Advice on BSPT ( Tapered ) manual thread cutting?

[bricol]

- the fitting is to make a tapered sealant joint into the tool, and a parallel ( easily removed for oiling ) joint onto the Whip.).
- I understand the ptfe application process. Normally this just scrunches the ptfe tape, but this badly cut tapered joint really, really minces it up into fragments when you undo it.
Never had a problem with other tapered joints, sure you might have to pick out the odd strand etc. But not a load of fragments and residue bits in the galling on the female threads.
- Totally agree, the last thing I wanted to do was tap into the tool - but in this case I made the exceptional choice.

hence would like advice on the tapping of tapered threads.
if it works, make life easy from then on.

As has been suggested, I bet the gun is NPT - the angle of dangle of the thread form is 55 deg rather BSP of 60 degree. But at this size, with tape or sealant it will be fine.

As others have said - screw the hose into the gun and leave it alone. Before using it, drip a couple of drops of oil into the hose and then use it - the air flow will carry it into the gun perfectly well, and possibly better as it will be atomised rather than a glug of oil.

These threads have been around a long time, as have the tools - no need to over-complicate things.

 

[mechman]

Lost me a bit with the wording. Thread form, Bsp is 55 deg, Npt is 60 deg.

 

[Submariner1]

Excuse the egg sucking, but there seems to be some confusion, so just going back to basics for one moment:

Have a look at the picture in this link

https://www.wurthusa.com/Shop-Supplies-and-Safety/Air-Hose-&-Accessories/Air-Hose/Air-Hose-Whip-3-8/p/189514151

The short "whip hose" is connected to the air tool, and a male fitting is attached to the end.
This then plugs in to the female of your airline from the compressor.

To oil the tool all you do is put a few drops of oil into the male fitting on the whip hose, connect it to the airline with the quick connect (ideally while holding it so the oil runs towards the tool rather than in to your airline).
Then pull the trigger a few times so the air blasts the oil in to the tool.

There should be no need to unscrew the whip hose once it is attached to the tool, so providing you have some thread engagement and it seals off I wouldn't worry about how many threads are sticking out.

You can screw the male fitting directly in to the tool eliminating the whip hose, but it can make the tool more awkward to use in some instances, and induces more wear in to the quick release fitting, which is why a whip hose is typically used.

Does that help at all??

Yes really helps On the oiling issue.
I didnt think it was good to put oil up the whip Hose. Worried it might get into the other air lines. But I was pretty dumb as the pressure would stop that.

I would however like to get a “good” connection at the gun, as I also want to use this PCL valve see photo below, to reduce the reverse speed (needed to remove blade brake bolt on Honda mower crankshaft, as I can hold the crankshaft at the other end by using the starter pull nut .... too much force and that nut could come loose, and to use a flywheel strap means taking off the magneto and resetting it ... a real pain, this is done every year to oil the BB Bearings.
its also used to slow air sanders.
This also sadly has BSPT male and female! And it too has problems i.e. only goes 3 threads into the gun.
So using this stainless adapter would solve all issues.

 

[Submariner1]

As has been suggested, I bet the gun is NPT - the angle of dangle of the thread form is 55 deg rather BSP of 60 degree. But at this size, with tape or sealant it will be fine.

As others have said - screw the hose into the gun and leave it alone. Before using it, drip a couple of drops of oil into the hose and then use it - the air flow will carry it into the gun perfectly well, and possibly better as it will be atomised rather than a glug of oil.

These threads have been around a long time, as have the tools - no need to over-complicate things.

I checked with PCL technical, and double checked if it could be NTP. Especially as I got it cheap on ebay, like was it export stuff for US Market.
they said “No all are BSP”.

 

[Submariner1]

Hello Submariner,

you say the female is tapered, are you sure?

Alec

Yes its tapered.
a rather skinny 1/4” tapered nipple I have goes in further, and a paralell nipple wont go in for more than 1/4 turn.
Checked with PCL most guns have Parallel female swivels, a few including this has a tapered BSP female.

Before I order any BSP T Tapered tap, I am still going to buy one NTP 1/4” fitting just to see how that fits.

