Threading rod

Threading miniature brass rod for model building.

This is the first draft of this how to. If there are errors or mistakes or things I should have included and didn’t please let me know so I can correct them. Your comments and suggestions will be appreciated. Please e mail me at rpace@largescaletrainsupply.com

 One project that seams to make model builders hesitate is using threaded nuts bolts and rod. The details and how to’s are hard to come by. Here’s what you need. This should help those that have wanted to make their own threads for their bridges and anything else you can think of that needs threads. I have put threads on many things in the past years but none have been more challenging then threading for miniature hardware.

Uses: There are many uses for threaded rod and other miniature hardware for the model railroader. The most obvious is for tension rods used on truss bridges. On a prototype bridge it’s actually the tension rods that give the bridge it’s strength.

Tools: HSS die of the size thread you want, die stock (die holder) to fit your die, small bench vice, air source (or some way to clear cuttings from the die after cutting), wire cutter or razor saw, cutting oil, (available at Home depot’s plumbing dept. for a few bucks a quart) (about ten year supply) and a grinder or some other way of tapering the end of the rod. Sand paper or a file will do in a pinch if you don’t have access to a grinder. You are also going to need a pair of tweezers and I would recommend a nut driver to fit for assembly. You can use needle nose pliers but that is making life much more difficult.

Die, tap & drill sizes
Die size: #00-90 #0-80 #1-72 #2-56
rod size: .047(3/64) .064 (1/16) .073 .086
tap size: #00-90 #0-80 #1-72 #2-56
tap drill size: #61 .055 (#55) #53 #50
clearance drill size: #55 .052 (#52) #48 #43
         
Rod & Hex Nut Scale Sizes

Scale

Item

1:20.3 Scale Size 1:22.5 Scale Size 1:24 Scale Size 1:29 Scale Size 1:32 Scale Size
#00-90 Scale Hex Nut, Flats 5/64″ (.078″)
1.58″ 1.75″ 1.87″ 2.26″ 2.49′
#0-80 Scale Hex Nut, Flats 3/32 (.094″) 1.90″ 2.12″ 2.25″ 2.73″ 3.00″
#1-72 Scale Hex Nut, Flats 7/64″ (.110″) 2.41″ 2.48″ 2.86″ 3.19″ 3.52″
#2-56 Scale Hex Nut, Flats 1/8″ (.125″) 2.54″ 2.81″ 3.00″ 3.62″ 4.00″
3/64″ (.045″) Dia. Rod .95″ 1.06″ 1.13″ 1.36″ 1.50″
1/16″ (.064″)* Dia. Rod 1.30″ 1.44″ 1.54″ 1.86″ 2.05″
5/64″ (.078″)* Dia. Rod 1.58″ 1.76″ 1.87″ 2.26″ 2.50
3/32″ (.093″)* Dia. Rod 1.89″ 2.09″ 2.23″ 2.70″ 2.98″

Note: There are two different types of hex nuts available in both the #0-80, #00-90 & #1-72 sizes. Example: the #0-80 “scale” nut is 3/32″ across the flats and .048″ high. The standard #0-80 nut is 5/32″ across the flats and .046″ high. This scale size nut will match the size of our, and others, hex screws and lag screws. The difference in the proportion makes the standard sizes look totally out of scale. All of dimensions of the nuts in the table above are “scale” hex sizes.

Preparation: Part of the job, as usual in large scale modeling, is to make the items that are available to us fit our needs. We usually have to modify things before they will work well for our uses. Note that in the tables above that the rod sizes required for threading are not the same as those available on the market. Example: For a #0-80 thread you need a rod that is .055″ in diameter. The only thing available is 1/16″ (.064) brass rod. The die will not easily fit it’s starting threads over this diameter.The easy answer, at least for me, is to roll the end of the 1/16″ rod against my moving grinding wheel…. very gently… Just enough to taper the end of the rod so that the end is under the .055″ needed to start the die. This taper needs to be as straight and even as you can make it so that the threaded end will run straight. I have found that if I take about .010″ off the end tapered to .0″ to about 1/8″ – 3/16″ up the rod it works fine. That gives me a good starting size for my die and slowly tapers to full width of the rod. When you make the tapers on the rod try not to get to heavy handed. You don’t want the rod ends to be pointed, that would make threads at the end that you can not use.When you insert your die into the die stock make sure the back of the die is sitting flat against the back of the die stock and it is locked in tightly with the screws in the die stock. The side of the die with the size printed on it is the front of the die, that is the side that has the starting threads. The front of the die is used to lead the way onto the rod when cutting threads.Procedure: Before you start on the good stuff remember practice makes perfect. Cut some extra pieces of rod and practice on a few pieces. I cut my rod to the length I need plus about 1/4″. That will leave room above the material surface so that I will have about 1/8″ of rod on each end to attach my washer and hex nut. I then dip the tapered end into a small jar lid of cutting oil. This will lubricate the cutting threads and reduce the heat from the cutting.

Place your tapered rod in the vice horizontally with 3/4 to 1″ sticking out to the side. If you have to much of the rod sticking out of the vice you might bend or twist the rod while cutting. Any bend can be straighten out with a hammer on the back of the vice a twist is not a problem if you don’t twist the rod off. I have several dies on my work bench with bits of rod in them just to remind me not to do that. Once you break one off in a die you usually can through the die away.

Place the die, in the die stock, against the end of the rod and carefully turn clockwise while applying enough pressure to start the threads cutting. The die should take hold by the third or fourth turn. It is important at this point that you get the die started straight. I have never been able to get the threads perfectly straight but they straighten out under the pressure of being tightened in the finished product. You wont see the deference.

Be gentle when turning the die. Remember you are cutting the metal and it should be done slowly with even pressure at the beginning. Once you have made ten or so turns you can be a little more aggressive with the die. I give the die 32 half turns, with a #0-80 die, to get about a quarter inch of thread. If you twist to hard you might break the rod off into the die…now you have a problem. DON’T..

If you want to you can place a nut on the rod and touch the end to your grinder to remove the tapered end of the rod. This will give you a nice flat end. Then remove the nut so it will straighten the burr on the end from grinding.

That’s all there is to it. It may take a few tries but once you have got it down it’s a piece of cake.


Leave a Reply