PDA

View Full Version : reguarding turning between centers



Bullshop
11-19-2012, 09:16 PM
Would someone please explain to me how to set up to turn between centers using a faceplate and dog. I am a beginning machining expert taking my first baby steps. I have only so far used regular chucks for turning. Have never yet turned between centers only between chuck and tail stock center.

bearcove
11-19-2012, 09:21 PM
I'm also clueless but put a dog on the chuck end the other is simple. Not sure how to "center" the chuck end on the bore.

I'd probably chuck up the barrel put the end on a center,, turn the end so bore was in "center", flip it around chuck the turned portion and turn it to dia.

bob208
11-19-2012, 09:29 PM
first you have to centerdrill both ends with a center drill. then use a lathe dog thsat hooks into the face plate. then install the tailstock center. then you are ready to go.

Reg
11-19-2012, 09:43 PM
First you have to center the part. You can start with one end in a chuck and set the other end in a steady rest. The center can be cut with a small boring bar or a center drill. Reverse the part and do the other end. Now the end running in the chuck might be running out a thou or so but subtend that out the length of the barrel and you come up with a error factor running out to five or six places. Close enough !! Most people cannot accurately measure that close.
Clean your tapers ( and the centers) pop in the centers and use the dog of your choice. Put a copper pad on the contact area of the dog. Do not over tighten the tailstock center and be sure to use a good sticky lube. As you cut remember that the barrel will elongate due to heat. Re-adjust your tail stock center frequently to allow for this.
Try to find a copy of the Atlas or Clausing Lathe Manual ( ebay ), they show you how to tie the special knot ( using a leather thong ) that will hold the barrel at the headstock end tightly in the center without causing distortion. You will need this to hold the barrel tightly to the headstock while you run the tailstock end in a steady rest for chambering.
This is the most accurate way of doing things.

Bullshop
11-19-2012, 10:53 PM
The part I am not getting is when I remove the chuck from the head stock and install a faceplate how do I hold a center (live or dead) without a chuck?
As I am trying to understand the faceplate/dog are only to transfer power to turn the centered piece so how then to hold the center? Its probably simple but I am not getting it yet.

bearcove
11-19-2012, 10:58 PM
I'm with you on that. It would seem that you would need to turn the one end at the tailstock concentric to the bore then put that in the chuck. I can't see how you coud indicate off the bore and get it centered in a dog after you turn it around.

Bullshop
11-19-2012, 11:05 PM
On those lathe manuals on ebay all I am finding are model specific manuals of parts and operation.
What exactly am I looking for?
Sorry for being a pain in the behind!

Mooseman
11-19-2012, 11:29 PM
The workpiece is clamped to the faceplate, typically using t-nuts in slots in the faceplate, or less commonly threaded holes in the faceplate itself.The faceplate was the ancestor of lathe chucks, an arrangement of three or more adjustable 'dogs' bolted to the faceplate providing a primitive chuck arrangement. Basically it would only be used for odd shaped pieces that wont go in a 3 or 4 jaw chuck or a flat plate like a flywheel shape /flat plate to face , etc.
Maybe this will help...http://www.cnccookbook.com/MTLatheHolding.htm

Rich

Reg
11-20-2012, 12:44 AM
The part I am not getting is when I remove the chuck from the head stock and install a faceplate how do I hold a center (live or dead) without a chuck?
As I am trying to understand the faceplate/dog are only to transfer power to turn the centered piece so how then to hold the center? Its probably simple but I am not getting it yet.

If I am reading this right, you are asking "what holds the center" ?
In almost all lathers ( there are a few exceptions ) there is a taper cut in the spindle of the headstock. Might be anywhere from a number 2 Morse to a number 5 Morse depending on machine size and even here there are a few exceptions that do not use a Morse taper.
After removing the chuck that taper is carefully cleaned along with the correct center and the center is snaped into the taper in the spindle. Don't try to make a home run with it , just pop it in and it will, if all being correct, lock into place. Tapers tend to lock.
This reinforces the need to keep tapers on both ends very clean and basicly keep the whole machine clean and properly lubed.
The tapers of the machine and the centers must be the same. Chips, dirt, grit etc, will cause a improper fit and will damage the tapers throwing off the accuracy. Cleanliness is next to Godliness in the machine world but then again you would never know it looking at some of the machines being used.
You are correct in assuming that the dog will only transfer rotation to the part ( the barrel ). Actually when setting the dog you want to make sure it dosn't bind. There will actually be a bit of "rattle" to it but when the cutting pressure is applied, the pressure will stop any rattle present. Any binding will cause the barrel to bend to a degree, throwing everything off.

