Turning with C-type steady rests without tailstock

I don’t have lot experience with steady rests.
I have two propeller shafts diameter about 200mm/ 8inch, which I should shorten 400mm and make thread inside etc, so I can’t use tailstock. Length is about 4000mm, so I think I have to use two steady rests.

We have two C-type steady rests, which go small enough. Side is open. One roll is straight down, one is at back and top roll is 15 degrees to front from centerline.

Steady rests are pretty much like in this picture, but it’s all solid, not swiweling top.

Steady Rest Type 5 -- H. Richter Vorrichtungsbau GmbH, Germany

I’d like to ask, is that kind steady rest safe to use without worry that shaft could ”jump” out of open side?

I think that it would be safe, but older coworker with more experience with that lathe thinks it might be unsafe. But he’s used those steady rests with tailstock, not without.

On right picture is same kind setup, with similar type steady rest.

SAFOP - equipments

If you are doing internal work the open sided steady rests won't provide any support for the cutting operation unless you can turn the steady rests around or you flip your tooling over and run the spindle in reverse.

Thanks Kenton, you brought up very good point.
I have to turn inside about 70mm or 3in diameter thread. I think rotating steady rests is not an option, turning in reverse might be.

Maybe have to call boss tomorrow and ask about one removable top steady rest in our other shop and it’s measurements.

But do you think these kind steady rests can be used if turning OD without tailstock?

Milling is also option on that lathe, but I think turning might be easier for that ID thread.

I don't think I would use them in that application, maybe if I had a standard steady rest at the end of the part. That is a lot of length for something to go wrong. There are others on this site that have a lot more experience than me with larger parts that may chime in. At the moment I think I would listen to the more experienced people in your shop.

You could compare the chordal distance between the top and bottom roller with the diameter of the shaft being turned. If it's 1/8" shorter, then I don't think the part is going to wick out of the slot. The mere presence of the open side doesn't mean it can't handle the load. I've never had a fantastic wreck using a steady, but for normal smooth turning, there's not a tremendous force exerted like there is in a crash situation.

Using this calc, Circle Calculator

15 deg on a 200 mm dia bar shows a segment height of 0.85mm or 0.033'' ???????????????????????? which while safe in theory ( you aren't going to compress steel bar) .....shall we say doesn't give much leeway should things not go quite to plan

Are you sure the bottom roll is straight down? Reason i ask is the steady i have seen like that the bottom roll whilst vertical was very much in-font of centre line by a good 1/2" or so, would be near impossible to crane a shaft into steadies like that if it was on centre line.

Jani73 said:

But do you think these kind steady rests can be used if turning OD without tailstock?

Click to expand...

They can be. They are.

The primary value-add of the legacy fully-closed-ring style is to provide tension - latch-down of the top, if you will - so the whole structure can be more lightly built for any given tasking. Ergo easier to move and place, in need of less long-axis "daylight".

The "C" style quite obviously has had to put more "beef" into the rear of the structure and the curve-over upper member that closes the "lips" (with rollers) of the "C" around the diameter so the bar cannot escape. It is only supported at ONE end. It - and the rear riser it depends on - both have to resist force in BENDING rather than in tension.

That makes its job harder.

Payback is faster and easier (or so they will claim to SELL these) cycling of workpieces.,

Nothing wrong with adding reinforcement across the open side - temporarily - if you fear a crash on an especially challenging tasking. Rough surfaces, imperfectly round forgings, a tube as may collapse and escape, wotever, until one can cut a path for the rollers or sleeve one onto it, etc.

Just have a care not to distort the frame and INCREASE that possibility by skewing the rollers, or altering the circle's effective diameter and/or its center of rotation so as to push the work TOWARDS a distortion from long-axis or round shape.

A bit of careful measuring before you commit, and again shortly after the first cut, can improve your confidence and comfort level. Or catch a problem, early.

Looking at it, I'd say that it would be fine. That's ASSUMING that the shaft will be positioned so that the top and bottom rollers will be closed smaller than the O.D. size. How on Earth this design is supposed to be better than a closed top I have no idea. The only advantage I can see is that it would be easier to put on or off the machine with work already in place. That and pre-puckering of the machinist running it's bunghole. Might prevent a crash better since the guy is apt to be a little extra careful. On the flip side if there lS a crash, he's more likely to need new underwear.

eKretz said:

it would be easier to put on or off the machine with work already in place.

Click to expand...

That may have been the decision driver, right there.

