Workholding is all about holding parts. There are many different ways to hold parts in the lathe, milling machine and when doing hand work on parts.
Centering and Aligning – sometimes it is worth the time to machine a part to make centering on the rotary table that much easier.
Clamping Kit – the mainstay for any milling machine is a set of nuts, bolts, clamping bars and jacks. This is a 12mm clamping set: note that this dimension of 12mm relates to the width of the open slot in the table.
Over the years I’ve gradually added to this basic set with more T-nuts that I’ve bought and made.
Holding a Disc of Material in a mill vice. For the fire grate on the vertical boiler project I made an aluminium recessed jig that would clamp the edge without damaging the part.
Machining Pewter Buttons – Perhaps less about machining pewter buttons and more about holding them so we could. The pewter buttons have been cast in an open one-sided sand mold.
Engineers Vice – one of the basic pieces of equipment you need in the workshop. 3″ wide jaws and the more sturdy the vice the better it is. A quick release mechanism is a great addition. These aluminium jaws have grooves to locate items that you’re clamping. Also, they have magnets embedded into the back of each so that they snap onto the steel jaws of the base vice.
This is designed to work on the milling table and with minimum intrusion to the working space. The only downside with this initial design is the low-ish clamping forces.
Finger Plate – A flat plate with a clamping mechanism that allows you to hold small parts so that you can file, saw, polish.
The one in the image is described in detail in the article.
The groove allows you to locate round bars and then work with a file, drill or emery cloth.
Milling is all about maximising the stiffness with which you can hold parts and so a solid vice is a must. I use a Soba Vice for my Sieg SX2.7 as this is a great balance between bulk and capability. The alternative is to use a precision tool vice, more care is needed setting it up and not as general purpose as the milling vice.
A useful tool for holder small drills that you want to operate by hand and with minimal force, but also useful to hold a round part accurately and sturdy enough that you can grip it firmly.
If you’re holding parts in parallel in the machine vice then sometimes the jaws will lock out on one part and the other part will not be clamped as firmly. One way around this is to use a thin shim of aluminium as this will give a small amount of compliance and allow the vice to clamp both parts.
The image shows two pieces of mild steel clamped for end milling with the aluminium shim sticking up above the jaws.
Stevensons 1-2-3 Blocks – these are useful if you want to raise a part up off a milling table or to add extra support.
These allow you to accurately locate and hold a rod for drilling or machining. In the image I’m drilling the hole for the gudgeon pin in an aluminium piston. 1 of 5 parts that had to be all the same.
One method of machining washers.
- drill holes in sheet material
- roughly cut out
- clamp all on a mandrel
- turn outer diameter.
I used this technique very successfully to make a set of soft copper washers.
Getting a good finish is all about reducing vibration. This means ensuring the milling machine itself is stiff and the workpiece.