Author Topic: How do you cut circles?  (Read 8186 times)

rvn85

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How do you cut circles?
« on: May 23, 2005, 08:12:36 AM »
after finishing my NG 1/100 Blitz ( i'm putting the justice aside for awhile nw), i decided to customise my MG Dom. i intend to include 2 gattling guns into its armanents but i'm encountering a problem. i have no idea how to cut the circles to hold my brass tubes together. i tried cutting it out by following the outline made by a compasses but can't seem to cut a decent one. so can someone help me? i've gt a circle template also.
PS: I'm trying to cut a circle abt 2cm in diameter.

fulcy

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Re: How do you cut circles?
« Reply #1 on: May 23, 2005, 08:26:55 AM »
Quote from: "rvn85"
after finishing my NG 1/100 Blitz ( i'm putting the justice aside for awhile nw), i decided to customise my MG Dom. i intend to include 2 gattling guns into its armanents but i'm encountering a problem. i have no idea how to cut the circles to hold my brass tubes together. i tried cutting it out by following the outline made by a compasses but can't seem to cut a decent one. so can someone help me? i've gt a circle template also.
PS: I'm trying to cut a circle abt 2cm in diameter.


I don't know if you can get them from local art stores, or from hobby shops (or even both), but there is a tool out there that can be used just like a compass, but instead of a piece of lead, there is a knife blade.  You can try looking for that, or if you are adventurous, try taping an exacto knife to your compass and try cutting with that...

ronin4122000

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How do you cut circles?
« Reply #2 on: May 23, 2005, 08:52:47 AM »
I bought a circle cutter yesterday from an electronics shop for £3 (i live in the U.K) the exact same one was in an art store for £8 so it really is worth looking around.

The one I bought looks like a slide rule with diameter and radius marked on it, you slide the point to what you want and there you have it.... sorry probably not the best description heres the link with a pic of the one I bought....funnyly enough I bought mine to make a gatlin gun too :shock:  

hope this helps
http://www.maplin.co.uk/Search.aspx?Criteria=circle%20cutter&doy=23m5

FichtenFoo

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How do you cut circles?
« Reply #3 on: May 23, 2005, 09:47:51 AM »
Ooooo.... gotta get me one of those!
Rust is beautiful.

rvn85

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How do you cut circles?
« Reply #4 on: May 24, 2005, 06:45:05 AM »
Quote from: "ronin4122000"
I bought a circle cutter yesterday from an electronics shop for £3 (i live in the U.K) the exact same one was in an art store for £8 so it really is worth looking around.

The one I bought looks like a slide rule with diameter and radius marked on it, you slide the point to what you want and there you have it.... sorry probably not the best description heres the link with a pic of the one I bought....funnyly enough I bought mine to make a gatlin gun too :shock:  

hope this helps
http://www.maplin.co.uk/Search.aspx?Criteria=circle%20cutter&doy=23m5

just to confirm with u ronin, how thick of a plastic sheet can it cut thru? more than 5mm?

fulcy

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How do you cut circles?
« Reply #5 on: May 24, 2005, 08:21:47 AM »
Sweet merciful - 5 mm plastic sheet?  You should probably be using a saw to cut that stuff, or you're going to be there forever with a knife...

ronin4122000

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How do you cut circles?
« Reply #6 on: May 24, 2005, 08:52:56 AM »
hi again,

I don't think it would do 5mm, however it would score the plastic possibly enough to act as a guide to sand it to shape.

I was having another think about it and another tool to cut thin plastic or score it would be the circle scribe (I think starshipmodeler did a review of it) and the makers site is here
http://www.circlescribe.co.uk/

Another way to score the plastic in in circle would be to use one of those map compasses with two points rather then a pencil (many high end compasses are able to do this too).

Or the easiest way to cut thick plastic would be a circle cutter on a power drill, i'm not sure what sizes these come in but from the same place as the circle cutter in my original post they are £5 a set.

Hope this helps I think I really need more practice with writing on these forums so I don't come across so long winded  :oops:

heavyarmscustom

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How do you cut circles?
« Reply #7 on: May 24, 2005, 12:34:26 PM »
Personaly I would go Find a drill bit at 2cm and drill away
clifton
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FichtenFoo

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How do you cut circles?
« Reply #8 on: May 24, 2005, 12:41:32 PM »
Quote from: "heavyarmscustom"
Personaly I would go Find a drill bit at 2cm and drill away
clifton


That's great if you want a hole... this is about making the opposite of a hole. :wink:
Rust is beautiful.

heavyarmscustom

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How do you cut circles?
« Reply #9 on: May 24, 2005, 01:01:24 PM »
Opps !
Sorry I read it wrong. I thought it was the holes to hold the rods in.
My Fault.

this idea my be for the birds, but how about  taking a compass making an outline of the circle and sawing around the plate and then sanding the plastic til you hit the compass mark

sorry again
clifton
Heavyarms custom would be an unstopable killing machine if the damn thing never ran out of bullets!!!!!

ronin4122000

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How do you cut circles?
« Reply #10 on: May 24, 2005, 01:30:28 PM »
I found this article on starshipmodeler the section on cutting circles is about half way down the page

http://www.starshipmodeler.com/tech/cj_scribe.htm

and I also found this circle cutter for sale in the U.S (i think) so you can see one that might be closer to home. It is very simular to the one I bought here in the U.K.... The problem I've found with mine is because of it's uneven shape (unlike a compass) it is quite hard to get an even presure round the full circle without actually stopping to move the plastic. I also found it quite helpfull on thicker plastic to take a very very fine pin vice bit and drill through the centre hole (left by the compass point) to the other side flip the plastic over and score that side too, and then pop it out this give a much more even surface and less sanding.

