Par­al­lels

The Shed - - Milling -

Set­ting up

Be­fore plac­ing the vice on the bed of the ma­chine, clean the bed as well as the base of the vice. Any swarf will in­tro­duce er­rors — when the vice is clamped up tight, the swarf will mark the bed and the base. Any marks al­ready present should be lightly stoned to re­move any raised ar­eas.

When the vice most suit­able for the job is placed in po­si­tion on the bed of the ma­chine it needs to be trued with a dial test in­di­ca­tor (DTI) mounted in a col­let or drill chuck.

The lever type is best suited to this, although a plunger type can be set up to do the same. Zero the DTI and wind the ta­ble of the ma­chine so that the DTI moves along the fixed jaw of the vice or along a par­al­lel clamped in the vice. Take note of any move­ment reg­is­ter­ing on the DTI. If there is move­ment, loosen one of the bolts clamp­ing the vice to the bed and move the vice slightly to re­duce the er­ror. Clamp up the bolt and recheck. Con­tinue un­til the er­ror is re­duced, ide­ally to zero. The greater the dis­tance you move the DTI over, the more ac­cu­rate the set­ting will be.

As one def­i­ni­tion has it, ‘par­al­lels’ are pieces of steel-bar stock ac­cu­rately ma­chined so that the op­pos­ing sides are par­al­lel to each other. They are used to raise a work­piece to give clear­ance un­der the com­po­nent for the drill not to dam­age the ma­chine ta­ble or the base of the vice. Par­al­lels can be bought in sets or you can make your own as you re­quire them, but al­ways make them in matched pairs.

You can never have too many par­al­lels. They come in vary­ing heights and widths, and can be stacked as re­quired, although you never seem to have the per­fect set for any par­tic­u­lar set-up. Typ­i­cally, the par­al­lels you buy will be hard­ened, mak­ing them wear-re­sis­tant and very good for in­dus­trial use. Non-hard­ened par­al­lels are gen­er­ally one for the garage en­gi­neer and have the added ad­van­tage that if you do clip one with a cut­ter or drill, it is far less likely to dam­age the cut­ter or drill.

A very good idea is to make a set of par­al­lels that are a good fit in the ma­chine bed slots. These can be used to aid set­ting a com­po­nent and give a good solid back­stop.

This re­lies on the bed T-slots be­ing in good con­di­tion.

Screw jacks

Screw jacks come in many dif­fer­ent sizes and can be very elab­o­rate or sim­ple in con­struc­tion. They sup­port your set-up, stop­ping the com­po­nent tip­ping when you are ma­chin­ing, or al­low­ing sup­port for an­other clamp to be added to the set-up.

V-block

When a round bar is held in a vice, there are only two points of con­tact. Any ma­chin­ing is likely to re­sult in the bar tip­ping over, but this can be over­come by us­ing a suit­ably sized V-block. This im­me­di­ately gives three points of con­tact to ap­ply fric­tion and re­strain any move­ment of the round bar. Don’t for­get, a good set-up is rigid and sta­ble.

Next is­sue, we’ll look at cut­ters and cut­ting speeds.

Screw jacks

Tru­ing up ma­chine vice with DTI

Round bar sit­ting on par­al­lel and held by V-block in ma­chine vice

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