What is the feed constant for my hobbing machine?
Feed formulas are found in the machine’s manual or on the machine itself. Table Feed as discussed here is the cutter table feed in a direction parallel to the workpiece centerline. It should not be confused with infeed or tangential feed. While some hobbing machines may be equipped with infeed or tangential feed, all hobbing machines are equipped with Table Feed. Some hobbing machines mark the machine with a whole number indicating feed (let’s call it K). If your machine or machine manual uses a whole number (e.g. 6 or 8 or etc.) for K then the units are “Revolutions of workpiece per inch of table travel” when feed gears are 1:1 ratio. CPC-HOB software uses the inverse number (1/K), where the units are “Inches of table travel per revolution of workpiece” (with 1:1 feed gear ratio). Thinking of it another way, 1/K is the number you would divide into actual hob table feed to get the machine’s feed change gear ratio. Your manual may show a feed ratio formula to be:Table feed = Gear ratio
