What if any differences might I notice when making and more importantly
using a 1/4" punch made of C360 brass vs C932 bearing bronze? The brass
will work harden, but I can only guess bearing material is not supposed to
harden up under use.
The punch would be just that- 1/4" x 4", tapered and knurled and used for
driving out stuck pins. I figure it's easy enough to make and will be
On Tue, 12 Apr 2016 16:27:51 +0000 (UTC), Cydrome Leader
Since you haven't yet gotten a specific answer, I'll just point out
that C360 is a great deal harder and stronger than C932. The bearing
bronzes are pretty soft and, in the case of C932, kind of "mushy." I
don't know its work-hardening properties.
My guess is that C360 is a better material for your application. Some
bearing bronzes would be similar to ordinary brass, but C932 is pretty
Went ahead and made it in brass, on a Sherline lathe. The taper was
guestimated with a compound attachment and blended with a file.
Knurling got messed up on the left side, but only with one cutting wheel,
it may have clogged up. It has this odd pattern, but whatever, it's a
punch. Used it yesteday to knock pins out of a casting.
May try to make another one in a different size to get it right.
The only problem is how much it flakes and clogs up the knurling wheels.
Cutting fluid like Relion seems to make cutting easier, but makes also
binds the flakes into the teeth. May need to setup some tubes, old
toothbrush heads and the shopvac to suck all the flakes out of the wheels
as they rotate. The wheels I have are 25TPI and 1/2" dia so it doesn't
take much material to fill them up.
On Thu, 21 Apr 2016 18:32:07 +0000 (UTC), Cydrome Leader
I haven't done it for a long time, but when my uncle was teaching me
how to run his (now my) lathe, he told me to use heavy machine oil, or
even motor oil, on knurling tools. I always have, and I don't remember
any clogging problems with brass. But that was decades ago. I don't
think I've knurled brass for 25 years. Maybe I just forgot about it.
How were you holding it? A 4-jaw chuck by any chance? Slightly
off center? With a push type knurler, that could result in one side
being light or unknurled. A scissors style would tend to follow the
workpiece, even if slightly off-center, since the force comes from a
knurl above and one below the workpiece.
Otherwise, knurling between centers makes sense -- and then turn
the needed features (striking end and punch end) after the knurl is done
And a Sherline seems rather lightweight for a push knurl. A
scissors knurl would make the job easier on the machine.
[ ... ]
I knurl brass moderately often. I use Vactra No.2 Waylube during
the knurling, and then spritz it with WD-40 to clean the lube and the
But I usually do it on a 12x24" Clausing with a BXA series
knurler which has a pair of arms off a dovetail on the tool holder, and
a knob which moves one arm up as the other goes down. Set it once
lightly clamped on the top and bottom of the workpiece, and set the
height nut on the tool holder block and then it is just a matter of
adjusting for the diameter. Move it into place for the start of the
knurl, crank down the knob which brings them together until you get a
good bite, start the lathe spindle, and keep squirting Vactra No.2 onto
Beware of trying to lube with an acid brush, It will grab the
bristles and pull them in. Makes a mess. :-)
It's symmetrical from all sides, just had the double tracking on the left
side from one knurl.
I indicated 3/8" barstock to "close enough" of about 3 mils in a 3 jaw,
centerdrilled and used a livecenter.
The OD was turned down to 0.369" (to give 29 multiples of 0.04" from the
25 TPI wheel). I did some test knurls on the punch side which was facing
the livecenter. Seemed OK.
I turned that to 1/4, added the taper and then cut the groove by the
striking side. It seems easier to cut knurls from a taper than just
cranking down on the holder for the wheels and then trying to start the
The sherline knurling attachment is just two blocks with pins for the
wheels that are clamped towards each other with two screws. Their bases
are held into the crosslide T-slots but must be left loose so both sides
can slide around and cut evenly.
Their attachment is more similar to the scissor type ones in that the
cutting forces other than required torque are not put on the lathe itself.
