cutting polycarbonate disc

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cutting polycarbonate disc

This topic has 10 replies, 9 voices, and was last updated 8 February 2012 at 22:46 by confused.eng.

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7 February 2012 at 22:58 #5930
capanab
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@capanab
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7 February 2012 at 22:58 #84140
capanab
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@capanab
I need to cut some 56mm diameter polycarbonate discs from 2mm thick sheet, with no hole in the middle.

Have so far tried

– hole saw in bench drill. – teeth get very quickly clogged up , bit like sawing mdf.

– fretsaw/piercing saw – pretty tatty edge , which takes forever to sand down to anything remotely respectable.

– lathe face plate , – difficult to make a tool that cuts cleanly without clogging up.

teenage daughter came home from school and dismissed my attempts saying I needed a laser cutter like they have in D+T.

useful suggestions welcome.
7 February 2012 at 23:23 #84142
MICHAEL WILLIAMS
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@michaelwilliams41215
Hi capanab ,

Lathe face plate works ok – I’ve done this many times .

A good tool to use is actually round with the top and end given a cutting edge – just like a D bit to look at – this automatically gives very nescessary side clearances . Slow speed and one or two tool withdrawals and should work fine every time .

Usually works ok dry but a drop of soluble oil does make cutting cleaner if plastic is very sticky .

MikeW
7 February 2012 at 23:47 #84145
Flying Fifer
Participant
@flyingfifer
Hi capanab,

Agree with your daughter laser is the way to go. Modern lasers give a very fine finished edge with no tool marks and consistent dimensions. All you need is is to draw the circle the size you want in Corel draw or Autocad, load to the laser & cut as many as you want.

Alan
8 February 2012 at 00:11 #84147
Ady1
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@ady1
With aluminium I would use the backgear because you get almost no heat.

Things clog up when you have too much speed because of the heat.

It may be a “cutting speed” thing with your perspex too

Try slower speeds and a nice sharp tool
8 February 2012 at 08:37 #84154
Jim Guthrie
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@jimguthrie82658
Posted by capanab on 07/02/2012 22:58:56:

I need to cut some 56mm diameter polycarbonate discs from 2mm thick sheet, with no hole in the middle.

Have so far tried

– hole saw in bench drill. – teeth get very quickly clogged up , bit like sawing mdf.

– fretsaw/piercing saw – pretty tatty edge , which takes forever to sand down to anything remotely respectable.

– lathe face plate , – difficult to make a tool that cuts cleanly without clogging up.

teenage daughter came home from school and dismissed my attempts saying I needed a laser cutter like they have in D+T.

useful suggestions welcome.

I cut perspex on my milling machine and I use carbide cutters and get an axcellent finish. Perhaps using a new – i.e. very sharp – carbide tool might give good results in a lathe.

Jim.

Edited By Jim Guthrie on 08/02/2012 08:38:18
8 February 2012 at 09:02 #84155
MICHAEL WILLIAMS
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@michaelwilliams41215
The only reasons why difficulties can sometimes arise when trepanning plastic discs are :

(1) Not enough side clearance on both sides of tool – tool has to work freely in a narrow , tightly curved and sometimes deep slot .

(2) Too high a cutting speed – just melts lumps of plastic and jams everything up .

The original posters problem can be solved with an ordinary HSS tool made in five minutes . All that is needed is just a parting tool shape with enough clearances to work in the curved slot .

MW

Edited By MICHAEL WILLIAMS on 08/02/2012 09:12:36
8 February 2012 at 09:32 #84156
maurice bennie
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@mauricebennie99556
Hi Capanab, I always cut perspex circles by cutting roughly with hacksaw and then grind to edge of circle with my 6″ grindstone .To accurately cut straight lines ,Clamp to top of bench with steel straight edge.Make a cutter with a Stanley knife by grinding a hook cutter on the blade and pull it along the line of the steel.Leave the edge of the plastic slightly over the edge of the bench so the cutter comes of without digging into the bench.With 1/8″plastic cut about half way through and bend the plastic upwards and it will crack of.With 1/4″ its easier if you cut both sides..Practice on some rough first.

Good luck Maurice.

PS you dont have to cut right through.
8 February 2012 at 10:19 #84158
Les Jones 1
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@lesjones1
Hi capanab,

Cut them out roughly with a hacksaw (Rough octagons) cut out a wooden disk just less than the diameter you require and centre drill it.

Mount another block of wood in the chuck and turn the end down to just less than the diameter of the finished disks and face the end. clamp the disk (or disks) between the blocks of wood using a live centre. Turn to the finished size taking light cuts. An alternative is to stick the disk to the block of wood in the chuck with double sided adhesive.

Les.
8 February 2012 at 13:33 #84167
Versaboss
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@versaboss
…and the Oscar goes to – Les!

Strange that one has to wade through 6 mostly off-topic answers for finding the only sensible one.

Btw, polycarbonate is neither perspex nor alu.

Greetings, Hansrudolf
8 February 2012 at 22:46 #84206
confused.eng
Participant
@confused-eng
Ask teenage daughter to make some in her D+T class!

Brand new good quality hole saw does work if run slow and eased through gently.

Too much force or speed and things get a bit warm and sticky.
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