December 1, 2011

Machined Cannon Barrels

One thing I observed over the years of visiting layouts is that O Scale modelers tend to have machine shops with all kinds of cool mills and lathes. Smaller scale modelers tend to do without such elaborate tools. Now I know why. I also learned that buying tools can be addicting, and expensive. I also remembered my respect for master machinists. Until you try to machine stuff accurately and repeatably, you don't appreciate the jobs they can do, even with CNC assistance.

I finally got my Sherline Lathe in operation. To learn how to use the machine, I started with some O Scale cannon barrels. I previously made some barrels using wood dowels and my drill in a vise as a lathe. These did not come out well enough to make masters.




I am still learning how to use the lathe, but I did come up with two final barrels that I can use as  masters for the 3 inch rifle and the 12 pound Napoleon. See the top two barrels in the above figure. Note the separately machined trunnions. I ordered some brass bar so I can make future barrels totally out of brass. That will allow me to solder in the trunnion pieces. Parrot rifles, howizters and naval guns are next.

A couple things I learned so far.

The trickiest operation I have to do is to drill an appropriate sized hole through the side of the barrel that is both perpendicular and exactly through the center.

 I currently have a cheap Dremel Motor Tool drill press which is inadequate for this operation. I am planning on buying a Cameron Drill Press, especially if I can find a used one. They are quite expensive, but are regarded as the best miniature drills out there. Made in the USA too. They look old fashioned, but have accuracy of 0.0002" runout! That is amazing. The Albrecht Chucks are very high quality too. No more cockeyed bits in the drill press.

Speaking of bits, I am having no luck with my Drill Bit City Tungsten Carbide bits. They keep breaking in my Dremel Press. The only luck I have had with them is when I mount them in the lathe tailstock to bore out the cannon barrels.

It is so cool to bore the barrel to within one thousandth of an inch of the scale bore. It makes me realize how beefy the Napolean gun was, especially compared to the three inch rifle.

The Sherline lathe has an option of rotating the headstock to cut tapers. But for very shallow tapers, it is difficult to get repeatable and accurate results. So I ordered a compound slide. I got one on ebay for about a 20 percent discount.  I just looks cool too. We'll see how it works.

While I was at it, I ordered a set of carbide cutting bits and a new drill index with #1-60 HSS bits. Eventually I'll need a grinder to make my own form tools if I want to do more small scale machining. See, tool buying is addictive.


Here are the aluminum barrels on my laser cut chassis.

My next major acquisition is a spin caster. That will allow me to cast both the barrels and the chassis. I haven't decided if the laser cut details will be add-ons to the casting, or cast in place. I may even try sculpting and casting figures.

2 comments:

  1. Say, isn't Bowser getting rid of some casting equipment?

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  2. Based on your note I looked into it. They seem to be selling a large set of tools, way more than I need or want, in a package deal. But thanks for the suggestion.

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