There is nothing more frustrating than completing a lengthy DIY CNC design cut, only to find the wood or aluminium material block has moved during the program – rendering the material and entire project cut-out attempt useless.
We “clamped down” on this problem long ago in our DIY workshop, but we always like to remind new CNC machine builders that you can never have too many clamps on hand.
The problems extending from small amounts of material slippage on a CNC table are often the hardest to identify. The problems are often blamed on other machine components, such as faulty CNC motor driver controllers, slipping shaft joints, structural flex, or backlash.
We’ve found that many of these DIY workshop problems are solved by having ample clamps and clamping positions available for use on the machining table. This ensures your projects stay securely in place and that they are cut correctly every time.
Hold down clamps in themselves are cheap and easy to make. Three to six clamps made of 5-7 mm thick steel with a slight bend at one end (coated in a tough powder coat paint), is usually enough to hold wood or aluminium material blocks firmly in place for most projects. Being made of steel, the clamps have some inherent ‘springiness’ in them making them easy to place on and off a part (unlike block aluminium clamp alternatives).
Making the ‘easy turn’ DIY knobs for your CNC machine clamps is also super easy …. using your CNC machine!
With our free g-code, dxf and crv files available for download, you don’t even need to design the knobs yourself. You can download the files and import them into your CNC machine design software right now!
The downloadable knob design provided is sized for M8 bolt heads (ie: bolt shaft diameter 8mm, head hex width 13mm) embedded in 13mm thick high density plastic material, but the basic CNC machine g-code or crv design file (for Ventric and other compatible design software) can easily be resized, recoded, or redrawn to suit other bolt sizes and material thickness’s.
Cut the CNC clamp knobs out of any tough, high density plastic.
Once cut, slide the knob design onto a bolt and gently hammer the bolt head into place.
(Tip: To make this easier, put the bolt through the hole in the plastic and dangle the bolt shaft through the gap of a workshop vice. Line the bolt head up with the orientation of the hexagonal shape on the plastic knob. Then, while resting the bottom of the knob on the top of the vice jaws, gently knock the bolt down into place.)
After mounting the knob on the bolt, a little extra shaping and finishing off is usually required. This is best done using a soft workbench mounted buffing (grinding) disc.
An even curve from the center shaft to the tip of each grip ‘arm’ can be achieved by letting the shaft of the bolt rotate smoothly in your hand as it is carefully buffed on the grinder pad. An even convex shape on the bottom surface of the knob stops the knob ‘arms’ hitting the steel clamp as the bolt head is turned and tightened down.
(We could have done a complete 3D CNC design for the entire knob, but 3D items usually take much (much!) longer to CNC cut. Manual workshop techniques are often far faster and more efficient than relying on the digital world for everything!)
As a handy aside, we also occasionally produce smaller DIY knobs in our workshop in a similar way. These are just as quick and easy to make as the CNC clamp knobs above. We find it is easier and cheaper to make them on our machine than to run to the DIY shop.
Once the nut knob designs are cut by CNC machine, we place a dab of glue on the surface of a nut and hammer it firmly into the plastic design.
We thread a bolt into the nut to make a temporary handle and form the convex shaping of the grip ‘arms’ in a similar way as with the hold down clamp knobs above.
Only a small amount of time and effort is required to make DIY hold down clamps and nut knobs. All going well, it is easy to have a handful of knobs in just 10-30 minutes. They work just as well as professionally produced and somewhat more expensive alternatives!
If you want differently styled knob designs, it is usually a quick task to generate the CAD or vector design and to then flip it into g-code for your CNC machine.
As a final word, if you want CNC clamp knobs which are easy to use, stay with only three or four ‘knob arms’. Any more and it is harder to twist and tighten , especially when wearing work or Winter gloves.