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View Full Version : Square block material hows that aligned on a lathe?



GeorgeD
04-08-2010, 04:53 PM
Ok,so I've bought me a DTI,however thats fine for round bar material but...

Square block material hows that aligned? same procedure for round bar?

Cheers :wink:

GeorgeD
04-08-2010, 06:53 PM
Hmmm,no answers as of yet.

The only way I can think of centralising a square block is drawing a diagonal lines across its corners and finding the center,then slip it in the chuck.

Stick a center in an arbour on the tailstock,offer up the tailstock to the workpice and adjust the center mark on workpiece to align with center.?

BillTodd
04-08-2010, 07:11 PM
Square block material hows that aligned? same procedure for round bar?Pretty much. You need to ensure the DTI is dead on centre then compare opposite faces by rocking the chuck for a minimum reading


The only way I can think of centralising a square block is drawing a diagonal lines across its corners and finding the center,then slip it in the chuck.Stick a center in an arbour on the tailstock,offer up the tailstock to the workpice and adjust the center mark on workpiece to align with center.? It is easier and more accurate if you trap another lathe centre between the tail-stock centre and the centre-punch dot, then set the DTI on the trapped centre (alternatively make yourself a wiggle centre like this - http://www.frets.com/HomeShopTech/Tooling/WigglyCenter.jpg/wigglycenter.html)

[edit] There are some real gems on Frank Ford's site (http://www.frets.com/HomeShopTech/hstpages.html), well worth reading.

Bill

GeorgeD
04-08-2010, 07:40 PM
Thanks for that,Bill.

Will have a look through that site.:clap:

bogstandard
04-08-2010, 10:02 PM
As mentioned above, here is a picture of the operation.

This can be used to centralise any pop mark in the four jaw.

Using two centres, one in the tailstock, and one between the tailstock centre and the pop mark. Then use your clock on the centre that is suspended in the middle.

http://i202.photobucket.com/albums/aa102/bogstandard_photos/rotbore6.jpg

You should find all good centres have a centre location in the small end, even ones with tangs on, and everyone should have two centres with their lathe, one for the tailstock, one for the spindle. Don't try to use a 'live' centre for the middle one.

Hope this explains it OK.

Bogs

GeorgeD
04-08-2010, 10:38 PM
Thanks Bogs.

No need for a big rod then. :wink:

Was going to email the bloke and ask him where he found his big rod. lol

Ross77
04-08-2010, 11:28 PM
Thats Bill, John, another techniqe to add to the list...A picture is definatly worth a thousand words

GeorgeD
04-08-2010, 11:31 PM
Ain't it just. :wink:

bogstandard
05-08-2010, 07:41 AM
This was shown to me about 40 years ago, and I took the shot during one of my builds, about three years ago.

People do have a tendency not to look to the past, but look around for modern marvels to solve a problem.

I used to go around boot sales looking for old engineering books. A 20p book from the past has solved many of my problems up to now, and will carry on doing so into the future.

Try it sometime, you will be amazed at what you can pick up, information wise.

There is very little new any more in setting up machinery and jobs, most are old ideas, brought up to date, and charged big bucks for.

Oldies but goodies.

Bogs

GeorgeD
05-08-2010, 08:42 AM
Very true that Boggy.

As the old saying goes...you cannot teach an old dog new tricks..or words to that effect. :wink:

We are well into the future and yet we're still riding round on four wheels that was born in the fourth Millenium BC. lol

BillTodd
05-08-2010, 10:10 PM
Very true that Boggy.That's Mr Tandard to you, young whipper-snapper :LOL:



No need for a big rod then. :wink:

Was going to email the bloke and ask him where he found his big rod. lolThe Hardinge HLV-H (Frank has a Sharp copy) tail-stock weighs about 35-40kg (about the same as whole of your clarke lathe) and, with 50 odd square inches of base, tends to 'stick' to the bed, making it a right b******d to move - So, you don't move it unless you have to, that's why Frank's has a big rod ;)


http://www.mycncuk.com/forums/attachment.php?attachmentid=302&d=1237608237

graffian
06-08-2010, 12:35 AM
I just use a DTI?

GeorgeD
06-08-2010, 06:01 AM
I just use a DTI?

Why the question mark?

graffian
06-08-2010, 07:37 PM
I was wondering what I was missing. Why pop the centre and use a pair
of centres when you can use a DTI? I have a few minutes I will set up a bit
of square and try and make a video if anyone wants to see it.

GeorgeD
06-08-2010, 09:22 PM
try and make a video if anyone wants to see it.

We're all eye's...well I am anyway.

graffian
06-08-2010, 09:35 PM
I set up a chunk of square, actually took longer to find a bit than
to set it up. The video is really crappy, I know what's going on cos
I was there;-) Holding a camera and doing something is too difficult
for me.

GeorgeD
06-08-2010, 10:10 PM
You should aquire a tripod then.:smile:

graffian
06-08-2010, 10:32 PM
I did try with a tripod, the lathe has a window behind it and all you could see was the sillohette of the gauge;-)
What it needs is a flexible, but lockable, arm to mount the camera on.
Seeing the marking on a DTI isn't easy if the picture shows much of whats going on. I did a video of a gear that
had runout, to show the people who supplied it, I used a 4" face gauge so you could see it. I don't think I can use
the big gauge to set a square as it probably won't clear the corners.

GeorgeD
06-08-2010, 11:06 PM
So your using the corners as a means to centralise the block?

graffian
06-08-2010, 11:28 PM
Moving the corners would be to complicated for me;-) I set up the flats.

