The section titled key data for thread at the end of the pdf may be of use
looks like 45mm tap drill from the last reference
The core diameter for a 1 1/2" BSPP thread is 1.7656", according to two
old books I have. If you need any other data just let me know. I have a
table which goes up to 18" BSPP which I could scan for you.
I thought about putting it on my website once, but never got round to it.
Wouldn't mind that as well, maybe it will just sit in the collection of old
data, as I currently use up to 3" on the farm, but it may be needed one
day... What about the drill sizes for 3/4"BSP and 1"BSP?
It's from "Fowler's Mechanics' and Machinists' Pocket Book 1942". Some
of the numbers are a bit fuzzy, but you should be able to figure out
what they are. If not let me know and I'll check the original.
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