Introduction: CNC Soft Jaw Vice

About: I make things and share videos of the builds on youtube.

I have an ooznest ox cnc and found that for some jobs I really wanted a vice to hold material. Fancy CNC vices are very expensive things so I decided to make my own.

This vice cost about £10 in parts.

Tools required:


Drill press

Material required:

~1.5m of 25mm box section

~200mm flat bar stock

~30cm of threaded rod

9 nuts

Step 1: Watch the Build Video

This is my youtube video of making this vice... read on for the steps.

Step 2: Cut the Box Section Lengths

First you need to cut the box section to the pieces you need.

the photo shows the basic layout we're going for. you need 4 pieces of the same length for the jaws. I made mine about 200mm long, but you can pick whatever suits you.

You also need 2 pieces of the same length to make the base 'rails' of the vice. This dictates how much you can open the jaws which relates to your total holding capacity. I made mine so that I could hold about 250 mm length wise.

You then need 1 length for the front of the base rails, that needs to be 75mm so that you space the base pieces apart so that one box section width will fit between. The other end will be held apart by welding the fixed jaw to it.

2 lengths as 'feet' for the vice, these will run along the sides and hold the whole vice slightly above the workbench. these can be any length really, they just need to be long enough to provide space to screw the vice down to your cnc bed.

The last piece of box section you need is going to be welded a 90degrees beneath the moving jaw that holds it in the 'rails'

Finally some sections of flat bar stock that will hold the moving jar from lifting out of the rails, and one section will hold the end of the threaded rod.

Step 3: Weld the Jaws and Rails

Weld the 2 pairs of 'jaws' to create 2 faces which are double height of box section.

Weld the 'rails together with the end pieces to hold them the right distance apart.

Step 4: Create the Mounting Points for Soft Jaws

To do this drill holes in the face of both your fixed and moving jaw. I used 4 on each face. You don't want these too close to the top of the jaws.

Drill the holes large enough to accept some nuts, which you can then weld in place . Then grind the surface as flat as you can get it.

Picture shows what you should have at the end.

Step 5: Weld the Fixed Jaw and Base Rails

Weld the fixed jaw to one end of your base rails being careful to keep the rails apart enough to accept a length of box section between them. Weld your 75mm length to the other end.

Step 6: Moving Jaw

You now need to setup the moving jaw. First weld on a 90 degree lenght of box section to the bottom that will fit between the bottom rails.

Then you need to take a short length of flat bar stock, drill a hole in the center large enough to accept your threaded rod, then bend it so that you can weld each end to the back of the moving jaw leaving a gap for the head of a threaded rod to fit through.

IMPORTANT - you need the threaded rot to be in place before you weld this section to the back of the moving jaws. The point is to trap it in there.

I welded a washer onto the end of my length of threaded rod to give it a head.

Once you have the moving jaw with threaded rod assembly, you can weld a nut to the back of the rails. This allows you to drive the moving jaw back and forth by turning the threaded rod.

The video shows where you should end up

Step 7: Weld on Retainers for the Moving Jaw

I found the moving jaw wanted to lift out of the rails a little, so I welded some short lengths of flat stock on the bottom to hold it i n place. For this I used some washers as spacers to avoid welding it too tightly to the rails

Step 8: Attach to Cnc Bed

I welded a length of square section along each side of hte rails and off-set slightly down so they would act as 'feed' and hold the rails clear of the workbench.

I had drilled holes in either end of these lengths to that I could screw them down to whatever surface I needed to.

For me I placed my CNC machine onn mdf board, and used some angle brackets to secure the frame of the cnc to the wooden base. This ensured that the CNC would not move relative to the board. I then screwed the vice down to the board between the frame of the CNC.

This allowed me to ensure the vice would always be in the same position relative to the machine.

Step 9: Create Soft-jaws

For this I created a model in fusion 360 to just lay out the holes that matched up with the locations I welded in the nuts to the jaw faces. The model drills out a recess enough to fit a bolt head so that it will be beneath the surface of the wooden jaws. This also means it is easy for me to create new sets of these jaws when I need them.

Bolt the softjaws into the vice. I tend to leave mine with extra material at the top so I can use the vice itself to face them down to the height I'm expecting.

Step 10: Mill Custom Supports

In the picture you can see that I have milled the top surface of a shape, and I have already prepared the soft jaws of the vice with the same shape so that I can turn over my awkward shape and clamp it securely in the vice.

Now you have a vice that gives you the ability to make custom work holding for strange shapes and allow you to mill accurately on both sides!