GeorgeD
06-08-2010, 11:36 PM
What if we have 3"x1" block :smile:

John S
06-08-2010, 11:52 PM
What if we have 3"x1" block :smile:

It will only be a 3" x 1" block twice per revolution, the other two times it will be 1" x 3"

.

graffian
07-08-2010, 12:26 AM
It's also √10" now and again.

Mr S got a couple of inches of 1" diam EN36 going spare?

John S
07-08-2010, 12:31 AM
Think so, check tomorrow, it's dark now and that workshop is bloody haunted.

.

graffian
07-08-2010, 11:42 PM
Had another go with a camera, not a very good video. I usually set up
a lot faster and don't talk bollocks while doing it;-) I will have to have another
go, I can't understand why it was so dificult.

http://www.youtube.com/watch?v=2CJNEyy3QiY

ecat
08-08-2010, 12:14 AM
Thank you.
I thought that was excellent, mind you I am a computer programmer ;-)

John S
08-08-2010, 12:43 AM
It is possible to set a bar up in a 4 jaw chuck to 2 thou easily or 1 thou with a bit of care using no specialised equipment at all.

Works on square, round or rectangular all the same method.

First thing to remember when using a 4 jaw independent chuck is to forget it has 4 jaws and tell yourself it has two sets of 2 jaws even to the point of marking opposite jaws with a different coloured marker pen.

On the front of a 4 jaw chuck is a series of concentric rings these are guide rings so you can line opposing jaws up using the rings for a guide, some of the cheaper, smaller chucks may only have 3 or 4 rings on, widely spaced.
There is no reason why you can't remove the jaws and turn some intermediate rings on with a Vee shaped tool.

Now put your piece of material in the chuck, we will assume it's square although the operation is the same for square and round and only slightly different for rectangular.
Using opposite jaws just nip the work up trying to get the ends of the jaws in the same position relative to the rings, this should get you within a post code of centre.

Now take any lathe tool and turn it round in the holder, blunt end out. This is your secret weapon, everyone has one of these but mat not have a dial gauge or other expensive toys.

Now with one face of your square bar vertical wind the blunt end in until it touches the bar and note the reading, if you can, zero the dial, now retract, turn half a turn to the opposite jaw and wind in to get a reading.

If you are dead lucky both readings will be the same, chances are they will differ by 10 thou or so. In which case work out the low side, that's the side you have had to wind in more and you will need to slack this jaw off a tad and tighten the opposite one up.

Repeat taking the readings on these two jaws, forget the other two, until the reading is the same on both sides.

Now deal with the other two jaws, this is easier as you know what the reading should be from the first two unless it's rectangular and you will have two different readings.

Sounds a bit long winded but believe me it takes far longer to type this than do it, after a few goes it's easy to get to a thou by this method, if you want better then break out the DTI at this point.

The main thing is to remember to just work on a pair of opposite jaws, beginners make the mistake of trying to work all 4 jaws at the same time which together with inexperience causes untold problems.

GeorgeD
08-08-2010, 11:16 AM
I usually set up
a lot faster and don't talk bollocks while doing it;-) lol

Try using two chuck keys to centralise,saves alternating between jaws.

To be honest I'm thinking the centers approach to this will be much easier,until I get the lathe then I won't know?

:wink:

GeorgeD
08-08-2010, 11:21 AM
Whats the name of those hollow tubes that you insert into the chuck for protection of the workpiece? ie supposing I want to turn the end of a threaded rod from 10mm down to 8mm I need to protect the thread from damage,whats the insert called?

irving2008
08-08-2010, 11:26 AM
I think there is no one 'right' way, it all depends on the job. The centres approach works ok if you are trying to centre a flat end face but might not work if the item has any shape on the surface. JohnS' approach works well and i use it, especially if you want to reduce square to round or the surface finish is so poor that a DTI would give fluctuating readings. A DTI approach works well in most circumstances but involves a little more setup effort in getting the DTI out and in position, and is the only truely viable approach when you want to centre a bore in the chuck irrespective of the external shape and particularly when the bore isn't central with respect to the outside edges.

irving2008
08-08-2010, 11:27 AM
Whats the name of those hollow tubes that you insert into the chuck for protection of the workpiece? ie supposing I want to turn the end of a threaded rod from 10mm down to 8mm I need to protect the thread from damage,whats the insert called?

soft brass shim, or even thick paper will do the job

GeorgeD
08-08-2010, 12:39 PM
soft brass shim

Nope,that brings up all manner of shims except the name of the item I'm looking for.

Can't find the youtube vid where the bloke propely named it befoe he used it on the lathe.

GeorgeD
08-08-2010, 12:45 PM
Oh bugger,I only need a soft metal tube near enough the diameter of the threaded rod then use a slitting saw to slice it tdown the middle. tsk!:rolleyes:

bogstandard
08-08-2010, 01:00 PM
I don't know about tubes, I always cut up an aluminium soft drink can into strips with a pair of scissors, to put between the jaws and the job to prevent bruising.

Bogs

Wobblybootie
09-08-2010, 10:34 AM
Would a collet be any good? (5C type etc)

GeorgeD
09-08-2010, 02:25 PM
I suppose its name is that of a collet since its a sleeve with a slit in it,made one out of a bit of 15mm copper piping...very easy to do. :whistling:

Hopefully my new toy turns up tomorrow,can't do any weldin today...its hissing down here. :mad: