Workholding

Last Update: 29 October 2019

Another aspect of learning how to use your CNC router involves knowing how to properly secure material down to the bed of the machine. Rigidly securing material to the machine bed is crucial when setting up to cut. Some clamping methods are rigid but are more intrusive, while others keep a low profile but aren’t quite as strong. Play around with these methods to see which ones you can use individually or in combination for your ideal setup.

Screws

Screws

One of the fastest ways to hold down your material is to screw it directly into your wasteboard. All you need is an electric drill, the right bits, and screws to mount your workpiece. Just make sure that your machine isn’t going to run into the screws!

Tips:

  • If the part that you’re cutting out has holes, try separating your job to cut the holes first, then use the holes to put the screws to hold down your part. This works well if your piece is going to come loose after you cut your part out.
  • Make sure to use the right length screws to avoid having them punch through your table
  • When you remove the screws from the wasteboard, they may leave a bump. Make sure to scrape them down before your next job, as they can make the surface uneven. A paint scraper works well for this.

T-Tracks

T-Track Table

T-tracks allow you to insert a variety of clamps along their length, such as toe clamps, making it a very quick and versatile way to secure items to your bed. You can find aluminum t-track and compatible clamps online and at your local woodworking store.

 

Tips:

  • Putting t-track in then putting thicker MDF slats in between like in the photo allows you to mill off the surface of the MDF to get a perfectly flat surface relative to your machine. It also enables you to make smaller wasteboard replacements, instead of needing to replace the whole board.
  • If you have a thick enough waste bed, you can use your machine to cut the grooves for your t-track. Just cut grooves to fit the width of your t-track.

Inserts

Threaded Inserts

Screw-in threaded inserts especially ones that are designed for wood is a quick and easy way to add mounting points on your waste board for clamping. Common size inserts like for 1/4″-20 bolts are a good option if you want to make your own table with inserts and clamps.

Tips:

  • Program your machine to put evenly spaced holes. Make sure to check that your holes are the correct size before you perforate your whole wasteboard. Add a counterbore if you want to sink the inserts below your wasteboard.
  • An electric drill can be handy for installing the threaded inserts quickly after the holes are prepared.

Carpet Tape

Carpet Tape

One of the fastest and easiest options for securing your material and can be found in most hardware and department stores. Carpet tape has surprisingly sticky adhesive on both sides, and works best when applied to flat pieces of material with a large surface area. Using carpet tape usually eliminates the need for workholding tabs since the final part is kept held down by the tape.

An alternate to carpet tape can be painters tape which is attached to both the bed and the workpiece, then super glue with some activator placed in-between. This can sometimes provide an even stronger holding force than carpet tape can.

 

Tips:

  • Ensure surfaces are clean before applying the tape.
  • Press firmly on your material to ensure both surfaces adhere properly.
  • Water will often cause the tape to loosen its hold on the tape; keep this in mind if you are using coolant.

Hot Glue

Hot Glue

Recommended by Nathan C.

Hot glue is a great workholding option for both flat and irregularly shaped materials. When used properly, it offers a higher degree of strength than carpet tape while eliminating the need for workholding tabs. Parts can be removed from the bed with a paint scraper or peeled off by hand. Using hot glue can sometimes be tricky since an even layer needs to be applied to keep the workpiece level. With some practice however, hot glue offers a quick, cheap, and effective workholding option.

 

Tips:

  • Hot glue will sometimes take chunks out of your material, especially with foam and soft wood. You can prevent damaging your work by applying glue strategically in areas that are not cosmetically important or apply it in thin layers which are easy to peel off.
  • Hot glue hardens faster on metals (due to their high thermal conductivity) compared to other materials like plastic and wood.¬†When using metals, apply glue to a non metallic wasteboard secured on the bed and place the material on top to secure it so that the glue has a chance to stick to both surfaces.

Vises

Vises

Vises come in all shapes and sizes for hundreds of applications. Because of it’s parallel facing jaws, a vice is perfect for holding square or rectangular items, but can be used to hold just about anything. Vises offer extremely high clamping forces, which are needed when milling tough materials. A low profile, 4-inch, cast iron drill press vise like the one shown below works well for firmly holding materials.

 

Tips:

  • Tall vises will decrease the height that the Z axis can travel. Make sure to pick a suitable vise which allows for enough clearance.
  • ¬†Ensure the jaws of the vise are not in the way during the milling operation.