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Kevin_Mc

Tamiya Shell Trimming

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which is the best method to trim down a Tamiya plastic shell?

I'm wanting nice straight edges and neat curves - scissors, dremel, craft knife, something else...?

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Which plastic,

See through polycarbonate or solid styrene/ABS?

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You can get curved scissors or arch cutting blades that cut arches perferctly.

Will

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I've also come across a compass like tool like we used to draw circles with at school. It had a blade where the pencil would usually be and was good for cutting wheel arches out with. If I had a straight line to cut I would score along it CAREfULLY a few times then just snap it away leaving clean line. Dremels are ok, although as they spin so quick they can usually melt what you are cutting away which can get in the way of the line/curve you may be cutting.

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yeah that's what i'm worried about with the Dremel, it tends to melt bits of car bumper away so i reckon it would destroy a shell

i think for the two straight edges i'll just score them a few times like you say, the wheels arches i can do with compass or special blade, the curved bumpers i'm not sure what to do

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get curved scissors for the tight bits, and long scissors for the long straight bits

finish any rough edges with sand paper.

maybe do a bit of dremelling, if there are some awkward bits (like on the '76 6 wheeler shell. sheeeeesh)

use a hole reamer/borer for making holes!

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Hi Kevin,

I've also found it easier to roughly trim most of the exess off first, leaving 10-20mm depth to remove on the final cut. It makes it easier if you need to flex the shell to cut round corners, etc. I usually use straight kitchen scissors for cutting straight lines, and a modelling knife / scalpel to trim wheel arches, with possibly a final tidy up with a dremel and a sanding wheel.

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that's exactly what i did earlier, trimmed off all the excess but i got fed up and succombed to the dreaded Uni work so i'll give it another go later this week.

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that's exactly what i did earlier, trimmed off all the excess but i got fed up and succombed to the dreaded Uni work so i'll give it another go later this week.

I mainly use a hobby knife for large edges, and a compass knife cutter for wheel arches. I use the score, bend and snap method. Score along the cutline on the outside of the shell to cut through any overspray film, then bend the polycarbonate back. You might need to cut chunks of polycarbonate away to make it easier to bend back along the score line. The polycarbonate will snap/tear along the score line. It does require a steady hand.

I use small scissors for harder to trim tricky details. I don't have curved scissors, but imagine they'd be handy for trimming some tricky body details.

I just use 400-600 sandpaper and block to tidy up any edges, or the back of my hobby knife works well for scraping away at the edge.

The heat from a dremel on moderate to high speed can cause polycarbonate to craze so it looks 'shattered', so be careful with it.

A hole reamer is the most useful tool for body post holes and cutting out smaller circular body details. Eg, it's useful for doing some of the curves on a Hot Shot body shell, for example.

- James

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I've used only curved scissors and a body hole reamer on 30+ bodies of the past 5 years.

They work great. Hit up the edges with some sandpaper if you want, but it's the curved scissors that do the trick.

As mentioned earlier, I first go around and cut to within 20mm or so of the "Actual" line to remove all the extra stock.

Then go and do each part with the curved scissors. Then ream body holes.

Cheers,

Skottoman

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The only place I can find the arch cutting blade/tool is eBay. Type in 'cut perfect arches in R/C body shells' and its the yellow compass looking thing.

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The only place I can find the arch cutting blade/tool is eBay. Type in 'cut perfect arches in R/C body shells' and its the yellow compass looking thing.

Look for Olfa brand. They make a few different sizes.

- James

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i managed to get it sorted with a pair or curved scissors, a pair of straight ones and a quick sand.

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i managed to get it sorted with a pair or curved scissors, a pair of straight ones and a quick sand.

Try the score method. I had for years been using "lexan" scissors and getting decent results. I tried the score method 2 years ago and HOLY ****, what the heck was I doing before wasting my time. It's so easy and I do it after the shell has been painted. Seriously, try it. So simple, no skill involved.

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I tried the scoring method before but it slipped off the line and ruined the shell. It was just for bashing but I learned the lesson of not using an edge to run against.

I'll maybe brave it on one of my less rare shells and see how it goes.

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Bumping this thread. I will be starting on my first touring car shell in a couple of weeks and I am honestly petrified. It looks so much more involved than a buggy shell and a lot busier with a lot of pieces. I have had somewhat decent luck with the score / break method but this new shell doesn't have many straight edges. I am planning on getting some good scissors which raises my question. For polycarbonate scissors, is there any brand that you guys highly recommend and any brand to totally avoid? Thanks!!

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I've been using a set of curved embroidery scissors from the local fabric store. They're 100% metal construction and come in three different lengths/curvatures. I've cut about 25 bodies with them so far: http://www.joann.com/metal-embroidery-scissors-3pk-2-1-2-3-1-2-4-1-2-/xprd357431/

Good lighting is key. The lights over my kitchen table reflect off the shell perfectly, and I can see the cutting line by angling the shell just right. Direct light shining down on the shell helps. Work slowly, and if you're worried about errors, have the scissors' curvature pointing away from the body. You can always remove more material later, but you can't add it back.

