Archimedes Drill Part

Hi all,

Just got this rather nice Archimedes Jewellers Drill from France.

The sliding section is a brass insert in the ebonised beech wooden part.

It should engage in the twists in the central spiralrod to rotate the shaft when pushed down but is completely worn out.

Anyone have any thoughts as to how I go about replacing this part? It does not matter if I have to turn a new wooden part in ebony or whatever.

The shaft ia approx 1/4" diameter and a very 'slow' spiral as shown.

I'd remove the three screws and take out the insert to see how its made. The grooves on teh spiral are quite deep and you may find its nothing more than a series of pins that engage the spiral that should be easy enough to replace

I wonder if you could cast the part around the existing spiral rod in some kind of resin, perhaps adding powdered bronze to it. PTFE spray or similar as a release agent. I'm sure others on here will know more.

Good luck.

David.

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Me too !

Incidentally; it's very nice to an Archimedean with so many grooves ... Well found, Martin.

MichaelG.

You might find all sorts of arranmegments inside. i would not be surprised if the 'nut' is only one or perhaps a small number of brass plates with filed slots and very easy to replace.

Neil

Sorry guys! First thing I did was to take out the three screws! Inside its just a piece of brass rod with a hole through it. At one time there would have ben (might !) a hexagon shape to the hole but very hard to tell. Will take it apart again and post a pic when I have a moment.

Neil: I suppose that it is possible that the end plate had filed gooves (points ) to fit into the spiral I will ;look more closely at it under a glass.david: like the idea of resin casting!

Michael G: Yes a particularly nice one, hence worth taking the trouble over, came from a french goldsmiths shop with a lot of his other tools.... yummy!

mine is a one piece alloy casting

Hi Martin

If you Google the following words:

epoxy bearing materials and method

You will find a few posts I made for an epoxy bearing material process I developed in 2011. There is a PowerPoint presentation attached to them showing the process.

It used Araldite (The slow cure version not the 5 minute) to cast a nut. It is available worldwide. I also used the material to re-bed my lathe saddle after the ways were reground. I still use the lathe and there has been minimal wear since rebidding it.

The material is easily turned. one method might be to after applying a liberal amount of release agent to the splines of your tool thickly coating the spline shaft then allowing it to set. After it has hardened for say 2 days turn the coating to an even diameter and tidy up the ends (without touching the splines!) and press it off. To make a nice job of your tool maybe you could replace the brass bearing with one counter bored from the inside so that the epoxy nut is unseen. You could epoxy the turned down cast nut into the brass section.

The epoxy coat has almost no shrinkage, maybe coating the splines with a liberal coat of shellac before you apply a release agent would be a good idea. It will provide some clearance once the shellac has been removed with methylated spirit later. Otherwise the cast nut will be a very tight fit. I still have the test nut I did in the presentation. It has never worked loose. It also has a metal sleeve.

The design uses metal powder. Recently I had to turn some hard brass rod down. the brass turnings came off as very fine flakes. I kept them! While a bit coarser than the metal powder I suspect they might work for your application. You could experiment.

Regards
John

Martin,

I've just found this list of patents for 'spiral drills' etc.

There may be something useful amongst them, if you have time to browse.

Note: All 'available' patents should be on espacenet, for viewing and download.

MichaelG.

Edited By Michael Gilligan on 27/06/2015 18:48:14

The brass that engages the spiral will not be very thick, it will have a star shaped hole possibly at each end of the bobbin , minimum friction is what's wanted.

Ian S C

Even if not that old it is a future antique. Therefore the original wood and brass should be retained and a small slug of brass soldered into the tube to file to the required shape,

make a two part mould and cast a new one around the shaft or just bin it

Thanks guys, I like the idea of 'casting' an araldite sleeve over shellaced core, will give it a go and report back.

regards,

martin

Mine has a brass centre piece and a bottom circular piece screwed on with a star shaped hole.

Bet that's what Martin's used to be like.

Neil

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Maybe / maybe not ... Martin's is unusual in that it has [six?] deep grooves in the spiral, whereas most look more like a Barley-Sugar twist. ... Pins or 'Blades' might be more appropriate.

MichaelG.