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View Full Version : Finally got to work in the shop, I have questions!



cybor462
12-19-2006, 12:49 PM
Hi all. I have been rather busy with the real job;) and finally got some time to go make a mess of the shop. Of course not being the brain of the machine world I have again run into trouble. So if you will allow me to vent here we go,,:eek:
I was trying to make some ring compressors on my 13x36 lathe and well it does not fit. I am starting with a tube of 6061 4.250 OD which I was able to chuck holding on the ID. The length of tube is roughly 18" long so I need a steady rest. I pulled out my brand new steady rest and it looks like it will only open to roughly 2-2.5 inchmax. size work. So the next option would be a bull nose center but mine are very small. I looked into Enco and they have a MT3 live bull but it is only 3.5" To get a 5" I have to have a MT4 tailstock which I do not.

I can't believe I am unable to hold this tube. Any suggestions? I know Get a bigger lathe, but that is not an option today.

HELP:(

hitnmiss
12-19-2006, 12:57 PM
I'd have a try at making a bull nose center for your existing center.

Take a round piece 4.25-4.5" dia about 1/2" or so thicker, turn the bull nose taper on one side and drill a center on the other. Then mount the center on your center (live center I hope) to convert it to a bull nose. Maybe drill the center first and turn the taper using the center so it'll run true.

something like this: (hope it formats okay)

... _______________________
../......................................\
/___________/\_____________\

pcarpenter
12-19-2006, 12:58 PM
If you could start with your tube over-length, you could perhaps find a cheap ball bearing that is a press fit inside with a small enough inner race that would fit a bull-nose center you could use.

I was going to suggest boring a step into which you could press a bearing...but that isn't going to work for the same reason you can't work with the material now :D

Paul

cybor462
12-19-2006, 01:01 PM
Wow this board rocks in minutes I have a response,,

Anyway thanks for the help my problem is all my live centers I mean the 2 I own are much smaller. One is permanent can't change it and the other is for small work I think the shaft size is maybe 1/2 inch so I am not sure it is heavy enough to handle that size bull. I did think of turning one but then I need a live center to put it in.

cybor462
12-19-2006, 01:04 PM
Would anyone know of a bull I could buy (live that is) that would have a MT3 taper but go to 5" like I need?

mklotz
12-19-2006, 01:32 PM
Make up a cat's head spider to fit the ID of the pipe.

JCHannum
12-19-2006, 01:36 PM
The tapered insert hitnmiss describes will work, or turn a plug to fit inside the tube with a center drilled in it.

The plug or tapered plug can be turned from hardwood, plastic or whatever similar material is available.

winchman
12-19-2006, 01:42 PM
Why can't you cut the tubing into shorter pieces? Surely the ring compressor you want to make isn't 18" long.

If you use a bull center, you'll only be able to machine the outside of the tube. You'll need to get to the inside at some point, and to do that you need shorter pieces or a bigger steady rest.

I'd be really careful holding that size aluminum tube by the ID. Unless it's got a very thick wall, you'll distort the tube if you grip it tight enough to take more than the lightest cut. You could use a backup ring made of 1/2" plate slipped over the end that goes on the chuck to increase the grip and reduce the distortion.

I've done quite of bit of machining of 2" thin-wall aluminum tube, and the best thing I've come up with is this holding fixture:
http://img.photobucket.com/albums/1003/winchman/000_13112.jpg
http://img.photobucket.com/albums/1003/winchman/000_13122.jpg

A larger version wouldn't be that hard to make, and it would give you the support you need. A bolt goes through the spindle to hold it in the chuck.

Another possibility is a larger version of this:
http://img.photobucket.com/albums/1003/winchman/000_1566.jpg

The left end is a slip fit inside the tube so you can hold it tightly in the chuck without distorting it. The other ring is a slip fit on the tube ID and on the fixture, so you can put it where you need it. The right end is cut to fit on a live center. It worked pretty well, but the other fixture gives me a more accurate result.

I'd leave the center part of the fixture at 1" diameter and just make the two rings large enough to fit the ID of your tube. That might give you enough room to get inside with a tool so you can do everything in one setup and part it off when you're done.

Roger

cybor462
12-19-2006, 06:45 PM
Well I did plan on cutting each to near size but I burnt up my cheapo HF bandsaw motor. I bought a bigger motor and just got it installed today. I was able to cut the tube and the new motor held up. So that is the direction I am headed. The wall thickness is roughly .250. I was concerned about distortion but I decided to make one and see. I will have to bore and cut a taper which will reduce the size overall. I will check into your fixture. Might be the way to go. I have turned the od (skimmed to clean) and faced both ends. Now I need to bore. I will let you know how it makes out.

Thanks

Jim

madman
12-19-2006, 10:34 PM
I took a morse taper three shank (for my lathe) mounted a chuck on it with bearings and proceded to weld extensions onto the existing hard jaws. (with my arc welder yECH) CAME OUT WELL ACTUALLY. tHEN I TOOK THE CHUCK CLAMPED A ROD INTO THE OLD JAWS INSIDE AND MOUNTED THE CHUCK INTO MY 4 JAW CHUCK INDICATED IT IN AND TURNED THE WELDED JAWS UP NICE. tHEN (WOW LOADS OF WORK) I REASSEMBLED IT AND MOUNTED IT INTO MY TAILSTOCK. nOW I JUST EXPAND THE SMALL LATHE CHUCK INTO THE INside bore of the tube and it works. I made a bunch of winches for a guy doing it this way with left hand lubow grooves. One of em was a 30 inch diameter. Hope this helps.

cybor462
12-20-2006, 12:20 PM
Thanks guys for all the info. Madman that chuck sounds like a bear. What size bearing did you use? Sounds too involved for me. Maybe too expensive as well. I do not have an extra chuck floating around. Sounds like one of the shop treasures. I too have made some stuff I look at later and ask why. But when they work you say what took me so long to make this. Me, well I get wore out thinking about doing it:confused: let alone doing it.
I did learn that scrap yards have no clue what type of alloy they are selling. This tube I was told was 6061 but it has to be the harder aircraft grade. That is why I wasted the bandsaw motor. This stuff cuts like hardened steel. A good thing for it's intended use but a bugger to machine.
Winchman I keep looking at your fixture. that would do well for boring the tube. What about turning the od?

hitnmiss,, sorry I did not understand what you were getting at. I think I see it now. basically I am making a device with a center drilled hole that will center itself in the bore and allow my tailstock live center to locate in. Is that your idea? Simple and easy. Some days my mind is in another world and I see things in another light. Today is a better day.

winchman
12-20-2006, 02:09 PM
I use the first fixture only for getting the ends of the tube square and the length correct. I don't turn the ID or OD, but I could turn the ID if I needed to.

The second fixture could be used for turning the OD. You could also do part of the ID if you positioned the loose ring partway out to the end of the part.

What kind of ring compressor are you making?

Roger

BillH
12-20-2006, 02:14 PM
DONT part between centers!