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Model-Building Tools used for Cutting

January 21, 2009



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Airfield Models (http://www.airfieldmodels.com)Cutting Tools used in Model-Building

Cutting is probably the most performed task in model-building.  There are many types of cutting tools that are made to deal with the vast assortment of materials we use and the equally variety of situations in which cutting tools are used.

This is one of those cases where having the right tool really makes a difference between enjoying your work or finding it extremely frustrating.

 
 

Please dispose of blades in a safe manner!

Dispose of razor blades safely. When I was a kid our home sported a central vacuum system that consisted of a hose with outlets all over our home.  I vacuumed a #11 blade and it got caught in the hose.

My sister found the blade some time later when it cut through the hose and into her leg.  I wasn't the most popular kid in the family after that.

The best way I have found to dispose of blades is to wrap a couple layers of masking tape around the blade first.

Embed old razor blades in epoxy for safe disposal.A good suggestion I received is to keep an old sour cream or yogurt container handy.  Put old blades in the container and pour leftover epoxy in the container.  I have started doing this and it has a nice side-benefit.

It used to be that I tossed out old blades after taping them as mentioned above.  That meant I never had dull blades on hand.  But when I need to cut sandpaper or scrape glue from my glass building board, I was ruining a perfectly good blade.  Now I can just pull a dull blade from the container to accomplish the same tasks, assuming I haven't already poured glue over the blade.

 
 

Blades

Various razor and scalpel blades with typical handles.Many people believe that a sharp blade is more dangerous than a dull one.  This is absolutely untrue.  A sharp blade is much more likely to cut where you want it to.

A dull blade requires more force and is more likely to jump out of the cut (slip).  It is when a blade slips that you are most likely to receive a deep razor cut.

I use dull blades for things like scrapping flash from plastic or cutting sandpaper to size where I am not cutting in a direction that would cause the blade to cut me if it were to slip.

Change blades frequently because a sharp blade is less dangerous and simply works better.  If you have two handles, you can keep a dull blade in one and a sharp blade in the other.

There is nothing I have found that is sharper than double-edge razor blades.  But holding a double-edge blade free-hand is dangerous so I don't recommend that you use them except in tools specifically designed to hold them such as razor planes.

Single edge razor blades are the next sharpest blade to a double-edge blade.  They are the primary tool I use for cutting and trimming covering and thin sheeting (3/32" or less thick).  A box of 100 blades purchased from your local hardware store should last at least a couple years.

Use a new blade when trimming covering because the last thing you want is a dull blade to get caught on the covering and tear it.  Single edge blades are also great for picking up small thin parts such as washers that get dropped on the floor.

I do not use knives for cutting parts from sprue because they are as prone to damaging the part as cutting it cleanly.  Instead I use a despruing tweezer (Micro-Mark catalog #82393) that is also an excellent tool.  It is built like a tweezer with a very sharp flush nipper.

Round Olfa cutters are razor sharp.  The first time I tried to used this tool to cut covering the cutter had a mind of it is own.  Even though I was using a thick straight edge the cut was anything but straight.  I managed to give myself a nice cut by rolling it straight over one of my fingers.  Other people I have talked to have said they love it so obviously I am doing something wrong.  If for any reason you need to remove a thick layer of skin from your hand this tool would probably a good choice.

I've since gotten it under control and find it to be excellent for cutting covering material and fiberglass cloth.

It took me years to discover how useful chisel blades are.  The problem I was having was that I was using them upside down so instead of chiseling they were gouging.  I use chisel blades so much now that I have three handles that have different size chisel blades in them.

If you look closely at the photo above there are three straight chisel blades.  The smallest is in the lower right hand corner and mounts in the micro knife handle in the next photo.

Also useful is the #11 saw blade.  I'm not sure of the actual blade number but it's the same shape as a #11 blade and has teeth instead of a razor edge.  This saw is useful for a lot of tasks.  I bought a pair of them and they're both still in good condition after having them for years.  Even though I don't use them often they have come to the rescue many times when no other blade would have done the job as well.

Sharpening Razor Blades

Every time I have tried to sharpen any type of hobby blade I have failed miserably.  There are a variety of devices that have come and gone over the years and none of the ones I tried actually worked.  The one that seemed the most promising looked like an electric pencil sharpener.  It was made to sharpen #11 blades in a #1 handle.  It didn't work either.

I've tried very fine stones, my disk sander at low speed with fine paper, etc., etc.  Blades are so inexpensive that unless you have a foolproof method of sharpening that takes a minute or less, it is easier to just dispose of the old blade and use a new one.

