Do It with Tools and Machinery
���A hammer with removable faces of any desired size or shape, of steel, copper or other soft metal to suit different work
��A tackle for unloading automobiles. The ropes are adjusted so as to lift vertically on each of the four wheels. The main member is a scantling suspended lengthwise of the automobile
���The same ham- mer at left with a steel face for ordinary work requiring heavy pounding. Other faces may be substituted
���A boiler ther- mostat for indi- cating heat in chemical vat3. A rod extending the length of the outer shell supports the bimetallic strip
���Above: A new valve grinder designed for engines equip- ped with valve caps
��In center: A new machine used in post- effices for tying envelopes into packages.
���A quick-action chuck with which a rotative tool can be re- moved and an- other inserted while the ma- chine spindle is revolving
�� ���Above: A nut lock which prevents a nut from backing off from a bolt
��It ties from twenty-five to thirty bundles a minute with a non-slip knot
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