One can pull the tips way back and side-tilt the ring ones into place, IF the bar is a good deal smaller than the loop, IOW "only now and then".

Once they get above a certain size it can be impractical if the "hook" you need to manage their mass already has the bar you are trying to get support onto slung to it.

Reason we had chainfalls as could work under the big traveler at Galis. Plant Manager had come up through the ranks, approved common-sense lifting gear automagically. Mining machines nor railway do not deal with kayaks nor canoes.

But Adam wudda also considered "custom" steady rests for "round stuff" about as relevant to getting a job done as converting the loo to Japanese style squat toilets! You either "knew your shit" or you did not.

Put the steady into approximate location. Swing top open. Lower bar into it. Later.. slide steady left or right as needs dictate, IF they dictate. Traveler was pendant-controlled. If I needed it - or the chainfalls - I simply brung it over.

Just how hard was that to figure out, anyway? This "shop" has but a clapped-out forklift and a Chinese "engine" hoist? And they have custom steady rests fabbed? Could have at least bought a stock gantry on wheels, spreader bar, pair of chainfalls instead. Or TWO such..

Limy Sami said:

Using this calc, Circle Calculator

15 deg on a 200 mm dia bar shows a segment height of 0.85mm or 0.033'' ???????????????????????? which while safe in theory ( you aren't going to compress steel bar) .....shall we say doesn't give much leeway should things not go quite to plan

Click to expand...

Diameter between rollers seems to be about 0,9mm smaller than workpiece. That doesn’t seem a lot if something unexpected happens. Called to boss today, so he can ask about closed steady rest in our other shop and it’s diameters.

adama said:

Are you sure the bottom roll is straight down? Reason i ask is the steady i have seen like that the bottom roll whilst vertical was very much in-font of centre line by a good 1/2" or so, would be near impossible to crane a shaft into steadies like that if it was on centre line.

Click to expand...

Can’t be sure. It is vertical. I check that at monday from drawings.

Jani73 said:

Diameter between rollers seems to be about 0,9mm smaller than workpiece. That doesn’t seem a lot if something unexpected happens. Called to boss today, so he can ask about closed steady rest in our other shop and it’s diameters.

Click to expand...

Wise move - IMHO

thermite said:

They can be. They are.

The primary value-add of the legacy fully-closed-ring style is to provide tension - latch-down of the top, if you will - so the whole structure can be more lightly built for any given tasking. Ergo easier to move and place, in need of less long-axis "daylight".

The "C" style quite obviously has had to put more "beef" into the rear of the structure and the curve-over upper member that closes the "lips" (with rollers) of the "C" around the diameter so the bar cannot escape. It is only supported at ONE end. It - and the rear riser it depends on - both have to resist force in BENDING rather than in tension.

That makes its job harder.

Payback is faster and easier (or so they will claim to SELL these) cycling of workpieces.,

Nothing wrong with adding reinforcement across the open side - temporarily - if you fear a crash on an especially challenging tasking. Rough surfaces, imperfectly round forgings, a tube as may collapse and escape, wotever, until one can cut a path for the rollers or sleeve one onto it, etc.

Just have a care not to distort the frame and INCREASE that possibility by skewing the rollers, or altering the circle's effective diameter and/or its center of rotation so as to push the work TOWARDS a distortion from long-axis or round shape.

A bit of careful measuring before you commit, and again shortly after the first cut, can improve your confidence and comfort level. Or catch a problem, early.

Click to expand...

Thanks for long answer. I don’t fear a crash. I’m usually pretty careful and sometimes check program without tool or away from workpiece.

eKretz said:

Looking at it, I'd say that it would be fine. That's ASSUMING that the shaft will be positioned so that the top and bottom rollers will be closed smaller than the O.D. size. How on Earth this design is supposed to be better than a closed top I have no idea. The only advantage I can see is that it would be easier to put on or off the machine with work already in place. That and pre-puckering of the machinist running it's bunghole. Might prevent a crash better since the guy is apt to be a little extra careful. On the flip side if there lS a crash, he's more likely to need new underwear.

Click to expand...

I’ve been machining since 1994 without bad crash. Mild crashes can be calculated with few fingers.

Jani73 said:

I’ve been machining since 1994 without bad crash. Mild crashes can be calculated with few fingers.

Click to expand...

4m of 8" bar poping out of thoes steadies would be more metal than some people succesfully machine in a life time as a crash! FYI thats not a finger remover at just a 100rpm, that would be like being a mouse chased with a pissed off rolling pin!

