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- Nov 19, 2011
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was wondering what are the pros and con of a live center vs a dead center thanks much mac:thinking:
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Live center vs Dead
- Thread starter irishwoodsman
- Start date
- Joined
- Sep 22, 2010
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- 898
A live centre is used in the headstock and is the driving centre. They are usually an unhardened centre so they can be turned in-situ for the highest level of precision and used in conjunction with driving dogs.
A Dead Centre is used in the tailstock and used to create heat, friction and gall the end of a shaft, even when copious amounts of lube are used.
The old favourite was White Lead. Dead Centres are available in a variety of types, Hardened, soft, half. Hardened dead centres are generally used in the tailstock to help overcome the friction and they have to be operated at slow speeds due to the immense amount of friction involved. Half centres allow you to face right up to the centre drilled hole so you can face the entire end of the stock. If your lathe is only being used at really low RPM, then the Dead Centre may be helpful, personally, mine only get used if I am checking a shaft between centres for straightness etc. Never or rarely used if the lathe is "ON". Dead centres are the prefered centre for cylindrical grinding operations where the work is being rotated at slow RPMs
A (Ball Bearing) or Bearing Dead Centre is used in the tailstock to support a shaft. This centre has been mistakenly called a Live Centre and the term has stuck. These centres are also available in a variety of configuration; economy, precision, short, long, cup, bull nose, spring-loaded, spider, chucking etc. These centres can be run at much higher RPM's than a non bearing type centre. They can have one or more bearing, with better ones having at least three.
I tried an economy centre when I frist started using a lathe and it was returned to the store I bought it from the next day, the bearing felt like it had gravel in it. I replaced it with a good quality Skoda Bearing Centre and never looked back. A couple years ago, when I upgraded to a larger lathe, 14x40 I found that the Skoda Centre was just a bit too short to reach across the saddle, so I ended up getting a Riten Long Nose Bearing Centre. This centre has a long slender nose and gives that extra room for bridging the saddle and also for getting the tool bit in closer to the centre. It is the number one gotot centre used in my shop.
Cup Centres are handy when you have a shaft that has no centre hole. There are sets available, Skoda and others that consist of a MT shank with Bearing and replacable types. These can be very handy.
Spring-Loaded Bearing Centres are used when high heats are present as the allow for expansion of the shaft being turned. They do not tend to be very common.
Bull nose and Spider Centres are used for larger diameter pipe and tubing.
One of my favourite centres is the 3-Jaw Chuck, Bearing Centre. Mine is a Bison Brand, and is used to support shafts that do not, or can not be centre drilled. They are fairly large, 3" diameter and larger, so they can be a bit cumbersome to work around, but their usefullness make them a fantastic accessory for any lathe. These centres have replaced the old Jacobs armature chucks for non centre drilled armatures.
Walter
A Dead Centre is used in the tailstock and used to create heat, friction and gall the end of a shaft, even when copious amounts of lube are used.
The old favourite was White Lead. Dead Centres are available in a variety of types, Hardened, soft, half. Hardened dead centres are generally used in the tailstock to help overcome the friction and they have to be operated at slow speeds due to the immense amount of friction involved. Half centres allow you to face right up to the centre drilled hole so you can face the entire end of the stock. If your lathe is only being used at really low RPM, then the Dead Centre may be helpful, personally, mine only get used if I am checking a shaft between centres for straightness etc. Never or rarely used if the lathe is "ON". Dead centres are the prefered centre for cylindrical grinding operations where the work is being rotated at slow RPMs
A (Ball Bearing) or Bearing Dead Centre is used in the tailstock to support a shaft. This centre has been mistakenly called a Live Centre and the term has stuck. These centres are also available in a variety of configuration; economy, precision, short, long, cup, bull nose, spring-loaded, spider, chucking etc. These centres can be run at much higher RPM's than a non bearing type centre. They can have one or more bearing, with better ones having at least three.
I tried an economy centre when I frist started using a lathe and it was returned to the store I bought it from the next day, the bearing felt like it had gravel in it. I replaced it with a good quality Skoda Bearing Centre and never looked back. A couple years ago, when I upgraded to a larger lathe, 14x40 I found that the Skoda Centre was just a bit too short to reach across the saddle, so I ended up getting a Riten Long Nose Bearing Centre. This centre has a long slender nose and gives that extra room for bridging the saddle and also for getting the tool bit in closer to the centre. It is the number one gotot centre used in my shop.