 
 

Hobby Knife Handles

You will use your razor knife for about everything.  Almost everyone buys the #1 knife handle and #11 blades at first.  While this is a good knife, it is not always the best all-purpose knife for wood models.  For general-purpose work the #2 handle is often a better choice.

The #2 handle is the same shape as the #1 handle but is larger and easier to grip.  Your hand will not fatigue as quickly and it cuts in fewer passes.  Newer handles have a rubber, ergonomic coating which makes the smaller handle much more comfortable and I am finding myself switching away from the #2 handle for sake of comfort.

I have a micro knife handle that I purchased from Micro-Mark (catalog #81067).  It is not a good general purpose knife, but it is a wonderful tool for plastic models.  It is not the standard flat scalpel handle you normally see.  It is a round, heavy, stainless steel handle that is approximately 5/32" in diameter and feels solid.  I use it mostly for trimming delicate parts.  The micro handle is also excellent for scraping flash from small parts and in hard-to-reach areas.

A swivel knife is good for cutting intricate patterns using frisket paper or similar thin material.  As the name suggests the blade can swivel so it works well using drafting curves as a guide.  The blade is extremely small and will not work for wood parts.  It is strictly for paper-like materials.

The Micro chisel has been somewhat useful with plastic models and I suspect it will be even more useful working hardwoods on my display pieces although I have not had the opportunity to verify this.  I do not really like the handle too much because it is not shaped properly for a tool that is pushed.

The handle is an adapted #1 handle with identical chucks on each end.  I am not really sure why they did that.  It seems dangerous to have a blade sticking out of both ends of a knife.  For safety reasons I only have one blade in the handle at a time.

The #5 handle is used with larger carving blades and razor saws.

Various hobby knife handles.

Typical Hobby Knife Handles

From Top to Bottom:

  • #6 Handle

    This is a heaviest duty hobby knife handle I've seen.  Next step up from this are utility and pocket knives.  This handle can mount the largest hobby blades as well as razor saws and gouges.

  • #5 Handle

    This handle can mount everything the #6 handle can.  The #5 is much lighter than the #6 and more comfortable for carving and sawing than the #2 handle.  The #2 handles is better for general cutting.

  • #2 Handle

    Like the #5 and #6 handles, the #2 handle can mount the largest hobby blades.

Note that the #2, #5 and #6 handle can mount all the same blades and saws.  Some #2 handles don't have a hole in the collet and can't mount razor saws or gouges.

  • #1 Handle

    The next three handles below the #2 are all #1 handles.  I don't have a "true" #1 handle any more because the first handle below the #2 is much more comfortable I own three of these handles.  Two of them have #11 blades and one of them has a #11 saw blade (discussed with blades in the previous section).  The third handle below the #2 has a chuck at both ends and was included in a chisel set.

  • Swivel Knife Handle

    Used for cutting around curved templates such as French curves.

  • Micro Chisel

    This handle is very small and best suited for fine detail work.

 
 

Razor Saws

Razor saws by X-Acto and Zona.  Also shown is an X-Acto miter box and a Craftsman coping saw.I suggest you purchase at least one razor saw with your first kit.  It will make your building time much more enjoyable (or at least less miserable).

Purchase a miter box for use with a razor saw.  Do not use your razor saws to cut metal no matter what the manufacturer says.  The blade will dull very quickly.

The old rusty blade second from the left is about 20 years old and goes with the miter box.  I have thrown out both the miter box and blade because they have been replaced by my table saw and disk sander.  If both of these items die, then I needed a new miter box and saw anyway.

I like the Zona saws much better than the X-Acto saws because of the one piece design as opposed to the separate knife/handle designs that allow the blade to twist around in the handle.

My coping saw does not see much use but I keep it around for those times when it is the only tool that will get the job done.  Not frequent, but it definitely serves a purpose.

 
 

Razor Planes

I had used a variety of planes that are on the market today and none of them were very good.  They cut too deep or not at all and there was really no way to adjust the blade.   I have heard good things about the Master Airscrew razor plane, but I have never used it so I can not recommend it one way or the other.

The Wil-Kro razor plane I use was handed down to me from my grandfather.  Unfortunately it is not being made any more.  It is a wonderful tool and has become one of my tool "treasures."  This one uses double-edge razor blades.

The blade depth is not adjustable but it is perfect, so it does not need to be.  In addition, the sole comes apart into two pieces that can be assembled in three different ways.

