Turning down to a dead/live center. What tool to use?

[zeeprogrammer]

I have a piece of steel I need to turn down to 0.2183 (and I'll be happy to get to 0.218x).

The piece is about 3" long and I'm using a live center. So things are going to be tight as I get to the target diameter.

Of the tools I've got (cheapies that came with the lathe)...the threading cutter seems like it would work.

To take care of the shoulder that will develop on the left...I'll angle the tool...then come back with another tool to square the shoulder.

The instructions I'm following seem to use a more rounded tip than the thread cutter. I would have no problem rounding the tip...should I? ??? ???

I suppose I can switch cutters as I work closer and closer.

I would appreciate any confirmation or alternatives. Thanks.

 

[zeeprogrammer]

Found a carbide tool insert (the triangular cutter).
Fits in nicely. Mounted with a slight angle for the shoulder.
I think I'm good to go. ???

[Edit: Nope. Interference between the tool post and the live center. Had to move the cutter out a bit. Not comfortable having a tool hanging out there. Seems it would have too much flex. ;D Still want to try the carbide insert. I think I'll have a go and see what changes I have to make as I go along.)]

 

[Foozer]

I have a piece of steel I need to turn down to 0.2183 (and I'll be happy to get to 0.218x).

The piece is about 3" long and I'm using a live center. So things are going to be tight as I get to the target diameter.

That reminds me to grab a dead center and grind it down to a half center for just that reason.

http://www.homemodelenginemachinist.com/index.php?topic=5037.msg52809#msg52809

Knew I saw it somewhere, and the pains I go thru that this simple gizmo avoids.

 

[zeeprogrammer]

Hi Foozer.

Yeah and it's in my own thread too!

But I think I'll go down the road a little further before I start grinding away at some tool. I'm still a bit nervous around grinding anything.

In the meantime my excuse is to 'go through the pain - I'll appreciate the knowledge and the difference a tool can make'.

Thanks.

 

[Foozer]

Hi Foozer.

But I think I'll go down the road a little further before I start grinding away at some tool. I'm still a bit nervous around grinding anything.

Thanks.

The skin over the knuckle does grow back, cant even tell anymore after 40 years or so

 

[mklotz]

Keep your eye peeled at swap meets for cheap MT drills with a taper that matches your tailstock. Cut the fluted part of the drill off and turn a 60 deg center on the remaining stub. Grind half of it away and, voila (not viola - that's a fat violin), you've got a cheap zombie center. It won't last as long as a hardened commercial one but such tools are used so infrequently by the hobbyist that it may well end up in your estate.

Actually, buy any MT drills you can find that fit your TS. They're generally cheap - especially if the drill is knackered - and there's all kinds of good things you can make with the cut off tapers, e.g., dedicated center drill holders, die holder, etc..

 

[zeeprogrammer]

Foozer: Oh I'll get there. But no marks yet.

Marv: Thanks. Good tip.

Having my coffee as you suggested in the other thread Marv.

The tail stock end of the shaft is within 0.003. The head stock end is within 0.005+

I'm not surprised. While turning, it seemed the live center was wobbly. I put a dial indicator on it...as close to the tip as I could...and it was bouncing around +/- .001 to .002. Not as much as it seemed...I think the light was fooling me. Still, multiply that by 2 and I've got wobble.

But is touching the other thread...

 

[Foozer]

The tail stock end of the shaft is within 0.003. The head stock end is within 0.005+

The piece nominal is 0.2183 so your saying the headstock end is 0.223 and tailstock is 0.221 ?

A 0.002 taper over 3 inches, skinny at the tailstock. That condition drives me up the wall, at least the process of reducing the taper does. Something my little lathe is great for, loosing tailstock position. Any time I move it, it bounces a thou or two in or out resulting in a taper cut. Can spend a good hour setting it to cut a six inch piece with less than a tho taper and its good for that time only. But if thats' what it takes to get the part its brew another pot of coffee time :0

 

[zeeprogrammer]

The piece nominal is 0.2183 so your saying the headstock end is 0.223 and tailstock is 0.221 ?

A 0.002 taper over 3 inches, skinny at the tailstock. That condition drives me up the wall, at least the process of reducing the taper does. Something my little lathe is great for, loosing tailstock position. Any time I move it, it bounces a thou or two in or out resulting in a taper cut. Can spend a good hour setting it to cut a six inch piece with less than a tho taper and its good for that time only. But if thats' what it takes to get the part its brew another pot of coffee time :0

Yep. That's right.
Unfortunately...too late for coffee. (And perhaps I shouldn't admit this...I'm an instant coffee drinker...I haven't the patience to wait.) Once I'm done with this piece...it's time to put the feet up and have the wine. If I'm lucky...things will have gone well (enough).

Thanks Foozer.