MJ Morse taper

Edited By sean logie on 18/05/2017 10:01:16

Hi Sean, are you sure where you saw mj written it wasn't a typo ?

Emgee

edited spelling

Edited By Emgee on 18/05/2017 10:27:19

There are lots of machine tapers, but four similar ones with the same rate of taper are Morse, Jacobs, Jarno, and Brown & Sharpe.

'Jarno' was the pen name of Oscar J. Beale, who in real life was basically the head of engineering at Brown & Sharpe in the late 19 th century.

Despite this, Jarno and Brown & Sharpe tapers are not the same. Go figure!

'MJ' might refer to a Jarno taper.

Edited By David Standing 1 on 18/05/2017 10:36:20

I suspect that emgee is correct ... but these tables might prove useful: **LINK**

http://littlemachineshop.com/reference/tapers.php

MichaelG.

Might be best to measure the thing Sean. That will reveal if it's an ordinary MT3 or a weird special. Possibly 'MJ' is a maker's mark or other irrelevant stamping.

As Michael suggested, from littlemachineshop.com, my bold:

David,

"There are lots of machine tapers, but four similar ones with the same rate of taper are Morse, Jacobs, Jarno, and Brown & Sharpe"

This is not the case - they all have similar rates of taper but certainly not identical ones. They are therefor not interchangeable.

Looks like you read it wrong Sean, should be JT not MJ.

JT refers to the "jacobs taper" that holds the chuck to the arbor, MT is the larger taper that fits into the machine spindle

Edited By JasonB on 18/05/2017 19:25:12

Hi Sean

The photo in your album shows the end of a standard 3 morse taper shank which has a 3 Jacobs Taper on the other end with the drill chuck attached to it. Hence the 3MT - 3JT stamping.

This is a fairly common size, hope this helps.

Phil

Jsaon must type faster than me !!

Edited By Phil P on 18/05/2017 19:25:53

Edited By Phil P on 18/05/2017 19:26:26

Arc should have the arbor and they also do the wedges for removing chucks

Edited By JasonB on 18/05/2017 19:53:07

Daft question:- When Mr Morse or whoever designed these taper fittings, why did they not settle for a standard taper angle and just vary the size of the big and small ends, depending on the diameter required????????????????? or would that be too simple?

Edited By Anthony Knights on 20/05/2017 08:37:07

That would have been far too easy.

My guess is that they were meant to be nominally the same, and Morse's factory worked by reference to some toolroom standards or jigs. these may not have been particularly accurate as they would have been used as masters for making both plugs and sockets in the same factory. Presumably the standard was retrospectively applied to the taper already being used with the result that they were all slightly different.

Neil

Just ordered a JT3 MT2 arbor from RDG tools

Edited By sean logie on 20/05/2017 15:00:33

Neil's supposition follows the standard explanation that the slight variation in the taper angle for different sizes of Morse Taper is due to errors in the master gauges. Plausible but I don't buy it. I think it deliberate policy.

Even in 1864, when the Morse Taper was invented, technology was well up to the task of producing accurately tapered master gauges. Albeit somewhat laboriously. Its setting the gauge plane that is difficult without accurate length measurement and adjustable standards. From a production viewpoint multiple tapers are a pain as needing separate masters and setting gear for each size. One size fits all, Jarno style, needs only one master calibration reference and one set up device.

The variations seem too large to be simple errors and the actual tapers per foot are extremely inconvenient dimensions. This suggests that the variation is deliberate. A plausible reason is that it would force firms wishing to make equipment to use Morse drills to buy gauging and maybe production equipment from Morse with obvious financial benefits. Single sourcing gauging equipment would also help maintain quality standards. Taper and similar self locking drill / tool holding systems had been introduced before and failed to become widely adopted due to machine to machine variations giving inconsistent performance. No proper drawing standards, or even drawings, in those days.

Another plausible reason for deliberate taper variation is to ensure that the system only works with the male taper fully inserted into the female one. Partial insertion of a too large male taper into a too small socket will not drive and is obviously wrong. Same taper throughout risked proliferation of odd sized and partial length variations. Probably accompanied by workers resorting to the BFH when things failed to behave. Still in the era of folk weighting down boiler safety valves!

Clive

Edited By Clive Foster on 20/05/2017 18:46:01

Hi Anthony

In later years the BT & ISO plus other range of arbors all have the same included angles but with different min/max diameters, so a BT30 arbor will fit into a INT30 spindle socket but the drawbar will need to be longer, BT tooling uses pull stud retention and doesn't have the parallel end.

Emgee