I was answering a neighbor's question today, and went back and looked up
Delrin and UHMW on the web, and found that I did not know what I thought
I knew. ;-) Apparently Delrin can be sanded and polished, while UHMW
is not good for sanding, according to what I found on a couple of websites.

So which plastics are good for sanding and filing? Is Delrin a good
choice? I am talking basically hand work, or perhaps using a belt
sander. I want something that can take a smooth finish, preferably is
food and dishwasher safe.

Thanks in advance.

Richard

Richard Ferguson writes:

Is Delrin a good
choice? I am talking basically hand work, or perhaps using a belt
sander. I want something that can take a smooth finish, preferably is
food and dishwasher safe.

Polyacetal (Delrin being a brand name) is a good material for that, yes,
BUT if you ever catch even a small bit of it on fire, it makes chokingly
toxic formaldehyde fumes. I imagine that is why you hardly ever see it in
consumer items.

Because UHMW is quite soft and the molecular chains are 4 to 6 million
molecules long, sanding produces a hairy surface. There are ways to get
what you want from it but you'll never get a polished surface.
Machining can give a fairly good surface that looks "shiny" but will
have tool marks to some extent.

Delrin....well, sort of. If you are looking for polished surface,
probably not. Delrin can be a little soft so polishing can go like a
dream or go bad really quickly if you happen to overheat a section.
However you can get a good surface with hand tools and sanding that
might be acceptable.

Maybe if you elaborate on what you are trying to do? Your description
sounds more like you want acrylic or similar.

Koz

Richard Ferguson wrote:

I was answering a neighbor's question today, and went back and looked
up Delrin and UHMW on the web, and found that I did not know what I
thought I knew. ;-) Apparently Delrin can be sanded and polished,
while UHMW is not good for sanding, according to what I found on a
couple of websites.

So which plastics are good for sanding and filing? Is Delrin a good
choice? I am talking basically hand work, or perhaps using a belt
sander. I want something that can take a smooth finish, preferably is
food and dishwasher safe.

Thanks in advance.

Richard

Depending on the desired app., acrylic (PMMA) has the added advantage
that it can be compression moulded into complex shapes rather than
always machining a part from a block.

bob g.

Koz wrote:

Because UHMW is quite soft and the molecular chains are 4 to 6 million
molecules long, sanding produces a hairy surface. There are ways to get
what you want from it but you'll never get a polished surface. Machining
can give a fairly good surface that looks "shiny" but will have tool
marks to some extent.

Delrin....well, sort of. If you are looking for polished surface,
probably not. Delrin can be a little soft so polishing can go like a
dream or go bad really quickly if you happen to overheat a section.
However you can get a good surface with hand tools and sanding that
might be acceptable.
Maybe if you elaborate on what you are trying to do? Your description
sounds more like you want acrylic or similar.
Koz

Richard Ferguson wrote:

I was answering a neighbor's question today, and went back and looked
up Delrin and UHMW on the web, and found that I did not know what I
thought I knew. ;-) Apparently Delrin can be sanded and polished,
while UHMW is not good for sanding, according to what I found on a
couple of websites.

So which plastics are good for sanding and filing? Is Delrin a good
choice? I am talking basically hand work, or perhaps using a belt
sander. I want something that can take a smooth finish, preferably is
food and dishwasher safe.

Thanks in advance.

Richard

I am not necessarily looking for a polished surface, just not a hairy or
rough surface. In other words, smooth to the hand, not polished to the
eye. I guess a hand can feel down to 0.002" of roughness or thereabouts.

I was hoping that I could rough out the shape with a belt sander, and
then sand it smooth, going stepwise from 80 grit to perhaps 400 grit.

Unfortunately, for various reasons I cannot explain the application, sorry.

Richard



Koz wrote:
Because UHMW is quite soft and the molecular chains are 4 to 6 million
molecules long, sanding produces a hairy surface. There are ways to get
what you want from it but you'll never get a polished surface. Machining
can give a fairly good surface that looks "shiny" but will have tool
marks to some extent.

Delrin....well, sort of. If you are looking for polished surface,
probably not. Delrin can be a little soft so polishing can go like a
dream or go bad really quickly if you happen to overheat a section.
However you can get a good surface with hand tools and sanding that
might be acceptable.
Maybe if you elaborate on what you are trying to do? Your description
sounds more like you want acrylic or similar.
Koz

Richard Ferguson wrote:

I was answering a neighbor's question today, and went back and looked
up Delrin and UHMW on the web, and found that I did not know what I
thought I knew. ;-) Apparently Delrin can be sanded and polished,
while UHMW is not good for sanding, according to what I found on a
couple of websites.

So which plastics are good for sanding and filing? Is Delrin a good
choice? I am talking basically hand work, or perhaps using a belt
sander. I want something that can take a smooth finish, preferably is
food and dishwasher safe.

Thanks in advance.

Richard

Delryn, acrylic, syrene, polystyrene, polypropylene, polycarbonate, PVC,
and ABS can all be machined or sanded to a smooth surface. Ditto
phenolic, polysulfone, Noryl and many others. Some or most of these will
probably not be suitable for your application for other reasons. If you
prefer not to say what the application is, then you must define all of the
relevant material characteristics and specs that are important or
desirable, and be able to prioritize them. Just the mention of dishwasher
rules out some of those mentioned above for various reasons. These might
include other matters like temperature range, strength expected, how
manufactured or assembled (glue, weld, threaded fasteners, ???), appearance
(color, etc), chemical resistance (e.g. dishwashing detergent), etc etc.

You should be working with a good plastics supplier. He'll have a lot of
questions. Another approach might be to find a similar product and find
out what it's made of.


"Richard Ferguson" wrote in message
...
I am not necessarily looking for a polished surface, just not a hairy or
rough surface. In other words, smooth to the hand, not polished to the
eye. I guess a hand can feel down to 0.002" of roughness or thereabouts.

I was hoping that I could rough out the shape with a belt sander, and
then sand it smooth, going stepwise from 80 grit to perhaps 400 grit.

Unfortunately, for various reasons I cannot explain the application,
sorry.

Richard



Koz wrote:
Because UHMW is quite soft and the molecular chains are 4 to 6 million
molecules long, sanding produces a hairy surface. There are ways to get
what you want from it but you'll never get a polished surface. Machining
can give a fairly good surface that looks "shiny" but will have tool
marks to some extent.

Delrin....well, sort of. If you are looking for polished surface,
probably not. Delrin can be a little soft so polishing can go like a
dream or go bad really quickly if you happen to overheat a section.
However you can get a good surface with hand tools and sanding that
might be acceptable.
Maybe if you elaborate on what you are trying to do? Your description
sounds more like you want acrylic or similar.
Koz

Richard Ferguson wrote:

I was answering a neighbor's question today, and went back and looked
up Delrin and UHMW on the web, and found that I did not know what I
thought I knew. ;-) Apparently Delrin can be sanded and polished,
while UHMW is not good for sanding, according to what I found on a
couple of websites.

So which plastics are good for sanding and filing? Is Delrin a good
choice? I am talking basically hand work, or perhaps using a belt
sander. I want something that can take a smooth finish, preferably is
food and dishwasher safe.

Thanks in advance.

Richard