Odd Sized Clamping W/o 4jaw?

Hello folks.

I am building an art deco "steampunk" bar/table top light. If you can't picture one just search eBay, you'll get the concept. I'm using 3 of those new vintage style "Edison" L.E.D. bulbs at some point I'll fab up cages to both protect them and defuse the light. The structure itself will be made from a hundred bucks or so worth of 3/4" steel grey pipe, nipples, fittings and caps. I just completed a trick conversion to a brass gate valve, that I've bored out and used to house a rotary on/off. Topping the whole project off will be some cool vintage 8" steam railroad gauges, a few geared machinery parts welded together for a base and maybe even a hidden 12v transformer that will light up some old vacuum tubes to add to the useless conversation piece's oddity.

To hold the light bulb sockets, I've bored out one reducer fitting and will J.B. weld the socket in one end and screw attach the other. For the other two bulbs, I want to use a 90 degree street fitting that are 3/4 on one end and 1" on the other, but when I went to bore the 1" threads out of it to fit the socket, like I did with the straight fitting, I realized I have no way to clamp the part (due to it's sweep) in the lathe. I don't own a 4 jaw, maybe this is my reason to order one. My other option it to clamp it in the mill vise, but I don't own a bit the 1-3/8 size I need to make the bore big enough to receive the socket either.

I could spend a few bucks and just buy a bi-metal holesaw to run in the mill, or I can keep trying to get the odd shaped part to stop wiggling loose in the 3 jaw chuck. I'd really like to do this will tools that I already own since all of the specialty parts for this project are starting to add up and I've kinda blown my budget for the month.

Thanks for your thoughts.

Clamp it to your tool post and clamp a boring bar off center in the 3 jaw chuck to bore out the hole you need.

Is there a way you could clamp it to your face plate and have enough clearance/swing?

Put it in a mill vice and use a boring head, if you do not have a boring head use a cheap fly cutter and move the tool off center until you reach the desired diameter. This is a slow process yet works every time. Use a dial indicator to measure the tool offset which will result in the bore size required within reason.

If you are a hobbyist and require finished dimensions in tenths this approach will be unacceptable.

DOH!

I was going to suggest firmly mounting it to a face plate, but then got to thinking of how hard it would be to
balance such a contraption. So I vote for the mounting it to your tool post or compound (milling vice?)
and using a boring head kinda thing. USE CAUTION steam punk stuff can get often get out of hand.

Regardless of how you do it, make sure that you get a full description of what you finally did, and PICTURES of
the final product.!

Chuck the grumpy old guy

If you have some 3/8" or 1/2" aluminum plate, you might try this ... Cut out a largish circle - radius a bit larger than the "swing" of the elbow. Mount it in your lathe chuck and cut out a circular hole equal to the OD of the elbow's end. Saw the circle in half, so it can clamp down on the end of the elbow. Then use the plate halves to mount the elbow in the 3-jaw and go to town on the ID.

Variations - (1) somewhat smaller OD on the plate, and let the "other end" of the elbow stick out between the jaws, (2) use radially arranged setscrews to secure the elbow in the un-sawed plate.

Thanks folks!

Some great ideas here. I am going to use John's idea of cutting extra plate stock to clamp it all up and turn it in the lathe. I have a few fly cutters but all are too big to adjust to the I.D. I need.

I'd also thought I could braze or weld a carbide lathe tool to a piece of round stock, or an old mill bit, to make a bore the right diameter for the mill. The problem is without the ability to adjust radius, I'd be guessing at the end diameter.

Photos of the completed lamp and outlet stand, I promise, but with any luck I'll have a few of the sockets yet this morning.

So I just couldn't get a good enough grip on it... "It" being the cast iron fitting in any lathe or tool post clamp. Ended up threading a pipe in and clamping the pipe in the mill vise. I cut a piece of steel off of an old transmission shaft. Turned one end down to approximate dimension I needed and TIGed on a cheap Chinese offset carbide from one of those Chinese tool clearing house places. it fit one of my R8 collets for the mill like this:



The only problem was that the only way I could change the hole size, was to bend and grind down the carbide..

Since the dimensions are not at all critical (it's art for crying out loud) I just got it close enough. I didn't even indicate the center of the fitting, just eyeballed it and went TLAR (that looks about right) deep.



Next I wired up and taped off the contacts so they wouldn't short on the pipe and epoxied the socket into the bore.



Here's the straight one too:



Thanks for all the great ideas!

Surprisingly the length of the tool and resultant flex was not a big factor boring the cast iron. I'm not so sure however that I would want to try this method to cut a hole in hard steel nor where the dimensions were super critical. By the way here's some more of the old stuff from the junk drawer that I may incorporate into my new found fascination with STEAMPUNKing.



I still need to buy one of those big brass steam pressure gauges and an old brass water meter. Does anyone think my floor lamp should also sport a see through gascolator sediment bowl off of a 1959 Allis Chaimers D-17 farm tractor?