Portable Bench Saw: A Lift-Out Power Unit on Trunnions, Its Motor on Spring Bars, Under a Tilting Platform (Henkel, 1928)

"It will thus be seen that the power unit has a three-point bearing which maintains it against accidental displacement, or, in other words, prevents it from getting out of proper alinement."

Make a rectangular frame 460 x 360 mm of 25 x 90 mm hardwood, glued and screwed at the corners. Bolt a 250 mm pine leg 45 x 45 mm in each corner through a short length of steel angle screwed to frame and leg, as his corner plates 4 and lugs 5. Cut a notch 30 in the top of each long side, 60 mm from one end, 21 mm wide and 25 deep, for the trunnions. Screw a steel arm 34 across the other end with a 10.5 mm hole, and a lug 50 with an M10 tapped hole on the side away from the hinges.

Cut 18 mm plywood 500 x 400 mm and glue a hardwood strip round its underside edges as the flange 8. Cut the opening 13 for the saw, 230 x 30 mm, and a hardwood block 15 to fill it. Rout a square groove 16 the length of the platform for the follower's bar. Screw two steel lugs 9 under one long edge, drilled to line up with holes 10 in the frame, and hinge it with steel pins held by split pins. Run an M10 tilt screw 49 up through lug 50, with a wing nut on its lower end as a handle, its top bearing under the platform.

Bolt two 40 x 6 mm steel flat bars 340 mm long into a frame 24 with spacers. Across one end fix a 20 mm round bar 28 whose ends stand out 25 mm each side as the trunnions 29. At the other end bolt two 30 mm flange bearings for the arbor 26, turned from 30 mm bar like the twin-saw table's, with a collar, a loose flange and an M20 thread for the blade's nut. Bolt a forked steel lug 31 on that end, its slot straddling the hanging screw.

Bend two strips of spring steel 37, 30 x 3 mm, with a slight bend near one end, and bolt them under the cross bar 28 so they reach out beyond the trunnions. Bolt the motor 36 to them, with cap nuts 40 on the bolts' ends: these are its feet when the unit stands alone. Fit a V-belt pulley 42 on the motor and one 44 on the arbor, and the A-section belt 43. Pivot an arm 45 on the arbor's bearing with a weighted pulley 46 at its free end resting on the belt to take up the slack. Have the motor wired to a switch.

Fit the 200 mm blade on the arbor. Hang an M10 screw 32 from arm 34 with its head 35 on top. Lower the power unit in, the trunnions into the notches 30 and the forked lug 31 round the screw, and run a wing nut 36 up under the lug. Turn the wing nut to raise the blade through the opening to the depth wanted.

Angle follower: a hardwood bar 17 sliding in the groove, with an angle fence 18 clamped at any angle by a wing nut 19. Rip guide 20: a hardwood bar across the platform held by two hook bolts 21 that hook under the flange 8, with wing nuts 22. Mark a scale 23 on the platform's ends to set it.

With the platform flat, check the blade is square to it with the square, rip a board along the guide and crosscut another against the follower. Tilt the platform with the tilt screw (and the block under it for steep angles) and check the angle with the protractor. Lift the power unit out, stand it on its cap nuts, swap the blade for the grinding wheel, swing the idler arm to the belt's other side, and run it.

**Fay M. Henkel** of New Rochelle, New York, US 1,695,188, dated 11 December 1928, filed 28 April 1927. He claimed a supporting unit with a platform and a power unit with a frame, "trunnions on the end of said frame, said supporting unit having recesses therein receiving the trunnions", a bearing and arbor, spring bars and a motor fixed to them, pulleys and a belt; and the spring bars' couplings serving as feet when the unit is removed. His frame, platform and legs are castings; ours are hardwood, plywood and steel. His bearing is a sleeve with a grease cup; ours are two greased flange bearings. He gives no sizes, motor or speeds; those are ours.