# cutting circles!



## rgs41 (May 14, 2008)

Im in the process of detailing my Accucraft c-19, and Im replacing the smoke bow front. But Im having trouble cutting circles. I made one out of styrene and it looks ok but I think I want to try it out of brass. What i was wondering is how, or what is the best way to cut a circle from brass or styrene?


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## david bunn (Jan 4, 2008)

OK here is how I have always done it, it works for me. 
Obviously you firstly need to determine the radius of the circle.Then grab a decent pair of dividers and set these to the desired radius.Make sure that the dividers are pressed firmly to the centre of the circle and mark it out, sometimes a centre punch helps to secure the point.Scribe the circle carefully making sure that the dividers don't spread and continue until you have a decent groove the size of the circle.Then take a fret saw with a fine blade and cut the circle,the deeply scribed line will help guide the saw if you take it easy.Finally gently clean up the cut with a small file.Voila!!you have your circle. 
Good luck 
Bunny


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## chrisb (Jan 3, 2008)

My approach would be to lay out using a circle template and ultra fine sharpie then rough cut the "disk" by cutting out side the line and then cut to the line using a disk sander or a belt sander clamped on it's side, watch out its going to get hot and sharp. A grinder may be too rough and too fast. If the disk has a hloe in the center it's easier. put a finish nail in a scrap of wood, clamp the wood on the disk sander so the center of the nail (cut head off) is a little more the the lentgh of the radius from the sanding surface, put the brass on the nail (nail though the hole) and cut to the lione by rotating the disk. This is an old trick for cutting wood circles on a band saw. Easy to do but hard to explain.


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## paintjockey (Jan 3, 2008)

They make a compass that holds a blade, this is good for thin material but probly not brass. To cut brass sheet, i put a hole saw with arbor in my drill press without the center guide bit i firmly clamp the brass to an oak board. Use hard wood to clamp to because the brass likes to bend before it cuts, the oak prevents this. If a center hole doesn't matter, ue the center bit it makes it much easier. This process also works for thin ply. 
Terry


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## jnic (Jan 2, 2008)

Get one of these:


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## paintjockey (Jan 3, 2008)

Yup thats the thing i was talkin about above. works great


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## rwjenkins (Jan 2, 2008)

I needed to cut a pair of perfect circles in styrene just last week to make the "DF" logos for the doors of my 50' NP boxcar (bashed from a couple of MDC cars)... 










I did each one by rough-cutting a 1/8" oversized disc (well, more like an octagon, it was that rough) from a piece of styrene sheet, glued a 1" piece of styrene tube perpendicular and centered to the back of it, then chucked the tube into an electric drill and turned the styrene disc against a file until I had it down to the right size. Normally, if I'm not concerned about a hole in the middle, I'll drill it and screw it into the cut-off wheel mandrel from my Dremel tool and chuck that into the drill. That method works for brass too, but if the hole is an issue you can solder it to a piece of brass tube instead.


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## rgs41 (May 14, 2008)

Thanks for the help guys I think Ill try that OLFA cutter.


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## cudak888 (Mar 22, 2008)

Another vote for the Olfa. Works very well, and it is stiff - won't bend when you put pressure on it. 

Stay away from the X-Acto variant of the same tool, for it bends easily. Virtually impossible to get a clean circular cut with it. 

-Kurt


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## rkapuaala (Jan 3, 2008)

I just use repeated shallow passes with a pair of dividers and it works really good on styrene, but I'd like to get that circle scribe jnic recommended. Looks like a lot faster, and easier.


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