Hold-Downs for Machining Small Hardwood Pieces
CNC operators suggest various ways to hold boards down for machining flutes and other profiles. June 26, 2006
Question
We have a flat table router and need to do some fluted boards and other hardwood pieces. How do you do things like this with a vacuum table? Really don't want to use the pods unless that is the answer. My thought was routing out spots for the hardwood boards to lay in, in a sheet of MDF, and use it like a fixture. Our vacuum is 40hp, but not sure if the vacuum will be enough under the machining.
Forum Responses
(CNC Forum)
From contributor K:
For most solid wood parts, we use a combination of the vacuum sucking through the spoil board and some hold-down clamps attached to the ends of our pop-up pins. The hold-down clamps consist of 1/2" thick by 1 1/2" wide aluminum bar stock. Our pop-up pins have a tapped hole in the top, and we run a bolt through the bar stock, into this hole. Our pins are moveable, so we simply adjust them to where the attached aluminum clamps won't interfere with the machining process. When we start the program cycle, the pins retract, and the clamp nails the part to the table with tremendous force. Works like a dream!
From contributor A:
I use a combination of the vacuum as well as blocks and tapered wedges screwed right to the spoil board - it is simple and fast, especially for things you may only do once.
From contributor R:
Sometimes all that is needed is a few strips of double faced carpet tape.
From contributor S:
We use glazing tape from the glass supply place to form a gasket that is close to the shape of the finished part, then drill a 3/8" hole through the bleeder board to get more direct vacuum. If this is a repeat project, you can make a dedicated fixture out of scrap MDF or particleboard that has gasket on both sides and reuse it. Sort of like making your own pods. When finished, fill the 3/8" hole with bondo, hot glue, or cover it with masking tape.
From contributor B:
A very simple low tech solution is to place the board to be fluted on the center of a 4x8 sheet of material. Screw through the back of the 4x8 into the back of the board to be fluted. Then you can run your system as always, holding the 4x8 in place. You can mount as many boards onto the 4x8 as needed. Only real issues with this are time involved to do the setup and accuracy of positioning. You would have to determine if those can be overcome with regard to the project.
From contributor C:
I cut the flutes and the edges so all lines up and the part is finished at the CNC. I sometimes cut out for electrical outlets also. I use 3/4 inch MDF with gasket and holes to a vac port in the table. With solid wood, I rout the end grain first. It works great.
