[jimglass]

Spent a couple of weeks thinking about this. Most of us have seen the floating chuck floating chuckfor lathe tapping. I wanted to make something similar for power tapping small taps in a milling machine. The goal is to have a drive system that would begin to slip before a tap breaks off. In the video I allowed the tap to bottom out to see if it would break off, it didn't and the tap retracted when I reversed the spindle.

Video of it working

This was the first tryout of the slip clutch tapping head. My problem was tightening the chinsey electric drill chuck so the tap didn't slip in the chuck. It was the only chuck I had available. I'll order a new chuck Tuesday.



The amount of slipage is completely adjustable by turning the knurled collar. I got the idea of the clutch from my automotive experience. The component held in the spindle of my milling machine I call the flywheel. Then the part attached to the Jacobs chuck I call the clutch disk. Inside the knurled housing is a spring loaded pressure plate where the slippage is adjustable. More pressure on the pressure plate, less slippage.

The flywheel, clutch disk and pressure plate are all machined or ground smooth and oiled to prevent galling when slipping.

I'll have to play with this thing to identify problems. For now I'm concerned with slippage remaining adjusted.

This thing will get rather limited use but I have wanted a tool like this for a long time. Seems like I'm tapping smaller holes all the time. 0-80, 1-72 and so on.

Now I suppose someone is going to tell me I could have bought one of these things for a $100 bucks. I made it in one day.

Jim

[Geof]

No it would have been more than $100 that is if you could have found one. Slip clutch tap holders were used a lot on Capstan and Turret lathes doing production work but I have not seen one in a tooling catalogue for decades (maybe I am looking at the wrong catalogues).

[jimglass]

I'm was told MSC industrial has them. All you need is $717

Standard Tapping Heads - Tapping Heads & Accessories | MSCDirect.com

I made mine in 5 or 6 hours. Even if I figure my time is worth $50/hr I'm ahead of the store bought tapping head. This was a rainy day project plus I enjoyed building the project. I don't plan to use this thing that often so $717 is a little hard for me to justify.
Jim

[jimglass]

I made a video demonstrating my slip clutch tapping head. It is only the second time I have used the tapping head so it took several attemps to get the clutch set for the tap that was used. Video stored on Youtube. Seems to load quickly.

See the video

Jim