1. Steady Rests, Follower Rests, and Mandrels
Unit 56

2. Steady Rest
Used to support long, slender work and prevent it from springing while being machined between centers or when machining end of workpiece held in chuck
Fastened to lathe bed; three jaws provide support
Usually soft material to prevent damage to work
Others have roller attached to jaws for support

3. Procedure to Set Up a Steady Rest
Mount work between centers OR set up and true work in chuck
If work not round, turn true spot on diameter at point where steady rest will be supporting work
If impossible to turn true diameter because of workpiece shape, mount and adjust a cathead on the work

4. Move carriage to tailstock end of lathe
Place steady rest on lathe bed at desired position
Adjust lower two jaws to work diameter, using paper feeler to provide clearance between jaws and work
Slide steady rest to desired position and fasten it in place
Close top section of steady rest and adjust top jaw, using paper feeler

5. Apply suitable lubricate to diameter at steady rest jaws
Start lathe and carefully adjust each jaw until it just touches diameter
Tighten lock screw on each jaw and then apply suitable lubricant
Before machining, indicate the top and front of the turned diameter at chuck and at steady rest to check for alignment

6. Follower Rest Mounted on the saddle
Moves along with carriage to prevent work from springing up and away from cutting tool
Positioned immediately behind cutting tool
Can be used to support long work for successive operations (such as thread cutting)

7. Procedure to Set Up a Follower Rest
Mount work between centers
Fasten follower rest to saddle of lathe
Position cutting tool in toolpost so that it is just to left of follower rest jaws
Turn work diameter, for approximately 1.50 in. long, to desired size

8. Adjust both jaws of follower rest until they lightly contact turned diameter
Tighten lock screw on each jaw
Lubricate work and follower rest jaws to prevent marring finished diameter
If successive cuts are required to reduce diameter of workpiece, readjust the follower rest jaws as in steps 4 to 7

9. Mandrel
Precision tool that, when pressed into hole of workpiece, provides centers for a machining operation
Valuable for thin work (flanges, pulleys, etc.)
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10. Characteristics of a Standard Mandrel
Mandrels hardened and ground and tapered .006 to .008 in./ft
Nominal size near middle, small end .001 in. under; large end .004 over nominal size
Both ends turned smaller than body and provided with flat to keep lathe dog from damaging accuracy of mandrel
Size of mandrel stamped on large end
Center holes large enough to provide good bearing surface and to withstand machining strain

11. Solid Mandrel Available for most of standard hole sizes
General-purpose used for variety of workpieces
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12. Expansion Mandrel
Consists of sleeve, with four or more slots cut lengthwise, fitted over solid mandrel
Taper pin fits into sleeve to expand it to hold work
Another form has slotted bushing fitting over tapered mandrel
Increases range
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13. Gang Mandrel
Used to hold number of identical parts for machining operation
Body parallel and has shoulder or flange on one end; other end threaded for locking nut
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14. Threaded Mandrel Used for holding workpieces having a threaded hole
Undercut at shoulder ensures workpiece will seat squarely
Not Canted on threads
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15. Taper-Shank Mandrel May be fitted to tapered hold in headstock spindle
Projecting portion may be machined to any desired form to suit workpiece
Often used for small workpieces or those that have blind holes
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16. Procedure to Mount Work on a Plain Mandrel
Secure mandrel to fit hole in workpiece
Thoroughly clean and apply oil
Clean and remove any burrs
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17. Press mandrel firmly into workpiece
Start small end of mandrel (large end has size stamped on it) into hole by hand
Place work on arbor press with machined surface down so hole is at right angles to table surface
Press mandrel firmly into workpiece
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18. Procedure to Turn Work on a Mandrel
Fasten lathe dog on large end of mandrel
Work held in position by friction
Clean lathe and mandrel centers and mount work
Use paper feeler between toolbit point and mandrel for setting toolbit (facing entire side)
When turning outside diameter of work, always cut toward large end of mandrel
Take light cuts to prevent work from slipping on mandrel on large-diameter work

19. Eccentrics
Shaft that may have two or more turned diameters parallel to each other
Not concentric with normal axis of work
Used in locking devices, in feed mechanism on some machines, and in crank shaft of automobiles
Where necessary to convert rotary motion into reciprocating motion

20. Eccentric
Amount of eccentricity (throw) is distance set of center holes has been offset from normal work axis
If center holes offset .250 in. from work axis, amount of throw would be .250 in and total travel of eccentric would be .500 in.

21. Three Types of Eccentrics
When throw enables all centers to be located on ends of workpiece
When throw is too small to allow all centers to be located on workpiece at same time
When throw is so great that all centers cannot be located on workpiece

22. Procedure to Turn Eccentric with a .375-in. or 10-mm Throw
Place work in chuck and face it to length
If center holes are to be removed later, leave work .750 in. longer
Place work in V-block on surface plate and apply layout dye to both ends of work
Set vernier height gage to top of work and note reading
Subtract half work diameter from reading and set gage to this dimension

23. Scribe centerline on both ends of work
Rotate work 90º and scribe another centerline on both ends at same height-gage setting
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24. Lower or raise height-gage setting. 375 in
Lower or raise height-gage setting .375 in. and scribe lines for offset centers on both ends
Carefully center-punch four scribed centers and drill center holes in each end
Mount work in lathe and turn diameter with true centers
Set work on offset centers and turn eccentric (center section) to required diameter

25. Procedure to Cut an Eccentric With a Small Throw
Cut work .750 in. longer than required
Face ends and drill one set of center holes in lathe
Mount work between centers and turn large diameter to size
Cut off ends to remove center holes
Lay out and drill new set of center holes, offsetting them from center position to required throw
Turn eccentric diameter to size

26. Procedure to Turn an Eccentric With a Large Throw
Set work on normal centers and turn both ends to size
Secure or make set of support blocks.
Hole in support block should fit turned ends snugly
Align both support blocks parallel on work and lock them in position
Counterbalance lathe to prevent undue vibration
Turn various diameters as required

27. Setup Required for Turning an Eccentric with a Large Throw
A setscrew in each block used to securely fasten support blocks to the work. The number of centers required should be laid out and drilled in the support blocks.
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