Author Topic: Cutting plastic  (Read 1683 times)

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chipper

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Cutting plastic
« on: 13 Jul , 2010, 14:36 »
Rokket.  First time on the forum and I'm very impressed!   I have a question about cutting plastic in preparation of installing new torpedo shutters, or opening the hatchways on the sides of the Cobia's fairweather.  I've read where you recommend drilling out as much plastic as possible then using a file to slowly enlarge the opening.  Micromark advertises a small solder tool with a knife blade that looks just spiffy for cutting plastic.  Anyone use one of these and is it worth purchasing?  Thanks

Offline Rokket

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Re: Cutting plastic
« Reply #1 on: 14 Jul , 2010, 01:17 »
Hi Chipper,

Thanks for joining the site!

I haven't used the MicroMark tool myself (is this it?)


It could be very useful. The only negatives I see are 1-danger of plastic bubbling up in "shoulders" at the edges - it might mean you have to stay far away from the finished edge (a good idea anyway, but maybe more so with the heat); 2-it could still be some effort, but I can't judge never having used one.

I prefer a Dremel, because it's fast, but that too means staying away from the edge, probably as much as the hot knife. You can also use the thinning technique, where you thin down with a ball or similar tip, from the back, until the plastic is wafer/tissue thin - then cut with a sharp knife.

Either way, the best is to keep from the edge and clean with a file, trst fit, file, test fit...

The tool definitely looks handy tho, especially for the price! I'd say buy and try!

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chipper

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Re: Cutting plastic
« Reply #2 on: 14 Jul , 2010, 06:27 »
Thats the tool.  Another negative, when the blade gets hot enough to cut the plastic how do you keep the plastic from sticking to the blade, dragging along making a bigger mess.  I'll let you know what I find.  Thanks.

Offline Rokket

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Re: Cutting plastic
« Reply #3 on: 16 Jul , 2010, 03:19 »
Yes, even with a Dremel on low/slow, you can get some melt-welding. If you get one muck about on some scrap. Any mechanical means should help, as long as you stay extra away from the edge. Keep us posted, because this could be a really good tool.
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Offline Pat

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Re: Cutting plastic
« Reply #4 on: 04 Nov , 2010, 21:34 »
Just came across this thread and have something perhaps of value to add.

I got one of these hot knives from X-Acto about 35 years ago and it's one of the best tools I've everused for modelling other than a pin drill.

To give a comparison, I was using a Dremel to cut away some plastic and continually had the problem of melt-welding and having to stop every little while to clean out the melted plastic from the cutter tip.  It was taking forever and I wasn't happy with the results.

I went to the hot knife and did the same job in a fraction of the time.

The hot knife doesn't get stuck with melt-welding because it stays hot, so the plastic doesn't stick to it.  If there is any welding behind the blade, it's almost cooled by the time the wet ends meet so it easily snap off with a pair of forceps.

With this knife, in the past I've undercut all the clothes on the old Airfix 54mm figures, so that you could see up the cuffs of sleeves, the lapels were overlapped as were the front of coats, ties could be separated from shirts and fingers separated to form actual 5 fingered hands.  You can almost take a solid block of styrene and carve it like balsa.

On the Revell 1:72 U-boat, I was able to cleanly cut out the long drainage opening between the saddle tanks and the upper casing in less than 10 minutes leaving a nice edge that only had to be lightly evened up with a scalpel.

It was actually easier to thin the plastic out after cutting the slot than it was before cutting it.  (recommended if using a hot knife anyway since thin plastic melts too easily.)

The one precaution is that before turning on the knife, make sure the blade is loose in its holder.  Otherwise, when the metal expands with the heat, it's almost impossible to get the blade out after, even when cooled.

The blade is easy to clean as the plastic stays wet and is easily wiped off (make sure not to burn yourself)

Also, I let the blade heat up for about 10 minutes before use.  It works best when at maximum heat.


Offline Rokket

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Re: Cutting plastic
« Reply #5 on: 12 Nov , 2010, 22:50 »
Thanks Pat, I never would've thought ..I might investigate one myself!
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