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Pigtail mop thread help

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Jon Gibbs07/04/2014 11:50:17
739 forum posts

Another question please.

I'd like to cut a threaded taper for a pig-tail mop mandrel but my lathe doesn't have either a taper attachment or a power cross-feed. It's a plain-old Myford ML7.

I think I could do it by moving my tailstock over but is there another way because I'm hesitant to change the tailstock alignment as it's taken me a while to get it right on centre wink

Any guidance or ideas would be very gratefully received.

Many thanks

Jon

Keith Long07/04/2014 12:19:55
842 forum posts
11 photos

At under £6 inc postage and vat from RDG is it worth the effort of making one?

Robbo07/04/2014 12:26:11
1504 forum posts
142 photos

You should be able to get a long enough taper for a pigtail just by angling the topslide.

Ian S C07/04/2014 12:51:24
avatar
7468 forum posts
230 photos

That's right Robbo, but he wants a thread on the taper also, and you can't do that by angling the top slide. Go for the 6 pound one. Last time (only time) I did a thread on wood, I used a triangular file, no lathe. Ian S C

Bazyle07/04/2014 12:56:47
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5391 forum posts
206 photos

Aren't pigtails threaded? You need to be able to link the topslide handwheel to the gearbox/change wheels to thread at an angle. This could be done with a flexible drive. Interesting but not worth the effort.

Jon Gibbs07/04/2014 13:11:25
739 forum posts

Thanks all for the guidance and discouragement wink

- I didn't think it was going to be straight forward but thought it'd be a fun thing to try.

I already have a cheap pigtail on a 1/4" shaft but another one on an MT2 arbour would have been pretty handy.

Anyway, at least I have the satisfaction of knowing that I wasn't missing something obvious.

Thanks again

Jon

John McNamara07/04/2014 13:45:48
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1313 forum posts
113 photos

Hi John Gibbs

If you have a boring head with a Morse taper that matches your tailstock? A cheaper Asian one will do; you can set it over to the required angle without disturbing your tailstock.

To use it make up a hard centre that fits in the tool holder hole in the boring head instead of a boring bar.
I don't particularly like hard centres so I made a small stubby Live centre that fits in the boring head hole as well.

I find it works rather well. The setup is a little less rigid, however for most work is fine, and it saves resetting the tailstock.

Boring head Images: **LINK**

Regards
John

Jon Gibbs07/04/2014 14:01:02
739 forum posts

Hi John,

Thank you for the suggestion. I did wonder about that possibility - possibly with a home-made offset centre based upon a blank-end arbour.

Is there a trick to ensure it stays horizontal in the morse-taper - A draw-bar through the tailstock perhaps?

Thanks

Jon

John McNamara07/04/2014 14:03:51
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1313 forum posts
113 photos

Re Pigtail Mop Mandrel

Images: **LINK**

They all look constant pitch to me, only the diameter changes.

A while back I had to make a part for an antique for a friend it was a coarse spiral on a short tapered steel part.

The solution was to use a piece of springy steel about 8mm in diameter and 300mm long, this was held in the three jaw, the part (Centre drilled) was attached at the other end. Using the boring head I set it over to the correct angle, forcing the thin bar to deflect. Using light cuts and slow revs I was able to cut my spiral thread, The bar did not break. It worked.....

I guess this story only needs a bit of fencing wire to complete it. I will save the wire and that story for later!

Regards
John

John McNamara07/04/2014 14:28:18
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1313 forum posts
113 photos

Hi Jon

My tailstock self ejects so I normally give the centre or centre drill a good shove when putting it in, it is 3 Morse taper. I keep it and all tapers that go into it scrupulously clean and almost dry so I get a good grip, I don't oil them, and just before I insert them I clean the hole with my finger and drag the taper on the tool through a clenched hand to check for any dirt.

The tailstock barrel is keyed so it cannot rotate and it has a lock to make it rigid, the turning forces should keep it against the key if it is loose in the key anyway and there is no lock. If your tailstock has a through hole you could use a draw bar.

I would not recommend this method for heavy or high accuracy work, the rigidity is not as good as using the tailstock. for small pieces it is fine.

I should have mentioned the boring bar movement axis should be horizontal, or you will not get a straight taper.

Regards
John

Jon Gibbs07/04/2014 14:35:27
739 forum posts

John,

Thanks very much. As you say the pigtail is not a precision taper/thread so a bit of movement will not be a disaster.

I will not use this for the Morse Taper.

Jon

frank brown07/04/2014 19:49:25
436 forum posts
5 photos

When you make your pigtail blank, centre drill one end, for a chuck mounted centre and driving dog. Turn the other to have a 60 degree short point on it, this is your live centre. Jury rig a piece of steel with a countersunk hole in it (female fixed centre) at a suitable offset from the lathes centre line to make the front side of the pig tail parallel to the lathes axis. Back the tailstock up against it and grease the centre. And go for the thread!

Frank

Jon Gibbs08/04/2014 07:48:31
739 forum posts

Thanks Frank. Suggestions much appreciated.

Jon

Robbo08/04/2014 09:32:53
1504 forum posts
142 photos

Hi IanSC

I'd let thoughts of the taper make me forget about the need to cut a thread on it. Ain't old age wonderful.

Ian S C08/04/2014 12:13:04
avatar
7468 forum posts
230 photos

Hi Robbo, the mop I mentioned, a wooden handle for a floor mop, I wasn't thinking engineering when I wrote up last night. Ian S C

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