What is this thread

[Rowan Sylvester-BradleyParticipant @rowansylvester-bradley37244]

<p style=”text-align: left;”>I have an air compressor badged Warrior, presumably made in China. The air filters on it, which screw straight into the cylinder heads have a thread which seems to have an outside diameter of about 15.2mm and a thread pitch of about 1.5mm. This seemed closest to M15 coarse, so I bought a small threaded part which claims to have an M15 coarse thread, to see if this fits. It does screw in, but is far too loose. So I’m now stuck. The thread does not seem to be any known metric, imperial or unified thread that I can find. Does anyone recognise what this thread may be? If I can’t find it I suppose I have to make an adapter trying to match the diameter and the thread pitch of the original filter as closely as I can. But it seems weird. They can’t just have invented a thread with no name can they? Not for a part that will periodically have to be replaced?</p>
Thank you – Rowan

[Tony Pratt 1Participant @tonypratt1]

Have you looked at BSP?

Tony

[JasonBModerator @jasonb]

Filters are available with M15 x 1.5 threads

Or cheaper on ebay https://www.ebay.co.uk/itm/315485156690

[Andrew CrowParticipant @andrewcrow91475]

It could be 3/8 bspt(taper) the major dia is about 16.6mm

Andy

[VicParticipant @vic]

It sounds like the major diameter might be 5/8”? Many threaded components are under size on the OD.

[noel shelleyParticipant @noelshelley55608]

My first thought is BSP ! The tank fitting will be that size on almost everything like that. Noel.

[Andrew CrowParticipant @andrewcrow91475]

Try also 1/4 NPT major dia about 0.540 inch

Andy

[Rowan Sylvester-BradleyParticipant @rowansylvester-bradley37244]

That isn’t big enough. The thread of the old air filter is slightly over 15mm. And I don’t think it’s tapered.

Rowan

 

[Peter TuckerParticipant @petertucker86088]

Hi Rowan,

It may be (ISO) METRIC CONDUIT; one of the threads on my compressor was that (different size though).

Peter.

[Paul Mills 4Participant @paulmills4]

Could it be a pg9 thread. Od is 15.2mm, pitch is 1.421mm. Thread angle is 80°

Paul

[Bill PhinnParticipant @billphinn90025]

I don’t know whether there’s meant to be a photo with your opening post, Rowan, but I can’t see it.

Anyway, here are two photos of a Chinese-made bearing puller of recent vintage. The intended thread is almost certainly M16x1.5. It displays the notorious (to me at any rate) Chinese undersizing of major diameters.

[JasonBModerator @jasonb]

As my post earlier you can buy these filters with a M15 x 1.5 thread so why look at other threads such as pipe threads which are not close to OD. Peters Conduit would also be a possible if the sales descriptions are a bit off, the steep 80deg of conduit thread may be worth checking by eye

1/4″ pipe is 13.1mm OD and 3/8″ pipe 16.7mm so neither are likely to be 15.2mm which falls between the two.

 

Isn’t Warrior a Clarke/Machine Mart brand why not contact them for filters.

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