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Discussion Starter · #1 ·
I need to perform some major surgery on the internals of a Hornby tender so I can fit a large speaker. It's a long time since I have done something like this but my memories are of long and awkward struggles to get a scalpel into just the right place and slowly hacking parts away at great risk to the model and my fingers. There's got to be a better way, so I was wondering what methods people use. I am considering a Dremel fitted with a cutting disc, perhaps running from a flexible shaft.

David
 

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Hi David,

Depending on the thicknees of the material you have to cut i use a combination of tools .... the minicraft drill is great with a flexible shaft drive and a diamond/slitting disc in at very low speed steady progress can be made, if you have the space and the thickness of the plastic isnt too great a nibbling tool used gently gives good clean cut results, the razor saw is another alternative to the disc.
 

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Other than when cutting through external parts (when a razor saw or sharp knife is the tool of choice) I rarely use anything but the dremel, and often with the flexible drive. The cutter of choice is a milling head about 10mm diameter with fairly coarse teeth, about 2.5mm pitch. At high speed this chips the plastic out, rather then tending to melt it, a particular problem with abrasive discs: one moment cutting, and the next producing volumes of plastic 'candy floss'. Some polymers cut best if left to chill for 30 minutes in the freezer, between attacks.
 

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I agree with everything 34C has said. Heat is the main problem with cutting/slitting disks but they can be very effective in short bursts. Modern polymers can be cooled to help before you start, but some of the older plastics can shatter when worked on after cooling! Either way, the dremel is the way to go!

Rob
 

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Discussion Starter · #6 ·
Thanks for all those ideas.


David
 

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QUOTE (neil_s_wood @ 7 Dec 2008, 21:30) <{POST_SNAPBACK}>I used a Leatherman blade with serated edge for the larger parts, a scalpel for the smaller parts and drilled small holes to allow more vents for the sound to exit.

Could you enlighten me as to what a leatherman blade is please Neil
 

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I have 5 types of Xuron cutters that I use plus a couple of jewellers saws. I have a Nibbler that chews out little pieces, it was orginally for cutting brass sheet but it became blunt and I use it on plastic now. I have a Dremel with a variety of cutters, cut off wheels, saw blades and dental burrs. And last but not least I have an old cast iron pedestal drill that I use a milling machine for milling out frames and stuff.

Charles Emerson
Queensland
Australia
 

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Discussion Starter · #10 ·
Well I decided to ask for a Dremel for Christmas and was lucky enough to get one. Having read all the safety and "running in" instructions I attacked the coal bunker of the A4 in the manner suggested above with success. I had laid in supplies of Express Models' 4 way mini-connector and as there is plenty of room inside a Hornby A4 body, swapping the Lenz Gold for an ESU LokSound was no problem. So now I have a sound fitted A4 and I'm a very happy person indeed.

David
 

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All of the above are valid and effective methods but one other method which is useful where a cutting disc can't reach is to drill a whole series of holes close together around the edges of an area to be removed (still using the trusty Dremel!), then cutting and breaking the remaining connections between the holes. Clean up with files afterwards if necessary (not needed if the area is hidden inside the tender).

If using the slitting discs, note that they are very brittle so if the plastic melts and "grabs" the disc it will stop momentarily and may shatter - usually accompanied, in my case, by a series of swear words! Moral: make sure you wear eye protection if doing any of this sort of work (I wear glasses anyway so am covered!).
 

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Discussion Starter · #12 ·
QUOTE Moral: make sure you wear eye protection if doing any of this sort of work (I wear glasses anyway so am covered!).

A very important point. I wear goggles over my glasses.

David
 

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Dremel do make the old style cut off disc which if pressed will break and on the odd occaison shatter. The disc to get is the fibre glass cut off disc. These don't break or shatter. Drilling a series of holes is time consuming and you still have to clean up the the holes after removing the piece. I use the the rotary cutters which if you are careful will remove the unwanted piece without having to resort to lots of little holes. Works in metal as well.

Charles Emerson
Queensland
Australia
 
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