Tap drivin' man (tap driver in AXA holder?)

I've done it using the tail stock (with 3 jaw chuck), and putting the lathe in back gear. I've only tried the quick change for long boring bars, but never a tap. Tell me how you know it's perfectly concentric both vertical and horizontal? ignator

I will often put a tap in a drill chuck but not very tight and leave the tailstock loose. Great for starting a tap. I have a tapping head in a turret lathe that will spin the tap before breaking it and it's spring loaded to compensate for feed.

You can, but a tap once started pulls the tail stock along just fine. I just sorta bonk the tailstock-mounted tap into the hole with the lathe running. The tap catches and the hole gets threaded. Problem with using power drive on the tap is if the stock slips rotationally in the chuck or collet then the tap must drive the stock axially in the headstock workholder or something must get barfed up or break.

I do this in my CHNC Hardinge. (CNC lathe) The taps last far longer if everything is rigid. A CNC lathe has virtually no backlash, if your machine has backlash, I could see trouble when reversing to back out.

I also do rigid tapping in my CNC mill. again, the taps last far longer. In fact my first job after coffee is drill and tap a dozen holes in a part I mounted up last night,

Karl

IMO, a tap driver in a lathe (if you mean the geared type, not just a tap held in the TS chuck) might be a bit of overkill. Sensitivity would be better served and give you more of the tapping experience if you put the spindle out of gear and turned it by hand. I have an outboard crank on the spindle which I use with this method.

in the TS chuck)

more of the tapping

an outboard crank on

Louis,

I only mentioned hand cranking of the spindle as a means to achieve max control when tapping in the lathe. For me, it makes a good diagnostic approach when trying to isolate threading problems in the lathe, both single-point threading and tapping. As far as procrastination goes toward making an outboard hand crank, don't make a crank. First try it out by hand turning the chuck with the spindle out of gear. The lead screw will still advance just as if things were in-gear.

If you decide to make a crank, I recommend obtaining a tail-pipe expander (HF) as a means to easily insert / remove the crank from the hollow outboard end of the spindle. I have 2 of these. One fits the spindle bore and the other fits my 5-C drawbar.

Bob Sw> IMO, a tap driver in a lathe (if you mean the geared type, not just a tap held

in the TS chuck)

more of the tapping

an outboard crank on

On a lathe with traditional QC gearbox, there will be so much backlash in the long gear train that there is no way at all to reverse the lathe to back the tap out. In many cases it will be more than half the thread pitch off, so either the tap will break or the thread will be destroyed.

You could use the threading feed to advance the tap, but you'd have to release something to allow the backing out.

Jon

The first thought was to release the half nut, but that does nothing for the lathe rotation... Think of it as a rota-bur...

The best way I found to tap in a manual lathe is to let the tail stock float unclamped feeding in with the tailstock handle. I use morse tap collets that hold the tap rigid in the tailstock. I never had a problem with broken taps. You could use a different tap holder or even a jacobs chuck to hold the tap but then tap slippage becomes a problem. When you feed in with the tailstock wheel it will tend to pull the tap in on its own, you just have to keep a little pressure on the handwheel to take up the movement of the tap feeding in. The tailstock itself will move with the tap but by turning the wheel you try to keep that movement to a minimum.

John

What do you mean by a "tap driver"?

I use taps regularly in a releasing tap holder in the bed turret on my Clausing. Feed is by hand using the spider, and as soon as the tap digs in, it pretty much self feeds, and you are simply following it.

When you reach the preset stop on the turret station, the spindle keeps turning and pulls the tap about 1/8" or so to disengage a dog clutch and allow the tap and its holder to spin freely. Then I stop the spindle and reverse it to back the tap out.

If you mean something like a TapMatic self reversing tapping head, that depends on the shank of the TapMatic (or other brand) rotating to power the tap forward and in reverse as the dog clutch releases the direct drive and engages the planetary gear to reverse the tap as you pull back.

If you mean a *rigid* tap holder, you may have problems stopping the spindle quickly enough to avoid overrunning the depth (in blind holes) or running up on the unthreaded part of the tap on through or deep blind holes. You need something which will release as soon as the carriage stops moving like a releasing tap holder for a turret lathe or automatic screw machine.

eBay auction #14016680222 is an example. This one has a 1" shank, which I think is larger than the boring bar holder for the AXA toolposts. I think that they limit at 7/8" or 3/4". Check yours.

But they have gotten a *lot* more expensive on eBay from when i was buying mine.

Aha! Here is a 3/4" shank one and it is even selling for somewhat less: Auction #310186077480

Anyway -- some of them just release, and you need to use the friction while drawing back on the tap holder to back the tap out. Others have a built in ratchet which lets it lock up when you reverse the spindle. But be careful to check before you use, as the ratchet direction is reversible by disassembling the holder and moving a part.

Enjoy, DoN.