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metaler
17th Oct 2016, 07:28 AM
The special feature of this tapping stand in my latest video is that it feeds the tap automatically at the pitch of the thread being made. This therefore, avoids the need to use a taper tap and a good thread is achieved from the first turn, especially beneficial when tapping holes in thin components.

The auto feed mechanism can also be used when tapping on the lathe.

The video can be found here
https://www.youtube.com/watch?v=SHsbBZywDpM (https://www.youtube.com/watch?v=SHsbBZywDpM)

Also, the page on my website for this tapping stance can be found here Tapping Stand with Automatic Feed (http://www.homews.co.uk/page41.html)
Harold

jhovel
18th Oct 2016, 12:29 AM
Hi Harold,
I've seen your design when you first publsihed it and was very impressed.
However, before you were 'one of us', I felt awkward to contact you with my query:
I understand you don't need to use a taper tap with this approach, but isn't ALL the cutting done by just ONE tooth at the very end of the plug tap (well, maybe even 4 or 6 of them, since most have a very short taper on the end)? That - just to me - also means the rest of the tap never sees any distributed wear and would make the first few teeth wear pretty quickly - or not? If not, why not, please?

metaler
18th Oct 2016, 03:48 AM
Thanks Joe for your post but you had no need to be reluctant to contact me by other means in the past. Now to your question.

Lets consider first using a taper tap followed by a plug tap on my tapping stand. The first stage using a taper tap would work in the same manor with the feed mechanism advancing the tap at the same pitch as the thread. However, when we come to using the plug tap the same situation will again exist, but with one major problem, how do you get the plug tap to synchronise with the already produce partial thread, as it would try to cut a totally new thread.

When tapping by hand the plug tap can be synchronised with the taper tap thread by a process of manually feeling that the engagement is correct.

The mechanism I use in the stand is identical to that used in motorised tapping machines in industry where large numbers of parts would be produced using just a plug tap. Perhaps now though computer control would be used to establish the required feed rate but a plug tap would still be used.

The purpose of the apparent cutting edges behind the first one or two on a plug are just to keep the tap moving in a straight line. Also, a plug tap will do almost as much work following a taper tap as it will if it is just plunged in as with my tapping stand.

Incidentally, I do now tend to use roll taps with my tapping stand as they produce cleaner threads and with no swarf to interfere with the screw being inserted. See my feed mechanism being used on a lathe at the end of the video.

Hope that helps Joe, but do not be frightened to come back with other questions.

Harold