Go over to rec.crafts.metalworking and post your question there. While the
group is nominally about metalworking, the machinists there know a lot about
the machining characteristics of various materials like the plastics.

Tom Dacon

"Geoffrey W. Schultz" wrote in message
. 16...
I have a KISS wind generator that develops vibration at certain wind
speeds. The problem is that there's a PVC fitting that goes over a 2"
stainless schedule 40 support pipe that is loose fitting. I want to
machine one with a sleeve bearing on a lathe and make it out of plastic.
However, I really don't have any experience machining plastic, I've been
looking at www.mscdirect.com under Raw Materials/Plastic Material/Rods for
3" material. To keep costs under control I'm looking at the following:

Nylon
Acetal
UHMW
LDPE
HDPE

Comments on the machining qualities, UV resistance, and overall strength
of
these would be greatly appreciated.

-- Geoff

Use a high speed bit with a lot of rake,and hone the point to about .010"
radius.UHMW and nylon will machine like butter,and do fine.

Benny
S/V Panacea

Use a high speed bit with a lot of rake,and hone the point to about .010"
radius.UHMW and nylon will machine like butter,and do fine.

Benny
S/V Panacea

I don't know if this CO. has any bushings the size your looking for. But
you may want to check
http://www.apfp.com/pdf/spacers.pdf

Jack
"Geoffrey W. Schultz" wrote in message
. 16...
I have a KISS wind generator that develops vibration at certain wind
speeds. The problem is that there's a PVC fitting that goes over a 2"
stainless schedule 40 support pipe that is loose fitting. I want to
machine one with a sleeve bearing on a lathe and make it out of plastic.
However, I really don't have any experience machining plastic, I've been
looking at www.mscdirect.com under Raw Materials/Plastic Material/Rods for
3" material. To keep costs under control I'm looking at the following:

Nylon
Acetal
UHMW
LDPE
HDPE

Comments on the machining qualities, UV resistance, and overall strength
of
these would be greatly appreciated.

-- Geoff

UHMW is my choice for just about everything. You wouldn't need the self
lubricating charicteristics for what you are doing. Nylon would work fine.

Neither one has any UV inhibitors though.. I'm not sure which other plastics
might have this.. If your fitting is mostly enclosed then UV wouldn't be a
factor. (my Aries windvane has nylon bearings and spacers but only the edges
have deteriorated over 25 years of exposure).

Nylon machines cleaner than UHMW but both can be frustrating to achieve an
acurate final dimension because of the flex and give.. This can be overcome
by using a modified tool angle, etc. I'm not a machinist so I just
experiment with this..

A fine finish is very difficult to achieve on UHMW.. You can't file or sand
it.. A sharp tool and a slow feed will help.

In the end, for bushings, this stuff is great and even if you do a sloppy
job of machining, you can just split the bushing and use clamping force to
adjust the clearance/fit.

If you don't have access to a lathe or milling machine, you can still do a
lot in a drill press.. I use Forstner bits for a nice clean hole of the
larger sizes. I have also use hole saws to rough out holes.

The UHMW is easy to tape/thread and if your part is thick enough, the
fasteners hold very well. It would be difficult to measure final torque with
this material and I suspect you could strip threads if your not careful.


--
My opinion and experience. FWIW

Steve
s/v Good Intentions

You might try www.mcmaster.com as an alternate to mscdirect. They have good
descriptions of all the plastics.

As far as choice of plastic, they'll all work. They mostly tend to catch a
little more than steel in the lathe -- more like copper, but you should have
no problem on a metal lathe. On a wood lathe, I suspect you'll have to be
very careful with tool angle -- closer to a scrape than a cut, but I'm not
sure as I haven't used a wood lathe in years -- you get lazy with a metal
lathe in house -- just set it up and go, even in wood.

Go with black (this is a little counter-intuitive as the black soaks up the
IR and gets hotter, but it keeps the UV out of the material).

If you need to glue it, pay attention, 'cause some of these don't like
gluing, especially HDPE.


--
Jim Woodward
www.mvFintry.com


..
"Geoffrey W. Schultz" wrote in message
. 16...
I have a KISS wind generator that develops vibration at certain wind
speeds. The problem is that there's a PVC fitting that goes over a 2"
stainless schedule 40 support pipe that is loose fitting. I want to
machine one with a sleeve bearing on a lathe and make it out of plastic.
However, I really don't have any experience machining plastic, I've been
looking at www.mscdirect.com under Raw Materials/Plastic Material/Rods for
3" material. To keep costs under control I'm looking at the following:

Nylon
Acetal
UHMW
LDPE
HDPE

Comments on the machining qualities, UV resistance, and overall strength
of
these would be greatly appreciated.

