Correct Shape For Steady Rest Fingers?

[cdhknives]

The old steady rest that came with my lathe has concave and deeply grooved/scored tips. I figure I need to regrind them for maximum surface contact. Roller bearing tips are a far off goal...

Most of what I see in pictures of new steady rests are convex. Is that the correct profile? It seems like so long as the concave end is of a larger radius than the workpiece I would get better contact and lube action from concave grinds...???

I have a belt grinder so I can set the platen to a fairly precise 90 degrees to the belt, so grinding the tip square to the work surface is no problem. I just want to know the tip profile for best work.

 

[rbjscott]

Most new one are flat that I have seen. Often machinist make replacements that are flat to begin with. On industrial lathes they are replaceable tips. A method to try (I always use this) Place a piece of emery paper between the work and steady rest jaws, grit toward the jaws or fingers. Catch the ends where the rest clamps together, Lube with way oil. You can also adjust the width of the emery for size. I know this sound strange but try it.

 

[Round in circles]

I gather that the aim is to have minimum points of contact to not only reduce friction loads on the motor & heat in the work piece but to also reduce the area that swarf might get caught up and mark a turned face. That's why the ends are usually rounded / bulbs

Roller bearing tips do suffer from the problem of picking up swarf /particles and embedding them in the work piece unless you have cutting fluid constantly washing them off.

Roller bearings with some sort of nylon tyre on them don't usually give enough support to the work piece & they always need to be perfectly aligned square with the work piece where as it does not matter so much with the rounded ends of the bras ones . I guess you could put brass tyres on the bearing types and form the edges over to retain them on the bearings

 

[rbjscott]

I have not seen the contact area reduced in size. It seems that you would need a larger contact area to reduce load or spread it out. Only time you would reduce the area is for a special needs. The new small lathes I have looked at have tapered tips. I don't know if I agree with the design, Opposite of what I have done for many years.

 

[John Hasler]

I gather that the aim is to have minimum points of contact to not only reduce friction loads on the motor & heat in the work piece but to also reduce the area that swarf might get caught up and mark a turned face. That's why the ends are usually rounded / bulbs

Roller bearing tips do suffer from the problem of picking up swarf /particles and embedding them in the work piece unless you have cutting fluid constantly washing them off.

You could install wipers running ahead of the rollers.

 

[rbjscott]

Roller steady rest tricks. Make a card board shield that fits over the shaft and fits snug in the rest. Use string to keep in place. A lot of rest are fitted with a small pipe that runs coolant on the fingers or rollers. This washes away swarf and cools material being turned as well as the fingers. Coolant also acts as a lubricant. As you work on a shaft the rest and shaft get hot, with a cooled rest. Keeping up with rest tightness is not as critical.