Re: Souces of Timing/Drive Pulleys

--- In CAD_CAM_EDM_DRO@y..., ptengin@a... wrote:

> In a message dated 05/23/2001 7:07:33 AM Hawaiian Standard Time,
> currinh@O... writes:
>
>
> > I haven't built any of these but as I envision them the tapped

holes can be

> > done before or after the taper. I would approach it with a

design similar

> > to the QD bushings. These have a flange on the taper which is

pulled

> > towards the pulley with bolts. Take a look at www.mcmaster.com ,

search on

> > QD, then "QD Bushings". The page that comes up shows a "QD

bushing" mid

> > page, picture worth a thousand words. Right below this is

a "Taper Lock

> > Bushing" which is I think what you're referring to? Either would

work.

> >
> > Hugh Currin
> > Klamath Falls, OR
> >
> >
> >
>
> Hugh,
>
> The QD type bushings have a large flange into which all bolting

and jacking

> holes are drilled and or tapped. On smaller drives, the flange is

often

> difficult to accommodate. There is a series of bushings that have

no flange.

> These have setscrews doing locking and releasing. The trick is,

they have the

> holes right on the parting line between the pulley and the bushing.

So, if

> the part requires a "threaded" hole, it must be drilled and tapped

before the

> taper is cut as the taper boring procedure will cut away roughly

half of the

> hole.
>
> Hard to describe, next time I find one in my junk pile, I will

take a pic

> and post.
>
> Peter
> THRD, Inc.

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.