Frank46
11-20-2012, 01:24 AM
I keep a box of cheap paper towels by the lathe, use them to clean centers. My lathe has a cylinder into which a #5 MT center goes in for the headstock. The tailstock gets a #3 MT center. Dead centers go in the headstock, live centers go in the tailstock. Frank

leftiye
11-20-2012, 05:51 AM
Am I missing something? The center can be on a faceplate or it can be in a chuck, or it can fit into the taper of bore of the lathe head. If the center is in the chuck, you must center it. Some faceplates are built centered (fit on to the mounting provision for the chuck), some fit into chucks and must be centered, some centers fit into tapers in the lathe head bore. The barrel bore is centered by the center, you can make and use a spud in the bore with a center drilled hole to fit the center and protect the bore. The other end goes on the tailstock center, also with a spud preferrably. Tighten the tailstock center against the work and the bore is centered. Run a dog in the slot on the faceplate or against the chuck to provide power to the piece. This "dog" is the teardrop shaped hole thingie with a bolt to tighten to clamp to the work, and a 90 degree "dog"leg to fit into the faceplate slots.

Bullshop
11-20-2012, 10:12 AM
OK Good!!!! I am beginning to get it. When I got the lathe with the tools I noticed there was a dead center that fit the MT of the tail stock but with it there was a sleeve that fit over the dead center that changes it to a larger MT that at this point I am assuming will fit the head stock.
Another thing mentioned here was to run the bent leg dog against the chuck. I had woundered about that. So if done that way will that eliminate the need for the face plate?
That brings up another question for me, what is a straight leg dog for?
I do appreciate all the help and hope you wont get sick of me asking. I am sure I will have many more questions.

bob208
11-20-2012, 12:16 PM
the headstock is made to take a moreis taper. on small lathes it is usly the next size larger then the tailstock. example. my 9 southbend lathe has a number 2 taper in the tail stock. the head stock has a number3 taper.

the larger lathes have even larger headstock tapers some even have tapered sleeves. this done so they can have a larger hole through the headstock.

this is all covered in the reprint of the southbend book how to run a lathe. i know people don't want to be bothered to read a book. but i have been doing machine work for over 40 years and i still go back to the book to get ideas for a set up or help with a problem. the books by guy lautard the machinest bedside readers are good reads with alot of ideas. maching is a contuing learning experince.

KCSO
11-20-2012, 12:18 PM
Go to you tube and look up South Bend video's they have a factory video from the 40's that shows it all. Turning between centers was a lot more common with the older lathes with small holes through the head stock. In the old ones you needed to center the part in the center rest to drill the centering holes as nothing over 3/4" would fit in the chuck. Watching the video is worth about 200% more than any written explanation.

454PB
11-20-2012, 12:48 PM
You can also make your own dead center for the chuck end by setting the tool holder at 60 degrees, and then use a live center on the tailstock.

I do this so I can use a 3 jaw self centering chuck and avoiding having to install a 4 jaw chuck and indicating in the work piece.

MBTcustom
11-20-2012, 04:55 PM
Dont bother with the faceplate. Use your chuck as God intended it to be used. If you are profiling a barrel, then you already have the bore for the centers, but you will want to make sure that you have a square end, and a 60 degree chamfer on the bore on both ends.
If this is a bar of metal that has no centers, mount one end in the chuck, and the other in the steady rest. Use a common 60 degree center drill to make the centers in both ends in this way.
Once you have 60 degree centers in both ends, find a piece of stock less than 1" in diameter, and about 4" long. Install this piece in the chuck and cinch the living bleep out of it, with all three (if you have more than one) key holes.
Set the compound crank to 30 degrees, 60 included (ie, set it up to cut the piece of stock in the chuck to a 60 degree point) and turn down the end to almost a perfect point (a little flat will not matter).
Now you have a center in the chuck that is perfectly aligned with the rotation of your headstock.
Install the center in the tailstock, and grease it with center point grease.
install the lathe dog on the end of the stock (with copper shim to prevent marking) so that the leg catches on one of the chuck jaws.
Take a skim pass over the piece of stock, or barrel blank to establish a measurable surface.
Adjust the tailstock to produce the desired taper, or parallelism.
Viola.

