Have a look in …

http://www.arceurotrade.co.uk/Catalogue/Chucks/Drill-Chuck-Arbors/MT2-Drill-Chuck-Arbors-with-Drawbar-Thread

​… usual disclaimer.

5th one down on the list should solve your query

George

I have always cleaned both tapers, put chuck onto taper, hold the assembly morse taper down and strike the tang on the bench with a quick tap. Do not hit the chuck with anything, if the jaws are extended you will damage the chuck. To remove open the chuck fully, put a piece of steel through the chuck, hold over a bench and strike the steel with a mallet, taper falls off ( hopefully onto the bench).

Tapers are 'Quite Interesting'. Morse Tapers are cut at an angle that locks to resist turning but will release when pulled or pushed out. The Jacob Tapers are cut at an angle designed to jam in the matching socket more-or-less permanently. Getting a JT6 chuck off the arbour is more likely to be a problem than getting it to stick in the first place: Arc sell wedges for the purpose.

I don't understand why one taper angle jams solid while the other releases. Clever stuff.

Dave

I would have thought the MT should let go first as that will be the one being forced out of the socket by the drawbar, ejector wedge, tailstock screw, etc

I've got a B taper on the chuck I use most on the lathe, never had that slip but have had the MT turn in the tailstock barrel

I wonder if the fact the B taper has a smaller area than teh MT is why it starys together. assuming the same force applied to both tapers then the smaller area of the B taper will mean more force per metric/imperial measure of area. For example if 10lls pressure applied to put the parts together then if ratio of area was say 3:1 the B taper would go together with 30psi and MT 10psi.

Edited By JasonB on 01/06/2017 19:10:44

Not sure why the wedges should make the MT let go as they act against the back face of the chuck and the large end of the MT taper not the nose of the spindle?

When I bought chuck and tapers from Tracey they came as separate parts I had to join together

B16 is not just the same taper as MT2, it's actually meant to be the small end of MT2 and B18 is the large end – all the B-tapers are actually stub versions of Morse Tapers.

Neither taper should let go when used with a drill, they are all 'self holding tapers'. Google tells me that 7 degrees is the typical angle for steel on steel.

Expressed as ratios 1:5 or less will easily separate, 1:10 will will detach with difficulty, 1:20 is typical for toolholding (e.g. Morse & brown & sharpe tapers are about 1:20, Jarno  1:24).

Jacobs have angles from 1.41 to 2.3 degrees, many of them have a significantly more 'open' taper than Morse or B tapers (about 1.5 degrees) , so the B-taper is NOT a retrograde step.

Neil

Edited By Neil Wyatt on 01/06/2017 20:02:53

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Neil,

Let's agree to differ on that one ^^^

I did not say anything about tapers "letting go" in use.

I did not suggest that the Jacobs taper would hold 'harder' than the Morse.

My only concern is that by using equal angles on both tapers, the behaviour when deliberately trying to separate chuck from arbor will be less predictable.

The JT fitting was designed to release before the Morse.

MichaelG.

Edited By Michael Gilligan on 01/06/2017 20:56:06

Michael, did you see my comment above about using wedges?

When separating chuck from arbor the forces are between chuck and the B or JT taper, the Morse has nothing to do with it, Will post a pic a bit later to show how the wedges act in use.

Thats similar to how we used to separate the old "K" taper masonary drill bits from there holders in the days before SDS, hit the socket between two 2 1/2lbs club hammers, probably best not to try that on a drill chuck though

.

Yes I did, Jason … and of course you are correct that this is correct practice.

I cannot honestly remember when, or by whom, I was given the logic behind using unequal tapers … but it was many years ago, and I have 'always' believed it to be true.

I have found no supporting evidence for my assertion … so I have bowed-out of the discussion.

I will observe from the sidelines, hoping that someone can explain why different tapers were originally specified.

MichaelG.

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For my pennance: http://www.jacobschuck.com/drill-chuck-removal-guide

Edited By Michael Gilligan on 02/06/2017 08:15:22