Dual use Jacot tool

[Peter Cook 6Participant @petercook6]

I decided to make the Jacot tool described by Henry Hicks in the September 2013 edition of MEW. I was attracted by the spring ball indexing method he used. Rather than the MT2 tailstock arbour he used to fit his Myford, I scaled things down a little and used a 7mm piece of silver steel to fit the tailstock of my watchmakers lathe.

I later spotted images of a cross slide mounted Jacot tool which Cowells used to offer for their CW90 lathe.
With a little careful design I thought I could produce a dual purpose tool which would both fit the watchmakers lathe tailstock, or could be mounted on the cross slide of my Taig lathe.
By making the main body holding the the Jacot wheels an appropriate size, it was possible to mount the tool upside down on the Taig cross slide such that the pivot supports were exactly on centre height. All I required was a suitable bracket to hold it there.

The bracket has a cut out which is a close sliding fit for the Jacot block, two tapped M4 holes to attach it and a 7mm reamed hole to accommodate the tailstock runner.

Two 10/32 clearance holes hold the bracket to the T slot on the cross slide.

Little 3d printed box to keep all the bits together.

Hope this idea is of use to someone.

[Michael GilliganParticipant @michaelgilligan61133]

Nicely done, Peter

MichaelG.

[Dave SParticipant @daves59043]

I thought Jacot tool beds were hardened so the burnishing would work?

nice looking tool tho.

Dave

[Peter Cook 6Participant @petercook6]

Dave  it’s possible that commercially made tools are hardened, but all the shop made ones I have come across build instructions for – or examples in use – have had brass support wheels. One article from 1991 suggests hard plastics such as Acetal or Nylon “…or even brass would do”.

The burnishing is carried out with a very hard burnisher on top. The Jacot wheel is there as a support. If the Jacot wheel was hardened, unless its finish was perfect there would be a real risk of any imperfections in the bed scoring the pivot – the opposite of what you are trying to achieve. Small imperfections in the burnisher are of (slightly) less concern as you keep it moving.

[DellParticipant @dell]

Nice work I made one sometime ago with a 5mm shaft & adjustable height Jacot.

[bernard towersParticipant @bernardtowers37738]

It appears a few of us have had similar ideas and I have also added a home-brew screwed polishing set up (have you seen the price of secondhand ones!!!)

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