Cutting Internal threads from First Principles
Cutting Internal threads from First Principles
(OP)
I just watched a Stephen Fry doco on the Gutenberg press.
I hadn't realised how many things he had to hack together, but the one that interested me most was cutting an internal thread.
To do this the TV team carved an external thread, then built a box of pegs to engage with it, which was used to drive a cutter through a wooden blank, to create a mating internal thread.
I like this idea. but.... does it pass the sniff test?
I hadn't realised how many things he had to hack together, but the one that interested me most was cutting an internal thread.
To do this the TV team carved an external thread, then built a box of pegs to engage with it, which was used to drive a cutter through a wooden blank, to create a mating internal thread.
I like this idea. but.... does it pass the sniff test?
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.





RE: Cutting Internal threads from First Principles
I'm under the impression that the 'traditional' way is to cut off part of the male thread and turn it into a tap.
Mike Halloran
Pembroke Pines, FL, USA
RE: Cutting Internal threads from First Principles
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Cutting Internal threads from First Principles
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Cutting Internal threads from First Principles
By 'box of pegs' I assume you mean a block fitted with dowels or something similar on a pitch to engage the male thread, like a crude forerunner of a half-nut and leadscrew?
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Cutting Internal threads from First Principles
I haven't seen anything quite like this before, and although it is ingenious I'd have thought that at least one of the many museums I've been to would have something similar, not that it would necessarily make a great exhibit.
Reasons I don't like it - the geometry would be a bear to work out, I haven't seen one, and a half nut chased by hand would be easier.
Reasons I like it - it is adjustable, robust (if the pegs wear, replace them, if the holes are in the wrong place retract the peg a bit, or carve a custom peg). In the spirit of Whitworth's approach to things, you could start with a single peg version, then use that as the register to move a box under a pillar drill and that way the box would automatically have the correct geometry (sorry that's a bit garbled).
Well according to google whatever it might be called it isn't a pegbox.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Cutting Internal threads from First Principles
I strongly recommend you read One Good Turn, A Natural History of the Screwdriver and the Screw, by Witold Rybczynski, Harper Books.
RE: Cutting Internal threads from First Principles
RE: Cutting Internal threads from First Principles
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.