Seeking advice on custom brass bending.

[SandyEggoJake]

So I'm seeking to develop a supply of a brass channel which the usual source do not produce. 

Specifically, "Hat Channel".  (see http://www.johnsonrollforming.com/display.php/display/A3/category/4)

That link offers to source channel down to 1/4" wide.. and a 2K ft min!  But such is still far too wide (and too much) for my needs, as I'm seeking N scale range (<1 mm wide). 

I understand modelers often bend channel using a brakes such as this.... http://www.micromark.com/mini-metal-shear-and-brake,9645.html 

But my experience with brakes suggests with my shape and size, roller forming might be better.  Any suggestions as to tools for DIY, or better yet a shop willing and able to produce such at fair pricing? 

[Philip H]

What's your thickness?

[SandyEggoJake]

Thanks for the reply.  Thickness to be determined. 

Scale would be using something like 0.001" stock, but such would yield a shape that is way too flimsy.   So thickness of stock likely to be gated not on scale, but desired rigidity of final shape, as one objective (but not the only) is to use these shapes to make prototypes for resin castings.   Of course, soldering the shape to the model will also add much added rigidity over the shape by itself.

I see the thinnest wall Special Shapes uses is a 0.01" stock (~1/4 mm stock? ~1.5" in N scale), but such would basically yield a C channel as the wall thickness is about the same as what I was thinking for each "brim" of the "hat".  So perhaps K&S 0.005" brass to 0.003?  And so I'm thinking it might require use of an oversized ribbon of stock to allow better forming, then, in a secondary process, trim sides of brim to desired final width?  So some experimentation expected. 

[peteski]

How about photoetching these out of brass?  You could half-etch the bend lines then make a jig to form them into the final shape. The bend lines would greatly assist in getting it into the correct shape.

[Philip H]

I don't have a way to draw it up but it would like you need three steel ball bearing rings set up to draw the brass through.

[ednadolski]

What are you making?   Forming metal < 1mm sounds pretty tricky.

Ed

[SandyEggoJake]

What am I making? 

I'm exploring the possibility to make the iconic AT&SF Sk-2 in N scale (rebuilt from AT&SF BX-3 & BX-6) with most of the body as a resin model (or failing that, PE brass).  I'm even more interested in making the Bx-3 & Bx-6 as resin cast, but there the hat channel, while it might be preferred, is not required to build a model of these cars for creation of mold.   

See: http://www.richyodermodels.com/santafe_history.htm

However such is all but required to give the SK-2 the right look, and would need to be a separate item added post body casting.  Each finished car would need about 30 cm of this channel. 



Also thought N scale hat channel might make great prototypical modern street sign posts, etc. 

[eric220]

What's your thickness?

That's rather a personal question, isn't it?

[ednadolski]

Seems to me it would be rather hard to make bends that small in individual pieces and still have them come out straight and uniform enough to look right.   You might want to consider an etched part instead.

Ed

[SandyEggoJake]

Yes, a 2 side PE is a definite possibility - particularly of I do PE for the rest. 

[Sokramiketes]

Does anyone remember an article way back when, where someone was forming locomotive stanchions out of .002-.003" brass sheet stock?  Supposedly they were fairly sturdy once formed, and was something I always wanted to try.

For what you are doing, and the thin materials involved, I think all you need is a stamping form... not a roller or bender.  Just smash the sheet between two forms. 

[SandyEggoJake]

In the 1931 Car Builders Cyc, p120, shows fig 24 for a Bx-3.  This drawing has dimension of the hat channels; cross section as 7.5" wide, 3" depth, hat width (w/o brim) of 5", and using 1/4" stock.  So each brim width would be 1.5".

1/4" stock scaled to N would be 0.0015".  Flimsy even with added rigidity of the shape and solder. 

So I suspect I will want to double that to 0.003" brass stock.
Such would allow me to use the following dimensions:

Nominal in mm:
width: 1.2 mm
depth: ~0.5
width of hat w/o brim: ~.75 mm
width of brim: .25 mm

Sure, small, but definitely a noticeable feature.

[SandyEggoJake]

@Sokramiketes   The micromark brake is basically just that (pushes die into a v shaped gutter).  I guess a custom die top and bottom could be developed that stamps out a hat, but with all these bends at once, I suspect thin stock would tear.  Might rather just make a c channel, then bend back the flanges on each side. 

But following up your tip, over the weekend dug into the library and I found an old school article on bending flat stock (0.005-0.01") into angle & C channel;  Aug 1970 issue of Model Railroad. pg 58, by Julius Marinaro.  Author then uses the tool to build a cantilevers signal bridge in brass 

The author calls for use of a modified hand seamers; 1) jaw surface filed deadflat to each other, 2) both jaw ends then filed flat perpendicular and square to the jaw surfaces, and 3) file a 50 degree relief in one of the jaws to the very edge jawlip.  Also details creation of a bending anvil (perhaps using Starrett ground stock) which is to be used with this tool, and includes tips on how to use to make crisp corners.  Seems less than 1mm will still be a challenge...the tool has an adjustable depth gauge for 1/4" or more.  And this method is practically limited to length of jaws. 

As for a bend sequence that will allow one to create a crisp z or hat channel?  This article offers no suggestions.  But I suspect such might be aided by perhaps additional blocking and/or slots included on the anvil, and perhaps a square rod milled to the inner channel dimensions.

[Lemosteam]

For what you are doing, and the thin materials involved, I think all you need is a stamping form... not a roller or bender.  Just smash the sheet between two forms.

this is plausible provided you can get the strip to remain centered.

An RP set of dies in a drill press or woodworkers parallel clamp might just work of the material is thin enough.  You could always start with wider stock and trim the edge parallel to the bends after forming.

there is no need to make each bend individually as on a brake and you could make them to the designed length instead of one long piece.

I will sketch up a die set for you if you can provide the dimensions of the hat section (or post here), including the inner angles.

[SandyEggoJake]

@Lemosteam

An RP set of dies...

"RP"?  Rotary Pressure?

Have drill press (overkill...15" Jet) and willing to consider.    I'm warming to this die stamp idea, especially if able to place rivets in the gutter at the same time. 

Stock assumed to be 0.003" brass, but might try 0.005 to 0.002 and in various materials. 

Final width is ~1.2 mm, with each "brim" being ~0.25 mm. 
Depth of channel to be ~0.5mm (luckily, the same as evergreen car siding sheet styrene 2020), with width of channel 0.75 +/- 0.05 mm.
All angles at 90.

Length is variable (at least two different car heights) and I suggest oversized, as I suspect each carside will need to be trimmed to fit after panel assembly.