Sunday, April 24, 2016

Indexing tool for watchmakers lathe

Hello friends
Today I completed the indexing tool for the watchmakers lathe. I've had on my wish list making some very fine rope knurl wheels and in order to do this I needed to be able to very accurately index the chuck. Having recently completed the new stands for the lathe with the accessory mounting t-slots, it seemed a perfect opportunity to design the indexing set up around just that. Below are the results
Watchmakers lathe indexing tool mounted and adjusted

I had used the indexing pin and holes that come stock on the back of the headstock phenolic pulley. It's very hard to get light into there to insure a visual confirmation of inserting the pin into the right hole. I designed this new unit to put the pin on the back of the indexing plate and I put the pin support arm out far enough for good light and good visual line of sight.

I designed and 3D modeled the mounting tabs that use a 1/4-20 bolt to slide into the T-slots. You can see the mounting here.
T-slot mounting for Watchmakers indexing tool

I also developed the indexing pin as a spring loaded assembly. The inside of the very end of the hollow tip is tapered so that when the pin slides home it locks in place with no play at all. The pin is shaped to fit exactly into the index holes in the spindle mounted plate. The back of the pin is also tapered to leave no play at all.
Withdrawing spring loaded indexing pin

indexing pin assembly

Indexing pin guide tip

Indexing Pin

Indexing pin parts

The arm of the assembly is quite robust to eliminate any flex. I slotted the head to be able to clamp down the pin assembly. very handy as I can leave it loose and position the arm angle correctly first, then slide the pin assembly into close contact and tighten it down.
Indexing tool swing arm

Indexing pin arm clamping head

I designed and shaped the levered nut for comfort and ease of repositioning.
Indexing tool with custom clamping nut

I'm happy with the whole assembly and especially happy that it now works as part of the new accessory mounting system.
Cheers, Kevin

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