Offers over lock machines.Model 81-63 thread over lock machine1 needle, 3 thread over edger for blind stitch hemming & plain seaming, can be made 2, thread also. Model 81-33 thread over lock machinesame as 81-6 but for plain seaming & serging on medium to heavy weight fabrics. presser foot lift : up to 5 mm stitch length : up 3.2 mm stitch width : 3 to 4 mm speed : 3600 rpm needle : dc x 1#11.14, 16, 18.