Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Machining HDPE question

I need to machine some HDPE to hold a bunch of specialized tooling for automation cell at
work. I need a 1.5D x 1.1 DP hole about 36 times. I bought a 1 1/2" and 1 3/8" spade
drill like the one you would use a hand drill to drill through pine.

My two thoughts were that the 1.5" one might do the job or the 1 3/8" one would make me a
nasty hole I'd hit with an offset boring head to finish. The work will be done on a
Bridgeport.

Thoughts, tips, tricks, warnings welcome.

Wes
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Default Machining HDPE question

Wes wrote:
I need to machine some HDPE to hold a bunch of specialized tooling
for automation cell at work. I need a 1.5D x 1.1 DP hole about 36
times. I bought a 1 1/2" and 1 3/8" spade drill like the one you
would use a hand drill to drill through pine.

My two thoughts were that the 1.5" one might do the job or the 1 3/8"
one would make me a nasty hole I'd hit with an offset boring head to
finish. The work will be done on a Bridgeport.

Thoughts, tips, tricks, warnings welcome.

Wes


Watch the rake on your cutting edge . If you allow the bit to self-feed ,
it will - all the way thru your stock . Cut the centering spur off the bit
and machine the cutting edge flat and square , it'll make a right purty hole
just a hair smaller than your cutter and a big pile of stringy shavings .
Don't try to clear the swarf until you're done cutting if you want to keep
your fingers . I use this stuff for one of the suspension system components
I make for the rubbermount Harley touring bikes .
--
Snag
Wannabe Machinist


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Default Machining HDPE question

On Sep 23, 4:14*pm, Wes wrote:
I need to machine some HDPE to hold a bunch of specialized tooling for automation cell at
work. *I need a 1.5D x 1.1 DP hole about 36 times. *I bought a 1 1/2" and 1 3/8" spade
drill like the one you would use a hand drill to drill through pine. *


A plunge router and a suitable circular jig would be my choice for
this.
Wood-cutting router bits are usually OK for plastic, but there are
specialty
sharpened ones available, too. Steel or carbide spiral upcut is
what I'd choose.

A spade bit will wander, doesn't self-feed at a reliable rate, and
isn't stellar
at chip clearance, either.
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Default Machining HDPE question

On Thu, 23 Sep 2010 19:51:39 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

whit3rd fired this volley in news:c22c8298-6339-48d0-
:

A plunge router and a suitable circular jig would be my choice for
this.


And my choice would be a Forstner bit. I make holes in HDPE a few dozen
times a year. Twist drills won't do. Spade bits make for rough holes.
Forstners - fed at slow rpm and an adequately fast feed rate to prevent
softening of the work - make for a smooth hole in one cut.

LLoyd


What he said, plus compressed air as a coolant/chip remover. Machining
plastic is the ONLY time I'll use air on a machine..........

Bob


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Default Machining HDPE question

On 2010-09-24, Bob wrote:
On Thu, 23 Sep 2010 19:51:39 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

whit3rd fired this volley in news:c22c8298-6339-48d0-
:

A plunge router and a suitable circular jig would be my choice for
this.


And my choice would be a Forstner bit. I make holes in HDPE a few dozen
times a year. Twist drills won't do. Spade bits make for rough holes.
Forstners - fed at slow rpm and an adequately fast feed rate to prevent
softening of the work - make for a smooth hole in one cut.

LLoyd


What he said, plus compressed air as a coolant/chip remover. Machining
plastic is the ONLY time I'll use air on a machine..........

Bob


Use sharp bit and very fast feedrate!

i
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Default Machining HDPE question

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

whit3rd fired this volley in news:c22c8298-6339-48d0-
:

A plunge router and a suitable circular jig would be my choice for
this.


And my choice would be a Forstner bit. I make holes in HDPE a few dozen
times a year. Twist drills won't do. Spade bits make for rough holes.
Forstners - fed at slow rpm and an adequately fast feed rate to prevent
softening of the work - make for a smooth hole in one cut.


I got a smooth bottom but rough sides using the spade bit on a sample. For the
application it likely is good enough but I do like to do decent looking work.

The Forstner likely would be better. I may just order a forstner bit. McMaster has HSS
or carbide edged, which would you choose?

Wes
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Default Machining HDPE question

"Snag" wrote:

Don't try to clear the swarf until you're done cutting if you want to keep
your fingers .


I wouldn't get near that bundle of chips with the spindle running if my life depended on
it. Wow is all I can say about chip production.

Wes
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Default Machining HDPE question

Wes wrote:
"Snag" wrote:

Don't try to clear the swarf until you're done cutting if you want
to keep your fingers .


I wouldn't get near that bundle of chips with the spindle running if
my life depended on it. Wow is all I can say about chip production.

Wes


I see you've some experience with this stuff too .

--
Snag
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Default Machining HDPE question

"Snag" wrote:

I wouldn't get near that bundle of chips with the spindle running if
my life depended on it. Wow is all I can say about chip production.

Wes


I see you've some experience with this stuff too .


One test hole. What ever tooling I use, I'm moving a trash can next to the bridgeport for
the chips.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller


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Default Machining HDPE question

Wes fired this volley in
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The Forstner likely would be better. I may just order a forstner bit.
McMaster has HSS or carbide edged, which would you choose?


HSS will last for hundreds of holes in natural HDPE, but carbide is
better in the black material -- some of the pigment particles are large
enough to be abrasive.

There's an outfit up the road from us that will make any sized Forstner
for you custom. I've seen such on-line, too. They're only marginally
more expensive than top-of-the line bits in standard sizes.

LLoyd
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Default Machining HDPE question

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

And my choice would be a Forstner bit. I make holes in HDPE a few dozen
times a year. Twist drills won't do. Spade bits make for rough holes.
Forstners - fed at slow rpm and an adequately fast feed rate to prevent
softening of the work - make for a smooth hole in one cut.



I took your suggestion and used a Freud carbide tipped forstner bit. 1.5" diameter holes,
32 mm deep, 40+ in all. If I pecked right the currlies flew off, if I pecked wrong, I had
to stop the mill and pick the wad off.

What would you consider slow? I was doing about 900 rpm, feed tended to be agressive in
order to get chips that would break off when I retracted.

Hole finish was way better than that spade drill.

That was fun.


Wes
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Wes fired this volley in
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What would you consider slow? I was doing about 900 rpm, feed tended
to be agressive in order to get chips that would break off when I
retracted.


I run about 700rpm doing holes that large, and feed as fast as the bit
will go through the work without hogging. With standard rake angles
you're going to get on non-custom bits, you really need to clamp the work
down well, and use positive feed, or 1) the work will climb the bit, or
2) the bit will self-feed at way to high a rate to break off the chips.

Most of my HDPE holing is in the range of 10mm to 22mm, so I run more
like 1000rpm on those, but the other rules still apply.

I also check my bits for running true before using them. The odd bit
(even the good brands, and ALL of the Chinese junk) will be slightly
larger at one gullet, or have a slightly deeper cutting blade on one side
than on the other. The tend to score the wall of the hole. With a
really good bit, I can get a hole in HDPE that almost looks polished.

LLoyd
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