Subject: Re: machining

From: [email-masked] (Jens)
Date: Mon, 09 Dec 1996 07:48:04 -0800

[email-masked] wrote:

>HELP!!!  I am an engineering student searching for information on
>machining plastics. I realize that this is for metal working , But this
>was the only newsgroup I could find that was even close. Any help would be
>greatly appreciated.
>[email-masked]

It always amazes me how people can possibly ask an open ended question
like that .....
The plastic bags from the supermarket slice very well with my pocket
knife. Hope that info helps !

And this from an engineering student .... makes me wonder what our
next generation of bridges will be like.

Jens

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From: "Les Whitaker" <[email-masked]>
Date: 10 Dec 1996 14:40:57 GMT

Wow! Geof, that was cold!! <laughing> . I routinely used to mill garbage
bags. Trick is to melt them into a holder...<g> Yes, engineering students
are that way, I used to make my living at McDD making them what they needed
rather than what they asked for. The good ones appreciated it, the others
didn't get a second chance. Les Whitaker

geoff beneze <[email-masked]> wrote in article
<[email-masked]>...
> In article <[email-masked]>,
> [email-masked] wrote:
> 
> Well, the last time I tried to machine a plastic bag, it wrapped around
> the cutter. 
> 
> It might help if you gave us just a BIT more information, "machining
> plastics" covers one hell of a lot of ground. I'm certain most of us
> are/would be more than willing to help, if ONLY we had some idea of what
> you're asking. These kind of "how high is up?" questions are just a bit
> much to handle.
> -- 
> geoff beneze ([email-masked])
> ******************************************************************
> *      Arizona Shooting Sports        *      BEAST Gunsmithing   *
> * http://www.primenet.com/~geoffben   *        Target Stands     *
> * The unofficial Dillon Tech Page     *  Air & Smallbore Postals *
> *         NRA Life member             *                          *
> ******************************************************************
>

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From: [email-masked]
Date: 10 Dec 1996 17:02:03 GMT

>was the only newsgroup I could find that was even close. Any help would
be

Ask away, we do it every day.

Peter

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From: Jim Harvey <[email-masked]>
Date: Tue, 10 Dec 1996 12:23:37 -0500

[email-masked] wrote:
> [email-masked] look in the FAQ , there is a section there on machining plastics.

Jim Harvey
[email-masked]
http://hre.com

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From: [email-masked] (Boris Beizer)
Date: Tue, 10 Dec 1996 15:36:18

>>was the only newsgroup I could find that was even close. Any help would be

Here's the short course:

1.  Make believe it's brass and shape your tools accordingly.

2.  Speed is not critical as long as you don't allow the plastic to
    get hot (or even warm).

3.  CRC or WD-40 is a fine lubricant/coolant.

4.  Tools should be very sharp and honed to a polish. 

5.  The softer the plastic, the more acute the rake angles.  For 
    soft stuff such as teflon, cutting tools are shaped almost with 
    same rake as for woodworking.

6.  Some plastics (e.g., Corian) are abrasive.  Formica wants to be worked
    very fast with carbides and very low feeds.  

7-8-9-10.  Sharp!  Sharp! Sharp! Sharp!  Hone! Hone! Hone! Hone!

11.  Don't agonize.  Generally, plastic is very forgiving as long as you 
     don't overfeed.  

Boris

---------------------------------------------------------------------------------------------------------
Boris Beizer, PhD                                 Consulting and Seminars on
1232 Glenbrook Road                          Software Testing and
Huntingdon Valley, PA 19006              Quality Assurance
TEL:  215-572-5580
FAX:  215-886-0144
Email: [email-masked]
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From: "Henry P. Szostek" <[email-masked]>
Date: 11 Dec 1996 00:03:04 GMT

Boris ! what do you mean by point 5 in your posting, the only 
time I have ever had any trouble with teflon machining was when I 
used too much rake on the tool. It then dove into the stock and 
made a mess of it.  I have found that the best results with soft 
plastics are achieved  with perfectly flat topped tools, zero 
gegree rake just like brass.Everything else in your post is right 
on I would add that most tips on machining plastics urge slightly 
more relief (below the cutting edge) than that used for metal 
This reduces heat buildup by assuring that there is no rubbing 
contact from a land below the cutting edge . 

Henry

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From: [email-masked] (Boris Beizer)
Date: Wed, 11 Dec 1996 08:22:33

In article <[email-masked]> Boris Beizer wrote:
>Date:	Tue, 10 Dec 1996 15:36:18
>From:	[email-masked] (Boris Beizer)
>Newsgroups:	rec.crafts.metalworking
>Subject:	Re: machining
>
>

>    same rake as for woodworking.

Apologies to all for my abuse or terminology.  I meant "relief, " not "rake."
The top of the tool should be flat.  The bottom angle should be more acute
than for brass.  

