graffian
Seer unto the end of his beard
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Shouldn't do. I tap in the mill and lathe, holding taps in a chuck.
If the tap is pulling the chuck out I would have thought drills would do the same.
- Thread starter Welderpaul
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Shouldn't do. I tap in the mill and lathe, holding taps in a chuck.
If the tap is pulling the chuck out I would have thought drills would do the same.
julianthegypsy
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Surely the tap is pulling itself into a pre drilled hole because once it gets started it's threaded, whereas the drill needs pressure to force it down. Let go of a drill and it stops cutting but as long as a tap is turning, down it goes...
MattF
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He has a depth actuated auto reverse system though, does he not? It only goes down if it isn't in reverse.
If it's fed and retracted correctly there is no problem, if it's mechanically fed as in this case the feed and retraction will match the pitch to a given rpm. It's the same as the lathe with screw cutting, its dictated by a gear box.
When feeding down there is no actual pressure at all as the feed rate matches the pitch of the thread. When retracting the same applies, with no pressure either up or down in theory a MT can not be pulled out of the female socket. This applies to paul's machine with mechanical gearing.
With tapping heads similar applies apart from nearly all tapping heads have a sprung nose, this means you get a + and - from the taps natural position in the head. This in turn allows for over or under pitching with no advertise compression/ tension in the head. Hope that helps.
Edit: sorry Julian, I really should have quoted you from post 21.
Kind regards,
Scott
It depends on the machine really, they vary. Not knowing Paul's machine I can only have a good calculated guess at what system his uses. I would think (as above)its a constant drive box. This is not a dedicated tapping machine (far as i know) as such it will be a constant drive ie the tap can only be reversed when that stop it struck. This is unlike dedicated tapping machines where if you stop the down feed you have a position in the quill (spindle) which will give you no drive. The machine is still running but the tap is not engaged due to no down or upward pressure. Some machines use dogs or a reversing cone clutch to get the required features . Down and upward drive and a neutral position.
Kind regards,
Scott
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I have a couple of Herbie's that reverse on the quill set on stop bars, they actually kick the motors into reverse, the problem with them is the shear brutality and if you haven't got everything set cock on your left with a tap in the hole, to go with that set up Iv got some old type tap holders, these allow for the quill not to exactly match the feed of the tap, and also some lateral movement, origanly they came from a ward capstan.
I have got some auto reversing heads which I find much nicer to use, and are fine for a non fed quill, there allot less brutal and the rubber Colet's take away much of the shock. big money for what they are tho. TBH when I tap in the lathe I normally dont bother with anything fancy, MT in the Jacobs leave the tailstock lose and let the tap be thead in, done masses of blind holes in EN8 this way.
I have got some auto reversing heads which I find much nicer to use, and are fine for a non fed quill, there allot less brutal and the rubber Colet's take away much of the shock. big money for what they are tho. TBH when I tap in the lathe I normally dont bother with anything fancy, MT in the Jacobs leave the tailstock lose and let the tap be thead in, done masses of blind holes in EN8 this way.
julianthegypsy
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No apology needed Scott, I was just trying to figure out what was going on and what seemed to be happening. I also wondered if the problem might be because the feedrate may be mismatched, since its not a dedicated tapping machine. Feed rate would have to depend on the pitch of the thread wouldn't it? Therefore you would need to have a range of tapping feeds to get it right? If the feed is changed by stops I can also see problems arising. I have a small, ancient tapping machine which looks like a dentists drill mounted on a pillar, quite bizarre but great fun to use. Like reversing tapping heads, it has two cone clutches. When you turn it on it reverses, the direction changes instantly when you press the lever and the tap contacts the hole to be tapped. When it gets to a preset depth it just stops, let go of the lever and it reverses. Very simple, incredibly quick, I only wish it were bigger!
