CENTERLESS GRINDING ADJUSTMENTS

 

Thrufeed and Infeed corrective adjustments of the centerless grinder that lend themselves to precision grinding.

 

Burn marks on workpiece

(1) Insufficient cutting fluid on workpiece 

(2) Dull or flat diamond 

(3) Wheel too hard

(4) Cutting on trailing edge of the wheel

(5) Grinding wheel dressed with too slow a diamond traverse rate

 

Chatter on part

(1) Work too high above center 

(2) Wheel out of balance

(3) Blade angle too steep (30 deg. standard) 

(4) Too thin or a warped blade

(5) Machine leveling screws not adjusted for even torque

(6) Glazed wheel caused by dull diamond, too hard a wheel, too fine a grit size or too slow a dressing rate

(7) Outside "Floor Harmonics" (vibration) 

(8) Motors out of balance

(9) Grinding wheel mount fits loosely on spindle

(10) Too heavy a stock removal 

(11) Blade not properly clamped

(12) Too long a blade being used for width of wheel

 

Dull diamond

(1) Diamond nib not turned periodically

(2) Excessive infeed of diamond

 

Erratic sizing

(1) Gibbs not properly adjusted on upper and lower slides

(2) Wear in infeed screw and nut

(3) Infeed lever not held tight (for thrufeed work) 

(4) Soft wheel 

(5) Insufficient lubrication on lower slides (infeed)

(6) Improper tension on backlash spring  

(7) Loose work support blade

(8) Parts overheating under cut due to improper wheel or insufficient flow of cutting fluid

(9) Regulating wheel camming 

(10) Work improperly roughed

 

Feed lines on part

(1) Grinding wheel not relieved on exit side 

(2) Work guides improperly set    

(3) Cut improper across wheel face

(4) On long bar fixtures-excessive pressure on work by roller hold-down

 

 

Finish

(1) Improper wheel grade

(2) Dirty or insufficient cutting fluid 

(3) Setup not correct  

(4) Too fast a diamond dressing traverse

(5) Erratic movement of truing attachments 

(6) Pick-up on blade

(7) Blade not tight in work rest 

(8) Blade angle too steep

(9) Unbalanced wheel 

(10) Loose, cracked or dull diamond

(11) Oil on face of wheel 

(12) Regulating wheel not tight on its mount

(13) Work too high above center

(14) Regulating wheel SFMsave

 too high

 

Fish tail marks on part

(1) Dirty cutting fluid

 

Grinding wheel problems

(1) Too hard

(a) May cause burn marks, heat checks, cracks, or glazing

(b) Can cause squeal or produce chatter

(c) Soft materials may "load" wheel

(d) Sizing trouble, due to no spark out

(2) Too soft

(a) Sizing trouble, because wheel breaks down rapidly

(b) Chatter may develop

 

Height above center of workpiece

(1) If too high chatter can develop

(2) Optimum rounding action will not occur if center height is too low

 

Intermittent cut

(1) Grinding wheel not correctly trued

(2) Regulating wheel "camming"

 

Jumpy truing device

(1) Air in lines (hydraulic)

(2) Gibbs adjusted improperly

 

Loading of  grinding wheels

(1) See grinding wheels

(2) Wheels too fine. Larger grain size allows more chip clearance.

(3) Ineffective cutting fluid due to the lack of lubricity of cutting fluid chips adhere to grit of wheel. Change to coolant with greater lubricity or increase amount of concentration in mix.

 

Low ends on work-chamfered (Barrel Shaped)

(1) Work guides deflected toward regulating wheel

(2) Face of regulating wheel not straight at work contact point. (Truing device worn or not set to proper angle)

 

 

Low center-High ends

(1) Work guides deflected toward grinding wheel

(2) Same as No. 2 above

 

Nicks in workpiece

(1) Do not drop parts into tote pans. Provide bumpers to cushion work

 

Out of round work

(1) Out of balance workpiece

(2) Work not high enough above center

(3) Workpiece bowed           

(4) Regulating wheel not dressed round

(5) Regulating wheel loose on mount

(6) Blade angle not steep enough

(7) Not enough stock to round up

(8) Regulating wheel speed too slow

(9) Interrupted cut due to keyways, holes, flats, etc.

(10) End stop or ejector may be worn on locating surface

(11) Grinding wheel off grade

(12) Flat diamond

 

Pick-up on blade

(1) Cutting fluid not lubricating work-to-blade contact point. Use cutting fluid with greater lubricity or increase concentration.

(2) Blade material (use cast iron or bronze blade)

 

Regulating wheel "camming"

(1) Collet screws loose

(2) Bearings worn

(3) Regulating wheel spindle eccentric or out of round

 

Sizing

(1) See erratic sizing

 

Spiral chatter

(1) Hard spots in wheel

(2) Chipped edge of wheel

(3) Loose machine elements

 

Straightness

(1) Work not straightened sufficiently before grinding

(2) Insufficient grinding stock left on workpiece

(3) Too much stock removal on first pass

(4) Wheel not cutting freely. (Part heats up, relieving internal stresses causing part to bow.)

(5) Insufficient cutting fluid (same thing happens as No. 4 above)

 

Taper

(1) Work guides not set properly

(2) Dirt under work rest or blade

(3) Loose gibbs  

(4) Failure to keep parts butted end to end on thrufeed

(5) Too much feeding pressure (race-grinding fixture)

(6) Non-uniform spark-out time from one piece to the next

(7) Wheel not cutting freely (surface temperature expands part behind leading end. This results in tapered part with leading end high.)

 

Vibration

(1) Check outside sources   

(2) Leveling screws not snug against floor

(3) Motors not balanced or drive belts too loose

(4) Faulty hydraulic  pump transmits  pressure vibrations to

 

 

Warped work (usually long bar or tubing)

(1) Insufficient flow of cutting fluid

(2) Wheel cutting inefficiently. Dressed too fine or too small grit size.

(3) Workpiece not straightened before grinding