Floating tap holder clearance recommendations

Due to limited space I'm planning to make a floating tap holder for the lathe. 3/8-16 max tap size.

The outside housing/shell will be built into the holder that bolts to the turret. Have some 4140 HT laying around to make it out of and some 1144 round stock to make the middle part.

Design is extension only and the normal slot, pin and spring design. Little fuzzy on the clearance needed between the two pieces. Figured .002" but not sure and also if a grease port is needed.

Any guidance would be welcomed.

How does a floating tap holder give you more space? Why do you need it to float? Shouldn't you address that?

Older cnc lathe no rigid tapping.

turnworks said:

Older cnc lathe no rigid tapping.

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Then do you need a "floating" tap holder or a spring loaded one? Neither will help with space problem that I can see. Lack of rigid tapping means you need axial variation not radial, which is what any "floating" holder I have seen provides. Don't know your machine but as an apprentice the shop I worked in had many machines without rigid tapping. They measured the actual z movement vs indicated and corrected it in the machines parameters. Most of them were then capable.

Maybe Im not using the correct terms. Need an extension tap holder so I can feed the tap in at a slower feedrate that would allow some give when the spindle slows to a stop and reverses direction. I always called the non releasing extension/compression floating tap holders.

Have G01,G33 and L97/L971 to play with and none of them will work for rigid tapping. Im limited on the length and OD of the tap holder hence the need to make my own. I can get away with the bigger OD ones but then I have to be careful how the turret rotates on tool changes or it will hit. Prefer not to have worry about it.

Lathe is a tiny baby emco 320 with siemens controller.

My concern was about the metals Im wanting to use and the clearance between the two. Don't want to get a few thousand parts in and it doesn't fully retract and crashes the tap into the work on the next part.