If you can find one on E-Bay or someplace and the price is reasonable, I suggest you snatch it up.  You will not be sorry.

Vintage Wil-Kro Razor Plane

The standard assembly is as shown here with the front piece of the sole extended straight out and is used for most purposes.

Vintage Wil-Kro Razor Plane

The plane can be assembled as a snub-nose plane by  turning the front piece perpendicular to the base.  It can cut right into a corner or inside concave surfaces.  Note that the front of the plane is to the left.  It looks backwards.
 
 

Files and Rasps

Files of all shapes and sizes come in handy for all kinds of tasks.  Even though files are primarily made for working on metal I do use them on wood particularly for cleaning up cutouts that are too small for a sanding block.

Use larger files for cleaning up the edges of dural landing gears even commercially made gear has burrs that need to be taken off.  Sandpaper or emery paper will work, but they will not last long.

File handles are used to provide a comfortable handle while you work.  I use file handles with larger files because it gives me better control and is safer.  The safety comes from less chance of slipping and running my hand over the sharp burr on the edge of the piece I'm filing.

The best file handles positively secure the file.  The first file handle I bought kept loosening which made it functionally worthless.  My current file handle has flat jaws for holding flat files.  The jaws have a groove that allow it to hold round files and files with tapered shanks such as the triangle and rat-tail file shown below.

A pin vise works well for holding needle files.  Normally I don't use anything to hold a needle file because I tend to choke up on these files to give me better control for the fine work they are designed for.

Common files and rasps.

The first item in this photo is a wood-working tool called a Four-In-Hand rasp.  The other files shown are for metal work.  I don't need to file things very often because most of the metal work I do is with wire.  A Dremel tool is usually a better choice than a file to clean up the ends of wire after it's been cut.

I most commonly use flat files for cleaning up the edges of tempered aluminum landing gear.

Round and tapered round files are good for cleaning up pushrod exits.

I have had problems cleaning aluminum from my files as you can see in the photo.  I use a file brush, but aluminum will gall and get stuck in the file.

Someone posted a tip in the Visitor's Book stating that rubbing chalk on a file before use will help resolve the problem.

Needle File Set

Needle files come in sets of 10 or 12 and are great with plastic models but can be used on metal as well.  They are generally too fine to be of use on wood.

These sets are inexpensive and come with several shapes including rectangular flat, tapered flat, triangular, rectangular, round, oval and half-oval.

I use the tapered flat, square, round and oval files the most.

All files get dull so they need replacement periodically.

Needle file sets include a variety of shapes. Most needle file sets include fine files.  There are coarse sets available which would be just as useful.  I've never owned a set of them but when I get serious about building my plastic kits again I'll probably pick up a set.
Riffler needle files also come in sets of a variety of shapes. These are riffler needle files for metal and plastic.  These are good for cleaning up concave surfaces and reaching around corners although they don't get as much use in my shop as I thought they would.

The cut on these files is also very fine.  I'm not sure if there is a coarse version or not.

Riffler Wood Rasps These are riffler wood rasps designed by somebody taking serious drugs.  I picked this set up in an art store in Germany for about $16.00.

Rasps are coarse and can rip away a lot of wood very quickly.  I use rasps mostly for hollowing and rough-shaping blocks.

Toothed Carbide Burr BitI bought a carbide toothed burr bit for my Dremel and it does what most of these do faster so I don't use these rasps as much as I used to.  Carbide burrs are expensive so I purchased one having the shape I thought would be most useful.  It is worth its weight in gold.  It even tears away aircraft plywood at a high rate.

Although it has shown some signs of wear it's not anywhere near worn out and still does a fantastic job after many years of use.  As I said, these are expensive bits but that's compared to other bits for moto tools.  Toothed carbide bits generally run from $10.00 to $15.00.

Wood Rasps are very coarse and great for ripping away a lot of wood quickly. My what big teeth you have!

"The better to hollow your wing tips, my dear."

 
 

Hinging Tools

Hinging is a tedious process.  There are a lot of tools on the market to cut hinge slots and holes.  Some of them are cheap gimmick tools that should be avoided.  The latest tool is the electric hinge slotter.  I have not used it because it looks like a gimmick tool to me.

My favorite hinges are Robart Hinge Points and they are always the first hinge I will use unless there is a reason why I can not.

I have used the Dubro forked hinge slotters for years with good success when installing flat hinges.  I do not think you will ever wear out the forked blades. I had an older set that fit into an X-Acto handle that were a little more difficult to use because the handle did not grip them tightly enough to prevent them from shifting.  The new set has integrated handles.

