Hard/Soft centres

[ScottParticipant @scott]

or maybe just cheap ones…

[ScottParticipant @scott]

Morning all

I recently bought a 2MT centre from a well-known supplier to the hobby market. It was described as a "2MT Dead Centre for Myford Lathe". Can someone please advise a newbie if this is likely to be a hard or soft centre?I've seen both mentioned in books. The reason I ask is that without any use in anger (it has only been inserted into the tailstock barrel a few times) I can now feel a ridge/hump on the taper where the end of the barrel would have been. It's not visible so it's not very big but the fingers don't lie. Doesn't seem right to me! :-/

Cheers

Scott

[David Clark 13Participant @davidclark13]

Hi There

The shank will probably be soft even if the end is hard.

Try using a needle file on the centre where it is unlikely to be used.

Perhaps the very point.

If hard you can use it in the tailsrock.

If soft, use it in the headstock.

regards david

[SteambuffParticipant @steambuff]

Scott,

Give the supplier you got it from a ring and ask them.

Dave

[KWILParticipant @kwil]

Scott, the taper will not be that hard, you will be able to see if the point is hard as they are usually inserted hard material.

[speelwerkParticipant @speelwerk]

Original Myford hardened dead centres are hard the full length, and are easily identified with a file. Niko.

[ScottParticipant @scott]

The file says it's soft, point and all. Thanks for the replies gents. Just didn't expect the body to be soft enough to deform after just being inserted in the barrel two or three times.

Cheers

Scott

[NJHParticipant @njh]

Hi Scott

The headstock centre should be soft. The way this works is you place the centre in the headstock, set the appropriate angle on the topslide, and skim the centre for the best finish you can. You know then that the centre is quite true. Then BEFORE REMOVING THE CENTRE make a centre pop in the face of the spindle and another adjacent to it on the centre. In this way the centre can be removed and replaced in the same place each time. Where absolute accuracy is required a skim can be taken as above before placing an item between centres for turning.

The tailstock centre should be hard

Regards

Norman

Edited By NJH on 07/02/2013 17:52:16

[BazyleParticipant @bazyle]

The supplier should make it quite clear. Since few people turn between centres these days most purchasers are probably expecting a hard centre for support to a chuck mounted piece.

Just checked a well known supplier's website and it's not clear.

A "Dead Center" does not move – hence tailstock hence should be hard. A "Live Centre" does move. That means it is in the headstock and turns. It does NOT mean it is a revolving centre.

[jason udallParticipant @jasonudall57142]

Posted by Bazyle on 07/02/2013 17:54:57:

The supplier should make it quite clear. Since few people turn between centres these days most purchasers are probably expecting a hard centre for support to a chuck mounted piece.

Just checked a well known supplier's website and it's not clear.

A "Dead Center" does not move – hence tailstock hence should be hard. A "Live Centre" does move. That means it is in the headstock and turns. It does NOT mean it is a revolving centre.

thats good to know..always heard of revolving centers as "live"..

useful distinction

Although my confusion is not solely my own link

Edited By jason udall on 07/02/2013 23:44:44

[ScottParticipant @scott]

Thanks for that tip Norman. Good to know!

Bazyle I agree that suppliers really ought to make it clearer what they are offering.Your observation is bang on – I did actually order it assuming it was a hard centre for the tailstock but at 3 quid it's not the end of the world.

I share Jason's confusion over live and revolving centres. Always thought they were one and the same. Probably got that from my father who always called a revolving centre a "live" centre

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Proper interpretation of ' live ' and ' dead ' is ' powered ' and ' unpowered ' in the same sense as for electrical systems .

Analogous to ' live ' and ' dead ' are ' fast ' and ' loose ' sometimes seen in old books – usually in reference to flat belt pulley drives .

High class turning was once done commonly between two dead centres with power going direct into the workpiece via a drive belt .

I leave you to conjecture what a ' loose poppet ' is .

Michael Williams .

[NJHParticipant @njh]

Michael

Conjecture is a good word and I've been searching for a "loose poppet" for years!

N

[ScottParticipant @scott]

I had one but the wheel fell off!

[BazyleParticipant @bazyle]

Just to add, The reason for the soft centre at the headstock is so that it can be turned true to the spindle as was necessary before the days of reliable morse tapers etc.
It probably is fair to say a revolving centre is also 'live'. It probably is ok for the actual centre of a revolving one to be soft though 'best practice' would deem it to be hard.

While we are on the subject of centres I wonder how many people with a Boxford and some similar lathes realise the purpose ot the hole in the front LHS of the tailstock casting mirroring the clamp hole. I only realised after watching an SB instructional youtube video after owning a Boxford for 20 years.

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