tapping issue using tapping head

1018, .625 deep, 29/64 hole, 1/2x20, 670, 630, or 440 rpm, drill press work using a tapping head with 3 flute straight tap w/spiral tip. first few threads are ripped out (for lack of a better term). tried shutting off before reversing and unscrewed by hand. top threads were "worn" or thin. when reversing they are virtually non-existent - so i believe there is damage going in and out. suggestions? thks

Is this the first time you have used the tapping head?

Sounds like you're over feeding the first few threads, ......like pushing down to hard to get a start?

For HSS taps your speed is very high, my Dormer book to hand says 20 to 40ft / min or for 1/2'' <> 175 to 300 rpm.

IME until you're used to them auto reverse tappers are best run slow.

sable said:

Is this the first time you have used the tapping head?

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first time with anything of relative size in steel

Limy Sami said:

Sounds like you're over feeding the first few threads, ......like pushing down to hard to get a start?

For HSS taps your speed is very high, my Dormer book to hand says 20 to 40ft / min or for 1/2'' <> 175 to 300 rpm.

IME until you're used to them auto reverse tappers are best run slow.

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i'll drop the speed and report back. (seems like my app said 690 best i remember)
and i am pushing relatively hard to start

cg285 said:

i'll drop the speed and report back. (seems like my app said 690 best i remember)
and i am pushing relatively hard to start

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MMMM? as soon as the tap bites - which you'll hear or feel, I just follow the tap down with just enough pressure on the handle to keep the tapper engaged.

the info with the tapping head said over 7/16 use 1000rpm
i don't have that so i went to 690 at first. dropping further didn't help. went to 1200 and was better but i think i will order a 2 flute and try that

cg285 said:

the info with the tapping head said over 7/16 use 1000rpm

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In steel? ....that's over 100ft min, ...for drilling turning and milling with HSS - possibly yes, ..........but for tapping, not in this guys shop.

Tapping heads are an absolute dream to use once you have the "feel" for them. I remember my dad bringing home a VHS tape from tapmatic that showed off their heads and the speeds that they could go... didn't understand much of it back then (nothing really) but my dad seemed very impressed. MANY years later I started using them and realised that speed is not really always what you want to get good threads (as Sami said, as soon as I clicked this thread I thought I would see a comment from him).

The problems I have found with setting someone up to use them is they try to force the thread... remember if all is good all you have to do is actually guide the "feed" down with not much pressure unless you are on a drill press or radial that has a really strong spring.

Then, start REALLY slow with your RPM and work your way up till you find the sweet spot. The guys that sell you taps want you to run the balls out of them but that does not always work.

Make sure that you are not forcing the head to go back to forwards revs by plunging it into the hole. They get sticky and tend to not always go clockwise again once out the hole so make sure that you are going clockwise before you go in.

Have a dead stop on your depth so that it gives enough run out for the tap, that's easily adjustable by babying the first hole to get it just right. I have seen it too many times that guys panic and try to pull up while the poor tapping head is trying to catch up and reverse.

Use LOADS of cutting paste/fluid/bla bla bla and make sure that chips are off the tap after each hole. A simple brush to put lube on and take off the chip from the last hole is a life saver.

There is a reason that decent tapping heads are pricey even second hand, they are a damn good invention, I would really like to shake the hand of the person that came up with an initial design. I tried to sell one to a shop up the road that I saw hand tapping all their holes to try to help them out. They returned it because they said they were breaking taps and were not willing for me to show them how to use it. Come to think of it, it is probably why their shop hand had pretty damn strong arms.

Persevere with it, you won't be sorry.

Limy Sami said:

In steel? ....that's over 100ft min, ...for drilling turning and milling with HSS - possibly yes, ..........but for tapping, not in this guys shop.

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Yup, from a quick guess that's 30M/min territory which is fine for a HSS drill if you can feed it hard enough. Tapping, the OP has bigger balls than me!

230-250 rpm, plenty of cutting oil.

Don't hang off the handle like an ape. Enough pressure to engage the tap, then just follow it down easy, with enough down force to keep it rotating the right direction. If it's a blind hole, back off the clutch so the tap doesn't jam in the bottom.

NAST555 said:

Yup, from a quick guess that's 30M/min territory which is fine for a HSS drill if you can feed it hard enough. Tapping, the OP has bigger balls than me!

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it's a 4:1 reduction on the head

If your haveing to push the tap in sounds like its a fucked tap, a good tap should just almost instantly pull its self on in, if its not dragging its self in you have probably destroyed it already. Look at the ends of the flutes with magnification for chipping, any and its no longer any good.

Tapping heads are a feel thing, taps do a lot of rubbing so you have to go slower than drilling, but with better coatings you can still go pretty quick, but 1000RPM on a half inch tap in steel is not going to happen,

adama said:

but 1000RPM on a half inch tap in steel is not going to happen,

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Sure you can....only your not going to get any nice threads.

I wonder if the tap is already toast, and the OP should start over with a
the new guidelines, as well as a fresh new tap.

adama said:

If your haveing to push the tap in sounds like its a fucked tap, a good tap should just almost instantly pull its self on in, if its not dragging its self in you have probably destroyed it already. Look at the ends of the flutes with magnification for chipping, any and its no longer any good.

Tapping heads are a feel thing, taps do a lot of rubbing so you have to go slower than drilling, but with better coatings you can still go pretty quick, but 1000RPM on a half inch tap in steel is not going to happen,

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maybe there was some miscommunication on the rpm. spindle speed 1000, tap speed 250

Right 4-1 reduction, gotcha

I still say you're going too fast, and as Adama says, check the condition of the tap, .........and while you're at it, as has been mentioned before - if it spins in reverse just hanging in the drill spindle, as some do, does it shift cleanly and smoothly in to forward drive.

Have you tried slowing the tap down so it's doing maybe 100 rpm? or less ..at 100 rpm your will still get 5'' of 20 TPI thread a minute, .which while not fast, isn't hanging about either.

IME the slower a tapping head runs, the more controllable it is for beginners.

Out of interest, which tapping head do you have?

cg285: I'm going to ask a dumb question, but do you perchance engage the feed when the tap starts in the hole?

JH

Limy Sami said:

Out of interest, which tapping head do you have?

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veratapper (ridgid)

James H Clark said:

cg285: I'm going to ask a dumb question, but do you perchance engage the feed when the tap starts in the hole?

JH

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not sure what you mean. using a drill press

cg285 said:

not sure what you mean. using a drill press

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How are you using your versatapper?