Rotary Table Centreing

[Bluechip]

Hi Folks ..

I have a 6" Vertex R.T., now I can centre it with a chuck OK. but how do I centre the thing without a chuck ??

It's easy with a 2 MT centre in it, but then I can't get at the table to bang the centre out from below  

I have come up with this idea, but is there an easier way ??

The screw thread will jack the centre out with a sleeve nut, I reckon ..

I've never seen this idea before, so I guess there is a better way ..




Dave BC

[bogstandard]

Hi Dave,

If you are using a DTI to centre the table with a chuck, then you can use the same DTI to centre it by using the MT2 socket that you want to drop the centre into.

Rather than clocking on the outside, you clock on the inside.


Bogs

[Bluechip]

Bogs ..

I've no idea how to use a clock to centre a RT.

What I've been doing is to use a feeler guage trapped between the two points, the look for the 'skew angle', like I did the lathe centres before I got a test bar.

I have a good few books on Milling set-ups but nowhere is a pic. of the technique.

Maybe if I trawled thro' my MEW's there is a description. ??

Not very bright, am I ??

Dave

[sbwhart]

Hi Dave

Ther's some pics of centering a RT on my Elbow Engine thread her

http://madmodder.net/index.php?topic=820.30

You want the post for 30th March

Hope this helps

Stew

[bogstandard]

Sorry about that Dave,

Because you had said that you had already centred it, I assumed you had used a clock, as that is the normal method.

Just like a smart**se, assuming again and dropping myself in the crap.

Stew shows how it is done using a clock. If you still can't understand how to do it, then please shout up again, and we will show you how to do it, and promise not to jump to conclusions again.

Having a finger clock is definitely the easiest and best way to do it, but there are other methods if you don't have one.


John

[Bluechip]

Hi Troops ..

Many thanks..

That answers my question perfectly.

I'm going up the wall with this milling machine .. should have bought a goldfish or summat instead 

Makes sense with a finger type DTI.  Why didn't I think of that. 

But it does raise another question. What happens if the spindle is not truly vertical ? Surely this would affect the DTI reading ?

I'm not sure how to tram the thing either..

With a tilting head, it must be possible to have the head not parallel to the column, but the column mis-aligned the other way, thus making the head appear at right angles to the bed ??
Surely this would appear to tram correctly ??

I have used a fly cutter in mine, and I get a pretty nice pattern of arcs, so I guess it's near. I have trammed it with a DTI, and it says about .0012 error over some 11", I reckon this is OK for me. Should it be better ?? What should I adjust, column or head ?

Warco WM16 machine.

Thanks again, sure Ill get it right one day

Dave

[bogstandard]

Makes sense with a finger type DTI.  Why didn't I think of that. 

Dave,

If you could think of everything, you wouldn't need help off anyone to do anything.

Your tram sounds fine, just a bit more than one thou over 11", most people would be VERY happy if they could get that accurate.

You either love or hate milling machines, I think it is because there are so many places you can easily make a mistake.
With a lathe it is fairly straight forwards, basically you mainly only use X and Y axis, and the material is usually in the same place each time.

With a mill, the material can be anywhere in relation to the tool.
Until you get to the stage where your movements become instinctive when moving the controls, it is very easy to make a mistake.

It is all to do with practice and experience, and normally you will go thru a frustration phase where nothing seems to go right, bad finishes, wrong sizes, broken tooling etc. All of a sudden a little light will come on and things will start to fall into place. Only then will you start to really enjoy yourself, and make bits and pieces how you want them to turn out.

Under no circumstances give up on it yet, you are most probably only a hop, skip and jump away.

John

[Darren]

It is all to do with practice and experience, and normally you will go thru a frustration phase where nothing seems to go right, bad finishes, wrong sizes, broken tooling etc. All of a sudden a little light will come on and things will start to fall into place. Only then will you start to really enjoy yourself, and make bits and pieces how you want them to turn out.

Under no circumstances give up on it yet, you are most probably only a hop, skip and jump away.

John

Spot on John....

I was only visiting that place myself no so long ago, the light has finally come on. It's dim, but it's on ....


Dave, hang in there and just ask if you are uncertain....

I have learnt more here in six mths than twenty struggling on my own....

[John Stevenson]

I have taught myself all I know and I still know nothing...................

John S.

[Darren]

I have taught myself all I know and I still know nothing...................

John S.

Come now, some of us might miss the bus a little too often but we aren't that slow...... 

[Bluechip]

Hi Troops

Thanks for the replies. I've had a lathe ( 2 Myfords and a 7x20 ) for 30+ years, so I've a fair idea what they will, or won't, do. This milling machine is a whole new can of worms. I must admit it's done all that I wanted it to do, bearing in mind it's a 600W motor, and not exotically expensive. I've only trashed one slot drill so far, mainly because guage plate ain't mild steel, and I can't recognise the two apart by eye !! I shall soldier on .. as you say, it will all come together sooner or later.

BTW Stew, had that compound table out of it's box yet ??