John 242
12-02-2012, 10:30 PM
The straight tail lathe dog is supposed to be more accurate than the bent tail lathe dog. When the straight dog is used, it is driven by a stud in the face plate. I have not used a straight dog, only the bent ones.

I have only recently been taught to turn between centers at school. We've turned various cold rolled steel rounds with a dog, face plate and live centers. I'll keep this simple because we are both beginners and I don't know much.

In preparing my round stock, I would initially cut it to approximate size with a cut off saw, leaving it about 1/8 inch too long, more or less, for facing (that's a lot but I get tired of re-cutting stock because I faced off too much).

Facing is simply making the end square to the axis (axis- I believe that's the right term). I placed the round stock in a 3-jaw chuck and faced off one end so it was square and then drilled it with a center drill (I've been using a No. 3). I then loosened the chuck, flipped the round stock around and repeated on the other end, but facing to the correct over all length.

After drilling and facing I removed the 3-jaw and attached the face plate. I installed a rotating 'live center' in the tail stock and mounted a 'dead' center in the spindle nose through the face plate (This center will turn with the spindle and actually becomes 'live' because it turns. A dead center in the tail stock would need to be lubricated, so we use a rotating live center in the tail stock.)

I then placed a lathe dog on the round stock and installed the tail of the dog into the slot on cut into the face plate (to provide drive). The dead center tip is aligned in the center drilled hole. I then moved the tail stock quill outwards until the 'live' center's tip moved into the other center drilled hole. With the stock secured between centers, the dog in the slot and every thing tight, you should be ready to turn.

There are many experienced machinists on here and I am not one of them. When I read some of their posts, sometimes it's a little overwhelming.

I have made some scrap, so if you goof up, don't let it get you down.

I have links to a lot of on-line lathe info. If you want me to post them, I will.
I read quite a bit and watched various videos about lathe operations before starting school and it helped quite a bit.
I strongly recommend Mrpete222's videos on Youtube. I also have links to an MIT lathe and mill series and various other things.
Still, nothing beats hands on experience.

We started with very simple straight mandrels and have progressed to shoulders, threading, etc. Each new operation is an opportunity to pull your hair out. Fortunately for me, mine's all gone.

Take care,
John T.

John 242
12-02-2012, 10:41 PM
install the lathe dog on the end of the stock (with copper shim to prevent marking) so that the leg catches on one of the chuck jaws.
Take a skim pass over the piece of stock, or barrel blank to establish a measurable surface.
Adjust the tailstock to produce the desired taper, or parallelism.
Viola.

Good point about the shim and adjusting for tapper.
We use bent pennies in the dog to keep from garfing up a finished surface.

We were taught to use a test bar and indicator to get the tail stock aligned, but I've found that unless it is way out of wack, dialing in adjustment following light cuts seems to work pretty good and is much faster. Not sure if that's the right answer or not, though.

Bullshop
12-02-2012, 11:08 PM
John 242
Thanks for the help. I am certanly overwhelmed just trying to learn terminoligy. I would very much like to get some schooling but for me that is out because there is nothing available anywhere near me.
The only way for me is to ask questions and just do it. Sure would be nice to have someone local to watch sometimes.

John 242
12-10-2012, 08:31 AM
Hey Bullshop,
Sorry about the slow reply, but last week was kind of crazy. Within the next couple of days I'll post a few links here that might be helpful.

If nothing else, you can get a grip the terminology and have a feel for the process.
Take care, John T.

Bullshop
12-10-2012, 10:02 AM
John242
Thank you thank you thank you, I just cant say thank you enough!!!

theperfessor
12-10-2012, 10:45 AM
Do you have a South Bend lathe manual? I think I have a scanned version of it somewhere that I could put on a CD or USB drive and send you. Some of it is specific to certain model features but most of it is just darn good basic information on how to do basic lathe operations.

