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loose nut
06-13-2010, 04:36 PM
This may have been asked before but I couldn't find anything in the search section.

Why do steady rests have 3 supports instead of 4. Yes 3 will give good stable support but is a bitch to adjust straight and true. Wouldn't 4 supports be better, you could adjust it the same as a 4 jaw chuck.

Since most steadies have 3 supports there must be a good reason.

Lew Hartswick
06-13-2010, 05:08 PM
Just for grins: it only costs 3/4 as much for the adjusters. :-)
...lew...

winchman
06-13-2010, 06:43 PM
Since the other end of the part is held securely in the chuck, you always want the steady rest to hold the outer end on the spindle axis. It only takes three points of contact to do that.

The purpose of a 4-jaw is to hold the part more securely, or to locate it on (or off) the axis of rotation with more ease.

loose nut
06-13-2010, 06:50 PM
But wouldn't it be better to centre the work along the centre line of the lathe axis in a 4 point steady??????:confused:

strokersix
06-13-2010, 06:56 PM
3 point the work will stay roughly on center for turning consistent diameters if you have to adjust clearance while running, just adjust the top support.

Conjecture on my part but I stand by the logic.

Carld
06-13-2010, 07:12 PM
Look at a three finger steady rest. The finger adjusters stick way out. Now think about how hard it would be to adjust the finger that is down in between the ways. That is one reason and the other is it's a lot easier to adjust three fingers than four.

rohart
06-13-2010, 07:30 PM
My first thought was that a four point support isn't easier than a three point to adjust. We think it is because we use four-jaw chucks with each jaw independently adjustable.

I'm so miserly, I've managed with a scroll three-jaw chuck so far, and I've become quite quick at adding shims and bits of paper to get my work centred. I can easily apportion highspots across the two adjacent jaws, and adjust for it.

Which brings me to a further question. Why aren't there independently adjustable three jaw chucks ? I know there are scroll chucks with each jaw adjustable too - that's the principle of the grip-tru, isn't it. But have I ever seen a straight three-jaw with each jaw independent and reversible ?

However, you get four-jaw adjustment with a steady if you use one of the steadies where the work fits through a massive ballrace. I made a 50mm bore one, but JS showed one a year or so back that could take with several inches.

drof34
06-13-2010, 08:18 PM
Four jaw steadies are not any harder to adjust, maybe 25% harder, than 3 jaw steadies. The two bottom jaws are roughly in the same place they are on a 3 jaw steady and not between the ways.

You will probably only see a 4 jaw steady(s) on really large lathes.
Consider turning a 20" dia. or larger shaft that is 40' or so long with an inch or two DOC and which way it is turning and where you are in relation to it and what would happen to you if it came out.

Dr Stan
06-13-2010, 08:28 PM
Which brings me to a further question. Why aren't there independently adjustable three jaw chucks ? I know there are scroll chucks with each jaw adjustable too - that's the principle of the grip-tru, isn't it. But have I ever seen a straight three-jaw with each jaw independent and reversible ?

That would defeat the purpose of the universal three jaw chuck. However I have used universal 3 jaws that have independently adjustable jaws, abet they have a very limited amount of adjust-ability.

j king
06-13-2010, 08:29 PM
I agree with the previous reply. Larger lathes have a heavier load to carry and thus more pads. Most of the large lathes i have ran have 5.One one the very bottom also.

Jim Hubbell
06-14-2010, 12:12 AM
I set up the steady I built to use three OR four points of support. I tried once or twice to center a workpiece using four points and was all over the place. I might add that I use a four-jaw chuck with no problem. Centering with three points is a snap and is the only way I use the steady. I can envision using the steady on a four sided workpiece and being glad I had it. As yet this has not happened.

winchman
06-14-2010, 04:49 AM
"I can envision using the steady on a four sided workpiece..."

I'll bet it won't spin very well. :D

Ian B
06-14-2010, 05:27 AM
Jim,

Are you referring to a cathead?

Ian

MuellerNick
06-14-2010, 05:43 AM
If you need to see variations in steady rests: Richter Lünetten (http://www.luenetten.de/en/luenetten01.php).
They even have digital ones.

Nick

Jim Hubbell
06-14-2010, 07:39 PM
Ian
You're right. Should have mentioned that it is the one I showed on here. Homemade using a large ball brg. Will take up to two inch in dia. Square is no problem.

06-14-2010, 08:04 PM
Well, just for \$h1ts & giggles lets gnaw this one over.

Why not a two jaw. The ends of each jaw would have a deep V cut in them. You could then slide the steady up to the chuck end, adjust them to the proper setting and then back off the steady to where it needs to be before turning?