Re: Souces of Timing/Drive Pulleys

--- In CAD_CAM_EDM_DRO@y..., ballendo@y... wrote:

> J.S.,
>
> I agree, it would be wise to match the taper standards of
> commercially available parts.
>
> I'm not sure what you mean about not being able to turn the pulley
> taper first, tho'...
>
> If the pulley is mounted in a 4 jaw, and indicated in... Then the
> taper bore is made... Then a drill mounted to the

crosslide/toolpost

> is used to drill/ tap the holes in the pulley (using indexing of

the

> spindle)...
>
> Doesn't matter which is done first, holes or taper. It is all
> one "chucking".
>
> The hub material is chucked up. Turned down to the major dia. of

the

> taper... Taper turned... Then the drill in toolholder is used, same
> as before, to drill and tap holes as needed... Finally, hub is

parted

> off... Again doesn't matter if the taper is before or after the

holes.

>
>

Ballendo

Copied below is a previous post that I don't believe you have read.
Just look at either of the first two photographs and then tell me if
you put the taper in first how you can drill an accurate hole half
in / half out a taper and then tap it still keeping it true and
accurate so it can mate up to a previously made hub.
Post below:-
*********************************
I was in the process of replying to this when Peter's post appeared.
Probably 30% of my work is on the repair of motors, fans, hubs and
pulleys so I have done a lot of these. Peter has described it quite
well but I've posted three pictures at
http://homepage.ntlworld.com/machines/fenner1.jpg
http://homepage.ntlworld.com/machines/fenner2.jpg
http://homepage.ntlworld.com/machines/fenner3.jpg
If you have a look you will see that the clamp holes in the pulley
marked 'C' are threaded and parallel but the bore is tapered at 8
degrees. The corresponding holes in the hub are just short plain
Clearance holes to allow the grub screw to push the hub into the
pulley. There are two of these holes roughly opposite. They vary from
size to size. The last hole marked 'R' for release is opposite. That
is the thread is in the hub and the short clearance hole is in the
pulley. This is what self extracts the hub.
As you can see from the photos it would be near impossible to drill
and tap these hole in after the 8 degree taper has been cut. In the
first photo you can see one of the drilling jigs with the two tapping
holes and the top clearance hole. I have a full set of these jigs and
also the CAD drawings for the range up to 4" shaft size.
Fenner2 is a close up of the hub pulley and Fenner 3 is a 1 1/2"
pitch duplex sprocket being swung onto the lathe for boring.

John Stevenson.