26-01-2019, 03:40 PM (This post was last modified: 26-01-2019, 03:51 PM by Chris KC.)
Confirmation of screw thread please?
- the two slotted grub screws which blank off the two oilway drillings, next to the oil pump and one on opposite side which rises towards the oil pressure gauge connector - 1/8" BSP (parallel)?
And do we know anyone who stocks these grub screws?
Joined: Aug 2017 Posts: 654 Threads: 16
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6 Location: The far North East of England
Car type: 1934 Austin 7 AVH Van (in bits & incomplete!), 1936 Morris 8 Series I Tourer
26-01-2019, 04:26 PM (This post was last modified: 26-01-2019, 04:33 PM by Jeff Taylor.)
Can't confirm if the thread is actually 1/8" BSP, however grub screws that are socket head rather than slotted 1/8" BSP x 10mm long are available here:
(26-01-2019, 04:26 PM)Jeff Taylor Wrote: Can't confirm if the thread is actually 1/8" BSP, however grub screws that are socket head rather than slotted 1/8" BSP x 10mm long are available here:
Hi,
I think you'll find they're 1/8BSP TAPER i.e. - 1/8BSPT. The thread is tapered so it tightens and seals as it goes in. Brass Allen heads make good replacements; available from that well known on line auction site. The originals can be a sod to get out; heat up and use an impact driver.
Dave
(26-01-2019, 10:26 PM)Speedex750 Wrote: The originals can be a sod to get out;
Amen to that! But now removed thanks.
Yes, I asked about source because there is a certain amount of vagueness about thread form on eBay. BSP sometimes turns out to be NPT for example, which is nearly but not quite. Will have a good look tomorrow.
(26-01-2019, 10:26 PM)Speedex750 Wrote: The originals can be a sod to get out;
Amen to that! But now removed thanks.
Yes, I asked about source because there is a certain amount of vagueness about thread form on eBay. BSP sometimes turns out to be NPT for example, which is nearly but not quite. Will have a good look tomorrow.
For the amateur few things were less adequately explained than pipe threads, and not overly clear even on the Internet. Few have an assortment of taps and dies to compare. There are taper (BSPT) (NPT) and parallel threads (BSPP) (NPS). A hunt through the data reveals the latter based on some medium point of the taper configuration. The exact designations not consistent down the ages. BP have Whitworth thread form; the NP American form and in some sizes different pitches.
Parallel of a sort can be cut with a two piece taper die suitably maladjusted.
Here for plumbing the BSP series is retained but given metric names!
The size in inches is as for an external thread with designated nominal size that of the bore in original thick walled 19th Century wrought iron pipe. Hence all threads are much larger dia than most expect.
Old die sets and taps can be picked up very cheap and are often handy for making or repairing things needing a large thread. Other large taps and dies tend to be expensive.