I owe this correction to  "Henry P. Szostek" <[email-masked]>
He say's zero (top) rake like brass and advises relief below the cutting
edge to reduce heat buildup by rubbing below the cutting edge."   

This makes sense to me and perhaps explains why I had been successful with the 
acute bottom angle.  Worked for the wrong reasons.  I will have to try it
Henry's way.  In any case, the important thing is SHARP! HONE!

Boris

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From: [email-masked] (Peter Brooks)
Date: 12 Dec 1996 21:56:45 GMT

Boris Beizer ([email-masked]) wrote:

: Here's the short course:
[concise list of plastics do's and don't's deleted]

Wow!  Now, posts like this make it worth sorting past the American vs
Foreign machine posts, not to mention the odd (very odd) True Believers.....

Thanks!

Pete Brooks

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From: [email-masked] (James Kirkpatrick)
Date: 11 Dec 96 14:29:18 MST

|>In article <[email-masked]>,
|>[email-masked] wrote:
|>
|>> HELP!!!  I am an engineering student searching for information on
|>> machining plastics. I realize that this is for metal working , But this
|>> was the only newsgroup I could find that was even close. Any help would be
|>> greatly appreciated.

You might check out the metalworking FAQ,
http://plains.uwyo.edu/~metal

In the FAQ, question 42 deals with machining some types of plastics such as:

        Nylon 101 and other type 6/6 Nylons
        Monocast (r) and other type 6 nylons
        Nylatron (r) GS,GSM,NSB,and NSM Nylons
        Acetal
        Delrin
        Delrin AF (Tm dupont)
        Q200.5 (Crosslinked Polystyrene)

As you might guess, procedures will depend on the plastic, the type
of machining operations, and the pre- and post-treatment of the plastic.

Jim

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From: Lee Marshall <[email-masked]>
Date: Tue, 10 Dec 1996 10:41:40 -0800

geoff beneze wrote:
> > machining plastics.

> you're asking. These kind of "how high is up?" questions are just a bit

Geoff, I agree with you re: lack of specific requirements. However, I
do  "machine plastics", specifically cast acrylic and delrin. I machine
a domed face on 1-3/4" dia bar stock in the lathe with a radius cutter
using a spray mist coolant. To protect myself from the fumes given off
by the acrylic, I made a box to fit around the collet with a fume
extractor pulling the fumes to the outside of the building. Prior to
doing this, I would get a massive headache that would last into the next
day.
I run the lathe at 1200 rpm and take about 1/8" cuts with carbide insert
tooling (the same tools that I use for steel). Delrin machines like
butter. The acrylic will chip if taking too much of a cut.
If you want to see the finished product, it is at my website, under
"consumables".

Lee Marshall
Bonny Doon Engineering     http://www.bonnydoonengineering.com

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From: [email-masked] (Fitch R. Williams)
Date: Fri, 13 Dec 1996 06:37:54 GMT

>Pete Brooks

Yeah, I notice that Boris is guilty of doing that fairely
often.  It *is* a feature for sure.

Thanks from me too.
Fitch

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From: John L Ferrell <[email-masked]>
Date: Tue, 10 Dec 1996 10:51:21 -0800

[email-masked] wrote:
> [email-masked] Atlas lathe manual & the Machinery's Handbook both address the machining of plastics 
so I expect you are in the right place. Check your library for a copy of the Handbook, 
and then come back with specific questions if possible. 

The guys who hang out around here can be pretty crusty at times, but in the long run 
they will help you find what you are looking for. 

John Ferrell in Julian NC..

I intentionally end sentenances with prepositions because it it annoys some people like 
a sqeeky chalkboard!

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From: [email-masked]
Date: 15 Dec 1996 02:59:15 GMT

In article <[email-masked]>, John L Ferrell
<[email-masked]> writes:

>I intentionally end sentenances with prepositions because it it annoys
some
>people like 

Most likely goes unoticed here John, I hope you get annoyed. <g>

Peter

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From: [email-masked]
Date: 10 Dec 1996 02:13:30 GMT

---

From: [email-masked]
Date: 10 Dec 1996 16:14:51 GMT

What do you need to know about machining plastics?  I'm a mechanical
engineer, and use some machined plastics in my designs, mainly delrin, but
also torlon(sp?), peak and vespel.  We have an in house machinist who has
done alot of plastic machining, so I could forward questions to him as
well.

Paul

[email-masked]

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From: [email-masked] (Rob Ryan)
Date: Mon, 16 Dec 1996 16:26:53 GMT

John L Ferrell <[email-masked]> wrote:

<snip>
>I intentionally end sentenances with prepositions because it it annoys some people like 

That is something up with which I cannot put!

Rob