The On-Line Magazine of Rideable Model Railroading
NUMBER TWENTY-FIVE

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© January  18, 2003 

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Making a
Louver Punch

Written by Kap Pullen     


photo by Kap Pullen

 

While building our 1/8 size industrial locomotive the problem of scale louvers was given much thought.  I didn’t want a “slab sided engine”, nor did I want home heating vents screwed on as is sometimes seen on miniature locos. We had seen an article, on louver punching, many years ago in Model Engineer but didn’t remember the particulars. When time presented itself various nibbling tool arrangements were tried. They produced a chewed up looking job.

Some years ago I scratch built a cannon, carriage, wheels and all. I welded  a wood  chisel on a rod to cut the spoke pockets square in the wheel hubs, and mortise and tenions on the trail.  The tool was used in the Bridgeport spindle with the brake tied on. A little grinding to the chisel to a 30- cutting degree angle, and radius on the corners and the chisel punched easily thru .05 soft aluminum. The Enco mill was used as a press and the vise jaw a bottom cutting edge.

A positive stop was needed ah….It started to come back to me.

Some years ago while working for an under-capitalized sheet metal shop (hole in the wall),   I had made a louver punch for a rush job, to replace a broken one. The punch was designed so the rear of the bottom die acted as a locator for the next louver. The back of the cutting die was flat so the louver would be “coined”. Thus the die is really a combination cutting and bending die. The cutting edge both sheared and bent the louver. That die was milled and ground from a chunk of tool steel and hardened. The radiuses were applied with a disc grinder-sander.

The 1/8 th. size one would be quick and dirty, like the full sized one. An old spade drill, from cannon boring days (about 1.25), was convenient because it already had a hole and wouldn’t anneal if gotten too hot. A chisel can be used. A clamping arrangement must be designed or hole drilled with a carbide drill. The hole could also be cut with a piece of copper tube, using valve grinding compound to cut.  Place the tube in the drill press, chisel in the vise. Build a dam around the hole with modeling clay. Fill thee hole with lapping compound slurry. Run the machine medium speed. Apply light pressure, maybe with a weight on the feed handle. Have an iced tea while it cuts. 

A wood chisel must be kept cool while grinding. It took some heavy hand grinding to take the tip and locating wings off the spade drill. The finish grinding was done on a Delta Surface grinder but a hand job would do just as well. With a slight crown on the tip, the punch would cut freer than my straight one. The radiuses were hand ground and polished. The nose of one end or my arbor press ram was milled, drilled and tapped for the blade. The bottom of the ram serves to coin the material while the blade shears and bends the louver. The press ram also has a ¾” hole in that end for various little punches and forming dies. An old machine vise was used for a bottom die. A ½” momax tool bit laid flat, is the cutting edge and the anvil (coining area),is of 1/8 x ½ steel strips  spaced by ¼” piece of   keystock.

 

   

The louvers are 1.25” long to make a scale louver about 10” long.  The louvers are “larger than life” making a muscular looking locomotive

 

The operation from the side showing the Momax tool bit cutting edge, the brass keystock spacer, and the 1/8 x ½ strips used as an anvil.

 

The arbor press gibs need to be snugged up. A couple thou clearance should left between punch and cutting edge.  The bottom “die” is blocked up to minimize the extension of the “punch”. A little WD-40 will help the punch operation.

 

  
click on drawing to enlarge                                                            click on drawing to enlarge

Drawings by Kap Pullen

 

The grain should run in a horizontal direction to minimize splitting at the corners. The material I use is .05 thick aluminum.  It is soft, bends and shears nicely, but suffers in the machinibility area. Hard material in the t-5  t-6  range is likely to split on the corners.

  

 

The material should be finished (sanded or polished) before punching. It’s hard to polish louvers. Of course the louvers should be painted after cutting.  The hood corners were “bumped” around on my Chinese 3 in 1 brake. To see more of my projects check;

 

 http://www.bluechipper.net/Bluechipper.html

  For photos of my “new” lathe tracer attachment Check   here: 

http://www.geocities.com/kapullen2000/photopage3

 the end


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