On 5/25/2011 10:55 AM, Carla Fong wrote:
Hi all -

I'm suffering sticker shock in getting some material for a project.

I need bar stock, either aluminum or plastic in 3/4" thickness by 3"
wide. Perusing the McMaster catalog I'm finding Delrin at about $20 per
foot, Polyethylene at about $5 per foot, Polypropylene at about $4.50 a
foot, PVC at about $11 per foot and 6061 aluminum at about $20 per foot.

Yikes!

I've prototyped the project on delrin - and it would work for what I
have in mind, but is any of the cheaper materials equally good for
machinability?

The 'poly' group (PVC, PE, etc) looks like a nice cheap option, but will
it gum up when I mill deep, narrow slots through the material? (I'm
taking 0.1" pecks in the delrin and getting OK finish)

Any better pricing on similar material, preferably closer to Portland,
Oregon?

Thanks in advance,

Carla

Science is like sex: sometimes something useful comes out, but that's
not why we're doing it. -- Richard Feynman

You should look for local sources first. With any mail-order place, you
are paying extra for cutting, and then paying even more for shipping.

Aldo if you like Delrin (acetal) then you'll end up paying for Delrin,
because there's nothing else like it. No other plastic machines as well
as it does. ...All the other stuff I've ever seen is not dimensionally
accurate or straight, plus is slippery (hard to clamp), soft, gummy
and/or stringy.

"DougC" wrote in message
...
On 5/25/2011 10:55 AM, Carla Fong wrote:
Hi all -

I'm suffering sticker shock in getting some material for a project.

I need bar stock, either aluminum or plastic in 3/4" thickness by 3"
wide. Perusing the McMaster catalog I'm finding Delrin at about $20 per
foot, Polyethylene at about $5 per foot, Polypropylene at about $4.50 a
foot, PVC at about $11 per foot and 6061 aluminum at about $20 per foot.

Yikes!

I've prototyped the project on delrin - and it would work for what I
have in mind, but is any of the cheaper materials equally good for
machinability?

The 'poly' group (PVC, PE, etc) looks like a nice cheap option, but will
it gum up when I mill deep, narrow slots through the material? (I'm
taking 0.1" pecks in the delrin and getting OK finish)

Any better pricing on similar material, preferably closer to Portland,
Oregon?

Thanks in advance,

Carla

Science is like sex: sometimes something useful comes out, but that's
not why we're doing it. -- Richard Feynman

You should look for local sources first. With any mail-order place, you
are paying extra for cutting, and then paying even more for shipping.

Aldo if you like Delrin (acetal) then you'll end up paying for Delrin,
because there's nothing else like it. No other plastic machines as well as
it does. ...All the other stuff I've ever seen is not dimensionally
accurate or straight, plus is slippery (hard to clamp), soft, gummy and/or
stringy.

PVC is pure ****....very very bad juju...suggest bid it WAY
high...purposefully force your competitors to get stuck with the job
instead.

Flat stock is typically laminated from several layers of thinner material
and it tends to fracture and largish chunks will break away from the parent
material seemingly at random.

Additionally, it is a death sentence to your machinery and to operators as
well because it releases chlorine during machining which combines with
moisture in air and in the mucous in your lungs and the result is copious
amounts of hydrochloric acid and next thing you know you will be coughing
and short of breath and your eyes will be all reddish and burning.

Also, if using soluble oil as coolant, the oil comes out of suspension and
forms a film on your chips, acting very much like a tramp oil skimmer on
steroids so you can figure on kissing your coolant mix goodbye...and the
water in your coolant very quickly turns highly acidic due to the above
mentioned chemical reaction which will ruin your ways and your way covers
and will get into your spindle bearings and into any pinholes in your
sheetmetal and will severely corrode everything that it touches.

Probably all of this is STILL not listed the MSDS but anyways, you've all
been forewarned.....

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