TIP
34--Lathe indexing, engagement lever and axis lock modifications/Jim Knighton
The photos above reference Jim's finished indexing system
(L) and engagement lever extension (R). Click on either photo to see a larger
version.
INDEX LOCK—The spindle lock/indexer should be self-expanatory from the
photo. The lock's body is CRS blued to match the color of the headstock and
secured with two 10-32 TPI SHCS. The pin is stepped with the fat end visible.
The skinny end fits through a smaller hole in the body not visible in the
photo. The skinny end is of a slightly larger diameter than the indexing holes
and with a conical end. This allows the pin to securely engage the indexing
holes without side to side play that would otherwise be evident. The locking
nut is a shop-built knurled brass head about 5/8" in diameter with a 4-40
TPI
shaft that fits into a matching hole in the pin. The pulley was modified by
mounting it in a chuck in turn mounted on a CNC rotary table. I drilled 48
evenly spaced holes so that when used as an indexing device I can obtain the
most frequently used divisions (2,3,4,6,8,12,16,24,48).
In use as a spindle lock, the nut is loosened and the pin slid to the left to
engage in any one of the holes. The lockup is positive and secure. When used
as an indexing device, the same procedure is followed but with the addition of
counting the appropriate number of holes each step for the desired number of divisions.
ENGAGEMENT LEVER EXTENSION—The engagement lever photo shows a brass
replacement for the utilitarian but dull standard part. It isn't a total
replacement. I modified the standard engagement lever by removing the stock
lever and turned the end so that it was smooth. I turned a 1" brass round to
the profile shown and on the back side bored a hole to match the diameter of
the modified stock piece. The brass round was then pressed onto the shaft with
a little Loctite® to keep everything secure. The brass lever is about 1.75"
long and angled towards the front by 20 degrees.
I use both modifications on a daily basis and while my opinion might be
unduly biased, I think both are very useful, attractive, and highly
functional improvements.
Photo on far left shows saddle lock screw in place, and
photo next to is shows hole in saddle with screw removed. The center picture
shows the table lock fixture, and the photo to its right shows the fixture with
the screw removed. The final photo on the right shows the two Delrin tipped,
knurled screws. (Click on any photo to see a larger image.)
I am also attaching photos of a simple modification
I made so that I could have attractive and functional axis locks on both the
saddle and the cross slide. Perhaps others would find this to be useful as
well.
SADDLE AND CROSS SLIDE LOCKS—The axis lock screws consist of knurled
brass heads turned from 1" brass stock (knurls are 7/8" diameter and the
stub end is 1/2" diameter), a length of 1/4-20 TPI threaded rod drilled out
to 5/32", and a short length of Delrin turned to match. The Delrin insert is
a tight press fit—no adhesives were used. The modifications to the saddle to
mount a small bracket for the cross slide lock and a threaded hole in the
skirt for the long axis lock are illustrated in the photos. The bracket is
CRS, 1" x 3/4" and secured to the saddle with 4-40 screws. The bracket was
blued so that it looks as though it "belongs" on the similarly colored
Sherline lathe.
--Jim Knighton
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