I got back on this again as I need to get on with the fuel pump and injector for the two stroke diesel. I looked up the manufacturers site for the Magafor reamers I am using. The figures for a 2mm reamer suggest ~2400rpm and a feed of 0.1 - 0.15 mm per rev. My lathe can achieve 2000 rpm and has fine feeds of 0.08 and 0.16 mm per rev. I decided on 0.08mm per rev. I also purchased new Titex drills in 1.8, 1.85 and 1.9 mm diameters. For these trials I didn't power feed the reamer but just followed the carriage by eye. The feed was much slower than I have been using previously.
All trials used the same 1.95mm H7 reamer
1st Trial
Center drill without countersink. 1.85mm dia. drill. Reamer held in a normal chuck.
1.96mm pin gauge passes through
1.97mm pin gauge enters ~5mm from the start end and ~2 mm from the exit end.
1.98mm pin gauge enters ~2mm from the start end
2nd Trial
As above but using the floating reamer holder. The reamer was difficult to start in the hole.
1.96mm pin gauge passes through
1.97mm pin gauge enters ~2mm from the start end but not from the exit end
1.98mm pin gauge no go
3rd Trial
As above but with a countersink from the center drill.
1.96mm pin gauge passes through
1.97mm pin gauge enters ~1mm from the start end but not from the exit end
1.98mm pin gauge no go
4th Trial
As above but 1.8mm drill. More force was required to feed the reamer.
1.96mm pin gauge passes through
1.97mm pin gauge enters ~3mm from the start end but not from the exit end
1.98mm pin gauge enters ~1mm from the start end
5th Trial
As above but 1.9mm drill.
The hole was over 1.95mm so the reamer passed through without cutting.
Conclusion:
Following the manufacturers recommendations helps. The floating reamer holder greatly reduces bell mouthing.
