The phrase “Skate or Die” got popular in the 80′s and although most of society would choose the Die option, this week’s shop tip borrows a page from the rolling reckless among us and courtesy of Pierson Workholding, a manufacturer of vacuum chucks.
A skateboard is a pretty simple device, but an easily overlooked component known as “grip tape” is extremely important when it comes to performance. To the non-thrasher mind, grip tape is simply sandpaper adhered to the deck of the board that adds traction between the board and the rider. So what’s this got to do with vacuum workholding? Let’s dig deeper…
All vacuum chucks work on the principle of removing the air that exists between a workpiece and the vacuum chuck. It is actually the air pressure around us that pushes the workpiece down as it tries to fill in the vacuum gap. Because of this, smaller workpieces are held with less force. For example, a 12″ square workpiece will be held with over 2,000 lbs of pressure, but a 4″ square workpiece will only be held with just over 200 lbs. That’s not nearly enough to hold a part securely and expect to mill the profile with normal feeds and speeds. The part will most likely slide laterally from the cutting forces and eventually kick-flip off the chuck.
Let’s get back to the grip tape. Simply sandwich a piece of fine grit waterproof sandpaper (400 – 600 grit) between the workpiece and vacuum chuck face up and the traction between the two will be multiplied exponentially. This greatly reduces any chance of lateral movement of the part. Fine grit sandpaper also has a very consistent thickness of around 0.008″. This means the part will be lifted just enough so you can finish the perimeter at full depth without cutting into your vacuum chuck.
Give this week’s tip a try and skate your way to more effective vacuum workholding.