CHUCK
HOLDING POWER
INFORMATION
MAGNETIC CHUCKS
  & SINE PLATES

Holding power varies greatly, depending on the size and thickness of the workpiece, the contact area between the part and the chuck, the material the workpiece is made out of, workpiece surface finish and air gaps between the part and the chuck. Things that create air gaps are air, protective coatings, paint, galvanizing, oil, rust, dirt, etc.  Holding power falls off at the ends and sides of the chuck (where the frame is and therefore no magnets).  Under near ideal conditions at the center of the chuck, using a ground 1" X 1" X 1" cube of CRS, the following average MAXIMUM holding powers were found.
MAGNETIC CHUCK
or SINE PLATE TYPE
AVERAGE
MAXIMUM
HOLDING POWER
8866, A-xx-MS,
B-xx-MS, DMB
90-100 PSI
9195, MAI 35-50 PSI
EMC, EMCB,
ESP, ESPC
45-55 PSI
MC, MCB,
MSP, MSPC
40-55 PSI
MTC 12-18 PSI
RMC 30-35 PSI


The holding powers above should be derated, based on material and surface finish, using the tables below.



LEVEL OF SURFACE FINISH HOLDING FORCE
GROUND 90-100%
FINE MILLED 60-80%
ROUGH MILLED 40-50%
CAST FINISH 20-30%
MATERIAL HOLDING FORCE
NON-ALLOY STEEL 0.1-0.3% C 100%
NON-ALLOY STEEL 0.4-0.5% C 90%
NON-DISTORTING ALLOY STEEL 80-90%
GREY CASTING 40-60%
NON-DISTORTING ALLOY STEEL
HARDENED TO Rc 55-60
30-50%
AUSTENTITIC STAINLESS STEEL,
BRASS, ALUMINUM, COPPER
0%
VACUUM CHUCKS

In theory 14.7 PSI can be obtained with a vacuum chuck.  In the real world, under ideal conditions, using a ground workpiece with all unused holes completely masked off a MAXIMUM of approximately 10 PSI can be obtained.  Dirt, warped parts, a rough surface finish and other factors can reduce this significantly.