Designation
                
                With shiled :638
	                
                
                Open type :638ZZ1
	                
                
                With seal VV :638VV
	                
                
                With seal DD :638DD
	                
                
                Principal dimensions(mm)
                
                d :8
	                
                
                D :28
	                
                
                B :9
	                
                
                B1 :9
	                
                
                r(min) :0.3
	                
                
                Basic load ratings(N)
                
                Cr :4550
	                
                
                Cor :1970
	                
                
                Basic load ratings{kgf} 
                
                Cr :465
	                
                
                Cor :201
	                
                
                Speed ratings(rpm)  
                
                Grease
                
                ZZ :28000
	                
                
                D·D :22000
	                
                
                Oil 
                
                Z :34000
	                
                
                Abutment and fillet dimensions (mm)
                
                da(min) :10
	                
                
                db(max) :12.8
	                
                
                Da(Max) :26
	                
                
                Db(min) :22.8
	                
                
                ra(max) :0.3
	                
                
                rb(max) :0.3
	                
                
                Weight(g) 
                
                Open type :28.3
	                
                
                With shiled :28.6