Tap alignment in the mill and lathe?

[John HinkleyParticipant @johnhinkley26699]

Some while ago, I made the Hemingway tailstock die holder and was extremely pleased with its effectiveness and design.  As I read through this thread, it occurred to me that a slight modification to the die-holding arrangement would allow a tap to be held in the device and the cone clutch of the die holder used to control the feed of the tap into the workpiece, thus avoiding, or at least reducing, the risk of tap breakage.  Sort of extension to Howard’s suggestion, above.  Of course, it does mean making the Hemingway kit in the first place, but that in itself is a worthwhile project in my opinion.

John

 

[Bo’sunParticipant @bosun58570]

Mmm.  Maybe there’s a market for a Tailstock Die Holder tap adaptor?

[JasonBModerator @jasonb]

They are available I’ve posted this before they are availably in this form and also ones that fit into the holder inplace of the actual die.

Tailstock Tap & Die Holder 9pc Set

https://www.chronos.ltd.uk/product/new-3mt-tailstock-die-holder-tap-holder-set/

[Bo’sunParticipant @bosun58570]

Thanks Jason,

Yes, I’ve seen those, but was a little wary.  They look to have the same style chuck that you see on ‘T’ handle tap wrenches (I could be wrong of course), and judging by Joe Pie’s video, they may not hold the tap true enough.  What was your opinion of them?

[John HinkleyParticipant @johnhinkley26699]

Not quite the same, Jason.  The Hemingway version allows you to ‘slip the clutch’ to give greater control of the tapping speed, irrespective of the speed of the lathe chuck. Ditto with a die.  Either procedure can thus be halted instantly just by releasing pressure on the lever. I also personally don’t fancy gripping a rotating tap or die holder with my tender mitts.

John

 

[JasonBModerator @jasonb]

Its not a problem for those with builders hands☺

Yes that one has the two jaws with a Vee in each like an old brace and bit. Not noticed any problems in use but I will have a measure tomorrow and see if there is any  thing worth worrying about. I see quite a few people here suggesting the use of tee handle type wrenches with a pin/ctr at the back so must be good enough for them too.

[John HinkleyParticipant @johnhinkley26699]

I agree, Jason. Simple is often better, I find.  But what’s the fun in that?  Nuts and sledgehammers come to mind.

John

 

[bernard towersParticipant @bernardtowers37738]

your suggestion John about a conversion piece for the Hemingway kit has its merits especially if made as an ER nose so tap holding collets could be used. I feel a project coming on!!!

[John HinkleyParticipant @johnhinkley26699]

Bernard,

I no longer have the Hemingway die holder in my possession, nor the lathe for I which made it. Nevertheless I went as far as looking for a suitable ER20 chuck with parallel shank suitable for such a conversion. Readily available in the ten to twenty pound range.

John

 

[bernard towersParticipant @bernardtowers37738]

John,

Yes i had thought of going that route but I think that a custom one that looks part of the original design might be better. will get back to you in xxxxxxxxmonths!!!

[Bo’sun]

On Bo’sun Said:

Thanks Jason,

Yes, I’ve seen those, but was a little wary.  They look to have the same style chuck that you see on ‘T’ handle tap wrenches (I could be wrong of course), and judging by Joe Pie’s video, they may not hold the tap true enough.  What was your opinion of them?

As I said they work, not sure how true you or Mr Pie feel you need but 0.001″ at the square end is plenty good enough for me, the business end will ctr itself in the hole.

So what Accuracy are YOU actually wanting?

[Bo’sunParticipant @bosun58570]

A single thou’ is more than adequate, just thought I’d ask.  That’s really good for a relatively inexpensive tool.  Thanks for checking it out.

[HollowpointParticipant @hollowpoint]

Sometimes I think Joe Pie talks utter carp. 😂

I’ve been using the method he describes for years and never had a problem. In his video he fails to eliminate the possibility of a bad tap holder by not testing any other holders. The two jaw type for instance are usually terrible. While mine (Eclipse and Starrett) don’t have anywhere near the amount of wobble his shows in the video.

Something else he fails to mention is that some taps have a squared end which will occasionally foul the radius at the bottom of the tap holders socket.

