self feeding tailstock

[baldrocker]

Hi all
To all the ML7 devotees.
At present I can tap using low speed and leaving the TS
loose so it is drawn along by the tap doing its thing in the workpiece.
Is it feasible to attach the tail stock to the saddle in some way
so that if using lowest gearing and engaging the leadscrew so as
to have self feeding tapping and drilling to a maximum of say 8mm.
I think I said that right. ???
Cheers
BR

 

[Lew Hartswick]

I haven't a clue as to what an ML7 is but on any lathe I've used what you propose
AIN'T gonna work. At least for long. Unless it's a through hole using a spiral
point tap you have to stop, back up to break the thread and clean out the chips
every couple turns.
...lew...

 

[BobWarfield]

ML-7 = Myford, The English Southbend (LOL)

Actually, I have seen an account somewhere, probably on Practical Machinist, of a lathe that had a sort of linkage you could attach from the carriage to tailstock. It was removable and intended more for drilling than tapping operations.

The spiral flute taps are pretty good at directing the chips up and out. Depending on the hole depth. I use them all the time power tapping and haven't had a problem. And of course, if its for mild steel or aluminum a thread forming tap can be used. They don't make chips.

I would be a tad worried about getting the feed rate exactly right, so if I were to rig up something like this, I imagine I'd use some kind of floating tap holder in the tailstock.

The thing is, it's really pretty easy to set up a drill chuck on a QCTP holder. If you've got a DRO, you can easily get it lined up on the centerline and then you don't have to worry about dragging the tailstock along.

Cheers,

BW

 

[Noitoen]

If you use a floating type tap holder it will feed itself. I use low speed and hold the tap holder by hand and if it gets "stuck" I just let the knurled holder go and stop the lathe without breaking the tap. Use this up to 12mm with good results.

 

[bentprop]

On top of all that,you would need a different feed rate for every thread pitch.This runs into hundreds of possible gear combinations.Sorry to rain on your parade,but it just seems a little impractical.

 

[John S]

Hans, I don't see the problem with the different gear trains it's only the same as screwcutting.

As regards about backing off production machines like turret lathes never back off, they feed in to depth then back off.

JS.

 

[gbritnell]

Hi BR,
When I was an apprentice we had 6, 15" American engine lathes in the shop. We machined all kinds of material for the casting industry. On some of the pouring basins we had to drill some very large holes (up to 2-1/4 inches). The carriage had several tapped holes on the tailstock side and to this they attached a bar that hooked onto the tailstock. The appropriate feed rate was set up on the gearbox and the feed lever was engaged and you had a powered tailstock. I guess you could do the same with a tap, the only problem being that you wouldn't know how much pressure was being applied to the tap. We would mount the tap in the appropriate sized tap handle, put a spring center in the tailstock chuck and bring it up to the tap, start the spindle at slow speed and hold the tap handle. If it felt like there was too much pressure on the tap all you would have to do is release the handle, let it turn, turn the spindle off and back the tap out.
gbritnell

 

[tel]

I've seen it done for drilling, but not tapping, tho' if you took the trouble to set up the correct gear train it should work - hand on the 'off switch' tho'.

 

[baldrocker]

Thank you gentlemen
BT