I found for wheel arches it's easiest to cut them all in a counterclockwise direction; that keeps the scissors to the outside of the shell and makes them more maneuverable. I've tried cutting in a clockwise direction around the wheel arches, but that places the scissors to the inside of the shell and there are usually corners or other features that prevent cutting in the right direction.

Sanding the edges of the shells with 220 grit or higher when you're done will remove any small irregularities from cutting. Sanding is also a great opportunity to blend and smooth corners. Speaking of corners, the bottoms of the wheel arches should have small radiuses on them to not get snagged on anything.

I usually cut most of the excess material off the molded shell first, then I work on the wheel arches. Then I cut all the bumpers and rocker panels. I'll cut some small radiuses at the bottoms of the wheel arches, and if it looks mostly good then it's time for sanding. Sanding helps correct small errors with blending.

If you're worried about cutting, wait until you have to start masking for four or five paint colors, and then start working on applying 80-100 stickers. Some of Tamiya's shells take a lot of effort to get right. In the past I've spent more time on the shell than the chassis -- the Xanavi Nismo GTR R35 shell really stretched my patience. After doing a few of those, HPI shells started looking more attractive both in terms of purchase cost and level of effort to complete.

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I usually use the score-and-snap technique described earlier, with an Olfa circle cutter for the arches as used by many others. However where I differ from many modellers is that I don't use a sanding disc or drum on my Dremel - I use a polishing wheel. I have found that it gives greater control as it removes material at a slower rate, and it also wicks away most of the material that it does remove, so you don't end up with clumps of melted lexan stuck to your shell.

I have a 3cm diameter one that I have been using for a while, and it now has a slight groove worn into the middle of it. This works really well, as it helps keep the tool on track since the edge of the shell naturally locates itself in the groove.

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I usually use the score-and-snap technique described earlier, with an Olfa circle cutter for the arches as used by many others. However where I differ from many modellers is that I don't use a sanding disc or drum on my Dremel - I use a polishing wheel. I have found that it gives greater control as it removes material at a slower rate, and it also wicks away most of the material that it does remove, so you don't end up with clumps of melted lexan stuck to your shell.

I have a 3cm diameter one that I have been using for a while, and it now has a slight groove worn into the middle of it. This works really well, as it helps keep the tool on track since the edge of the shell naturally locates itself in the groove.

hmm - i've never tried using a dremel on lexan. will have to try that. as for me, i found that it's far too easy for me to mess up scoring the cut line and leaving stray cuts or scratches on the body itself. others may not have this problem, but i switched to the curved lexan scissors and will never go back. i use a pair with very short curve blades and i just work my way along the cut line slowly with the curve facing away from the cut so you err on the outside rather than ruining the body. as said above, you can always take off more later. one important thing is never close the blades all the way as this leaves a star-shaped crack in the lexan that can radiate outward. just cut continuously along, even around corners and such... the lexan will bend out of the way in most cases. sometimes i will flip it around and cut from the inside out to avoid bumping up against an edge. when there is an area that's too intricate i just leave it alone to deal with using sanding or one of the very precise tamiya files. i have the circle cutter but so far haven't tried it since i don't cut too many lexan bodies with round wheel arches. no matter what you'll want to sand down all the edges so they aren't sharp and jagged, and the sanding removes a surprising amount of lexan, so it's easy to fine-tune the edges if you leave too much material. the only problem i've found with sanding lexan is it produces this awful, incredibly fine dust that gets everywhere and can't be good to breathe in. i may start using a surgical mask while doing this (bigger filtered masks tend to fog up my glasses too much to use for this). to cut internal parts use the reamer to make a hole for the scissors to cut from, sort of like the way you drill through wood to allow for a band-saw blade.

in terms of how to attack the cutting, as others have said, i'll first trim roughly around the outside of the cut line to remove the entire flat part and a good chunk of the excess around the body. then i cut all around the body along the flat edges and pass directly across wheel wells, etc to get to the next flat section. then i go back to work on the fine cutting parts like wheel wells, and other indentations. it has worked pretty well by keeping the excess out of the way so as to not distract from the detailed work.

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I use a combination !

curved scissors are great for wheelarches - i work from both directions and meeting the middle

the score and snap method works well when you can put the area to be cut on a flat surface and use a steel rule as an additional guide - good for the side skirts/sill area

just take your time and work in good light, preferably daylight rather than under a spotlight in the evening.

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curved scissors are great for wheelarches - i work from both directions and meeting the middle

that's exactly what i do and i've been happy with all the arches so far

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Is there any scissors to avoid? I can just roll with what my LHS has. If I drive my road car like my I do my buggies, new shells are going to be a more frequent orrurance than I would like.

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