 

[Submariner1]

As has been suggested, I bet the gun is NPT - the angle of dangle of the thread form is 55 deg rather BSP of 60 degree. But at this size, with tape or sealant it will be fine.

As others have said - screw the hose into the gun and leave it alone. Before using it, drip a couple of drops of oil into the hose and then use it - the air flow will carry it into the gun perfectly well, and possibly better as it will be atomised rather than a glug of oil.

These threads have been around a long time, as have the tools - no need to over-complicate things.

I also suspected it was NTP despite PCL assuring me its BSPT !
Yes oiling up the whip would do, but wouldn’t solve using the Speed Reduction Valve.
Hence my reason for wanting to use the additional parallel SS adaptor.

 

[Submariner1]

As has been suggested, I bet the gun is NPT - the angle of dangle of the thread form is 55 deg rather BSP of 60 degree. But at this size, with tape or sealant it will be fine.

As others have said - screw the hose into the gun and leave it alone. Before using it, drip a couple of drops of oil into the hose and then use it - the air flow will carry it into the gun perfectly well, and possibly better as it will be atomised rather than a glug of oil.

These threads have been around a long time, as have the tools - no need to over-complicate things.

Odd thing is
1/4” NTP is 18 tpi
1/4” BSPT is 19 tpi
but I did see on UTube them fitting together, not too well but OKish.
what they didnt say was, was it 1/4” or 1/2” as in 1/2” and 3/4” the tpi are the same for BSP and NTP.

 

[Submariner1]

Why do you have to take it off? I'm lost. Just put the oil up the whip or pcl fitting

I didnt initially realise one could oil up the whip hose, without contaminating the other hoses. My first compressor, and have frequently seen people say have seperate lines for spraying.
I have Now been educated but doesnt solve my other problem of using the PCL Speed Control Valve, both tapered
-

that has the same issue, if not worse in that it will only go in 3 threads

 

[Submariner1]

A bit of grease on the tap will hold the chips. If you can arrange to tap upwards, the chips fall downwards away from the gauze.

Plug tap will be OK as there are already some threads there to guide it, but you will need to screw it in until it hits the gauze, unscrew it, grind some off the end of the tap and repeat. Tap should therefore be considered expendable.

The different tapping drill sizes are just for different percentage thread engagement. A slightly larger drill helps in harder materials; the threads won't tear out.

Thank you so much for the advice on tapping. Much appreciated as most replys challenged doing it, rather than addressed the requested tapping info.
Especially the grease tip.
Yes I will do it inverted manually, first oiling the existing threads with cutting oil using a cotton ear bud, and grease the Tap To “collect” the chips. And blank off the gauze as a precaution.
There comments were however welcome, as it does solve half the problem, namely its OK to oil up the whip hose.

 

[Guzrik]

Did anyone suggest undercutting the male parts, and leave the expensive gun as is?
Maybe screw Them into another Solid block once do they deform a bit?

 

[bricol]

Lost me a bit with the wording. Thread form, Bsp is 55 deg, Npt is 60 deg.

I couldn't remember - and picked one way round . . .

 

[Submariner1]

Dont think this female is NPT.
Just seen apparently nominal diameter of BSPT is 13.16mm and NPT is 13.54mm
As it jams up early say after 4 threads, if the female was NPT it would be built for 13.54mm male, and its only getting a 13.16mm diam. male, so it should be loose if anything. ??

That said, there is the issue of pitch, where 1/4” bspt is 19 tpi and NPT is 18.
So possibly the early lockup is when the 2 diff threads finally conflict enough to stop rotation ....

 

[Submariner1]

All Sorted.
I tapped it with a BSPT , previously ground down so not to chew up the pressed in gauze.
I did cut a circle of electrical tape and a circle of rubber to stop swarf entering the inlet.
Basically did it but by bit with cotton bud clean outs about 5 times.
It looked as through the rubber disc stopped everything but when I pealed off the electrical tape, there were a few bits of swarf, where the cutting oil had melted the adhesive.
Luckily it was just around the concave surround, and the sticky stuff did a perfect job, so nothing on the filter gauze. Nevertheless I still sucked it with a big hoover just in case.

The tapered tap is sacrificed but will do if ever I need to bet a better or deeper female 1/4” BSP T thread .

Before