Let me know if you're interested.

David2011
12-10-2012, 12:33 PM
Am I missing something? The center can be on a faceplate or it can be in a chuck, or it can fit into the taper of bore of the lathe head. If the center is in the chuck, you must center it. Some faceplates are built centered (fit on to the mounting provision for the chuck), some fit into chucks and must be centered, some centers fit into tapers in the lathe head bore. The barrel bore is centered by the center, you can make and use a spud in the bore with a center drilled hole to fit the center and protect the bore. The other end goes on the tailstock center, also with a spud preferrably. Tighten the tailstock center against the work and the bore is centered. Run a dog in the slot on the faceplate or against the chuck to provide power to the piece. This "dog" is the teardrop shaped hole thingie with a bolt to tighten to clamp to the work, and a 90 degree "dog"leg to fit into the faceplate slots.

Leftiye,

There are several sets of correct but confusing information presented here.
1. You would only need to center drill if turning barstock on centers.
2. The method that discusses dogs in T-slots on the faceplate is for irregularly shaped objects, like a rectangular block that needed a round shape machined internally or externally.
3. If you're machining a barrel blank or other tubular item that already has a hole down the center you would turn it in the live and dead centers as described, using a lathe dog to drive it. The cool thing about turning on centers with a lathe dog is if you're threading, you can remove the workpiece from the lathe and return it without losing your indexing as long as you return the dog to the same slot or stop. Goodsteel described a great way to make a dead center on the fly. If the lathe bed is too short to accommodate the barrel between centers with the center in the chuck, then you will need a dead center that fits the spindle's tapered bore. That will give you several more inches between centers.

"How to Run a Lathe" is still in print and available at Brownell's. It's a bargain at $7.95: http://www.brownells.com/books-videos/books/gunsmithing-books/metal-work-books/how-to-run-a-lathe-prod18158.aspx

David

David2011
12-10-2012, 01:51 PM
OK Good!!!! I am beginning to get it. When I got the lathe with the tools I noticed there was a dead center that fit the MT of the tail stock but with it there was a sleeve that fit over the dead center that changes it to a larger MT that at this point I am assuming will fit the head stock.
Another thing mentioned here was to run the bent leg dog against the chuck. I had woundered about that. So if done that way will that eliminate the need for the face plate?
That brings up another question for me, what is a straight leg dog for?
I do appreciate all the help and hope you wont get sick of me asking. I am sure I will have many more questions.

Hi Bullshop,

The fit of the dead center in the tailstock without the sleeve is common. If actually turning, you would need to use the live center in the tailstock so it's free to spin with the workpiece. The dead center turns with the spindle and lathe dog so it doesn’t have to be able to spin.
There are two options for the dead center. One is Goodsteel’s excellent method of making one from barstock in your chuck. That method will make the most accurate possible dead center. If you remove it from the chuck and later re-use it, you would need to cut a new taper to true it up but that should only take a light pass or two. With that method you would drive the lathe dog with a chuck jaw.

The other method is still very good; just not as close to perfection as making a dead center in the chuck. That is to remove the chuck, clean the spindle taper and dead center as described in another post, seat the dead center and install the slotted faceplate to drive the lathe dog. The dead center doesn’t transfer torque to the workpiece; it just holds it in the centerline of the spindle so it doesn’t need to fit super tight in the spindle. It will get tight enough on its own.

Be sure to put a piece of ¾” ply over the ways to protect them from the chuck or other accessories falling when you change them out and keep the fingers above the center of heavy parts.

Hope this clarifies a bit.

David

Bullshop
12-10-2012, 02:19 PM
theperfessor
That is very kind of you but right now I dont have a way to run those.
David2011
Thank you every bit helps.
I did get a reprint on one of the old how to books but it seems incomplete. I will try to get the one from Borwnells. I say try because today is my wifes b-day so not appropriate to ask today.

