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SirLesPatterson
11-27-2015, 01:38 PM
I would like to run this by you folks before doing it.

I have plasma cut a 6" diameter disc out of 1/2" steel. I would like to clean up the edges and face the side that will be visible but need to find a way to hold it. My thought was to face the head of a 3/4" bolt then weld it to the part. The bolt would then be held in the chuck. The bolt has a decent length of non threaded section to grip. The disc is mystery metal but I would call it mild steel since it seems easy to work with. The bolt I have is grade 5. The side of the part I would be welding to will be hidden so it doesn't matter that removing the bolt will leave a scar.

Yes/No? Thank you.

Mcgyver
11-27-2015, 01:44 PM
what size chuck do you have? if welding a stub, instead of a bolt, make something large dia - ie 3" pipe with a few stitches, it'll be more solid. Its a tough cut, plasma cut edges can be very tough, can take the end of hss in a rev ....and being intermittent its hard on carbide. A thought would be carbide endmill and a rotary table with enough of cut to get under the out layer. no need for welding, use three clamps and leapfrog around them - move them as required, then face in the lathe.

Mike279
11-27-2015, 01:47 PM
I like to use a disc sander to smooth up the edges of a rough cut. That is usually faster and easier than using the lathe. Unless of course you need it really accurate. Mike

The Artful Bodger
11-27-2015, 01:47 PM
Hi Les

The disk will wobble if just welded to the head of a bolt. What you need is some way to hold it against your face plate.

My suggestion is to weld a nut to the centre of your disk and use a length of threaded rod through your lathe headstock spindle to hold the disk firmly against your face plate.
Another and maybe better way would be to weld three or more studs to the disk and use those to bolt the disk to the face plate.

As already suggested remove the hard cut edge by grinding before mounting on your lathe.

Ian B
11-27-2015, 02:27 PM
Les,

Can you just hold the disk by 1/3 of it's thickness, skim the outer diameter that's sticking out, then reverse it, skim the rest and then skim the face? Some kind of parallels on the chuck jaws will help to hold the disk flat when you're tightening the jaws.

Ian

rklopp
11-27-2015, 02:27 PM
I have trimmed up 11-in disks in an 11-in lathe by tacking on four nuts and grabbing in a big 4-jaw with jaws reversed. Easy-peasy.

Mcgyver
11-27-2015, 02:39 PM
I have trimmed up 11-in disks in an 11-in lathe by tacking on four nuts ant grabbing in a big 4-jaw with jaws reversed. Easy-peasy.

I like that idea.

R.Bolte.Jr
11-27-2015, 03:01 PM
Put a center hole in the side that will not be visible, use a center in the tailstock to press it against the chuck jaws, clean up the edge to spec, flip it over and grab it by the edge to face it. I think its called "pressure turning" it worked for me in almost the exact situation.

https://turnstylemedia.smugmug.com/photos/i-G8qprmQ/0/M/i-G8qprmQ-M.jpg

SirLesPatterson
11-27-2015, 03:08 PM
Yeah, my original plan was a pipe but I'm concerned the pipe scraps I have around might be iron and not take the weld well. I posted about the bolt because I had reservations. Thanks for the feedback, I will explore the ideas mentioned.

J.Ramsey
11-27-2015, 03:40 PM
Face a piece of pipe,tube,round stock.
http://i.imgur.com/QvlcTYw.jpg

Center and weld three places.
http://i.imgur.com/PsZYoJQ.jpg

Turn and face.
http://i.imgur.com/H7R29nV.jpg

Grind welds off.
http://i.imgur.com/2hQdKRr.jpg

Just did this piece of 1/2" x 5"

SirLesPatterson
11-27-2015, 03:48 PM
That's what my initial plan was but how do i tell if the pipe I have is suitable? I think I read that black iron pipe may not weld well. The pipe I have is short with no markings and has an internal raised seam.

J.Ramsey
11-27-2015, 03:52 PM
If it has a weld seam it should be steel.

Rosco-P
11-27-2015, 03:56 PM
Yeah, my original plan was a pipe but I'm concerned the pipe scraps I have around might be iron and not take the weld well.

Black iron pipe is steel. Or are you thinking of something else?

metalbender
11-27-2015, 04:28 PM
The bigger the pipe, the better, as long as you can grip it in the chuck. Less chance of harmonics, vibration as in surfacing brake rotors.

Rosco-P
11-27-2015, 05:58 PM
That's what my initial plan was but how do i tell if the pipe I have is suitable? I think I read that black iron pipe may not weld well. The pipe I have is short with no markings and has an internal raised seam.

How do you think the Indians or the Arabs (UAE), closed up the seam after rolling the strip into a cylinder? Some sort of majik?

Quite possibly SMAW. Prep the two pieces to be joined, tack it in a couple of places and see if you can break the tack welds.

Fasttrack
11-27-2015, 06:22 PM
I've literally done this hundreds of times. First step is to blast through the rough flame cut part with an angle grinder. No need to be precise, just get edge cleaned up to make it easier on your cutting tool. Use a divider or caliper to mark the approximate center and center drill it. Then put a piece of double sided carpet tape on a faceplate or face of your chuck. Mount the disc and use a live center (or dead - just be sure to keep it well lubricated) to hold it firmly against the faceplate/chuck. Then turn as normal. I've done many 304 and 316 stainless steel discs/flanges this way. They require very aggressive feed and hefty DOCs - I think I've only had one slip.

boslab
11-27-2015, 06:34 PM
I've done flanges up to 12 or 13 on a Harrison, I use a peice of plate on the one side, a well used bit of 3/8", and back it up with the tailstock centre as mentioned, it isn't coming out of that set up.
Low revs and get under the skin, it's actually quite relaxing, but I'm a bit mad!
I use a stellite toolbit in a holder, or cobalt if I can't find the stellite, cut from the face to the face taking the HAZ off in one cut, plenty of coolant.
You can then slit the welds with a thin disk and chisel the drive off, bit of flap wheel to remove the weld snots.
Mark

SirLesPatterson
11-27-2015, 07:06 PM
Ok, I went ahead and welded a stub of 2.5" pipe to it and it worked out great. Used a grinder to knock the edges down first as per suggestions. Thanks everyone.

rklopp
11-27-2015, 08:41 PM
I like that idea.

When one is in junior high and desperate to build the biggest disk sander possible, necessity is the mother of invention. I wish the lathe was 12", but you go with the flow.

SirLesPatterson
12-06-2015, 04:41 PM
Ok, everything turned out well. I am making something that needs to swivel so I decided to use an old 5-lug wheel hub then make this adapter plate to weld my project to. I got to use my rotary table for the first time. It's a 15" Bridgeport table that came with my mill. I had been avoiding it because it was a PITA to move around. After figuring out how to hold the piece on the table things went very smoothly - a nice slip fit. I plan on putting some large nuts as spacer under the plate, around the lugs, for it to tighten against. This whole thing really is overkill but it was fun to get back in the shop again. Thanks for the help everyone.

1. Plasma cut disc
2. Welded pipe stub
3. Turned disc on lathe
4. Made holes on rotary table in the mill

http://www.doaks.net/projects/machining/5lug-01.jpg

http://www.doaks.net/projects/machining/5lug-02.jpg