Drilling & tapping with vertical mill

DynMetalworks · May 19, 2017

I have a job drilling and tapping 1/4-20 holes in 1/2" CR steel bar. Approx 200 holes. I do not have a tap attachment for my mill. What would be the next quickest method? Thanks

Finegrain · May 19, 2017

You can just chuck a tap into a collet holder and feed it in, reverse the motor, and follow it out with the quill. Not the most elegant way, and if you push/pull too hard as the tap exits you can tweak the start of the thread, but it works.

Really need to be paying attention though as a bit of inattention at the bottom of the feed and you might make a little kaboom.

Regards.

Mike

michiganbuck · May 19, 2017

through hole yes.. dead end holes and then you need to count you turns..

tnmgcarbide · May 19, 2017

run the mill in back gear @ 100rpm or so, set the quill stop to slightly lower than final depth . DON'T TAKE YOUR HAND
OFF OF THE REVERSING SWITCH !!!!!!! if these are through holes, just put the part on parallels and don't bother with
the quill stop . just watch the tap and quick-reverse when you see it disappear , otherwise watch the quill stop.

i just use a drill chuck for anything 3/8 or smaller. let the machine do the feeding in and out, the quill will follow the thread , give it a nudge as it
exits. it becomes second nature.

Monarchist · May 19, 2017

tnmgcarbide said:
run the mill in back gear @ 100rpm or so, set the quill stop to slightly lower than final depth . DON'T TAKE YOUR HAND
OFF OF THE REVERSING SWITCH !!!!!!! if these are through holes, just put the part on parallels and don't bother with
the quill stop . just watch the tap and quick-reverse when you see it disappear , otherwise watch the quill stop.

i just use a drill chuck for anything 3/8 or smaller. let the machine do the feeding in and out, the quill will follow the thread , give it a nudge as it
exits. it becomes second nature.

+1

Took the 'clockspring' off my Walker-Turner DP .. what? ...forty years ago? .. to make tapping easier, got accustomed to that for drilling as well, no plans yet to put it back on.

Cole2534 · May 19, 2017

Thru holes? Drill on the mill then tap with the Milwaukee cordless.

Sent from my SM-G930R4 using Tapatalk

CarbideBob · May 20, 2017

On a manual mill I'd drill all the holes first then power tap at about 200-300 RPM as noted above.
Thorough are easy. Blind we sharpie color the tap at the depth to tell us when to hit reverse. This gets you within 2 turns.
Sometimes we will wrap the tap with electrical or duct tape at depth but if you hit the tape you have to retape.
On say 5-10 holes maybe you drill and then change to the tap before moving.
Drill chucks work best on blind holes as if you blow the depth the tap will spin in the chuck if you do not overtighten it.
The will also spin when the get dull without breaking if done right.
There is a bit of a learned art on how tight to turn the chuck key for different tap sizes and types.
Less is better as you learn. Better to stall shallow in the hole than to break in the hole.
Bad thing being you don't learn the high limit you can push until you break some.
The quill must be very free to retract and/or gets some help on the way out or you make "loose" threads.

Power tapping is scary at first and many use too low of a speed for the cutting tool to work efficiently and have a long life.
Bob

michiganbuck · May 20, 2017

Guess I would consider the application need . CR holds a good solid thread. Yes if a jobber job need to go with the spec. percentage.

Tap drill charts vary from #7 at .201 to 13/64 at .204

One can even go larger .204 is a 70% thread, #4 at .207 is a 65% thread and #3 at .211 a 60% thread.

I would use a new name brand tap and perhaps a fresh tap after 100 holes. Tap Magic to be a little safer.

DDoug · May 20, 2017

With 200 holes, the job should be done by now.

I agree with Bob, standard drill chuck will hold 1/4-20 just fine.

Ray Behner · May 20, 2017

Or you could use a Wahlstrom chuck and speed things up a bit.
Wahlstrom chuck: drilling, chamfering and tapping 5/16-18 - YouTube

Onepass · May 20, 2017

I'd send them out to a machine shop

Mcgyver · May 20, 2017

Ray Behner said:
Or you could use a Wahlstrom chuck and speed things up a bit.
Wahlstrom chuck: drilling, chamfering and tapping 5/16-18 - YouTube

Thats a pretty neat chuck. I don't tap with a keyless though....looks like its not an issue with that chuck

The OP hasn't said what the parts look like, but where ever possible, do the ops sequentially - drill everything, counterbore, tap etc using a vice stop for positioning so you're not swapping tooling. Not having a Wahlstrom, its a lot faster imo to swap parts out the vise

wawoodman · May 20, 2017

For 200 holes, I would look at it as a great excuse to buy a Tapmatic or a Wahlstrom!

And if they are through holes, use a spiral-point tap.

EPAIII · May 20, 2017

I agree. You can probably pick up a used one. I have used them and they are great: feed down until you reach full depth then feed up. You don't have to reverse the motor. And they usually back out faster than when they are going in so the job goes fast.

wawoodman said:
For 200 holes, I would look at it as a great excuse to buy a Tapmatic or a Wahlstrom!

And if they are through holes, use a spiral-point tap.

CalG · May 21, 2017

I would use the tap-matic

but don't they make "Dr-aps";-) Drill and tap combined? Very useful for pedestrian applications.
1/4"-2 Coarse Thread Combination Tap & Drill Bit | Fastenal

dian · May 21, 2017

does everybody have a mill with a reversing switch? none of mine has that. nor have my drill presses.

CalG · May 21, 2017

dian said:
does everybody have a mill with a reversing switch? none of mine has that. nor have my drill presses.

What? It's the big switch on the electrical cabinet.

A Drill press take some doing to get useful. A VFD makes the task easier. ;-)

CarbideBob · May 21, 2017

dian said:
does everybody have a mill with a reversing switch? none of mine has that. nor have my drill presses.

Welcome to the real world.

DDoug · May 21, 2017

dian said:
does everybody have a mill with a reversing switch? none of mine has that. nor have my drill presses.

I'm so sorry for you.....

A couple of my drill press's I have wired reversing switches
(along with a foot pedal) very handy.

Onepass · May 21, 2017

dian said:
does everybody have a mill with a reversing switch? none of mine has that. nor have my drill presses.

I remember back when I was a teenager (some guy named Ben had invented electricity the year before), a friend and I had come up with something to make and sell but we needed a mill. We went to a local machinery dealer that specialized in smaller machines and the home shops. He kept trying to sell us a single phase mill-drill but I was insistent on getting a 3phase and a rotary phase converter. The sales guy thought it was not smart to pay extra money like that and "that's why they have single phase motors on machines, so you can use them at home". He never did understand that instant reverse was a good thing!!
As far as tapping a bunch of the same size holes, I've got a few of those Procunier and Tap-Matic taping heads as well as an old Leyland-Gifford multi spindle drillpress with a taping function built in on one of the heads. Of course, it depends on the job but I'd probably just end up sticking a 1/4x20 gun tap for a through hole or a spiral flute tap in a blind hole in the jacobs chuck tightening it a little past hand tight and just go to it. ( 3 phase power and a reversing switch on a B-P )

Drilling & tapping with vertical mill

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