Turning between centres on Super 7

Having piqued my own interest in face drivers I stumbled across that same picture Nigel, I can see this might get on the stuff to do list one day. I can also imagine a saw cut across the end of the job could be used to reduce some of the end thrust required. Plenty of food for thought.

Mike

I just found this old thread on Myford centres, so I thought I'd reply.

When I bought my Myford it came with many accessories. Among these were three centres that are shorter than standard: soft, hard and half centres. I expect these were originally supplied by Myford to be used with the relatively short pin on the standard catch plate and their bronze drive dogs. Coincidentally, I made a longer pin for the catch plate recently, to work with a standard centre (forgetting I had the shorter centres!).

I notice from the Myford literature that as well as supplying the standard hard, soft and half centres for metal turning, and the hollow and wood prong centres used for woodturning or with a drill pad, 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 problem I find with turning between centres with a catchplate or faceplate on the Myford is the gap in the bed. To turn the far left hand end of the job, the saddle has to be half off the bed or the topslide cantilivered way out there. I gave that up as a bad joke and made a drive dog that engages with one of the jaws on the three-jaw chuck. Then just make a quick centre by turning down a piece of scrap bar held in the chuck.

The drive dog was made from two bits of aluminium 12mm x 50mm flat bar bolted together at a right angle. One side has a hole in it for the job to pass through and bolt to clamp the job in the hole. The other side has a slot cut in it just wide enough to fit over the chuck jaw so it is not flapping around loose. Works a treat.

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

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

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.

That's a good tip!

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

Ian P

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

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

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.

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