John 242
12-17-2012, 08:30 PM
This is the MIT website I spoke of. If found it to be more helpful in understanding milling than the lathe, but there is some lathe info.
http://techtv.mit.edu/collections/ehs-videos/videos

Another site that I really enjoy is Mr Lyle Peterson's Youtube page. Mr. Peterson used to be a shop teacher and he makes some very informative videos.
http://www.youtube.com/feed/UCKLIIdKEpjAnn8E76KP7sQg/u

I downloaded a 'free' copy of Southbend's How to Run a Lathe manual. It's a 1950's version, but that really doesn't matter much. It's a PDF file.
http://campkahler.com/files/How_to_Run_a_Lathe_SB_1of2.pdf

I have a bunch saved to my favorites. More to follow...

John 242
12-17-2012, 11:15 PM
Here is the South Bend How to Run a Lathe book for sale at Brownells.
It A 1942 edition, which means the free one I linked above is actually newer. Regardless, the Brownells version is by Lndsay Publications and is of good quality. The price is $7.96 and the stock number is 100-001-043WB.
http://classic.brownells.com/.aspx/pid=18158/sku=100-001-043/Product/How-To-Run-A-Lathe

This is the US Army correspondence course for lathe operations. This contains basic lathe operator information and includes chapter tests and a finals exam.
http://www.hnsa.org/doc/pdf/lathe.pdf

I forget where this came from, but I think it’s translated from Japanese or Chinese. Regardless, it covers a few basics and is somewhat educational. Not my best link, but okay.
http://www.nmri.go.jp/eng/khirata/metalwork/index_e.html

Here’s a link to Hong Kong University. Again, some basic information and the Chinese/English translation is pretty good.
http://mmu.ic.polyu.edu.hk/handout/0102/0102.htm

This is the Virtual Machine Shop. A very good site with lots of information.
http://www.kanabco.com/vms/library.html

A good amount of lathe info here, along with other shop info.
http://www.astronomiainumbria.org/advanced_internet_files/meccanica/easyweb.easynet.co.uk/_chrish/techindx.htm

Not really much here for beginners, but an interesting site none the less. This site focuses more on the mini-lathe and some of the information is a little dated, but Varmint Al is a shooter so I figured I’d include his lathe page here.
http://www.varmintal.com/alath.htm

You Tube-
South Bend's How to Run a Lathe Video
http://www.youtube.com/watch?v=9O-9_3rc6VE&list=PL4F5EA31713885847&index=8

South Bend Instructional Videos
http://www.youtube.com/watch?v=7S-zap1Q3nI&playnext=1&list=PLA23F3B4136F119DC&feature=results_main

Smithy put out a surprisingly good video series that describes basic operations
http://www.youtube.com/watch?v=H0AyVUfl8-k

Lathe video series by Duke University
http://www.youtube.com/playlist?list=PLBFAB15BAA84879F4

An okay basic lathe video, but can be challenging unless you if speak Canadian.
http://www.youtube.com/watch?v=fmFQEnDZy6E

These videos include rifle barreling and chambering, which is not exactly beginner level, but interesting all the same.
http://www.youtube.com/user/suar08161991/videos?flow=grid&view=0

I hope this will work for now. If you need more, let me know and I'll see what else I can dig up.

John 242
12-17-2012, 11:26 PM
If this helps, here are a few picture of a bolt mandrel being turned between centers. Note the lathe dog, face plate, dead center in the head stock and the live center in the tail stock.

56155

56157

56156

leftiye
12-26-2012, 08:31 PM
Leftiye,

There are several sets of correct but confusing information presented here.
1. You would only need to center drill if turning barstock on centers.
2. The method that discusses dogs in T-slots on the faceplate is for irregularly shaped objects, like a rectangular block that needed a round shape machined internally or externally.
3. If you're machining a barrel blank or other tubular item that already has a hole down the center you would turn it in the live and dead centers as described, using a lathe dog to drive it. The cool thing about turning on centers with a lathe dog is if you're threading, you can remove the workpiece from the lathe and return it without losing your indexing as long as you return the dog to the same slot or stop. Goodsteel described a great way to make a dead center on the fly. If the lathe bed is too short to accommodate the barrel between centers with the center in the chuck, then you will need a dead center that fits the spindle's tapered bore. That will give you several more inches between centers.