-- Geoff

McMaster has the same material plus PVC. Any will do but I would go for
Acetal (Delrin) for the strength and UV resistance. For any of them the
tooling should have a positive rake and plenty of relief. The bit
should also be polished as well as possible. Plastics don't disburse
heat as well as metals so you don't want anything draging on the
surface. Turning and drilling are done at about 600 fpm and feed about
..010 to .015. Depth of cut can be pretty heavy but I don't get as good
a finish with fine cuts so plan your last pass carefully to take off at
least .02". Keep in mind that plastics expand a lot more than metal
when they heat up and deflect more under pressure of the bit. The two
factors combined make getting high tolerances right tricky. Mill to a
few thou over size and let it cool before measuring. Then take the last
couple of passes.

When it is cutting correctly acetal does not produce chips. It makes
one long ribbon that piles up on the bit and the part. You have to keep
pulling it away or it will snag on the bit and cause a rough spot.

For Delrin AF and nylons, increase the speed to about 700 fps and cut
back the feed to .007 max.

Boedeker has a pretty good page on machining plastics
http://www.boedeker.com/fabtip.htm

Geoffrey W. Schultz wrote:

I have a KISS wind generator that develops vibration at certain wind
speeds. The problem is that there's a PVC fitting that goes over a 2"
stainless schedule 40 support pipe that is loose fitting. I want to
machine one with a sleeve bearing on a lathe and make it out of plastic.
However, I really don't have any experience machining plastic, I've been
looking at www.mscdirect.com under Raw Materials/Plastic Material/Rods for
3" material. To keep costs under control I'm looking at the following:

Nylon
Acetal
UHMW
LDPE
HDPE

Comments on the machining qualities, UV resistance, and overall strength of
these would be greatly appreciated.

-- Geoff

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Tue, 11 Nov 2003 14:45:26 GMT, "Geoffrey W. Schultz"
wrote:


Nylon
Acetal
UHMW
LDPE
HDPE

Comments on the machining qualities, UV resistance, and overall strength of
these would be greatly appreciated.

I have limited experience in the others but like Delrin (Acetal). It
is very durable, easy to work with (for an amateur like me), and is
easy to get a good finish on in a machine. It is also available in
versions with very good UV resistibility, much better than Nylon.

http://plastics.dupont.com/NASApp/my...0&locale=en_US

http://www.sdplastics.com/ultravioletresistance.html



/Marcus

--
Marcus AAkesson
Gothenburg Callsigns: SM6XFN & SB4779
Sweden
Keep the world clean - no HTML in news or mail !

What kind of speeds are producing this effect? My KISS doesn't
produce any significant vibration up to 30 kts or so. That is as fast
as I have run it. Have you checked the balance of the blades? A
slight unbalance in the blades might induce a vibration in the
mounting. I chose to use 2" SS tube rather than sched 40 pipe. The
PVC fitting is a snug fit. The KISS came with an assortment of
fittings to fit a number of different kinds of pipe. If the 2" tube fits
the KISS better than the sched 40 pipe, perhaps attaching a short
length of 2" tube to the top of the pipe for mounting would be a
simpler solution.

Doug
s/v Callista

"Geoffrey W. Schultz" wrote in message
. 16...
I have a KISS wind generator that develops vibration at certain wind
speeds. The problem is that there's a PVC fitting that goes over a 2"
stainless schedule 40 support pipe that is loose fitting. I want to
machine one with a sleeve bearing on a lathe and make it out of plastic.
However, I really don't have any experience machining plastic, I've been
looking at www.mscdirect.com under Raw Materials/Plastic Material/Rods for
3" material. To keep costs under control I'm looking at the following:

Nylon
Acetal
UHMW
LDPE
HDPE

Comments on the machining qualities, UV resistance, and overall strength
of
these would be greatly appreciated.

-- Geoff

Once again Glenn comes up with the winning response in a later
message. The only thing I'll add is that nylon is moisture sensitive.
It absorbs moisture easily and expands with moisture content (at
least when compared to most other plastics).

If you are looking at something like a tight fitting sleeve bushing then
I'd avoid nylon and use acetal or UHMW.

"Geoffrey W. Schultz" wrote in message
. 16...
I have a KISS wind generator that develops vibration at certain wind
speeds. The problem is that there's a PVC fitting that goes over a 2"
stainless schedule 40 support pipe that is loose fitting. I want to
machine one with a sleeve bearing on a lathe and make it out of plastic.
However, I really don't have any experience machining plastic, I've been
looking at www.mscdirect.com under Raw Materials/Plastic Material/Rods for
3" material. To keep costs under control I'm looking at the following: