DoN. Nichols wrote:
On 2016-04-21, Ed Huntress wrote:
On Thu, 21 Apr 2016 18:32:07 +0000 (UTC), Cydrome Leader
wrote:
Ed Huntress wrote:
On Thu, 21 Apr 2016 16:56:03 +0000 (UTC), Cydrome Leader
wrote:
Ed Huntress wrote:
On Tue, 12 Apr 2016 16:27:51 +0000 (UTC), Cydrome Leader
wrote:
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.
[ ... ]
Went ahead and made it in brass, on a Sherline lathe. The taper was
guestimated with a compound attachment and blended with a file.
http://www.panix.com/~presence/brass-punch.jpg
Looks pretty nice -- at least from this side.
It's symmetrical from all sides, just had the double tracking on the left
side from one knurl.
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.
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
nicely.
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
lathe.
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.
And a Sherline seems rather lightweight for a push knurl. A
scissors knurl would make the job easier on the machine.
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.
[ ... ]
Doncha love the way brass takes to knurling? It's beautiful.
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.
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.
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
flakes off.
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
the knurls.
Beware of trying to lube with an acid brush, It will grab the
bristles and pull them in. Makes a mess. :-)
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.