"DoN. Nichols" wrote in message
...
On 2017-02-17, Bob La Londe wrote:
Overall I am pretty happy with my Chinese made Precision mathews
PM1440LBE
lathe. However there are some little things that just make me go,
"Hmmmmm...."

The 1440 mostly gets used for quick and dirty single setup one off
projects.

[ ... ]

Recently my success and happiness with the little 3C hand wheel
closer on
the small 8.5x18 HF lathe got me thinking that there would be jobs
that
would be handy to do with a 5C closer on the 1440.

I recently picked of a lever style collet closer. The price was
cheap
enough I don't mind using it as a learning tool, or even scrapping
it after
learning how to make one if necessary. Now to figure out how to
setup a
spindle adapter. I've found MT5 to 5C adapters. The factory
claims the
spindle bore is MT6, but it also came with a "MT6" to MT4 adapter
so I can
turn between centers if I so choose. I figured a cheap import MT6
to MT5
adapter would atleast get me in the right ballpark to start
figuring stuff
out.

I didn't even have to put the import adapter in the spindle to see
it didn't
match up. Its a different taper angle than the adapter that came
with the
lathe. So...

I dropped Precision Mathews an email and asked what the heck the
spindle
bore really is. This is their reply.

************
"Hi Bob, They are listed from the factory as MT6. But our other
machines
are listed the same way, and its actually an MT 5-1/2 So that
might be
it."
************

Ok.... I had not heard of half sizes before and a cursory search
doesn't
bring them up.

Interesting. In _Machinery's Handbook_ 29th edition, page 956,
table:

"American National Standard Ring and Plug Gauges for the
self-holding taper series ANSI/ASME B5.10-1994(R2008)"

I see what I always knew as the only half-size Morse taper, MT-1/2.
The
table was made up of three earlier tapers, with the middle being the
Morse tapers -- 1 through 7. Before that are some decimal fraction
tapers (Brown & Sharpe tapers), and after are 200 through 1200.
(1/4"
per foot tapers" with no other name showing. I found them
identified
by name in a similar table a couple of pages earlier, but with less
detail about other maters.

.... grumble grumble grumble ....

Now for the fun part. The lever closer did come with a 5C adapter.
I don't
know what the outside is, but... It doesn't fit in a MT4 or an MT5
sleeve.
Is it an MT4-1/2?

It likely is. That was made (I believe) from part of the MT-5
taper. It is the smallest which will accept a 5C collet, and I have
that taper in the spindle of my 12x24" Clausing, which came with a
lever style closer.

LOL.

A little more sarching and I discover Morse Tapers are all
different angles?
What? Dang-it!

The reason for that is that the Morse tapers were developed
before it was easy to measure taper angles in degrees. So, they
were
defined as a length, a small end diameter, and a big end diameter,
which
worked out to weird tapers. The MT-4-1/2 is designed for that, and
for
a 1-3/8" spindle bore to clear a 1-1/4" drawtube.

The other tapers are constant taper per foot .50200 for the
early ones in the table -- Brown & Sharpe, and 0.75000 for the later
ones, which are simply called "3/4 inch per foot taper".

Can you get a hardenable steel taper to fit your spindle? If
so, silver braze a ring to the front to aid in extracting it, then
bore
it cylindrically and bore the closing taper, then drill from the
side at
the right place and put in an index pin for the anti-rotation groove
in
the collet. If you are working from a spindle which accepts
MT-5-1/2
(no data on that size). Perhaps bore and taper slightly undersized,
and
then use a toolpost grinder to get the finish good and to final
dimensions. (Of course, protect the ways from the grinding
products.)

Good Luck,
DoN.

I have a good 5C taper adapter with the pin and a less-good one whose
pin had been sheared off, which I use most of the time. The pin isn't
really necessary even with a handwheel closer.

The bouncing-ball hardness of the adapter reads between RC35 and RC40.
http://www.detroitflame.com/HardnessTester.htm
-jsw