CNC/machining hold down clamp

CNC Hold-Down Clamp – Build Guide

Introduction

I designed this hold-down clamp to securely fasten materials onto the wooden surface of CNC mills without drilling holes or damaging the workpiece. This clamp can also be used for various applications such as sanding, milling, scoring, most things that need to be held down.

After testing different materials, I found that printing this clamp in Nylon PA-12 provided the best strength and durability. While I designed the model to be as robust as possible, the section holding the nut tends to break under relatively low pressure when printed in PLA, so I highly recommend using a stronger material.

👉 Important: When using the clamp, it must be screwed down to a stable surface such as a workbench, CNC spoilboard, or table to provide a firm hold.

Parts List

• 1x M6x40 bolt
• 1x M6 nut
• 1x M6 locking nut
• 1x M6 washer
• Nylon PA-12 (or another strong material)
• Superglue

Assembly Instructions

Print all parts – I recommend using a brim while printing, as PA-12 tends to warp. Once printed, clean up any excess material.

Install the non-locking M6 nut –

• The non-locking M6 nut should be glued into the clamping piece (the smaller part).
• Depending on the material and tolerances, the nut may fit tightly. In some cases, you may need to gently tap it into place or clean up the hole for a better fit.

Attach the knob –

• If possible, print the knob with a fuzzy skin texture for improved grip.
• Superglue the knob onto the head of the M6x40 bolt and allow it to fully cure.

Assemble the base –

• Insert the M6x40 bolt (with the knob attached) through the top of the base piece (the larger part).
• On the underside of the base, place the washer and then secure it with the M6 locking nut.

Attach the clamp piece –

• Align the clamp piece with the corresponding notches on the base and slide it into place.
• Thread the clamp piece onto the bolt.

Secure the clamp to your workspace –

• To use the clamp effectively, it must be screwed or bolted onto a stable surface such as a CNC spoilboard, workbench, or table.
• This ensures that the clamp remains fixed while securing your workpiece in place.

Fine-tuning for smooth operation –

• If the clamp action feels too tight or rough, lightly sand the notches to improve movement.
• A small amount of grease can be applied to ensure smooth operation.

Now your CNC hold-down clamp is ready to use! Simply turn the knob to adjust the clamp height and securely hold down your material.