If you have, you've got further in a week than I did in a 4 years 

Dave

[sbwhart]

BTW Stew, had that compound table out of it's box yet ??

If you have, you've got further in a week than I did in a 4 years 

Dave

Not yet Dave, I've got one or two projects standing in its way yet 

I've got it safely stored away for w winter project.

 

Stew

[Stilldrillin]

Sorry Dave!

Only just found this post......  

Don`t think you saw my mill(?). When are you calling in again?

But, you`ve probably, already solved the problem......

David D

[Bluechip]

Hi Dave

Was thinking of a visit later on this week, bring the gear wotsits up.

Last Monday the hard drive departed this life on my other PC. Been trying to get some sense out of the think all last week. No freakin' back-ups of course.

Having spent a lifetime in the IT industry, being fully aware of the awful consequences of the 'NO BACK-UP' syndrome, you would have thought I would be well endowed in that aspect ???

Alas !!  NO !! 

What a pratt ......

Nothing particularly vital gone .. just annoying, having to re-create the useful stuff.

Will phone later today.


Dave

[Bernd]

This milling machine is a whole new can of worms.
Dave

Dave,

The milling machine is nothing more than a lathe turned 90 degrees on it's end. In the lathe the part moves and the tool doesn't. It's just the opposite in the mill.

Bernd

[Bluechip]

Hi Bernd

I have a bit of personal tuition arranged with the illustrious Dave Stilldrillin later on this week.

All, or at least the bit that's stuffed me for the time being, will be revealed ..

Dave BC

[Darren]

Great, It's good to get together, even a quick chat often helps to solve some problems even if you didn't know you had one 

[Bluechip]

Darren

I don't have problems ....I don't need to .... I AM a problem in my own right ...   or so my XYL said a few months ago, before departing in a huff.

Still, lifes got a bit less expensive of late. Clouds and silver linings an' all that ...

Dave

[Darren]

MY turn now.....

I thought I understood this, but I now realise that I don't.....


If you use a clock to center the RT as shown by Stew earlier, surely all you are doing is centring the work piece to the RT itself?

How do you find the centre of the RT and position it to the mill quill centre to set the table zero's.

What am I missing here 

[sbwhart]

Darren

You've two centers to think about

1:- The centre of the RT it self you can do this any where as I demonstrated on that link, what you,re doing is getting the work on the centre line of the RT

2:- Finding the centre of the RT in relation with the centre of the mill quill, you do this by putting a finger DTI in the mill chuck and rotating it around a datum thats centered on the RT, you move the X and Y axis on the mill until you have no movement on the clock so this shows that the centerline of the mill quill is on the same centre line of the RT. Then you just Zero the dials/DRO on the mill then you can index the off sets to give you pitch circle diameter of holes slot or what aver feature you want to produce.


If you've got something set up on you RT like the adaptor plate I made and the M2 screwed adaptor you made, when you put the chuck on this its automaticaly on the RT centre line so you can skip action 1 above:- In this instance you can treat it like a lathe

Hope this makes sense

Stew

[Stilldrillin]

Clock the hole in the centre of the r/t, which centres the spindle to it.

Zero X & Y axese...... Lock slides.

Mount your chuck/ component to r/t. Tap true to clock. Tighten onto r/t.

Pace out as necessary......

Rotate r/t as necessary...  

Wot Stew said!

David D

[Darren]

you do this by putting a finger DTI in the mill chuck and rotating it around a datum thats centered on the RT

Bingo...penny has finally found it's hole......

Thanks Stew & David, "rotate" the quill, simple 

[Stilldrillin]

you do this by putting a finger DTI in the mill chuck and rotating it around a datum thats centered on the RT

Bingo...penny has finally found it's hole......

Thanks Stew & David, "rotate" the quill, simple 

Sorry........ 

[Bluechip]

Yup, OK when you've seen it done. Not so obvious if not ..

I had no idea it was OK to grab the finger thingy, and point it where you liked, without destroying the clock ... 
So I've sorted mine out to look a bit like Dave SD's arrangement ..

Works well for me now   thanks to Dave SD all is sweetness and light.. till summat else crops up I suppose ..

Dave BC

[Darren]

Mine has a little lever on the back that adjusts the arm position, well i assume that's what it's for.

Mine has a very short arm, a longer one like yours would be handy....

[Stilldrillin]

Yup, OK when you've seen it done. Not so obvious if not ..

And when you`ve done it for a while........ You take it for granted, that everyone knows...... 

Works well for me now   thanks to Dave SD all is sweetness and light.. till summat else crops up I suppose ..

Dave BC

In which case, you know where I am, and me number....... 

David D

[kvom]

The DTI method is the most accurate, but can take a bit of time.  One fairly quick method is to clamp a bull center in the spindle and adjust the table until the center seats evenly in the RT center hole.  This is accurate to a couple of thousands.  Another method is to have a plug in the RT hole with a bored hole in the center.  Chuck a piece of drill rod that matches the hole and center the table so that the rod can enter that hole.

[Darren]

Sounds good to me