[Bo’sun]

On Bo’sun Said:

A single thou’ is more than adequate, just thought I’d ask.  That’s really good for a relatively inexpensive tool.  Thanks for checking it out.

Umm, as I understand it the requirement isn’t for thou accuracy.  Though taps need to be centred approximately on the hole, the important bit is that the tap be aligned axially with the hole – an angle, not linear measure.  A correctly adjusted tail-stock provides the necessary alignment on a lathe.  As does the spindle on a vertical mill.

The problem holders address is that hand-tapping tends to start taps skew-whiffed, which spoils the thread and/or breaks the tap.   To stop those evils the holder only needs to be good enough to start the tap cutting straight; once a few threads have been cut correctly into a bore, the tap follows them with no need for an accurate holder.

Dave

[SillyOldDuffer]

On SillyOldDuffer Said:

[…]  the important bit is that the tap be aligned axially with the hole – an angle, not linear measure.  […]

A good point, well-put, Dave

Presumably something you learned whilst helping your daughter put Jack back in his box 🙂

MichaelG.

[Howard LewisParticipant @howardlewis46836]

My taps are held in ER25 collets! If things get tight, the Tap slips in the collet, saving a broken Tap and scrap job.

Some long time ago there was an article in MEW describing making a drill/Tapping extension for a vertical mill. (Can alo be nounted in the Tailstock, and used in the lathe.

It had the ability to drill and then, by disengaging the drive pin, tap manually, with the Tap, held in the drill chuck. It is also possible to hold a knurled ring whilst the work rotates, to tap small sizes.

Howard

[bernard towersParticipant @bernardtowers37738]

John, you got me thinking about the Hemingway die holder so spent 3 or 4 hours cutting metal and ended up with the adapter for taps to er16 size and yes it works  very well. Thanjs for the idea.

[John HinkleyParticipant @johnhinkley26699]

Glad it worked out well, Bernard.  Perhaps Hemingway might be interested in incorporating your design into their range of accessories?  They do say on their website that they encourage new or additional tooling etc.  I’d be interested to see a picture, myself.

John

 

[bernard towersParticipant @bernardtowers37738]

Took these this morning

[John HinkleyParticipant @johnhinkley26699]

Neat job, Bernard.  I expect Neil could be interested in an article if you ask nicely!

John

 

[HollowpointParticipant @hollowpoint]

I like the er chuck adapter! 👍

I found these 2 similar ideas online.

[PeroParticipant @pero]

If going the ER route it is possible to purchase ER tapping collets. These typically have a round hole at the front and a square hole a the rear. I think you would likely be unable to fit more than one size tap size per collet so cost is a factor. However slip would be impossible, apart from axially if the collet was not properly tightened properly.

Pero

[JasonBModerator @jasonb]

I suppose it comes down to what will slip first, worn or abused MT tailstock socket, worn chuck jaws or a collet. Sometimes a bit of slip is desirable and better than a snapped tap, scored work or a tool spinning in the tailstock socket

[John HinkleyParticipant @johnhinkley26699]

That is precisely the point I was trying to make with my suggestion of the tap holder for the Hemingway tailstock die holder as splendidly demonstrated by Bernard, above.  The Hemingway die holder incorporates a double cone clutch to provide a sensitive feel to the threading procedure and allows the work held in the lathe chuck, to continue rotating once the thread has reached its desired length.  The examples shown by Hollowpoint appear to require the tap to be restrained manually with the ball-ended handle and the tapping to be started and stopped by switching lathe spindle rotation on and off.  Unless this is somehow achieved instantaneously, it will result in under-or over-length threading.  I acknowledge, again, that my suggestion presupposes the possession of a Hemingway die holder.

John

[JasonBModerator @jasonb]

I use my grip of the body in the same way that the hemmingway one has a clutch, just release my grip when I’m deep enough or if the tap is struggling. Small taps I can just use finger and thumb to grip the holder so there is some feel.

It is the types of holders that either have the long bar to stop them rotating or a pin in the fixed MT spigot that could benefit from some slip in the system.

[Author]

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