Screw core plugs

[Reckless Rat]

How do you get them out? I've never been brave  enough to try.

I've a well knackered block with screw in core plugs. I'll have a go at getting one out this afternoon

Steve

I have removed them only by milling them out of a scrap block. From memory they are 1 1/4" x16 t.p.i

Well I don't have a mill and I should, probably, not offend the engineering principles of both Alan and Robert that I respect greatly but I've just got one out by 'other means'. I've got it here on my desk and I agree with 1 1/4" x 16tpi which doesn't seem to match anything listed by Mr. Zeus. My more crude method didn't damage the boss in the block so it can be done

Steve

Edited to Add: See Page 114 of 'The Companion'. Size confirmed and, in 1956 at least, these were available in the electrical trade as '1 1/4" Male Bushes'.

Steve. Would I be right in assuming that the removed core plug wouldn't win any prizes in a beauty contest? What are we talking about here - big stilsons and Mr warm spanner?

[Steve Jones]

You would be very correct, Bruce. Re-use of the plug was never part of the plan.

Mr Bloody Hot Spanner, actually, and the Stilsons need an initial helping hand from Mr Hammer and his mate with the pointy edge but please don't tell Alan or Robert or they might never speak to me again!

Steve

[Steve Hainsworth]

Hi
 I must apologise to  Ian Williams as the thread is actually 1-1/4" Conduit (electrical ) thread -16 TPI.
Standard Whitworth Form  55 Degrees -depth of thread .040 " ( Forty thousandths of one inch)
The thing to look for is a conduit blanking plug in brass.
I will look into availability  and if hard to get make a few hundred in brass if there is demand.
Cheers Steve Hainsworth

---

Forgot to mention. To get the old ones out (destructive ) They are cast iron and quite brittle
Drill a 5mm pilot hole as close to center as possible-right through.(but not into the cylinder walls!)
 Open out to  8 then 13 (as big as a battery drill will go ) Don't drill too fast as they will blunt your drills.
Using  a hacksaw blade (18TPI ) in a pad saw handle carefully  cut from the center out til you hit the major Dia of the thread.
Make the cut opposite to form a cut both sides.repeat process at 90 degrees so you have the plug quartered.
 A few judicious taps with a  chisel or pin punch will collapse the pieces inwards so yo can extract them with a magnet or rod.
I have done this to 3 blocks recently with no damage to the block thread. Clean the threads up with an internal thread file.
Cheers Steve Hainsworth.

[Charles P]

As it would happen I bothered to knock the core plugs out of my spare block and it's flipping clean as a whistle. Better that way than full of crud. I just now have to make some core plugs!

[David Cochrane]

As it would happen I bothered to knock the core plugs out of my spare block and it's flipping clean as a whistle. Better that way than full of crud. I just now have to make some core plugs!

Charles - I have a new one you could borrow to use as a pattern if that would be any help.

David

[Charles P]

As it would happen I bothered to knock the core plugs out of my spare block and it's flipping clean as a whistle. Better that way than full of crud. I just now have to make some core plugs!

Charles - I have a new one you could borrow to use as a pattern if that would be any help.

David

Thanks for the offer David but I'm sure that I can turn ones from bar stock

Charles