The torque requirements seem to push the limits though.
I learned about the brush the hard way. Just had fun with a paper towel
getting pulled onto a chain drive this week too. Will try the vactra 2,
have a gallon of it anyways.
I hate to agree with you but I never heard the term "mil" until very
recently and I worked in and around the business since I was in High
School. It was always 3 thousandths (.003) or 3 tenths (.0003) for
Well, I wasn't around the shops in the "late 1930's" :-)
But I did for a couple of weeks run a lathe that the cross slide was
calibrated in 1/128th of an inch. The owner of the shop reckoned it
dated from "Civil War Days".
When they're that old, you should sell them to interior decorators for
use as foliage planters. They look nice with a Wandering Jew twined
around the bedways, standing between a miniature palm and a ficus
In 1977, I was one of the writers for American Machinist's 100th
Anniversary issue. For a year, we all poured through the old AM
archives, going back 100 years. The term "mil," for thousandth,
appeared all of the time in the old volumes, as a slangy shorthand,
like the way we use the term "tenths" today.
Then, I'd say roughly in the late '30s, the term "mil" all but
disappeared. Universal use of gage blocks, sub-thousandths accuracy,
aircraft and military specs combined to add another decimal point to
required accuracies. American Machinist adopted a style point of using
numerical values to express accuracy, with a zero before the decimal
point for metrics, and with no leading zero for inch-based dimensions.
Written out in English, we used "thousandths," "ten-thousandths," and
"microinches." Metrics were a problem child, as we first used
"micron," and then, when SI came in vogue, "micro-meter."
Anyway, the point is that no one here is old enough to remember the
use of "mil" for thousandths of an inch, but some of us who were
deeply involved in metalworking history have seen it used a lot in the
BTW, don't get me started on "gage" versus "gauge." That one has a
history, too. There used to be an important distinction, but that
distinction has been lost in time.
Well, this was when I was in High School and the shop was at least 2nd
generation in the same building. It was owned and operated by two
bachelor brothers who didn't talk to each other. The entire shop
except for some bench grinders operated from a single electric motor
"out back" driving an overhead shaft system. Strangely I don't
remember thinking it was an odd place to work :-)
One of the brothers had an absolutely like new Henderson 4 cylinder
motorcycle that he used to ride to work occasionally which certainly
As a summer hire apprentice I wasn't doing any high tech stuff, they
had me making nuts on the old lathe. Even then, making 50 cents an
hour, I can't see how the finances worked. 12 ft of hex stock in an
antique lathe, Drill, tap, part off, advance the stock a bit and do it
again. Sort of a human screw machine :-)
But they paid every Friday afternoon at quitting time. Cash in the
At least he didn't have you start with round bar stock...
When I hear stories like that, I wonder how the United States, and the
West in general, ever managed to produce anything that anyone could
Just before wire EDM came into use, I started covering tool and
diemaking, and visited a lot of t&d shops. I watched diemakers rough
out blanking dies with a bandsaw, breaking the blade, threading it
through the work (they milled out a really rough hole first, but it
usually was nowhere near the final size), and then re-welding the
blade back together. Then they'd break the blade to remove the die
from the saw, and they'd go to work with diemaker's chisels, cutting
close to the line and chiseling in some die relief. Then, possibly, on
to the die-filer. Next, hand-filing with files down to jeweler-file
size. After that, the die would go out for heat-treating.
When it came back, out came the slips and stones, trial-mating the die
with a punch, re-stoning to fit, over and over.
That was for simple diesets. Anything complicated was likely to
require a multi-part die, which had to be fitted together in pieces
that were dowelled to the die base. My God...
When I was at Edwards AFB they had an "Electric Spark Machine". I was
there for about a year and saw it used just once. A guy made a set of
dies to punch out counterfeit quarters for the Coke Machine.
Interestingly he tried a number of alloys for his counterfeit quarters
and the Coke Machine rejected them all :-)
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.