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Holding The Workpiece

Holding the workpiece

It is essential that the work is held securely before you start any routing operation, otherwise you will have great difficulty controlling the path of the cutter and risk damaging the work. At worst, it may be spun off violently with potentially disastrous consequences for you, the work, the cutter or the router itself.

There are literally dozens of ways of clamping the work, using a variety of strategies depending on the type of work and the cut you are trying to perform. You can use many of the traditional methods like G-cramps, bench dogs and vices, but also add to these a wide range of homemade devices such as folding wedges, cams and pegs or even a purpose made workboard. Sometimes you may have to combine several clamping methods for particularly awkward jobs.


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The aim is to get secure clamping but at the same time minimising any interference with the path of the router or side-fence, which is not always an easy compromise. You also want to be able to clamp quickly, particularly if there are lots of components to machine, so over-complicated set-ups are best avoided.

Whatever method of clamping you choose, remember that you need to protect the work from any damage. Use pads of MDF or cardboard underneath any metal jaws,
though many specialist cramps are now fitted with plastic shoes for this purpose.

Wherever you work you need a stable and rigid working surface, preferably quite high up, so you don’t need to stoop too much to see what is going on.

 

In the workshop this can be your normal workbench, or if space allows, you can make a dedicated router bench with that all-important extra height and built-in provision for a range of different holding devices.



Tip

You will find a dial caliper another invaluable aid for checking both inside and outside measurements. The dial type are not prone to subjective interpretation, you just read off the measurement. An expensive engineers type is not necessary, as you often only use comparative measurements rather than high precision ones.

Tip

In many situations, the use of a special router mat will provide all the support you need. link     This has a specially designed rubbery consistency that resists slipping. Just lay it on the bench, drop on your work and away you go. Being so simple and effective, a router mat is always my first choice for holding small components, but it maybe less effective on bigger pieces.

Traditional bench vices are only suitable for holding pieces that can project clear of the jaws, but they are useful for edge work on large boards if you can provide some additional support to stop them pivoting.

A tail vice is the most versatile as you can use it in conjunction with a variety of bench dogs to hold flat work.

One very handy trick is to use a sash cramp gripped in a bench vice for holding a workpiece by its ends, but make up a couple of wooden saddles to support the work and stop it twisting over

A standard G-cramp will often suffice if the wood has to be held flat on the bench, but you will need plenty of overhang on the bench top so you can locate it well clear of the routers path. 

Although you can exert great pressure with a G-cramp, they are slow to use as their screw action takes some time to adjust to different openings.

Quick action clamps are probably a better option as you can adjust the clamping width in just a few seconds. They are also available in a huge range of sizes, up to really big ones for clamping doors and the like. I particularly favour the type that you can operate one handed, enabling the user to secure a guide batten onto the work at the same time.

End socket cramps are a great way to secure fences and stops but leaving the surface free of any obstruction. However, you need to drill a 9mm hole to locate them and the minimum recommended material thickness is 18mm.

Toggle clamps are available for either top or side clamping. They can be screwed directly to the bench or to a special workboard and are particularly useful for repetition jobs as they allow the work to be positioned quickly and then secured.

They will accommodate work up to 60 mm in thickness and their low profile means minimal interference. Quick release mounting plates for use with toggle clamps allow rapid repositioning of the clamp and often reduce the number of clamps required.

Workboards are the most convenient way of holding small pieces, and you can design one to take a range of different fences, stops and holding devices. They are easily made from pieces of MDF or laminate covered board and are secured by screwing a batten to the underside which can then be gripped in the vice. For extra versatility, drill holes in the board to take pegs or cams, or cut tee slots and fit toggle clamps. Cams or eccentric clamps are made up from scraps of timber and are best used in pairs.

Rubberised work support blocks

The use of non-slip rubber mats to hold a workpiece has been shown earlier but an extension of this idea are rubber surfaced blocks called Bench Cookies or Loc Blocks.  Placing these Blocks under the four corners of the workpiece will secure small or medium sized workpieces to the bench and allow them to be routed or sanded without the need for clamps.

They also raise the workpiece from the bench by 25mm, which allows complete access to every edge, so making it ideal for painting or varnishing.  The Trend Loc Blocks linkare a development of this idea and have interlocking edges that lock to each other so that different configurations of the blocks can be made.  For example all four can be interlocked to form a square of 173mm per side, for supporting smaller items.

The top and bottom surfaces of the square blocks consist of anti-vibration, non-slip, non-marring(marking?)rubber pads.  They can be set-up in seconds and grip both workpiece and bench.

To set them up, the blocks are placed on a clean, non-polished surface and arranged according to the size and shape of the workpiece, which is then positioned on top of them.  When used for router edge moulding, the blocks should be positioned as close to the edges of the workpiece as possible to prevent tipping, and the cut made in several light passes

Vacuum clamping

Vacuum clamping provides a very effective method for holding and releasing the workpiece and is therefore ideally suited for repetitious batch work. It is generally used only in professional workshops where speed is vital, as it can prove an expensive option for the occasional user. However you can rig up suitable homemade devices that offer a very reliable method of holding while avoiding the need for separate clamps that can obstruct the routing operation or spoil the workpiece. Vacuum chucks are made using flat self-adhesive foam sealing material or round neoprene strip formed into individual cells. The workpiece itself then completes the sealed chamber from which the air is removed through an exhausts port built into the chuck.

To get the necessary suction you need to buy a dedicated vacuum pump or couple up to a domestic vacuum cleaner. This latter option is obviously more cost efficient for the home user, but only short periods of clamping are recommended as continuous restriction to the airflow will overheat and damage the unit.

Having created a vacuum beneath the workpiece, the external air pressure is sufficient to hold it firmly in place. Some vacuum clamping devices have multiple cell chucks, which are divided into several chambers that are shut off independently with automatic ball valves. This allows various sized workpieces to be held, as unused cells remain completely airtight.

Proprietary multiple cell chucks for use with a vacuum cleaner are readily available in a variety of sizes and these are ideal for the amateur user who is dealing with lots of small components. They can also be used for other jobs like holding work for sanding, etc.

However, for the chucks to work properly, it is essential that contact is made all round the seal, so bowed or warped pieces won’t normally hold. You can even make your own specially curved chucks contoured to a specific shape.

With any vacuum holding system, always check that the work is held down securely before you start cutting.

How does it work?

The top surface has a rubber gasket with a matrix of cells in two sizes which when used in combination provide maximum holding area for small or awkward shaped workpieces. The lower surface has a rubber gasket with one large vacuum cell which is used to clamp it to the workbench.

The timber is pushed down to activate the air valves in the cells to engage the vacuum. The vacuum suction then holds the workpiece securely onto the bed.
A red handle is used to release the vacuum.