Tailstock ram doesn't extend enough

[digiex-chris]

On every lathe I've used (granted, only 3 of them) all of different brands and sizes, the tailstock travel is never long enough so that if one end of my work is held in the chuck, and the other end in the tailstock live center, I can't cut the entire length from center to chuck in one pass. I need to have my compound parallel to the lathe axis, and crank the tool to the right a bunch to get up against the live center, then to the left a bunch to get up against the chuck. This works, but if I need a specific length I've got an additional set of numbers to keep track of, and I need to indicate my compound straight if I want any kind of accurate diameters at both ends. And what if I needed my compound set at a specific angle, like in threading the entire length of a piece, and couldn't use it to adjust how far left or right the toolbit is compared to the carriage?

What am I missing? Or is this not normal, and the lathes I've been working with happen to be odd?

 

[bret4]

Not all lathes are created equal. Larger lathes like my 13x40 Harrison M300 has no problem turning a part the way you explain. I may have to set the compound at an angle about like this slash mark \ to reach but maybe not even that much of an angle. At work my EZ path lathe can also turn from the tailstock to the chuck with no problem.

I wonder what lathe you are using? What kind of tool holders? Seems to me I remember when I had a 7x12 mini lathe I could turn from the center to the chuck just fine too. Maybe you could post a picture of your setup. Seeing your setup may help us help you.

 

[Swifty]

Are you fouling on the live centre? The live centre that came with my lathe is fairly large dia where the bearings are, however I have another live centre with interchangeable points on it. This allows you to have longer / smaller dia points which allows you to get the tool bit in and machine shafts between centres in one go.

Paul.

 

[Charles Lamont]

You should be able to get the tailstock centre to reach all the way across the saddle. With some lathes, if the job diameter is small, the back of the topslide interferes with the tailstock body, so you have to slew the topslide to provide clearance.

If you have a QC toolpost, an extended tool-holder can help. A rather old web page of mine shows the general idea:
http://www.charleslamont.me.uk/iqc_toolpost4.htm

 

[prof65]

Hi Chris, here are some tools that could help you:

A "long nose" revolving centre (third from top):
www.rdgtools.co.uk/acatalog/2MT_REVOLVING_CENTRE_SECTION.html

A small diameter revolving centre (top of page):
http://www.arceurotrade.co.uk/Catalogue/Centres

Extension sockets:
http://www.arceurotrade.co.uk/Catalogue/Extension-Sockets

Sometime, when I have to turn a very small diameter and the tailstock doesn't allow me to do the right job, even with a small centre, I use a piece a bit longer, cut it as close to the tailstock as possible, then cut away the end.

Roberto

 

[digiex-chris]

I feel a little foolish. I put my compound back on and set it up like my question (I had taken it off to do some milling). I didn't have the usual 1/4" brazed carbide bit mounted in the tool post, so I grabbed one of the 1/2" bits I had in a drawer, and one of the sizes that the manual says is the size to fit the toolpost. And with that change, my solution revealed itself.

Here it is, compound set at 29.5 degrees for threading. Doesn't quite reach the end. WAAYY better than if I'd been using the 1/4" bits, it would have the toolpost fouling on everything to the right of the work. Looks like 1/2" bits with a little more extension than I'm used to are the key, I need an extensomatic bit holder for the 1/4" guys.

http://imgur.com/a/6D1qR#0

Not quite reaching the end
http://imgur.com/a/6D1qR#1

Withdraw the compound a bit, good! With the 1/2" bit I have enough cross slide travel to reach the centerline! That's the biggest problem I had before, if I set the compound to the right angle, I had to crank it forwards a bit to reach the centerline, then the toolpost would be too far to the left.
http://imgur.com/a/6D1qR#2

Yes, fouling on the center a bit, nothing that's not solved by a cut-away center or grind my tool a bit for clearance.
http://imgur.com/a/6D1qR#3

So the hint given about what tools am I using pointed me in the right direction! Anything else you can see about my setup that can be improved?

 

[bret4]

I'm glad you figured it out. That's why I mentioned setting your compound at a angle. Didn't know what size tool you were using. Yes, now just grind a tool to clear the live center and you will be able to turn really close.