Today I made a prop-driver, collet and washer for a 'Boddo' (CS) Mills .75 that was recently given to me. It had never run.
The original (cast) prop driver was fractured into three pieces and the prop washer had a 5mm hole for the 4mm shaft.
As the tapered drive collet was only 4mm long it was impossible to accurately measure the angle (about 5.5° – so after grinding a micro-boring tool from a 1/8" hss blank (it had to fit in a 4mm hole) the tool was put upside down in a q/c toolholder, the top-slide set over to 6° and used to bore the hole (in the far side of the 4mm shaft hole) to a taper to suit a new collet. It required about 20 'spring' cuts in the dural to obtain a straight taper due to the slenderness of the tool.
The tapered collet was turned conventionally using the top-slide still set to the 6° taper, parted-off and slit with a razor saw. The prop washer was drilled with a #20 drill, shaped and parted off.
On with a 7"x4" prop, onto the test stand, a few flicks and away it went, so not a bad afternoon's work.
This is exactly the sort of job that I originally purchased my C3 lathe for!
* Danny M *
Edited By Danny M2Z on 27/01/2016 09:59:20
Edited By Danny M2Z on 27/01/2016 09:59:59
Edited By Danny M2Z on 27/01/2016 10:00:28