The set comes with a parallelogram jig that does a good job if you use it right.  It is best to secure the wing so you have both hands free.  Then you align the jig over the slot location and simply push the forked blade through.  The jig is soft and flexible and will allow the hinge fork to enter the wood at a poor angle if you are not careful.

The set also comes with a digger tool that is used to clean the slot out.  I have always found it to be simple and fast.

Various hinging tools by Dubro and Robart

Typical hinging tools

In the upper right are the newer hinging tools from Dubro.  I like these because of the integrated handle.  They are easy to use but do take a little practice.

In the middle right is the Dubro hinge guide system.  At the bottom right are the older style Dubro hinge forks.  These were designed to go into hobby knife handles.

In the upper left are large flat hinge dummies that I use hold parts in alignment after the hinge slots are made.  At the lower right are hinge point dummies serving the same purpose.  In the left middle is the Robart hinge point guide which works extremely well.

A Hinge Fork.

The trick the to forked blade is that the tips must be very sharp.  But the edges are square, not tapered like a knife.  Do not taper the fork or it will not work right.  When you see a tip in a magazine telling you to sharpen the edges of a hinging fork like a knife, ignore it.
 
 

Scissors, shears and side-cutters.Miscellaneous Cutting Tools

A cutting mat is very useful.  These can be found in craft stores or at Wal-Mart.  These are marketed as being self-healing (which they are not) but they do last a long time.  Be careful not to warp it because it will never lay flat again as I found out after it was stuffed in a box by movers.

All of these tools get frequent use.  The items at the bottom are mainly used with plastic models.  Toward the middle of the image is the micro knife handle I mentioned earlier.  Directly above that is the tweezer type sprue cutter.

The large pair of scissors is excellent for cutting large pieces of covering or large sheets of paper (cutting plans apart).  The small scissors are mostly used for trimming decals.

One other cutter you may use is a compass with a cutting blade.  This comes in handy when you need to cut out anything round.  It is a pain to use so I reserve it for when the cut actually has to be nearly perfect such as circular paint masks.

Drill bits will be needed throughout construction.  I do not know the number sizes off the top of my head but the most useful sizes are 1/32" to 1/4" with 1/16", 3/32", 1/8" and 1/4" being used the most.  It is worth purchasing a set of general purpose bits as well as brad point wood bits.  The smallest brad point bit I have come across is 1/8".

You can find a Tap and Drill chart on the Aircraft Proving Grounds site.

If you build plastic models then a set of micro drill bits is almost a necessity.  Of course you will need a drill and most likely you will need a pin vise for the smaller bits.  A pin vise is basically a tool for holding small bits and needle files.  You twist the pin vise by hand to drill the hole.  There are also micro drill chucks for putting small bits into a drill or drill press.

Pin Vises are very useful tools.

Pin Vises come in a variety of sizes.  The vises at the top and bottom of the photo each contain two double-ended collets that allow bits to be used from 0" to 1/8" in diameter.

The pin vise in the middle of the photo only allows very small bits, such as wire bits and pins, and is correspondingly small for better control.

I have yet to find a commercial drill bit that cuts balsa cleanly.  Usually holes in balsa only need to be accurately placed but they do not need to be pretty.  Nevertheless, I do not like seeing chewed up holes in my construction.  The only way I have found to cut a clean hole is to use a piece of sharpened brass tubing.

K & S makes brass tubes in various diameters.  All you need is a piece about 2" long.  To sharpen the tube hand twist a countersinking bit in it until the edge is as thin as you can get it without the edge distorting.  You will have to sharpen it fairly often.  I always use this method for cutting holes in ribs for wing jig rods.  Other holes are taken on a case by case basis.

Another thing you can do is use a razor saw to cut notches in the end of the tube to create a hole saw.  Either way works but I prefer the sharpening method because the hole saw method is kind of hit and miss as to its effectiveness.  The bit will not work well in a drill.  You can either glue some rubber tubing on one end to twist it by hand or put it in a pin vise.

You will need to push the plugs from the tubing with piece of wire so chucking the tubing into a pin vise gets to be a pain.  In fact, the method is really tedious.  If there were one tool I would like someone to make is a good set of drill bits for soft woods.

Also see

Taps become essentially fairly early on.  You will need at the minimum 1/4 x 20, 4-40 and 6-32 sizes.  Other sizes you might use are 8-32 and 10-32.  You can buy a basic tap set that includes all the sizes listed above and includes a handle at a reasonable price.  You will not need dies for anything that I can think of.

 
 

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