The Home Machinist!

Hi,

At the request of a friend I created a 3D print of the PRR junction box. This will be available initially on Shapeways, later I plan to offer it, and other details, in lost wax castings. I used good photos of the original at the RR Museum of PA as well as prints. BTW these are 1.5" scale.

My questions are about what size handrails will people use and how would you like to connect them to the box? As many know the Shapeways "bronze/steel" is very hard to machine and tapping VERY hard. Soft soldering is an option. They parts can be had from Shapeways in brass but would be pricey.

The sprue with the 4 objects are pipe plugs used where no handrails are required. They can be soldered, or even loctited in place. The lid is attached with 00-90's.
Let me know your thoughts!

Paul

Paul, knowing first hand about the hardness of the Shapeways bronze/steel, you're right.. It is very hard, and carbide tooling is really the only thing that will cut it.. And even with carbide, it still wasn't easy.. I have successfully soft soldered it, and it seemed to take the solder fairly well.. I would say if I was going to use these on my locomotive, I'd soft solder the dummy plugs in, and make up some sort of a hex coupling to accept the hollow pipe for wiring.. That hex coupling would also be soft soldered in.. Good luck with this project, I'll be buying a few for my G...

FORGET TAPPING any of that stuff....even the brass is a tough go

why not use silicon bronze...forget that shapeways

'shapeways' is just a 'generic' name for material used by 3D printing.

as a general concept...drilling and especially tapping of most of the 3D printed metals is very difficult

It does not matter if you get the part from 'Shapeways' or any other 3D printing service house...you are going to face the same difficulties.

Roll form taps work well in this material. It pushes the material to form the thread rather than cutting, and the tap itself is much more rigid than a fluted tap. Drill needs to be substantially oversized, since material gets pushed inward creating the final minor diameter.

While teaching at the U of Washington Seattle (20+ years ago), I was involved in developing 3D printing in metal, as a research project.
Stainless powder was the material. The bonded object was them immersed in molten bronze which got sucked into the matrix.
My involvement: Defining the machinability of the product. It was very difficult, especially to tap.
Any thread smaller than 1/4-20 (or metric equivalent) was a tap-breaker.
i'm surprised the material technology has not advanced at Shapeways.
RussN

Print your parts about 5% oversize, use the part as a master pattern, make a rubber mold from your master, shoot your waxes and cast from that. You could also, if your drawing software allows you to convert your drawing into a reverse file and print a mold in anything that will take the temperature and heat of molten wax. Shoot the wax into you mold and make your investment casting from that. Any investment foundry can make a mold in rubber and make your casting for you. Smaller foundries that do jewelry are the places to go to. Industrial foundries are probably not interested in that type of work.

Shapeways is a printing service house...they use the materials provided by the machine manufacturers...like 3D Systems...if you are interested in what is going on in the 'printing materials' world...start on their www site.

Thanks all and Anthony great idea on the form tap. I use them so I should have thought of it!

I guess I never answered your question about the handrail size...
I don’t know the actual diameter of the PRR handrails, but I was planning on using 5/32” brass tube for mine, if that’s not available then 3/16”..
John

My prototype is 5/32 but a couple of others have asked foe 3/16" Anyone else??