Turning between centres on Super 7

[C JParticipant @cj88518]

I did machine the part between centres in the end, as I was skimming a brake drum, and that gap can come in handy

[Neil LickfoldParticipant @neillickfold44316]

I have made parts between centres, where I use the centre taper to be the driver. I make the taper as big as I can and make the parts with excess material on that end to allow for the bigger centre. I just take light cuts and no drive dog. Works a treat. My head stock end centre has a shoulder so it pushes onto the face of the chuck jaws. I trim the 30deg deg angle to suite the centre taper. Some jobs I end boring the centre, and if it is not required to be changed with the tailstock end, have make the taper more shallow at 10 deg per side. It gets an better grip on the bar that way.

Does not suite everything, but does help if the drive dog becomes an issue with the turning of the part.

[C JParticipant @cj88518]

That's a good tip!

[Ian PParticipant @ianp]

Posted by bernard towers on 21/02/2022 18:53:52:

Sorry chaps but between centres turning is what it says anything else is not.

No need to apologise to the chaps, but please could you clarify what you were trying to say?

Ian P

[HopperParticipant @hopper]

Posted by Neil Lickfold on 21/02/2022 20:56:51:

I have made parts between centres, where I use the centre taper to be the driver. I make the taper as big as I can and make the parts with excess material on that end to allow for the bigger centre. I just take light cuts and no drive dog. Works a treat. My head stock end centre has a shoulder so it pushes onto the face of the chuck jaws. I trim the 30deg deg angle to suite the centre taper. Some jobs I end boring the centre, and if it is not required to be changed with the tailstock end, have make the taper more shallow at 10 deg per side. It gets an better grip on the bar that way.

Does not suite everything, but does help if the drive dog becomes an issue with the turning of the part.

Now, that is a cunning trick. Thanks for the tip. You learn something new every day on this site.

[peak4Participant @peak4]

Posted by Mike Donnerstag on 20/02/2022 14:51:56:

………………..

……….. they also supplied square centres and fluted centres. Does anyone know what these were used for? I can't even picture a 'fluted centre'. The square centre had a steep square taper on the front; in fact there is one on eBay at the moment.

Many thanks,

Mike

Edited By Mike Donnerstag on 20/02/2022 14:52:19

The square centre is good for cleaning up damaged centre drillings on work which you want to re-mount, say the damaged end of a motor armature that's been hammered or dinged.
Also handy for re-centring an off centre centre drilling.

The fluted centre looks a bit like a centre drill, but without the starting pip at the end.
I've never seen one in real life, so I'm not sure if it's intended to cut, or to provide a sharp edge to bite into the work, a bit like a self driving centre.

There's diagrams of both in one or more of the older Myford catalogues, but I'll not reproduce here for copyright reasons; I got them off the old Yahoo Myford groups files before ithe groups were removed.

Bill

[John MCParticipant @johnmc39344]

Nice tip from Neil L, I'll try to remember that.

Machining motorcycle brake drums, no point in doing that unless the hub is laced in to a rim. The spoke tension will distort the drum.

When I do that job I put the live centre in the lathe spindle and the dead centre in the tail-stock. This forces the (complete) wheel to revolve on its own bearings as it would in service. It is debatable if this is really necessary but it eliminates another possible source of error.

John

[HopperParticipant @hopper]

Posted by John MC on 22/02/2022 10:59:40:

Nice tip from Neil L, I'll try to remember that.

Machining motorcycle brake drums, no point in doing that unless the hub is laced in to a rim. The spoke tension will distort the drum.

When I do that job I put the live centre in the lathe spindle and the dead centre in the tail-stock. This forces the (complete) wheel to revolve on its own bearings as it would in service. It is debatable if this is really necessary but it eliminates another possible source of error.

John

Good luck fitting the whole wheel in a Myford though! Minibikes only.

At the factory, the drums are usually machined before the wheel is laced up. Works good enough for general use. But the racing guys like to do as you do and skim the drum with spoke tension on the hub to get a perfectly round drum in service. Then skim the brake shoes to match while they are mounted on the brake backing plate with a couple shims to put them them in the working position.

[Steamer1915Participant @steamer1915]

Posted by Neil Lickfold on 21/02/2022 20:56:51:

I have made parts between centres, where I use the centre taper to be the driver.

I finish parts in the same way. The centre shafts for the carriage dial are roughed out using collets and then finished between centres.

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