http://www.misterart.com/store/view/001/group_id/8132/Olfa-Standard-duty-Circle-Cutter.htm

rvn85

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How do you cut circles?
« Reply #11 on: May 25, 2005, 05:09:02 AM »
perfect! thanx for the load of info u shared with me ronin.... unfortunately, i live in singapore so it might be quite hard to find it so try my luck at the hardware and art shops that i knw of.... thx

the OLFA Standard-duty Circle Cutter might actually help do the job for me....

rvn85

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How do you cut circles?
« Reply #12 on: June 16, 2005, 05:22:22 AM »
finally gt the circle cutter rouni reccomended..... though it cuts circles fine but i can't really cut small circles......  :cry:

p-trax

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How do you cut circles?
« Reply #13 on: June 16, 2005, 10:52:21 AM »
Quote from: "ronin4122000"
I bought a circle cutter yesterday from an electronics shop for £3 (i live in the U.K) the exact same one was in an art store for £8 so it really is worth looking around.

The one I bought looks like a slide rule with diameter and radius marked on it, you slide the point to what you want and there you have it.... sorry probably not the best description heres the link with a pic of the one I bought....funnyly enough I bought mine to make a gatlin gun too :shock:  

hope this helps
http://www.maplin.co.uk/Search.aspx?Criteria=circle%20cutter&doy=23m5


Bother!   I wish i had know Maplin sold these, I forked out for the olfa one from my LHS, guess I got ripped off :(

ronin4122000

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How do you cut circles?
« Reply #14 on: June 17, 2005, 12:22:12 AM »
It does say on the link I put on that it cuts circles 10mm to 150mm.
 I've been looking for something which cuts smaller circles too and I came across this item (see link). It's called a screw punch you can change the end to fit various sizes. I'm not sure though if it actually will cut a circle or just a hole and at that price I'm not going to be finding out anytime soon :x
It's £40 for the basic model in the U.K and then extra for the cutters.
http://www.wilde-ideas.com/Vndrs/Whsl/ScrewPunch.html

Tazman3

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How do you cut circles?
« Reply #15 on: June 17, 2005, 07:12:39 AM »
Nope, that item just makes a hole, not a "circle" to go along with it...have you guys thought of using punch and dies sets?  Waldron and Armor Detials both makes a couple different sets...they are pricey though...

http://www.steelmodels.com/prodotti/Armour.htm

http://www.greatmodels.com/~smartcart/cgi/display.cgi?item_num=wr0018

Later,
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Bawoo

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How do you cut circles?
« Reply #16 on: June 21, 2005, 12:30:32 PM »
I have 2 methods that I usually use:

1.  Cut the circle as close as you can by hand/whatever means necessary.  Make sure the radius is properly marked with something fairly permanent (sharpie, etc).  Then use files to shave the edges down to finish the circle.  Holding the file flat while rotating the part (keep moving, don't work the same spot for more than a stroke or two!) emulates the action of lathing it.  I promise, with some practice you can make near perfect circles this way.

2. If you can find a copper/brass/aluminum pipe of the right diameter (2cm is probably pushing it), you can sharpen the edge of it using a file, then use it to cut the circle.  Once it's sharpened, press it into the plastic, rotating the pressure until you get enough of a groove that you can start rotating the pipe.  Eventually you'll get pretty much all the way through, then you can do final cleanup with a file or sandpaper.  Probably wouldn't work on anything more than 2mm thick plastic though...

Files are better than sandpaper for rounding circles!  The back and forth action of the sandpaper is more likely to make your parts out of round, whereas the single cutting direction of the file lets you rotate the part as you cut.  Definitely better!
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ronin4122000

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How do you cut circles?
« Reply #17 on: July 13, 2005, 12:03:12 AM »
O.K after much searching I finally found the answer in the Gundam scratch building manual.... Hollow punches or Wad punches these can be bought in many different sizes from a couple of millimetres the a few centimetres. I've enclosed a link so you can see them, The only other piece of advice is if you use them apparently it's best to hammer them into a piece of end grain (i.e. block of end grain styrene sheet on top and then hollow punch hammered through) this helps the punch to cut through in one go cutting a perfect circle. Hope that helps.

http://tngdirect.com/catalog/product_info.php?products_id=282&osCsid=51dba2a8a72f2a48ad89936f68266a07

Oh and did I mention how cheap they are

hugedom

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How do you cut circles?
« Reply #18 on: July 13, 2005, 09:32:22 AM »
Sorry about joining this late, but I just use a drafting circle template, tape the template to the plastic and scribe the circle size you want.

rvn85

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How do you cut circles?
« Reply #19 on: July 26, 2005, 08:50:55 AM »
right now depending on the size of the circle, if its real big, then i wld use the circle cutter or just a circle template and using a pen knife to cut it out. for small circles which cant be cut out using the above methods, i usually use a hole punch and punch a hole thru the sheet. if the circle's smaller than that, then i guess i just have to ask u guys for advice.
anyway, thanx for the efforts guys really appreciate you all helping me find the solution which i already did. thanx a million.