Is this Morse shank removable?

[Ian PParticipant @ianp]

Does anyone know how this male Morse shank is fastened to the main body?

I can see a small circumferential line on the steel shank where it reduces to about 12mm diameter in the gap (about 2mm) between the cast iron body and the shank. The line could be a thread although it does not look helical so I wonder if the two are just a press fit.

Although my lathe has a Morse 3 tailstock it is more or less permanently sleeved down to MT2 (and it a major job to extract) so I would like to convert this turret to MT2.

Ian P

[Ian PParticipant @ianp]

Its MT3 and I prefer it to be MT2

[BazyleParticipant @bazyle]

It looks more like the picture is a cut and paste job……

[Ian PParticipant @ianp]

The picture is as you describe. The unit I have is identical but was not accessible to take a picture of when I posted.

Ian P

[Martin ConnellyParticipant @martinconnelly55370]

It's possible that a standard chuck arbor has been used. The head could easily be made with a Jacob's taoer and the two parts pressed together. The gap would allow wedges to be used to separate the parts.

Martin C

[Ian PParticipant @ianp]

Must admit I never considered a taper. I thought it might be threaded or just a parallel press fit. A taper especilly a Jacobs make a lot of sense.

I did try prising with two screwdrivers but only managed to flake of some paint. I will try to be a bit more scientific and use wedges tomorrow.

Ian P

[John ReeseParticipant @johnreese12848]

Since the body is cast iron and the shank is steel you can be certain there is some kind of a joint. The problem is determining if it is a Jacobs taper, a straight spigot pressed into the casting, or a threaded spigot screwed into the casting. If a Jacobs taper you can use wedges as Martin said. If not, disassemble the unit to see if there is a way to press out the shank. If it is threaded you should be able to see the start of the threads.

It would seem reasonable that a Jacobs taper was used. I would bet (a small sum) it has a JT shank.

[HopperParticipant @hopper]

Bit of heat from a propane torch to the main body might help ease the shank out if its tapered or press fit, and break any Loctite grip if its threaded.

At a pinch, you might be able to set the whole thing up between centres, using a piece of bar held in one of the tool-holder mounting holes, and turn the existing taper down to size.

Edited By Hopper on 10/12/2018 23:22:08

[Mark RandParticipant @markrand96270]

Just out of paranoia, have you taken the rotary bit off the turret to ensure that there isn't a screw holding the body onto the shank? Unlikely, but possible.

[JasonBModerator @jasonb]

ARC sell an identical looking one, may be worth asking them if they know the construction, or Neil may know as he has one, they sell MT2 and MT3 versions.

Edited By JasonB on 11/12/2018 07:54:19

[Ian PParticipant @ianp]

Martin was spot on!

It is a taper, I have not measured yet but I am sure it will be a standard Jacobs so will order one today.

I did not have any ready made wedges but I ground down an old worn spanner and drove it in the gap with a lead hammer. It was much harder going than I anticipated even though the taper angle was very shallow. It moved out about 1mm and was still stuck firmly so I was convinced it was a parallel stub. After packing the wedge a couple of time it eventually popped out to reveal that I had sheared off a roll pin!

I think in future I will either rely only on the taper itself, possibly with a locking compound. The hole in the body is blind

Oddly the roll pin is 1/8" diameter although as far as I can tell all the other dimensions are metric.

Ian P

[JasonBModerator @jasonb]

A quick google may have found that pin a bit earlier. both look a bit shallow to be a B or Jacobs taper

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian P on 11/12/2018 11:43:44:

Oddly the roll pin is 1/8" diameter although as far as I can tell all the other dimensions are metric.

.

I think the vast majority ['though perhaps not all] of the available Roll Pins are Imperial

… I found this useful page last week, whilst working on a microscope: **LINK**

https://almabolt.com/pages/catalog/pins/springroll.htm

MichaelG.

[JasonBModerator @jasonb]

Metric ones about, you can see from this table that a nominal 3mm pin is larger than the hole which makes sense otherwise it would just drop out.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the link, Jason

I sorta knew they must exist … hence my cautious wording.

MichaelG.

[Ian PParticipant @ianp]

I think Jason is correct in saying that the taper shown on the sectioned drawing is not a common one.

I measured the male part of the arbor to the best of my ability and tools and so far have not found any standard chuck taper that is matches. Maybe someone will recognise what it is.

It would have been nice if I could just have bought a standard adapter but making one from a soft MT2 arbour is not too arduous

Ian P

[JasonBModerator @jasonb]

Not far off 1:50 or 1:25 included

0.3 x (14.7/50) = 1.02mm in 50mm

 

Edited By JasonB on 11/12/2018 20:42:11

[Ian PParticipant @ianp]

Maths is definitely not my best subject which probably explains why I cannot understand the connection to a 1:50 slope.

Where does your 0.3 value come from?

I drew the part using the two diameters and the length measurement in 2D CAD and then let is dimension the angle, I know its a lazy way to do it but it need no brain power.

Ian P

[JasonBModerator @jasonb]

10.2 – 9.6 = 0.6mm difference in diameter

So if you take it as the slope along one side you have a triangle 14.7mm long and 0.3mm high

The other way to do it is say 14.7/0.3 = 49 as you say there may be a bit of doubt on the actual size so assuming it is made to metric sizes the 1:50 is most likely, imperial would tend to be 1:48 or 1/4" per foot.

[Ian PParticipant @ianp]

I understand that now, thanks.

Seems odd that the manufacturer would have chosen a non standard taper rather than use one that matched a readily available chuck arbor. As the taper socket is blind they would have to use purpose made short taper reamer unless they cut down a 1:48 or 1:50 taper pin reamer.

I tend to think of taper fits in terms of angles rather than ratios, although when driving I regards hills as 1:20 say rather than the percentage we see on road signs!

Out of interest, before I dismantled the tapers I machined a bit of scrap in the lathe and gripped it, a stub Mandrel, with a drill chuck in one of the turret positions. I then checked the MT3 taper for run-out (the small end so quite a long way from the chuck jaws) and was surprised that it was less than 0.1mm. Changing the turret position and re-gripping the mandrel showed consistent readings and I hope my home made adapter works as well.

Ian P

[Clive Brown 1Participant @clivebrown1]

Posted by JasonB on 11/12/2018 20:56:45:

10.2 – 9.6 = 0.6mm difference in diameter

10.2- 9.4= 0.8 gives 1:18.4 inc. taper

[JasonBModerator @jasonb]

Thanks Clive, maybe closer to 1 in 20.

I expect it is just cut with a CNC machine so no need for making reamers so just about anything goes

[Howard LewisParticipant @howardlewis46836]

It may be a Jarno taper.

All sizes are 2 degrees 15 minutes, half angle .

Just a thought.

Howard

Edited By Howard Lewis on 12/12/2018 15:00:40

[Ian PParticipant @ianp]

Not Jarno.

I have measured the parts several times with different mic's and calipers but whatever I do the angle comes out within a gnats xxxk of 3 degrees.

Ian P

[not done it yetParticipant @notdoneityet]

Where exactly did this number of 9.6 come from?

Perhaps needs reading again?

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