Follower rests---Forces in play while turning/threading a slender shaft

Question about if one were turning a slender shaft in an engine lathe, and using a follower rest: Which jaw would be taking the greatest thrust? The upper or the opposite jaw of the follower rest?

Does anyone have data? I'm now curious as to whether to force deflecting the work back away from the cutting tool is stronger than the force of the work trying to climb up on the tool, or vice-versa......

Why all the variance in design when it comes to this attachment? I've seen them "plain" that had one jaw perpendicular to the lathe tool, and one dead opposite. I've seen others that had the top jaw tilted toward the operator, and the back jaw angling up from below center to meet the workpiece. Other variances I've noted as well.

Seeking: Thoughts, experience, knowledge, plagiarized responses from reference materials at hand (naaaahh, not on THIS board!)??? --- anyone.......?

Thanks,

Richard

cant say I learned this from any books but from lots of experience I would say it is probably about equal.Might push back a little more if tool wasnt sharp.
The cutting action is a shearing action and it takes alot of pressure to shear as it lifts the metal.It would really matter the size of the stock being cut also.You would have gravity helping to hold the shaft down if the shaft was substantially larger.Just my opinion. Jim

Hi Guys,
I made a few steadies ( 600mm 3 point )
(200mm traveling) with a choice of anvils ie
hardend, bronzes, cam followers, vesconite
and a few others. I looked at the config of a rollerbox of a 3a Ward. They all worked
well. I maintain that the pressures should be equal and usually try and keep the shavings to flow away from the wear pads.
When doing heavey cuts with negative tools,
I use cam followers. Finishing I go for
positive if I can't otherwise 04 rad with
hard points give less vibration and use the coolant to lubricate and keepem clean.
Anyway, rollerboxes work hard and well so I
think that is what made me choose that setup.
Andy

Look at a well used follow rest and compare the wear on each bearing.

if serious bed wear is present ,would think the steady would tend to help truth by bending shaft as carriage drops thereby imparting more thrust in vertical plane.......
best wishes
docn8as

Yes, in a follower rest (Travelling Steady) there is a force pushing away from the tool and a force pushing up as a reaction to the cut.

Thes forces are changeable and not predictable.

They are the product of:

The shape of the tool
The keenness of the tool
The tensile strength of the material
The cutting speed
The rate of feed

A cut might be analyzed by finding values for all of the above and setting these values up in a group of simultaneous eqations and solving them.

The solution would be good for only one cut.

Lathe work is a fine craft. it stubbornly resists mathematical analysis, but it yields gracefully to the sklled and patient hand.

Follower Rests? Mess around with them, try all kinds, you'll find one that works nice.

It's Lathe work.

doc said:

if serious bed wear is present ,would think the steady would tend to help truth by bending shaft as carriage drops thereby imparting more thrust in vertical plane.......
best wishes
docn8as

Click to expand...

I know this effect, very well

So much so I had to use vise grips to un wind it at the chuck end. Compliments of a 'just do it' attitude from above.