MATE Building Instructions - Page 2
- Centre phosphor-bronze stock and extend 37mm from chuck jaws. Finish turn to Ø12.7mm and face end.
- Centre-drill and drill Ø8mm x 35mm deep.
- Break edges and part-off at 30mm from faced end.
- Centre (Ø19mm) aluminium stock and extend 27mm, finish turn to
Ø9.5mm and face end. Bell-mouth with a centre-drill.
- Drill Ø3mm x 27mm deep, then drill Ø5mm. Finish venturi bore to size with a Ø5.5mm drill, fed slowly at high spindle speed. Break edges and part off at 22mm from the faced end.
- Centre other end in chuck and extend 5mm. Finish turn to Ø7.5mm x 4mm.
- Transfer the venturi to the milling machine vyce, clamping it firmly at the ends. Mill the first .75mm deep slot with a 1/4" slot drill centred 10mm from the bell-mouthed end.
- Turn the venturi through 180 ° and clamp again, resting on a narrow piece of parallel packing under the first slot to ensure alignment. Mill the second slot.
- Move the venturi sideways to centre its axis under the machine spindle. Centre-drill and drill the Ø3mm through hole for the spraybar.
- Centre the (Ø31.75mm) aluminium stock in the chuck and extend 20mm. Finish turn to Ø27mm x 14mm long.
- Face end and bore recess to Ø20mm x 9.5mm deep. At 2.5mm from faced end, plunge cut to Ø23mm with the 1.6mm wide parting tool.
- Turn down to major thread Ø24.5mm and chamfer a 45° x 1 mm deep vee with your chamfer tool, centred at 11 mm from the faced end. This will be our thread run-out.
- Proceed to cut a 1mm pitch thread x .615mm deep, entering at the 1.6mm wide recess. The thread depth specified assumes a minimal tool nose radius and you may have to adjust yours accordingly.
- Part-off the backplate at 11mm from the faced end. In the unlikely event you anticipate some difficulty obtaining a smooth part, allow a further .5mm over length. Reverse the backplate, mounting it on a mandrel. Face off the surplus.
- Place the backplate, its threads protected by paper, in a chuck, which is in turn mounted vertically on the milling machine table. Cut the 2.5mm wide x 1mm deep tightening slots with a slot drill. De-burr with a needle file. A suitable steel blade, not a pair of long-nosed pliers, will be used across these slots to tighten the backplate against the crankcase.
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