I think he meant that the number of crashes he has had in a lathe can be counted on a few fingers.

adama said:

4m of 8" bar poping out of thoes steadies would be more metal than some people succesfully machine in a life time as a crash! FYI thats not a finger remover at just a 100rpm, that would be like being a mouse chased with a pissed off rolling pin!

Click to expand...

One indelible night, long ago..

Day shift foreman has stayed over to "demonstrate" to a card-carrier (eg: actually DO a Union Member's work, but within the bounds of the contract..) how to press a shaft into a driver with the ancient Niles 600-ton "wheel press".

"The usual" bushing about a foot of 10" diameter heavy-wall "hydraulic" tubing, faced, both ends. And - for lack of any interest in where it roosted, settin' next to it, the drop, faced only ONE end, saw-cut not so true opposite end, from back when we had cut all that.

"Somehow" Dick gets the old Dinosaur kerchunking its triple pistons way.. with the ever-so-slighty slanted drop as bushing instead of the one faced-true.

Which, of course, causes a massive axle to want to bind. USWA guy is just looking bored and sayin' little.

Foreman must have been up around the 400 - 500 ton pressure level when the old Niles finally tiddly-winked the slope-head bushing clear through the ten-inch concrete block wall adjacent the "cell" we ran that press in with the sound effects of a heavy artillery round and a leetle bit.. of a cloud of dust and concrete frag.

Union brother, was, of course, not even cracking a smile, just pretending to look puzzled, and stay helpfully "on-standby" for the next installment of "demonstration".

Pay was the same, after all, work or just watch the Foreman. No ear-buds nor "hand held" electronics, those days, so it weren't like we had cartoons or porn for entertainment or such, neither.

If I was turning that shaft I'd prefer a conventional three point steady. If that came out it would be a pretty interesting episode. Make sure you tighten the chuck really tight and the steady is set up perfectly. Steadies can encourage the job to begin walking out of the chuck if they're not set up correctly.

One guy I knew was turning a large chilled iron rubber mill roll in a " Craven " lathe. It must have been about 12 ft long and weighed over 5 tons ( 10,000 lbs ). He had it set up between the chuck and a large revolving centre in the tailstock.

For some reason he was finish turning one of the roll bearing journals with the saddle moving towards the tailstock instead of the conventional direction of tailstock to headstock. He'd casually left the tailstock wrench lying on the bed near the tailstock.
It was about 30 minutes for the cut to go from end to end so he sat down in his chair about 8ft away from the lathe and picked up the novel he was reading. It must have been a pretty good book because he didn't notice the saddle jam the wrench against the tailstock and start pushing the tailstock backwards !

I was working 30 ft and two bays away with two brick walls between me and the lathe. All of a sudden there was the sound of an almighty crash and the feeling of a large impact in the concrete I was stood on.

When I got to the lathe the roll was on the floor at the back of the lathe. The work light, coolant pipes, guard at the end of the cross slide were all mangled and the drip tray was flattened at the back. The operator didn't look too well and he was shaking a bit.

This particular lathe was back to back with another large " Craven " about 8 ft apart and I had the habit of just nipping between the lathes to get to other machines. That was the last time I did that.

The upshot was that a notice went up banning the reading of novels but you were still allowed to read magazines and newspapers if you had a long cut running.

Regards Tyrone.

Tyrone Shoelaces said:

The upshot was that a notice went up banning the reading of novels but you were still allowed to read magazines and newspapers if you had a long cut running.

Regards Tyrone.

Click to expand...

LOL! My ex once said that I shut out the world so firmly when reading I'd not notice if the house was burning down around me. I had to give that a bit of thought.

Said: "Not so. I would be taking peripheral notice. I just might not choose to let it distract me."

OTOH, read on the job? Never. Surely not with a spindle turning. Not even to check a blueprint.

Mind - some of that may have been due the USWA bargaining-unit aversion to being "multi-tasked". Couldn't let sneaky "company" get double work out of us for but one set of hours clocked!



Light up a Camel, put-back a tool, clear-chip, apply some oil or such was about all the leeway we got. Or wanted.

Bor-ing? Yah. In between the odd peaks of sweat and pucker-factor! Kinda averaged itself out.

You wanted to make more money, you pretty well had to switch from United Steelworkers to United Mine Workers, go chasing after coal in a deep mine running off rations a tad short of best safely practice.

We were proud to not be quite that desperate.