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Author Topic: Another plasticard cutting question  (Read 1038 times)

warspite

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Another plasticard cutting question
« on: February 03, 2019, 08:59:01 PM »

As those who watch the Victory thread will have noticed I did a bit of cutting, the score and snap then clean up method is generally used for the straight lined pieces, BUT - what methods do others use for cutting, (I persevered with scoring until I got through, it was laborious and wished for an easier way) :-


Circles
Circular inside corners
square inside corners
very small stepped or angled cuts


For instance - a window 10 mm long x 3 mm high in a structural item, there are a couple of options I would suppose, would you - drill two holes 3 mm dia and the score between them, then file the corners to square.
Do a bigger hole for a say structural item and then skin it in thinner material.


Reason is if you wanted to do some work like the french frigate thread - how would you get that quality finish - answers on a postcard  %)
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CGAux26

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Re: Another plasticard cutting question
« Reply #1 on: February 03, 2019, 11:34:39 PM »

I am scratch building a ferry, mostly from 0.060" styrene.  I score it 3 strokes, then snap.  This works well on curves of a sizalble radius.  For sharp corners I can usually score-and-snap, too, by over cutting the lines a bit.  I use pliers to snap the plastic for small pieces.


I have also used heavy duty scissors for some odd shapes, and large and small side cutters, too.  Then there is the bandsaw, with a fine tooth blade.  There is some melting, but it's minor and cleans up with a swipe of sandpaper.


I will be interested in how you cut window frames.  I have several of those to do, in 0.040 card.


What do you use for glue?  I use MEK from the hardware store, with a bunch of styrene chips dissolved in it, to help fill small gaps.  Apply it with a small artist's brush.  To illustrate the strength of my joints, I had to clamp an assembly in a vise to cut a hole with my Dremel.  It took that abuse with none of the joints cracking.
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warspite

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Re: Another plasticard cutting question
« Reply #2 on: February 04, 2019, 11:56:41 AM »

I have a dremel, I also have the pillar stand that they make, but as yet I have not used it fully, the usual score and snap technique, but in the last bit I did it's 1.5mm thick for supporting the servo's, so some rigidity required, so again scored the line using an old steel rule and G clamps to secure it whilst I scored, but you get the usual over run due to impatience, using a Stanley knife (box cutter) to 'dig' into the corners to prevent the over run.


Due to the thickness one or three scores doesn't cut it - so to speak - trying to snap it won't work as the piece that you are creating may break as well as the piece you are trying to release - hence the question what do others do for even more complex shapes to be cut out.


Is a dremel being held and the piece moved following the line a more effective way of doing it - like the router project in one of the threads.


I have used a dremel / Multi-tool in the past to the point it starts to melt the plastic, you spend more time cleaning up the part than cutting it out, lol
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dougal99

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Re: Another plasticard cutting question
« Reply #3 on: February 04, 2019, 12:14:07 PM »


For thicker sheet >1mm I use a plastic cutter which scores a groove in the sheet making it easier to snap. You do get plastic swarf though.


Squires do them http://www.squirestools.com/files/13-13.pdf  scroll to page 188


Larger curves I rely on a compass cutter.
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ballastanksian

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Re: Another plasticard cutting question
« Reply #4 on: February 04, 2019, 08:34:06 PM »


For straight cuts in thin plastic I cut right through or cut several times and snap.


Small internal corners: Drill holes and enlarge with a triangular file spun in my fingers like a reamer until I get the correct diameter and adjust them with a round file as sometimes they come out like rounded triangles.


Large internal corners, like Dougal, I use a compass cutter. after twenty five years of regular use, I managed to snap one of the bars of the inner section and will have to invest in a new one for larger curves  :((


Square corners: I cut through in thin plastic and cut through partly and either chain drill to release the majority of the material before trimming with a scalpel and sanding, or drill a hole in the middle of the square, cut a cross and then use a razor saw to cut down the scores and snap the triangles out. The former technique reduces the chance of some material in the edge breaking away with the material you want to move and is best when using 2mm or thicker plastic.


Watch out for the type and age of the styrene you are using. If it is yellowing at the edges or on the surface it will be unreliable and may break where it wants despite your cuts etc. Some styrenes are more brittle than others and can be stored badly by the shop owner and thus will come out warped. The bluer styrene seems better than the creamier type but with care it is all pretty good unless perished.


For stepped or angled cuts, I draw a line along where I need to cut/file to to get my angle. You will probably get a slightly variable angle along the line so be careful and adjust where necessary. Remember, like wood, you can add slivers of plastic and when cured sand/trim back. Obviously we want to get it right first time, but it is forgiving. Steps I do by laminating thicknesses of styrene and reduce the dimension of the area to be stepped in one layer. So to step a 20mm square window down to 19mm, the inner layer has a square 1mm less in dimension. If making oddly shaped stepped areas, then mark and cut the larger dimensioned piece and then draw round it on a piece of styrene sheet and carefully reduce the line to get the inner dimension you need.


Styrene strip tips: Evergreen make good strips that have square corners, so can be used for accurate work, The ends are often useless, so cut the first 3-4mm off before making any accurate marks etc Also they can have tags of uncut material on the side at the end so watch out for that when using a set square.


They make good tubes but not good rod. The later is often not round and can have elongated voids like when stretching kit sprue.