Cup Centres are handy when you have a shaft that has no centre hole. There are sets available, Skoda and others that consist of a MT shank with Bearing and replacable types. These can be very handy.
Spring-Loaded Bearing Centres are used when high heats are present as the allow for expansion of the shaft being turned. They do not tend to be very common.
Bull nose and Spider Centres are used for larger diameter pipe and tubing.
One of my favourite centres is the 3-Jaw Chuck, Bearing Centre. Mine is a Bison Brand, and is used to support shafts that do not, or can not be centre drilled. They are fairly large, 3" diameter and larger, so they can be a bit cumbersome to work around, but their usefullness make them a fantastic accessory for any lathe. These centres have replaced the old Jacobs armature chucks for non centre drilled armatures.
Walter
- Joined
- Nov 19, 2011
- Messages
- 966
Well Mr Walter i think you covered them all and i truely thank you for that. I see so many tools out there for lathes and me being at it only a yr i dont know what half of them are for, i bought 10lbs of lathe bits for my lathe picked out the ones i knew and put the others in a tray waiting for the time that i will half to find one to do a certain job lol. i will probally read your info a hundred times so it stick in this brain of mine. again ty so much for the info:biggrin: mac
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British Steel
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Revolving Dead Centre - a Live centre's driven under power by the machine (compare to "Live Tooling" on a CNC machine - traversed cutters driven by either the main spindle motor or auxillary motors in their own spindles on the carriage, similar to milling spindles on manual lathes).
This may be the right term, but that doesn't mean that people will use it...
Dave H.
This may be the right term, but that doesn't mean that people will use it...
Dave H.
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- Sep 22, 2010
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- 898
Starlight....not to start an argument, but don't you have that turned around? Any time I used a dead center I used it in the headstock in conjunction with a lathe dog and faceplate. That lets the center, the dog, and the faceplate all turn together whereas you won't be galling the part. The live center goes into the tailstock and will spin with the part to prevent galling of your center drilled hole.
- Joined
- Sep 22, 2010
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The original nomenclature for tooling is that if it is driven by a motor, it is live and if it is not powered it is dead.
A milling cutter or drill bit held in the quill of a mill, or a collet in the lathe and driven under power is live. That same cutter held in the tailstock is dead.
A centre held in the tailstiock is dead, whether it contains bearings or not, the same centre held in the headstock is live, as it is the driving centre.
This definition has changed over the years and now the "accepted" term is that if the centre has bearings it is refered to as a live centre, not that that makes it correct, but that is the common term.
This is the same way that one would not go gather a "f a g g i t" of sticks anymore.
Walter
A milling cutter or drill bit held in the quill of a mill, or a collet in the lathe and driven under power is live. That same cutter held in the tailstock is dead.
A centre held in the tailstiock is dead, whether it contains bearings or not, the same centre held in the headstock is live, as it is the driving centre.
This definition has changed over the years and now the "accepted" term is that if the centre has bearings it is refered to as a live centre, not that that makes it correct, but that is the common term.
This is the same way that one would not go gather a "f a g g i t" of sticks anymore.
Walter
- Joined
- Sep 22, 2010
- Messages
- 898
Thanks Bill
When i was a young pup, I took a Millwright/Machinist course in trade school. I was majoring more in the millwright side, but the two trades are very closly interlinked. It was drilled into my brain by a few of the instructors that "a spade by any other name is still a spade" and that by calling a centre in the tailstock live it confused the issue as to whether it was a driving centre or not. I have learned to adapt and I know how to differentiate, but that does not change the fact that it is being referenced by a technically incorrect term.
Walter
When i was a young pup, I took a Millwright/Machinist course in trade school. I was majoring more in the millwright side, but the two trades are very closly interlinked. It was drilled into my brain by a few of the instructors that "a spade by any other name is still a spade" and that by calling a centre in the tailstock live it confused the issue as to whether it was a driving centre or not. I have learned to adapt and I know how to differentiate, but that does not change the fact that it is being referenced by a technically incorrect term.
Walter