"How to Run a Lathe" is still in print and available at Brownell's. It's a bargain at $7.95: http://www.brownells.com/books-videos/books/gunsmithing-books/metal-work-books/how-to-run-a-lathe-prod18158.aspx

David

Thanks, but I've had a copy of that since 1974.

Willbird
12-31-2012, 04:32 PM
Also Bullshop a trick I picked up from my gunsmith. Just face the end of the barrel off nice and square with a sharp tool (with the barrel of running in the steady rest) then run the tailstock live center right on the sharp corner of the bore. Works nifty...then if it is a taper barrel I set the compound to match the angle of the barrel but just a bit more taper. Then turn the OD true(usually there is some runout) then put the steady back on the OD and face the end AGAIN, then again turn the OD true. Each time you do it the end gets more square to the bore, and that makes the OD run more true. Doing it twice usually means the bore will be within .0001 with the OD on the steady.

You can make an aluminum ring to clamp on the barrel OD if you to want to turn or otherwise mar it. Then just take a light cut from the ring to true it.

Some folks chamber barrels with the left end on a dead center in the headstock, and they hold the barrel back against that center with surgical tubing pulling it back. The right end runs in the steady rest.

JIMinPHX
01-07-2013, 03:38 AM
Another trick that I've used many times is to tap a threaded hole in the face of a piece of stock, insert an Allen bolt, then run the Allen bolt in the slot on the faceplate, rather than use a dog.

There is more than one way to skin a cat & as you gain time on the machine, you will probably come up with a bunch of new methods that work well for you.

Being a machinist is a thinking man's game. The more you can think ahead, the less extra work you will need to do.

Good chess players usually make good machinists.

MBTcustom
01-07-2013, 07:58 AM
I have used the bolt trick. Just be sure to use a stout enough bolt! I had a low grade 3/8-16 bolt driving a big work piece once. I was threading the end of this shaft, and the bolt bent. Almost jacked up my threads, but I was able to save it. Good quality bolts can take more side load than the cheapies. Whoda thunk it?

fast ronnie
12-12-2014, 02:39 AM
Another good way to drive between centers is to use a one piece shaft collar. Take out the set screw and replace with a grade 8 bolt of enough length to drive against a bolt through the face plate. This is the method we use on a cylindrical grinder that I sometimes run. The collar doesn't have to be a perfect fit on the shaft. It just has to be large enough to fit over the shaft. If marring the shaft is an issue, a piece of aluminum or brass shim can be used under the bolt.

DCM
12-13-2014, 11:49 AM
Another good way to drive between centers is to use a one piece shaft collar. Take out the set screw and replace with a grade 8 bolt of enough length to drive against a bolt through the face plate. This is the method we use on a cylindrical grinder that I sometimes run. The collar doesn't have to be a perfect fit on the shaft. It just has to be large enough to fit over the shaft. If marring the shaft is an issue, a piece of aluminum or brass shim can be used under the bolt.

Excellent tip! A collar like this would usually be easy enough to make too, especially as the collar itself doesn't need to be precise.
I love KISS solutions.

ProfGAB101
12-13-2014, 04:47 PM
A few points:

If using a faceplate with a MT reducing sleeve and dead center in the spindle be sure to indicate the center to be sure its running true. Now days with so much cheap imported tooling there are 4 surfaces that have to be near perfect for that dead center to run true, each surface that has dirt, grit, dings or just sloppy manufacturing etc. multiplies the run out.

A small piece of 4140 or 4340 pre-hardened mounted in the chuck can be turned with the compound to make a disposable center, doing this guarantees that there will be NO run out until you loosen the chuck. Likewise on your workpiece, if it has a hole in each end you can indicate the part in a 4 jaw and use a small boring or other tool to cut the center angle. I use this method often for OD turning pipe.

Lastly - if using a dead center in your tail stock you need to keep your speeds down and re-lube the bearing surface of the tail stock center before each pass. This needs to be a very EP grease, and you can get grease labeled as center grease.

Tip - if you start getting harmonics during the cut, slow the rpm down a bit and place a shot bag or bag of small bullets on the tail stock body (not on the quill portion). This also works good to drape a shot bag on your compound, just be sure doing so does not alter your depth of cut. Don't have any shot bags - make some from the lower pant legs of worn out blue jeans.