Plastruct (not slaters plastikard) make reasonable strip but make excellent rod in a variety of diameters from .3 up to 6.3mm. It is matt and so easy to mark and is solid. Their tube is good as well.


Sllater's Plastikard is alright. Their rods are oval or of a brittle plastic and are not the best unless you are not after perfectly round rods.
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RST

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Re: Another plasticard cutting question
« Reply #5 on: February 04, 2019, 09:57:45 PM »

Hmm, please don't get me wrong.  Plenty of ideas given.  Mags, books and internet is just bursting with ideas but if you really want to know how to cut a square hole from a round window I really think it's better to try and encourage the the old fashioned methods (polystyrene sheet and knives are cheap!).  You already sound like you know the principles :-))   What works for one don't work for the other.  And I am in the same boat as you looking at others work in admiration!!!!
Rich
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warspite

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Re: Another plasticard cutting question
« Reply #6 on: February 05, 2019, 02:54:04 PM »

Thanks - some really good tips there, it's been a while since I cut the thicker stuff, several years ago, I bought some sheets at an event at the club I was a member of, they were extremely large 3' x 4/5' long (yep foot not inch), so still deciding what to build and its been in the loft for many a year so should be still in a good enough condition to use, the problem I had was what do others do when cutting the thick and thin stuff to get the intricate shapes that some attain, Midori is the perfect example with his french warship.

[/size]the new sander will help as will the multi-tool and its sander option.     {-) not
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ballastanksian

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Re: Another plasticard cutting question
« Reply #7 on: February 05, 2019, 06:58:02 PM »

Keeping your styrene out of sunlight was very wise as that will perish it after a while. When cutting or sanding it mechanically be careful as it is easy to melt the area which might jam up the tool. This can damage the work you are doing, and at very worst damage the tool. Cutting styrene with a bandsaw causes molten swarf on the underside which needs removing periodically. I am probably too impatient!!!
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Baldrick

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Re: Another plasticard cutting question
« Reply #8 on: February 05, 2019, 07:31:29 PM »




One thing I have found useful in cutting plasticard to irregular and circular shapes is to use a very sharp carpenters chisel and cut vertically down onto the card laid flat on an old cheeseboard . I try to get as close to the final shape by score and snap and then with the chisel pare back to the final pencil line. I can do this on up to 2mm thick material , take only small bites and work back to the line. I made the Cervia stern lettering this way. albeit card is only .6mm thick using a 3/8 chisel. Cut this way the plasticard slices like cheese (OK a hardish cheese)



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grendel

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Re: Another plasticard cutting question
« Reply #9 on: February 06, 2019, 07:56:06 AM »

would a powered fretsaw do the job without melting the plastic for the thicker cards, though the big problem with those is following the line
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warspite

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Re: Another plasticard cutting question
« Reply #10 on: February 06, 2019, 10:10:30 AM »

Trouble is any friction causes heat and by default the plastic to melt, so powered tools are by their nature difficult to control the melting with, in the schnellboote I have, I refurbed her from the original fit out by cutting the deck out between the bottom and the false bottom (the sides are like an L shape with the curved keel a separate piece for a waterline model) I used a multi-tool and at times relied on the friction to melt through the styrene to remove the majority as there was little room to manoeuvre, finally using the tool to cut back to the hull sides, messy but it worked for me.
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Brian60

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Re: Another plasticard cutting question
« Reply #11 on: February 07, 2019, 06:26:29 PM »

For openings like doors or windows even with rounded corners, I used to use the score all round method, but then do a diagonal corner to corner score. Then drill out a hole in the centre to weaken the parts, then just push through with pressure over the hole.

RST

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Re: Another plasticard cutting question
« Reply #12 on: February 07, 2019, 09:51:29 PM »

Just to say if you're cutting big sheets -external edges like decks or big structural things I would suggest trying "aviator shears".  OK, they're really for thin metalwork but in my experience they will cut 2mm polystyrene or ABS no bother with a relatvely clean and controllable cut.  I bought a set of 3 (left, right and straight) from Homebase last year for about 8, down from 30'odd (our Homebase massively changed to become a proper DIY contender -fantastic tool dept, then closed just 6 months after all the investment!).  I also use a small set of straight modellers metal shears for thin stuff, toenail scissors are also handy and quite accurate for cutting small discs or curves.  You have to use your imagination.



Baldrick:  The way you desribe cutting that lettering I bow down in envy!  As a proletarian I would just have cheated and used the Slaters model railway polystyrene sprue with the characters stuck down, painted over with the bulwark then cut back to white with wet and dry paper.
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Baldrick

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Re: Another plasticard cutting question
« Reply #13 on: February 07, 2019, 10:13:20 PM »





Baldrick:  The way you desribe cutting that lettering I bow down in envy!  As a proletarian I would just have cheated and used the Slaters model railway polystyrene sprue with the characters stuck down, painted over with the bulwark then cut back to white with wet and dry paper.


  Would never have thought of that, interesting. Actually carving the lettering is not as traumatic as it sounds . If you start off with a very sharp chisel , a swig of brandy, a pair of magnifying glasses all you will then need is a handful of Paracetamol for the headache you will get at the end.


  Actually I also did my Confederacy stern lettering the same way.


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