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would this be an acceptable way to mount small work pieces in a lathe...?

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jonogt:
I'm just getting into machining, and one of the things I've found sort of annoying is that quite a bit of the material is unavailable for turning because the chuck is in the way.  This is only an issue for me because I'm on sort of a budget and only want to use the amount of material I'll actually be turning. 

what I have in mind is getting a piece of steel stock, like 1" dia by 8" long, and turning the front half of it down to where I can put standard half inch male bolt threads on it.  When I want to turn a part, I'll put it in the chuck and drill/tap it for matching half inch female threads.  Then I'll just put the male threaded piece I made in the chuck and screw my work piece on to it.  Since I drilled it on the lathe it will be true, the direction of the threading will keep it tight, and the only waste will be the short portion that I drilled and tapped.

The setback I can think of is the work piece might get screwed on excessively tight, but this could probably be remedied by putting a rubber grommet or something in before screwing it on.

What do you guys think?

Bernd:
jonogt,

Have you ever heard of the term "turning between centers'?

This method allows you to used the length of material that is required by the job. What you need to do is to center drill both ends and then put the part between centers in the lathe to turn you part.

This is just one method. You will probably get many different answers here.

I realize that it may be difficullt to visualize what discribed above so will do a set up and take some pics. Check back in a day or so.

Bernd

bogstandard:
Hi J,

That is perfectly feasible, and I think a method that wood turners have used for a long time.

The only problem is accuracy. Unless you use a collet chuck system or four jaw independant chuck and clock, every time you reinsert your mandrel back in a three jaw, it will wobble slightly, because you can never get it back in exactly the same position it came out from.

Also, for perfect concentricity of the original threaded hole for the stud, it would need to be bored and single point internally threaded. There are a few easier ways to obtain a concentric screw thread sticking out of a block of metal.

Maybe if you really wanted to go this route, remove your chuck and purchase a blank end arbor to fit into your spindle nose (very cheap), then drill and thread that for holding the parts.

There is another way, and that would be to buy a set of soft jaws for your chuck (if you can get them for your chuck, they are not too expensive). These allow you to bore a very shallow but high grip recess for mounting thin or short parts, and is a very easy way to obtain super accurate tolerances on very thin or short parts. I use this method a lot, and if you precut your piece parts fairly accuratley to begin with, very little wastage.

John

John

jonogt:
thanks for the replies guys,

Bernd I think I mostly get the idea... the workpiece is basically "pinched" between the tailstock and headstock in a position far enough from the chuck that the tool has full length access to it, right?  I assume the tailstock end would be held by the live center?  But what holds the headstock end?  Is it a mandrel similar to what I described, but with more of a spur deal instead of threads?

now that you've mentioned the concept, I have seen parts in the shop that look like they may be used for this process.

am i on the right track here?

bogstandard:
http://www.angelfire.com/d20/lathework/page9.htm

John

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