum or bronze tube, I don't know yet .
NPT (normal pipe tapered) and NPSM (normal pipe straight male) are two different animals. Also BSPP (British Standard Parallel Pipe) and BSPT (British Standard Pipe Taper) are two more different animals.
 

bertsmobile1

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I don't mean to sound condescending but i think you're over thinking it some....go to your hardware store. Buy a 3/8 NPT tube, male thread on both ends and buy a cap or valve to fit on one end.
Teflonsealing tape on both ends. Install it. You're done.
Or you can call Briggs And Stratton and ask them what size thread the 31p777 engine sump drain plug is.
Scrubby.
I thing you will find Bange is in a third world country so there is no Harbour Freight 10 minutes down the road.
This is why he is doing the work arounds.
One of the downsides of the new format is the location tags have been deleted .
 

Scrubcadet10

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Scrubby.
I thing you will find Bange is in a third world country so there is no Harbour Freight 10 minutes down the road.
This is why he is doing the work arounds.
One of the downsides of the new format is the location tags have been deleted .
didn't realize that
 

Bange

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Scrubcadet10
The world here is another one of my friends ... 3/8 is not standard for ordinary people, just for industry and nobody sells a 10 or 15cm piece, only 3 or 6 meter sticks. In addition to conical threads here it is only for materials under pressure (gases or fluids), minus the public water service.
I saw the plug and it didn't look like a conical thread ... it's actually cheap there ... but what I'm thinking about is a piece of pipe so that the oil falls out of the chassis so it doesn't get dirty.

StarTech
Yes, in numbers there is a small difference that is significant when the materials are hard ... aluminum is compliant and ends up sealing, even with this small difference.
In the materials I have seen so far, the female thread allows for a tapered or parallel male ... the seal, in the case of straight, can be a little damaged and you should abuse teflon tape or put a soft metal washer (aluminum , copper), to compensate.

bertsmobile1
Bingo! This is one of my biggest problems with imported parts ... difficult to find, to have in stock, with a reasonable price ... which never happens.
 

Bange

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Continuation...
Yesterday I researched the market and found 3 stores and only 1 accepted to sell me, a piece as said by Scrubcadet10, if it were in iron it would be quite cheap, but I prefer in aluminum or brass, I found what is called here "long nipple" , in brass, whose value is BRL 55.00 (+ -USD 11.00) and the plug for BRL 22.00 (+ - USD 4.2) ... total BRL 77.00 (+ - USD 15) ... but I didn't buy it.
Today I bought a hexagonal piece in brass 7/8 with 10cm long for BRL 40.00 (+ - USD 7.5).
I also made a test piece with the water valve that came in place of the plug, but the piece only went halfway, signaling that either the thread was obstructed or the taper of the NPT is in the housing.
Since I don't have a 3/8 thread opener, I improvised one that solved the problem.

torneando a válvula.jpg
Peça de teste.jpg
Roscando um eixo 1.jpg
Roscando um eixo 2.jpg
Roscando um eixo 4.jpg
Refazendo a rosca.jpg
Peça de teste encaixada.jpg

The plan now is to make an extended plug with the purchased hexagon and other pieces of my scrap.

O plano.jpg
 
Last edited:

muddy51

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Hey Bange,
The drain plug is probably National Pipe Thread (NPT)
I got these sizes on line
Nominal Pipe Size 3/8"
OD .675"
Threads per inch 18
Angle between threads 60degrees
Taper 3/4"/ft
Use teflon tape or pipe dope to seal
Need some way to attach tool to tighten and loosen
If what's there now works leave it as is.
 

slomo

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Looks similar to a bathroom faucet stem. LOL

slomo
 

Bange

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muddy 51
Yes, friends have already passed on this information ... but I imagined that the taper (angle) was on the male thread (plug) but after placing the test plug I saw that the angle is on the female thread (engine).
But when passing the improvised tool, the NPT thread was changed to a normal thread (without an angle) ... this will facilitate my project.

Slomo
Yes, in fact it is a bathroom or kitchen faucet (I didn't know the name "faucet" ... google previously translated it as a water valve).
The kitchen faucet improvised by the previous owner, served for me to make the test plug.🤷‍♂️
 

Bange

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Evolution ...
Turned and ready parts, lacking a nitrile rubber, a soft washer and a small chain to hold the lid.

Preparation of the exagonal part.
Preparo da peça exagonal.jpg

Internal turning with the same size as the connection pipe
Torneamento interno do adaptador.jpg

Detail of the internal channels for better sealing.
Canais auxiliares para vedação.jpg

Turning the sealing pin to the opposite side of the pipe
Pino de vedação oposto.jpg

Preparation of the connection pipe
Preparo do tubo de conexão.jpg

Parts to be pressed
Before pressing, the brass one goes to the oven, the aluminum one goes to the freezer.
Conexão prensada.jpg

Chemical lock
Trava química.jpg

Chemical lock application
Aplicação de trava química.jpg

Using the lathe to press
Prensando as peças.jpg
 
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