Late coil oil filler thread...

[Ruairidh Dunford]

Can anyone tell me what this is, off the top of their head please?

[dickie65]

Hi,
I suspect it is a bicycle thread as its a large diameter fine thread.
Without finding a tube and measuring the diameter and putting a thread gauge on it I cant help further.

https://britishfasteners.com/threads-bsc

The above might help have a look at the BSB threads.

[Ruairidh Dunford]

Thanks Richard, I will do that, if nobody knows for sure.

[Steve Jones]

Just measured one, Ruairidh, and it was 1 1/4" x 20 tpi. Tracy Tools web site lists both taps and dies in that size - BSC Thread - but no stock of taps, only carbon dies.

Steve

[Ruairidh Dunford]

Very kind Steve, appreciated.

R

[Stuart Giles]

Just measured one, Ruairidh, and it was 1 1/4" x 20 tpi. Tracy Tools web site lists both taps and dies in that size- BSC Thread - but no stock of taps, only carbon dies.

Steve

I'd be surprised if that was a 20 TPI cycle thread (60 degree), more likely to be a 20 TPI WF thread I would have thought -All the other 'non standard' threads on the A7 are 55 degree WF. But, once again, Tracy tools only have stock of a carbon die in this size. If Ruairidh is just doing a 'special' oil filler tube, it might be easier (and certainly cheaper) to screwcut the thread in a lathe. A 20 TPI Whitworth tap will do as a chaser if the 'real thing' isn't available to put the finishing crest on the thread. With a milling machine as well as a lathe making a carbon tap from a piece of Silver Steel wouldn't be an impossibility in the absence of a buyable tap.

[Bob Culver]

The world got by with carbon taps into the 1900s and, as with drills,  only the norm since 1960 or so.

[Hedd_Jones]

I had an issue with an engine I bought years ago where the engine was allegedly a runner to go in an APD I had, it was missing the filler (with a rag pushed in), and I thought nothing about it. Trying to recommission it became apparent some numpty had damaged the threads.

Being impatient, and not knowing in those days about Tracy tools etc, I just found the mankyiest filler with good threads from the spares pile (some animal had used a stillson on it). I put it in the vice, cut I think 4 slots in it the full height of the thread, then smartened up the cuts to debur and 'sharpen' with a needle file (if you know how to sharpen your own taps you will understand what I mean). I also drilled a hole right through it near the top to insert a T handle, then used this as a makeshift chaser. I screwed it in and out 3 or 4 times with some lube and this worked perfectly. Clearly it put a load of shite in the crankcase so the sump and gauze had to come off.

I have never seen the tool from that day to this, so I assume my father weighed it in.

[Ruairidh Dunford]

Thank you Stuart -will let you know how I get on.