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Old 27th Jan 2020, 8:02 pm   #1
astral highway
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Default Cutting perfect circle in acrylic

Hi folks,

I have limited workshop facilities and although in the past Iíve used a home made cutter with nichrome wire and a hefty current at low volts , I want this one perfect without having to spend ages cleaning up the edges.

Alternatively , if anyone knows where (specifically ) I could get this done or if ok with mods/ forum rules , is up for doing it for a reasonable amount , please let me know by PM.

Itís only about 14 cm diameter.

Thank you
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Old 27th Jan 2020, 8:39 pm   #2
Radio Wrangler
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Default Re: Cutting perfect circle in acrylic

To clear up ambiguity, do you want a perfectly circular hole in a piece of perspex, or do you want a perfectly circular disc of perspex?

Perspex can me machined, but needs care over speeds and feeds to avoid chipping the edges or shattering everything.

A local machine shop could turn you a disc. If a centre hole is wanted, then things are easier, if not then it's a double-sided tape job. I can do 12 or 13 inches in the gap bed of my lathe. If you want a circular hole, then a router on a trammel is a possibility but revs need to be controlled and feeding has to be very steady. A shallow cut from each side and then a deeper cut etc until the disc breaks out. Tidy up with abrasive paper then rubbing compound and perspex polish.

David
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Old 27th Jan 2020, 9:16 pm   #3
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Default Re: Cutting perfect circle in acrylic

Hi David ,

It’s the positive , a circular disc, that I’m after.

Sadly, any kind of conventional workshops have long been squeezed out of my area by gentrification. I used to go to a local collective with shared kit, including lathes and a laser cutter, but it closed 5 years ago .

If you’re potentially up for doing this for me in exchange for an appropriate fee , can you let me know and i’ll DM you and we can see if it can work.

Thank you for your really informative reply, as usual

Or if a
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Old 27th Jan 2020, 9:19 pm   #4
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Default Re: Cutting perfect circle in acrylic

Plenty custom ones on eBay, e.g.

https://www.ebay.co.uk/itm/Glass-Eff...xNKP4DtGLrU51w
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Old 27th Jan 2020, 9:47 pm   #5
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Default Re: Cutting perfect circle in acrylic

Thank you , Yesnaby! That’s great to know and solves this problem for me .

Mods close thread if you like ?
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Old 27th Jan 2020, 11:43 pm   #6
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Default Re: Cutting perfect circle in acrylic

If you are handy with( or know someone) with a router( the woodworking type) it’s a fairly simple job.
I’ve used a router a couple of times, and they make a good job of acrylic provided the cutter is sharp.
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Old 28th Jan 2020, 2:13 pm   #7
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Default Re: Cutting perfect circle in acrylic

Hi Tim, thank you

I don’t have more than very basic workshop equipment but this of course is a good solution for someone who does.
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Old 28th Jan 2020, 4:36 pm   #8
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Default Re: Cutting perfect circle in acrylic

It does depend on your definition of a 'perfect circle', but a decent glass merchant should be able to sort you out.
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Old 28th Jan 2020, 5:25 pm   #9
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Default Re: Cutting perfect circle in acrylic

You'll probably find greater willingness if you buy the material and ask them to cut it, rather than just walk in with the material in your hand .

B
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Old 29th Jan 2020, 11:44 am   #10
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Default Re: Cutting perfect circle in acrylic

Hi,
The places to cut perspex/acrylic sheets these days are Sign makers.
Virtually any shape can be produced as Computerised Cutters are used.

eg. I can think of a number of places in Park Royal that do this.
Regards - Mike
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Old 29th Jan 2020, 1:09 pm   #11
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Default Re: Cutting perfect circle in acrylic

Quote:
Originally Posted by paulsherwin View Post
It does depend on your definition of a 'perfect circle', ....
Iím rehearsing walking into the glass shop!

