Banjo fitting

[J. Tranter]

How do you make one? I know what they look like but get how to make one. I need one for a steam loco. exactly like Shred made but I can't Figure it out.
Help please.
John Tranter

 

[joeby]

John,

If you are referring to the fitting at the steam dome with the supply line attached, which is the only banjo fitting I can see, it shouldn't be too hard to make one.

A typical banjo fitting is nothing more than a thick washer with an groove cut (undercut) around the inside diameter. The through hole allows enough clearance for the hollow bolt (blind hole drilled along the bolt axis, stopping short of the head, and a hole drilled through the side into this blind hole), while the groove allows fluid or gas to travel around the bolt to get to the hole in the side of the bolt. Turn the OD, drill through for a reasonably close fit on your bolt, then using a boring bar, cut a groove around the inside diameter. Part off, and drill a hole through the side into the groove. Solder in a length of tubing or a fitting as required and you're done.

I hope I understood your question correctly and this is of some help to you.

Kevin

 

[shred]

This was another of those "everybody knows that, so nobody documents it" things I found when doing the loco.

I made mine just a little differently-- I made a thick washer and cross-drilled it for the steam pipe (which I silver-soldered in, but don't do that until later).

Then I turned up the bolt-- turned the shank to a close fit to the ID of the washer, threaded it, then (as Kevin says), blind-drilled from one end up to close to the head. Over to the mill to cross-drill through to connect with the blind hole. Back to the lathe (Note to self: get to work on lathe-cross-drill attachment) and the parting tool to put a shallow groove around the bolt at the cross-drill so steam can circle around to the steam pipe, wherever it may be. Part off and done.

If you make the un-threaded part of the bolt a close fit to the ID of the washer before cutting the groove, especially if you leave a bit just under the head of the bolt before the groove, it helps with sealing later on. If you plan to O-ring, account for that extra space as well.

While my way has the advantage of easier construction since you don't have to go undercutting a washer, it does make the bolt considerably weaker. A small, grooved, cross-drilled, hollow, brass bolt is not a robust thing, so no horsing on it.

 

[J. Tranter]

Thank you guys. Once I read it I could picture how to do it.
Thank You
John Tranter

 

[1Kenny]

These are a bit larger than you are working with, but it may give you a visual image. I started with stainless steel bolts to make these. The outside fittings are made from bronze and I machined a groove inside.

Kenny

 

[John S]

Another way is to make a ball knob with a straight shank and then mill two flats on the ball and bore it to get the banjo, then thread the shank or drill it for the pipe.
Not all banjo's are straight sided

This one is external thread but you get the idea of the banjo shape.

JS.

 

[J. Tranter]

Thank you all for the help.
John Tranter