Power Tapping Question , How To ?

[Subwayrocket]

Up til now i've drilled my holes (axis's locked) , removed the drill , replaced that with a tap guide and hand tapped with the machine holding some downward pressure ... recently I made a 3/4" alum plate to hold flat parts horizontal... kind of a mini pallet thing, it had alot of holes that I had to tap by hand. I saw Tom Liptons power tapping video and tried a few bumping the Fwd/Rev . The tap was very prone to spinning free and I didn't really want to honk down too hard with the chuck to stop it. Short of buying an expensive tapmatic tapping head, what do I need to hold the tap for tapping using the mill ? Or do I just tighten the chuck more ? Seems like i'd damage the drill chuck jaws with the tap letting loose frequently . Yep it's a noob question but it's my first year owning a mill , any help appreciated ...response or link .

Thanks much , and everyone have a great New Year !

~Steve

 

[f350ca]

A tapping head would be great to have, but, limited funds have me tapping with the drill chuck. The shanks on the taps are hard, so I haven't noticed any wear in the chuck jaws. Spiral point ones are supposed to be better but I use hand taps as I have them. Run them in under power till they slip, then release the chuck and use a tap wrench to finish the thread. By starting them under power I know the tap is perfectly straight. Can't recall ever breaking one, they're pretty strong in torsion, not so strong in bending if you don't keep the tap handle straight.

Greg

 

[Wreck™Wreck]

Hold the tap in a drill chuck or collet and have at it, if the machine supports rigid tapping all the better.

 

[Subwayrocket]

Thanks Greg . This is pretty much what I ended up doing...power tapping with the drill chuck and the tap would go in maybe 1/4 to 3/8" before coasting to a stop . The problem was that if it slipped first, then I couldn't back it out with the mill.
Then I had to loosen the chuck, lift the quill and turn the tap back a quarter turn or so with a small adjustable wrench , re-lower the chuck back onto the tap and back it out with the mill.
I guess I could have tightened the drill chuck jaws even more but it thought I was pretty tight. The alum plate was very gummy and the chips weren't dropping thru too good.
Some holes tapped no prob , others I had alot of chips filling the flutes...and on a couple holes those extra chips dug out a few threads.
Maybe a 2 flute would have been better ??

 

[bfd]

advantage of spiral pointed taps is that the chips go down if its an open hole then the chips are not a problem. if you use a regular type tap the chips do wrap up in the flutes and can cause the tap to break. also drill chucks grab the soft end of the drill bit with fine ridges on the jaws. spinning a hardened tap end does ruin the chuck. but we all do it when required. please stick to spiral pointed taps for best results. the lisle tools have a set of sockets that drive a lot of the smaller taps up to 1/2" I drive mine with an old 1/2" cut off socket extention with flats ground on it to fit the chuck jaws. this does not slip. bill

 

[Subwayrocket]

Thanks Bill , i'll have to look up the Lisle tool . These are the taps I was using . First the 4 flute , then I went to the 3 flute .

edit: I found Lisle tap sockets , but I don't see any with flats to fit the chuck jaws . Have to keep looking.
-----------------------------------------------------------------------------------

 

[bfd]

sorry I don't know what you know about taps so I will bore you anyway. the bottom tap is a standard bottom tap notice that the end is almost complete with just a chamfer? you have 3 taps to a set, starter. taper and bottom. the starter has many partial threads on the end 7 or so depending on the size, used first, the taper tap has less missing complete thread 3 to 5 again depending on size this tap is used second then the bottom tap like above to clean up the bottom of the hole no missing threads. this is for ease of tapping harder and gummier materials like stainless. the top tap is a spiral tip tap. it can be used first, the chips are wound up and sent down through a thru hole best for power tapping. you can use it on a blind hole but be aware the chips will clog up the bottom. after you use it remove the chips with air or pliers then use the bottom tap to finish up the hole. notice that these taps are undercut after the threads that means that you can go deeper than the length of threads on the tap good for deep holes. finally the spiral tap can be run straight through since the chips clear out of the way. but the normal taps need to be turned about 1/2 turn then stopped rotated back until the chip breaks then go down again. the chips will curl inside the flutes and jam the tap and contributes to broken taps bill

 

[bfd]

add make sure you use some kind of cutting fluid don't tap dry unless you like breaking taps. remember you will break the tap at the most inopertune time never when it doesn't matter. always on the last part with no extras murphys law will always happen Ive broken my share and then some bill

 

[Subwayrocket]

Yep , that's why I went to using the top tap in the picture above . Even with this one the chips still jammed quite a bit . I used tap magic , also tried WD40 and regular cutting oil. All worked pretty much the same. I don't know the grade Al of these plates I have , but the chups that came off were very hard , almost like mild steel . Makes me wonder if it is 7075 , a fab shop that drops at my buddies scrap yard often brings stuff with labels on the ends , and i've seen both 6061 and 7075 .
Thanks Bill , no prob on the extra info . I appreciate it. I've watched the all encompassing video on taps by mrPete a while back so yeah I know what each type is .

 

[T Bredehoft]

No one has mentioned Spiral Fluted taps, they are for non-through holes, the chips come out the back, toward the drill chuck. No binding of chips in the flutes. I have a 4 40 Spiral Fluted tap that works a charm. I do not tap to bottom with the mill, though, I finish the tapping by hand.