Power Tapping

[shopandmath]

Power Tapping in the milling machine without a tapping head
This some times unconventional tapping technique that has become mainstream

Watch as I demonstrates a method to tap on a Bridgeport mill
(this video is intended for apprentices and people new to machining)

[marksbug]

Ive taped many holes on mine.

[Toolmaker51]

Ive taped many holes on mine.

Me too; but not with my drill chucks! Shops with the worst drill chucks are those where wholesale tapping is done with same chucks they drill with.

Taps are harder Rc then drill shanks; and gall the jaws when they slip, even more so at the top flats [drive square]. The evidence shows when a drill then slips, and upper end is burred more than other areas.
There are all kinds of economical tap drivers; comparable in cost to equal size quality chuck. I use the Hardinge TT; 5/8" shank Ø, less daylight needed to switch out and tap stays mounted. Favorite chuck is also mounted on 5/8" Ø shank.
Though, normal procedure is to locate and drill an entire pattern and return to coordinates that get tapped after chamfering, also dependent on quantities, size and other variables.
Expecting disagreement, but I'm not chipping out broken taps, scrapping parts, or needing to replace chuck jaws. And favorite chuck is a keyed Supreme; still holds many sizes just hand tight...

[shopandmath]

very well put
I do agree with you
in the in the environment of this shop (not a money thing)
we need to limit the number things in the space example there is only one coolant and only one oil
each piece needs to be painted a color for each machine
Ray

[Crusty]

I used to see the guys in the shop thread holes using the floor drill press. They'd get the tap spinning at a pretty good rate, switch off the power to the drill press, and quickly bring the tap into the hole where the inertia would usually carry it on through, and I don't recall seeing broken taps. This all changed though when the shop foreman finally bought a Tapmatic.

[Toolmaker51]

I like normal tapping heads for drill presses, as few have reversing spindle, or too much inertia for a 'smooth' deceleration and reverse. The little Hardinge TT [including all the similar de-clutch drivers] don't need a torque arm [tommy bar] and are 1/3 or 1/4 overall length of ETTCO, Tapmatic etc. Can tap blind using depth stop by adding the .100 for the body to disengage pin driven collet holder. Cascao, homeengineer, Paul Jones..., can't recall who, made one DIY. A threaded body compresses a decent valve or die spring, threaded body adjusts the drive torque. [Excellent student project!] Also productive on lathes...engine, chuckers, turrets.
They all disengage while tap is down hole and feed lever is lifted. While body spins, tap is static. Can wait all day to reverse spindle.
Only 'drawback' is when many holes are encountered, via normal tapping head, increase RPM to back out tap. Serious time saving, easier on taps also, with proper coolant in play.

[Crusty]

Not really finding much information on how the Hardinge operates, could you elaborate a bit? Does it require a reversing spindle to back the tap out? Is it viable for use in a drill press? I've got a Jarvis head but it's really too big for most of my needs and the Supreme Push/Pull I have is best suited for a hand drill, so I'm looking for a good, affordable solution for my drill press threading holes up to 3/8" or thereabouts. Is the Tapmatic 30x a good choice?

[Toolmaker51]

Not really finding much information on how the Hardinge operates, could you elaborate a bit? Does it require a reversing spindle to back the tap out? Is it viable for use in a drill press? I've got a Jarvis head but it's really too big for most of my needs and the Supreme Push/Pull I have is best suited for a hand drill, so I'm looking for a good, affordable solution for my drill press threading holes up to 3/8" or thereabouts. Is the Tapmatic 30x a good choice?

Morning Crusty!
It does need a reversing spindle, but...
The TT is pin driven...literally engaged or not, by a small [3/32?] pin, but no clutch adjustment. The body is 5/8" shank, would take an awful large daylight eating, centrifugal force generating, drill chuck. A better drive would be a Morse Taper end mill holder in 5/8". Shank's counterbored for SHCS, screwed into the closely fitted collet holder, and compresses the return spring. Had mine before even the Bandit Bridgeport 2 axis [X, Y & quill Z] CNC mills arrived, worked perfectly there too. A full set of collets hold #4 [or #6 ] to 1/2", don't think any tapper has that range or compactness. Conveniently [thank you, gods of standardization] metric taps are same shank sizes. Mine is currently mounted in a quick-change R8 Sandvik C6 holder. Sometimes I want tapping by coordinates, others I drag across on table. It is a semi-floating arrangement, allowing for some X-Y misalignment, with some linear too.
If the machine spindle advance 'falls behind' feed rate of tap, it disengages, just needs fingertip pressure on feed lever to reach depth. It does need a reversing spindle. On a chucker or turret lathe, reverse is a required feature, and feed depth are individual stops for each index, which is what they are built for. But it does fine on a mill too.
As you know, a Supreme works like machine tappers with built in reverse, after and during retraction. It's not a good idea to pump or peck a tap through like acceptable for drilling, due to chip evacuation. If tap does not reach intended depth; it is dull, ill-prepared hole, or inadequately sized tapping head.
Tapmatic 30 sized [lots of copies] will pull 1/4-20 in steel, maybe 5/16-18 in aluminum. Also, most tappers have clutch adjustment for driving torque. I start at lowest setting that will drive successfully; which becomes a monitor for tap getting dull.

Awhile back, debated finding a Supreme tapper for 240 tapped 1/4-20's in 10 foot lengths of 3/8" hot roll, borrowed a Tapmatic 30 instead. TT would've hindered that job, one hand needed to manipulate stock, another on the quill, can't reach reverse switch with my non-Pinocchio'n nose...Used mill and three outboard roller supports, a guide rail clamped over 1 Tee slot, holes positioned over the next slot to accumulate chips. Not counting set-ups, drilling and chamfering each side first, did 60 holes per bar in 9-odd minutes, with a single fresh R&N TiN tap and drip fluid.

[Crusty]

I just went out and looked at my DP motor and it's a capacitor motor, so rewiring it for fwd/rev is a no go. Looks like I'll have to find a reversing tapping head to use it for threading. I'd like a tapper as short as possible because it's a bench DP and I want to give up as little headroom as possible. I'm open to suggestions of tappers you might know of that might fit my bill. I have used that Supreme Push/Pull successfully in my DP but it's a three handed PITA procedure.

I actually have a South Bend drill chuck on that DP which will hold 5/8" tools. Unfortunately the spindle end is a JT3 with no way to change it (hey it cost me $20 and it drills fine) so that limits how I can drive a tapper.

[Toolmaker51]

Yes, a couple road blocks vs cap start motor and J spindle...eventually I'll post reversible DP next to turret mill Bridgeport clone [mine is 5hp Comet], with a counterweight table to add out-feed perch.