"robobass" wrote in message
...
On Saturday, November 12, 2016 at 11:25:44 PM UTC+1,
wrote:
On Sat, 12 Nov 2016 13:23:22 -0800 (PST), robobass
wrote:
On Thursday, October 13, 2016 at 1:59:47 AM UTC+2,
wrote:
On Wed, 12 Oct 2016 12:34:02 -0700 (PDT), SteamboatEd Haas
wrote:
Hey gang I'm making some parts out of delrin; they've got fins on
'em and when they're cut to length the fuzz is everywhere! I'm
thinking of using my brass tumbler with walnut shells unless
someone's got a better idea. Here's a link to the problem:
https://www.flickr.com/photos/steamb...7673545442262/
Walnut shells might work. If they don't then tumbling with abrasive
media and water will. I have deburred acetal plastics, both Delrin and
Acetron, in one of my vibratory tumblers. I used trianglar and
cylindrical abrasive shapes. The only problem is that the plastic will
get a matt finish. For your eventual use I don't think that will
really be a problem. Even walnut shells, if they can remove the burrs,
will give you a matt finish. You can tumble the parts after deburring
with polish but it takes a very long time, in my experience, to polish
acetal plastics in a vibratory tumbler. You might want to try an
abrasive filled nylon brush first to remove the majority of the burrs
first. I have had good luck doing this. It is easy to melt the plastic
if a light touch isn't used though. Even brass wire brushes tend to be
too aggressive.
Eric
Eric, can you point me to a source for fine abrasive filled nylon
brushes? I spend a lot of time cleaning 5/16-24 brass threads. I use .2mm
bristle brass brush wheels and tripoli. It works, but I'm on the lookout
for something better.
Does MSC sell to your part of the world? They sell Weiler brand nylon
wheel brushes that have a filament diameter that is nominally .018 but
can be as small as .010. I have used these brushes and the ends can
wear to a point which is what you need to get into the root of a 24
TPI thread. Weiler does make good brushes and with that name may be
made much closer to you than me here north of Seattle. Have you
considered fine steel brushes? They cut fast and can be too aggressive
on soft metals like annealed brass. But a light and quick touch could
result in a roughing op. that leaves the surface perfect for a fast
tripoli treatment. You could try a jewellry supply company for the
brush but they tend to carry ones that are too small. I have had the
occasion more than once to polish small brass threaded parts and found
that E5 emery on the right buff will cut fast, get to the root of the
thread, and leave a finish that is usually already good enough and if
not then either tripoli are rouge can be used. For REALLY nice color
on brass I like Fabuluster. But that's probably more work than you
need to do if you are stopping at the Tripoli stage. BTW, did any of
the sprayer suggestions here pan out?
Eric
Eric,
I did try a .010 nylon bristle brush from McMaster but it didn't do
anything. Here is a photo of what I'm doing:
http://i389.photobucket.com/albums/o...psxgwuln1x.jpg
Now I am applying something called Stop Ox II with an airbrush, which
minimizes waste quite effectively. Upper right is the typical result after a
vinegar pickle in a ultrasound bath. Lower right is when something went
wrong and I had to torch the part for way too long. Upper left is after
using a .008 brass brush with tripoli, and lower left is after finishing
with a cloth wheel and fine compound. I was happiest when running a drill
press mounted 3" wheel at 2350rpm, but I simply can't get those wheels
anymore. The suppliers will insist that they are brass, but they are all
plated steel these days. I have a 10" brass wheel that I run on the lathe at
1100rpm, which is maybe too fast. I get good fast cleaning, but a bit too
much scratching, and I can't just drop it in the ultrasound bath to clean
it. Overall I'm in pretty good shape, but I'd still like to find a bristle
wheel for the fine polishing stage. McMaster has Tampico brushes which look
good, but I wonder how long they will last, as they aren't exactly cheap.
================================================== ======
Did you try adding hydrogen peroxide to the acetic acid? Should do a much
better job of cleaning. Probably still won't be good enough to replace the
Stop Ox II, but maybe on pieces that need extra heat it would help.
-----
Regards,
Carl Ijames