Provision for chip clearance

Though both jigs and fixtures require the provision for chip clearance, it has to be given top most importance in jigs. Not providing proper way to chips to come out, improper chip removal and failure to remove chips entirely will produce defective products. Ample space has to be provided for chip removal. Corner relief and contact area relief has to be provided, failing which a trapped chip will prevent the mating of surfaces. Chips produced in drilling will have its abrasive action on drill bushes that reduces the bushes life period. The provision of chip clearance will allow the chips to flow below the bushes.

The above figure shows the effect of providing corner relief arrangement. The small pieces of chips, which get accumulated, due to improper cleaning or due to the loading pattern will get trapped between the table and the work piece. This will misalign  the work with the table resulting in a defective part.

As a milling fixture is always bolted down to the table in a fixed position, provision for cleaning should not necessitate its removal from the table. Openings in the side of the fixture can be made but it is better to prevent the chips from entering and thus do away with the necessity for cleaning. In considering methods used in the location of work in milling fixtures, attention must be paid not only to the position of the locating surfaces, but also to their accessibility for the purpose of cleaning.

When springs are used to clamp the work piece the chips will go inside the springs causing improper tightening of the clamp and faster wear in the springs. Also it is difficult to remove all the chips that got trapped between spring coils. So it is better to conceal the springs which will result in higher life for the springs.