Odd thread size.

I have an archimedean drill whic Ii was given on my 7th birthday along with other tools (Thanks Dad for getting me interested in making things!), so it is now 70 years old. It has a type of brass pin chuck and the end cone is missing.

The thread is 24tpi and the diameter at the top (beyond the 4 saw cuts is 0.3150" So nearest standard O/D would be 5 /16". A bit dodgy as the diameter is oversize for 5/16". So what is the thread? As the pin chuck is brass , I thought Brass thread, but they have a standard tpi of 26. Difficult to tell, but it looks as though it is a 55 degree thread, but could be wrong unless I dig out my Shadowgraph.

So what thread is it? I would like to make a new end cap and get it back to working order, but I am stumped.

Andrew.

Andrew

0.3150 is 8 mm.

Possibly 8 mm fine which can be 1 mm pitch.

I'd not care to try distinguishing between 24 tpi and 1 mm pitch without my excellent bench magnifier with its built in light.

Confusingly 0.75 mm pitch is also listed for 8 mm fine.

Clive

https://journeymans-workshop.uk/downloads.php
My goto for finding threads.

Edited By Keith Wyles on 19/07/2023 13:23:41

Your description brought to mind a fretwork set I was given at a similar age; not only are the company who made it still going, they still stock the same items and seem as popular as ever.. ..I wonder whether yours is the same..?

Pebaro.de - Tools - Fretwork drill

Hobbies Ltd springs to mind

Roy

Diogenes,

That is amazing! A very careful scan of the top handle, using a loupe reveals the letters Pe..... . So it seems that Clive's suggestion of M8 fine, with a pitch of 1 mm is correct.

The drill came in a set of children's woodworking tools, which included a saw and a mallet, plus some other items which I can't now recall. I still have the saw.

The only modifications are the top handle, which is mushroom shaped on my version and the pin chuck which has been simplified, my version is knurled and is like a small version of an Eclipse pin chuck.

I shall buy the modern version just for old times sake.

Thanks everyone for the journey down memory lane!

Andrew.

Diogenes,

That is amazing! A very careful scan of the top handle, using a loupe reveals the letters Pe..... . So it seems that Clive's suggestion of M8 fine, with a pitch of 1 mm is correct.

The drill came in a set of children's woodworking tools, which included a saw and a mallet, plus some other items which I can't now recall. I still have the saw.

The only modifications are the top handle, which is mushroom shaped on my version and the pin chuck which has been simplified, my version is knurled and is like a small version of an Eclipse pin chuck.

I shall buy the modern version just for old times sake.

Thanks everyone for the journey down memory lane!

Andrew.

8mm X 1mm is a thread size used in some electrical fittings so not uncommon - Tracy tools do them ! Noel

Please ignore my comments on the cap being like an eclipse pin chuck version! It is from another drill that I have. So no idea what the original look s like.

Noel , I already have taps for the M8 Metric fine thread needed, but thanks for the info. As the drill was at least 70 years old, I never dreamed that it would be a metric thread. Didn't think of the possibility of European manufacture!

Thanks again,

Andrew.