ĎMorning, please cut this acrylic on a line defining a closed loop with every contiguous point at exactly the same distance (140mm) from the centre. Thanks , Iíll be back in twenty mins.í
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Old 29th Jan 2020, 1:28 pm   #12
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Default Re: Cutting perfect circle in acrylic

The ones at the link in post #4 above by Yesnaby seem to fit the bill perfectly.

I've got a lathe, routers, bandsaws, and acrylic sheet, but I wouldn't dream of faffing about to make a disc, given that I could get a laser-cut perfectly round 14cm disc (or any other diameter) for a little over £3.00 post free. There are other suppliers on eBay who can supply more of less any sized acrylic disc in any colour, in a wide range of thicknesses for little cost.

No need to even get off the chair - two mouse clicks and it's on it's way!

Why look for complex solutions to simple problems?
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Old 29th Jan 2020, 2:15 pm   #13
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Default Re: Cutting perfect circle in acrylic

I'd likely go through a lot more than £3 worth of perspex in breakages before getting my first usable disc.

David
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Old 29th Jan 2020, 9:07 pm   #14
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Default Re: Cutting perfect circle in acrylic

I have a piece of 1" Perspex in the workshop, about three feet square. It is ex-BBC when they wanted to film an elephant footsteps, from underneath! I've been wondering what I might do with the Persepex for years.
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Old 29th Jan 2020, 9:26 pm   #15
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Default Re: Cutting perfect circle in acrylic

David4EBT: yes, I’m all for simplicity!

Richard: ahah, are you saying you now have a plan for that giant bit of Perspex? That sounds like an interesting story about a BBC production ...
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Old 30th Jan 2020, 9:50 am   #16
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Default Re: Cutting perfect circle in acrylic

Hi Al, I think there is a national company, Brisbay Plastics, they supply all sorts of plastic materials to builders, sign makers etc and have all the equipment to do what you require

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Old 30th Jan 2020, 5:37 pm   #17
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Default Re: Cutting perfect circle in acrylic

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Originally Posted by Ed_Dinning View Post
... national company, Brisbay Plastics, they supply all sorts of plastic materials to builders, sign makers etc and have all the equipment to do what you require
That looks like a handy contact , thanks Ed!
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Old 31st Jan 2020, 12:26 am   #18
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Default Re: Cutting perfect circle in acrylic

For ultimate accuracy, I think my PCB mill could do this for thin Perspex, certainly for 3mm but probably up to 5mm thick. However, my previous attempts at cutting plastic haven't been that successful. I think it needs a fairly fast router speed to prevent the plastic from melting. I think my machine can run as fast as 180 inches/min but I rarely run it above 24 inches a minute as this is scarily fast when cutting a series of small arcs for example.

The other issue I found was that the plastic can turn into a hard adhesive when it heats and cools and it gums up and ruins the tool really easily.
I remember milling and engraving a tiny steering wheel for a model boat for my neighbour from hard plastic and that took several attempts and a few tools before I got it right for that particular material.

The specs for my T-Tech 7000S mill are similar to those below and it is impressively accurate. Just draw a 140mm circle shape using the Isopro software and then ask the machine to cut it out using the same software.

https://t-tech.com/shop/product/quick-circuit-qc7000/

I think the best bet is the online vendor. Looking at their other stuff they must be very experienced at cutting Perspex! I think I'd ruin several tools on my mill before I got anything clean and accurate.
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Old 31st Jan 2020, 1:01 am   #19
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Default Re: Cutting perfect circle in acrylic

You can use a hot wire cutter to cut acrylic. Just need some nichrome wire, some maths and a car battery
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Old 31st Jan 2020, 4:28 pm   #20
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Default Re: Cutting perfect circle in acrylic

Quote:
Originally Posted by MrBungle View Post
You can use a hot wire cutter to cut acrylic. Just need some nichrome wire, some maths and a car battery
Yes, see post #1 ...

Iíve done it many times but itís not neat enough for show
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