Using a tap in the tailstock

[badabec]

Hello, I'm machining some M9 x 1.25 nuts.
I mount the tap in the tailstock and the lathe at 65rpm.
Should I lock the tailstock and wind the wheel or leave the tailstock unlocked and loose and then push the tailstock into the work?
Or something else?

 

[Erie Fred]

How good are you at cranking the wheel ?

 

[Seadog]

Unlocked and pushed into contact until it's in sufficiently to draw itself.

 

[badabec]

That's the trouble, I never know how fast to wind.

 

[brightspark]

all i do is leave the tailstock unlocked and push it in by hand and slip the clutch so it slowly pulls its self in

 

[brightspark]

That's the trouble, I never know how fast to wind.

you dont wind it in if tail stocks loose the tap pulls its self in

 

[Kram]

None of the above. Usually I tap them by hand with a tap wrench, just using a centre in tailstock to get it centered and started. If your using decent taps it is quite enjoyable.

Turn a bar to to in the tailstock and a thick wall tube to slide over it with a slot and pin key way to stop rotation. The open end of the tube you fit a tap holder - the difficult bit, getting it concentric, and to fit a range of taps with square drive.

I have not made one for taps yet but I have made a sliding die holder.

I was looking to get a set of ratchet tapping collets which would be ideal, until I saw there are three standards, DIN, ISO and JIS, each with slightly different diameter and square. Ofcourse my taps are a good mix and the collets are not cheap!

 

[Agroshield]

Whay do the nuts look like?

Are they individual hexagons, not too tall, with a hole in the middle?

Are they all joined together in a long piece of hexagonal bar with a hole in the centre?

If they are the former style of nut blank, it could be faster to hold the tap in the headstock, let the nut blank wind itself onto the tap and then off the top of the threads on the tap. You only need to stop the machine when the tap shank is full. They make nut taps, that have a longer, slighly reduced diameter plain shank so it will accommodate a bunch of nuts before removing them.

 

[Morris]

Unlocked and pushed into contact until it's in sufficiently to draw itself.

That's how I do it. Lowest gear and inverter set at about 25Hz. Never had any issues with it.

 

[badabec]

Hello, 14mm hex bar, 7.8mm hole up the middle. I'm only making 7 or 8.
I've drilled the hole, tapped as far as I could then parted to give 10mm length. Back in with the tap.
I'm hoping the extra nut length will make up for any deficiencies in the metal strength.
M9 x 1.25, typical Citroen DS

 

[not done it yet]

I would do about the same. Drill hex for tapping size, tap about two nuts deep. Part off one, drill deeper and tap the next. The tailstock would be free for every one after the first few threads as the already threaded bit will pull in the tap, and the tailstock would go with it.

 

[Guzrik]

I undo the drillchuck and hold it by hand while it is only slightly centered by the MC in the tailstock.
This way I can just let it slip when it bottoms out in the hole.
If the chuck is big enough (13mm keyless Albrecht) this works up to m10.

 

[Seadog]

Hello, 14mm hex bar, 7.8mm hole up the middle. I'm only making 7 or 8.
I've drilled the hole, tapped as far as I could then parted to give 10mm length. Back in with the tap.
I'm hoping the extra nut length will make up for any deficiencies in the metal strength.
M9 x 1.25, typical Citroen DS

1-1.5 x the thread diameter seems to be the recommendation with steel. Twice the diameter for aluminium.