Techniques for cutting large objects like 1/43 truck trailers or O scale diesel shells

I would appreciate some more details on what's in your tool box - brands, types, etc. 

I thought about using Sharpies to mark the edges. I will definitely prime the next set of bodies. I was cutting a dark green unit with a black roof.  

I had some luck with a rotary tool after I clamped a guide to the body. But it only worked on the sides. Couldn't find anything rigid, but flexible for the curved roof. 

Thanks, jeweler's saw it is. None of the razor saws I used produced a fine cut, or an aligned cut.  

What brand of saw do you use?

Do you any type of miter box with your saws?

As their "jeweler's saws", I've considered having a friend of mine who is a jeweler make the cuts. 

Good points,  I studied my drawings again, and the roof is the place to start as there is a raised edge on radiator fan housing as a guide. The cuts proceed down the sides of the carbody using molding on panel edges as guides.  The panel edges line up with the fan housing.  AND, I have a whole box of shells I picked up off ebay!

Often the cut line will not be a true cross section. In other words, you might want to cut the roof at a location where there is a panel edge across the top, and the sides at a different location where there is some sort of vertical division like the edge of a louver. In fact, you might take the roof off entirely at the drip line around the top and do the surgery, then extend the length of the sides each according to what works best for each. Asymmetric features include cab doors on one side only, etc.

Definitely count on two shells for each finished modified one.

Tankerbuilder had a good point in your other thread- follow the logic of the real engineering designers. That makes it more interesting.

Bill

GMorrison

I take a somewhat different approach to cutting up parts. Saw cut edges are not reliably true enough to be used as joining edges.

Creating mating surfaces by block or draw sanding on a flat surfaces provides better contact between parts and minimizes gaps.

And often cutting up a large part like a ship hull can benefit from more aggressive but less accurate means like scribe and snap or clippers.

I mark the line of the final edge to be created with tape, with the tape itself on the "keeper" side.

Then I spray some color along the edge. Remove the tape. When the paint is dry, cut or saw to within 1/16" or so of the masked edge of paint, in the painted area.

Tape down sand paper on a hard flat surface. Carefully draw sand the part across the surface until the remaining painted  area is removed.

 Bill

 

That's a really good point, Bill.  When i have built up resin ordnance for my aircraft, i use the jeweler's saw to cut the casting block off, but leave a good amount of extra material on the part,which I then sand away.  On my F-4B ordnance, I fabricated sanding jigs out of some scrap aluminum from work.  They were exactly the right dimensions to slip the Mk-77s and LAU-3/As into and held them firm while I used a little power sander I got from Micromark.  Once the sander hit aluminum, the resin inside the jig came out square and flush.

Hi Bill:

        There are times,When say lengthening a large ship model such the "Blue Devil"(U.S.S.Melvin) that I will make a line from the keel using a square to mark the flat sides then Carefully extending the line to the keel.

        On liner models such as "Life LIke's" version of the President liners I again use a square sitting flat on the tabletop while the ship sits in a cradle of LEGO to support it and it too is sitting on the tabletop. I usually count on the area near midship at the keel to be fairly flat!

         Revell's old Flat Bottomed fleet is easily done this way. Especially the Carriers and Battlewagons. The Oiler in that line is easily stretched this way into a 1/425 version of many that were stretched then put in Laker service!

I take a somewhat different approach to cutting up parts. Saw cut edges are not reliably true enough to be used as joining edges.

Creating mating surfaces by block or draw sanding on a flat surfaces provides better contact between parts and minimizes gaps.

And often cutting up a large part like a ship hull can benefit from more aggressive but less accurate means like scribe and snap or clippers.

I mark the line of the final edge to be created with tape, with the tape itself on the "keeper" side.

Then I spray some color along the edge. Remove the tape. When the paint is dry, cut or saw to within 1/16" or so of the masked edge of paint, in the painted area.

Tape down sand paper on a hard flat surface. Carefully draw sand the part across the surface until the remaining painted  area is removed.

 Bill

l use a Zona saw rather than a razor saw.  The Z saw has offset teeth so it cuts better, and it is very stiff and inflexible, so it cuts in a straight line.  I have both types of saws and find both are needed for various jobs.  I now consider a razor saw those PE blades that are very thin and have no offset teeth.

Hi1

 I too use a jewelers saw. With my Scroll saw type spiral blades. Fine cuts, minimal kerf, and straight lines! Best thing I have in my Toolbox!

I would highly recommend a jeweler's saw with a deep throat to it.  Get some spiral blades for it that go down to #2/0.  You'll be able to make fine, delicate cuts with it...but it also works very quickly because there is so little friction between the blade and the plastic due to the minimal surface area.  It also allows you to easily follow irregular shapes and contours and removes about the thinnest amount of material that you'll be able to get.  I have several razor saws that I have collected over the years and they almost never get used anymore.  Its all about that jeweler's saw and the spiral blades now.