Re: Scratchin cast iron-Turcite


gorvil
 

I just typed Turcite into Yahoo's search engine and I got back links
to Boedeker plastic's data sheet on Turcite. It is related to Delrin
which is a plastic material I've used before. Very easy to machine,
takes a high polish and is extremely strong and "slippery".


http://www.boedeker.com/turcax_p.htm

Glen Reeser

I now have three SB's
9" A
9" C
10" C This one I haven't seen yet. I get to visit it this weekend.


--- In southbendlathe@y..., Thomas.G.Brandl@c... wrote:
--- In southbendlathe@y..., earl@w... wrote:
Earl,
I looked at the South Bend Page and they use turcite in their
new
products. I was wondering what exactly it is and where its
available
from? How is it attached to the ways, Glue Soildering?
Tom Brandl
Some may recall my earlier post (back in May) regarding an SB13
scraping project. As an update, I would like to say that the
machine
is now up and running and doing very well ......... for a critter
old
enough to be eligible for SS.

It did not, however, reach completion in the fashion I had
earlier anticipated.

To make a long story short; as I was reaching the final stages of
way
scraping and saddle fitting, a pristine SB13 bed appeared on
ebay.
Since the seller was here in the west, I bid on it ......... for
the
grand sum of $51 ....... and was successful. It cost more in
gasoline
to retrieve it than it cost to purchase but it was worth it.

The bed was as advertised and worth every nickel of the cost.

So, the ultimate scraping project may not have ended in total
completion ........ as a scraping project ...... but much was
learned
along the way and a useful tool has been resurrected from, what
was,
mostly useless cast iron.

I just found a nice, more recent vintage, compound slide with the
newer and larger micro dials and a face plate, which will lend
greater
ease of use to the machine.

As matters now stand, this machine has it's birth in 1934
.........
with various appendages replaced along the way. The headstock and
gearing is all original. As is the tail stock, saddle and apron.
The
bed is early 80's with turcite build-up in the saddle. ........
maybe
a bit like Johnny Cash's old tune about the auto worker who set
out
to
scrounge parts for a Cadillac. .......... for those old enough to
remember the tune.

BTW, the "Turcite" buildup is really a slick way to compensate
for
wear in sliding parts. It performs well, cuts "stick-slip" and
has a
lower co-efficient of friction. It is easy to do (relatively),
easy
to
replace, if need be, and done properly, can bring an old machine
back
to original standards.

In this machine, the turcite was installed to compensate for wear
in
both the original ways as well as the saddle itself. Since the
bed
has
now been replaced with one having factory dimension ways, the
saddle
is now riding .020 high. Being fundamentally lazy and unable to
see
any problem with a saddle riding .020 higher than original, it
will
remain at the present level ........... unless something presents
a
reason to conclude otherwise.

I did, however, shim (down) both the apron and the rear gib by an
equivalent amount in order to accomodate the longitudinal gear
rack,
lead screw and the rear gib surface. In the meantime, it has
about
100
years of wear ahead of it, before the saddle returns to original
height and the shims can be removed.

The tail stock baseplate was built up with a wear resistant
epoxy. I
would have used Turcite again but didn't have any in thin
sections.

Surprisingly, it only required .010 on the flat and .005 on the
inverted V. But the inverted V was flared several thousandths, at
the
forward end.

The base plate was shimmed level and to proper height for spindle
center. Narrow brass shims were super glued in place for the
epoxy
phase. A strip of wax paper serve's nicely to prevent adhesion
to
the
ways. Weight the base plate and check for level and square to the
center line axis.

The wear resistance epoxy is very tough and resistant to wear. A
cold
chisel is required to remove it ............ or better, heat to
300
or
400 degrees and scrape it off.

My only long term concern is that it may prove deleterious to the
cast
iron ways. But that's an easy matter to keep an eye on. If
there's
any
sign of scratching or wear, the epoxy will be replaced with
Turcite.

I put a Phase II CXA, wedge type tool post on it. The original 3
PH
motor was replaced with 1 1/4 HP DC motor and speed control. The
leather belt was replaced with a flat belt from a local
distributor.
I
have taken .030 (.060 total) cuts in steel without belt problems.

I'm still in the test and sniff (for problems) phase but so far,
the
accuracy is within my limits of testing and it is performing very
well. ........... but it has been a time consuming project.

Tip: With a DC drive and speed control, there is no reasonable
way
to
determine spindle RPM, without a tach. I solved the problem with
a
length of allthread and a stop watch.

Wrap tape around the nut ......... or otherwise build it up
........
so it fits securely inside the spindle. Time the advance of the
nut
as
it's being driven down the length of allthread by the spindle.

Measure the distance the nut travels and multiply by the pitch of
the
threads. If timed for one minute, that will equal the RPM.

A fine pitch thread, like 1/4 - 20 will work better for higher
RPMs.

And of course, some care should be taken since the rod must be
hand
held.

I did the measurement for each pully step and each 10 unit
advance
on
the speed control. A handy table of spindle speeds, now adorns
the
face of the speed control.

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