MTFCA Forum

What is the best way to drill/punch the hole in the runningboard apron for the acetylene gas hose? The red hose I purchased from Langs looks to be 1/2" outside diameter. I was going to drill a larger hole in a block of wood and use it for support under the hole area, drill a smaller diameter hole in the apron and use a punch to enlarge and round off that hole to the 1/2". I thought about using a dremel to cut little triangles that would round downward before usIng the punch. I'm checking with you guys before I do anything. Art

I'm sure some have a higher-tech way than I did one a long time ago, I just bought a HIGH QUALITY hole saw that was super hard and apparently super sharp as it could cut through stainless steel and went at it. Produced a nice clean hole, I was happy with it.

Tim, I am not wanting a nice clean hole. I want to duplicate the punched hole with the rounded triangles on the bottom side as in this picture. Art

Where should the hole in the running board be made (position9?

Ahhh, Art....guess I didn't realize ur desire. Really going for authenticity eh?

I do want it to look correct and the rounded edges on the hole was to protect the rubber hose. Art

This is on a 1913

Art

you are going to need a lathe

a female stump is turned which will have a hole the diameter that you want, plus 2x the sheet metal thickness plus about .005". The ID of the stump needs to have a small radius
a male punch with a bullet shaped tip is turned to the diameter of the desired hole. At the base of the "bullet", there needs to be a flat surface to press against the die to flatten things out.
a smaller hole is drilled into the sheet metal *
punch and die will make a correct hole and will extrude metal down into the die...that metal is nipped with nippers and carefully folded over with a small hand held punch and small hammer

* the initial hole will need to be about 1/2 to 2/3 of the final hole size to allow for enough material to extrude to fold back on the underside

The design of the punch/die is best done as a piloted punch (the pilot captured in the die) such that everything remains concentric

When I make these things, I use a drill blank for the pilot, and ream both the male and female portions during their manufacture, then loctite the drill blank into the portion of the tool that makes the most sense for the job. A Harbor Freight or similar press finishes the job.

If it were me, I would make a larger hole, and simply swage the material down into the hole which still makes a nice smooth safe hole for the tubing. Doing this minimizes the stress of the extra material swaging down, which in turn minimizes the potential for metal distortion at the top face. You don't end up with a bunch of metal to fold back on itself, but is still a method found on other T parts such as metal firewalls in later cars. FWIW

Just my 2￠ worth. This hose died of old age, not vibration.

Rich

that is the type of hole I'd be inclined to make...just a simple rolled edge...not one crimped back on itself.

This is what I ended up with. I will roll the points up a little. Art

I did it not long ago. As I recall, I first located where the hole should be using my original splash shield on a 1913 runabout as a guide. I center punched that location, and drilled it with a 1/4" drill. I got a piece of soft wood and drilled a 1/2 hole it it, and put it on my floor jack directly under the 1/4" hole. I raised the floor jack to the correct position, and using a taper punch proceeded to enlarge the hole until the tubing would just snugly fit. This worked for me.