# Centering the rotary table



## BRIAN (Jan 14, 2015)

I needed to set up the table on the mill for a quick job that had to  be reasonably accurate 
 and I thought that if two centres are good enough to determine lathe accuracy they may well do the job on the mill
I am probably not the first to try this  but it's worth a mention.



It worked perfectly for me, the centres can also be tested for accuracy  by revolving the quill or table.

Brian.


----------



## Bishop (Jan 14, 2015)

Looks like a slick solution to me, will have to give that a try. 

Thanks
shawn


----------



## mzayd3 (Jan 14, 2015)

This is a technique that I adopted.  It works really well.


----------



## Knobley (Jan 14, 2015)

Thank you Brian.  I like that idea.  Never thought of it.


----------



## zmotorsports (Jan 14, 2015)

That looks like it should work.

I use an idea I got from one of Tom Griffin's videos, a machined plug/adapter that tapers into the rotary table and the other end simply goes into a collet.  Center it over ther RT until it slides easily in and out of the bore on the RT then lock the RT down.  It is pretty quick and simple once you take some time to machine the adapter.


----------



## RandyM (Jan 14, 2015)

mzayd3 said:


> This is a technique that I adopted.  It works really well.





zmotorsports said:


> That looks like it should work.
> 
> I use an idea I got from one of Tom Griffin's videos, a machined plug/adapter that tapers into the rotary table and the other end simply goes into a collet.  Center it over ther RT until it slides easily in and out of the bore on the RT then lock the RT down.  It is pretty quick and simple once you take some time to machine the adapter.



Instead of making the adapter I just use a center chucked in the spindle.


----------



## Holescreek (Jan 14, 2015)

Forgive my ignorance, the setup is truely unique in that I've never seen anything like it before.  How is this faster or more accurate than putting an indicator into the spindle and tramming the center hole? Won't you still have to do that before using the table?


----------



## arvidj (Jan 14, 2015)

Holescreek said:


> How is this faster or more accurate than putting an indicator into the spindle and tramming the center hole? Won't you still have to do that before using the table?



I don't have a great deal of experience in this area but will offer an opinion anyway.

I think you are correct that you 'should' measure it after you have used one of the short cuts ... the 'measure twice, cut once' mantra. But I think it allows you to get much closer to "right" the very first time you do measure it, possibly not having to change anything at all.


----------



## zmotorsports (Jan 14, 2015)

I agree with confirming after setup.  I like the motto of trust but verify.  I trust my rotary table will be within a few thousands by using my adapter but then by throwing my test indicator on the quill and running it around the center hole I merely verified its accuracy or had to move it ever so slightly.  It is still much faster than setting up by test indicator alone in my opinion.

I have heard friends tell me that they hardly use their rotary table or hate to remove their vise from the mill table because of the time it takes to set them back up and dial back in.  I really don't understand that because after very little practice you can have a vise or rotary table dialed in rather quick.  I have just found the little trick I use helps me get there a bit faster.


----------



## Holescreek (Jan 14, 2015)

Again, I appologize for questioning a new (to me) method, but I get an occasional visitor to my shop that will wonder why I'm using an indicator to tram a rotary table in when all I gotta do is eyeball a steel rule for parallelism to the table.  



zmotorsports said:


> I agree with confirming after setup.  I like the motto of trust but verify.  I trust my rotary table will be within a few thousands by using my adapter but then by throwing my test indicator on the quill and running it around the center hole I merely verified its accuracy or had to move it ever so slightly.  It is still much faster than setting up by test indicator alone in my opinion.
> 
> I have heard friends tell me that they hardly use their rotary table or hate to remove their vise from the mill table because of the time it takes to set them back up and dial back in.  I really don't understand that because after very little practice you can have a vise or rotary table dialed in rather quick.  I have just found the little trick I use helps me get there a bit faster.



I'm out of time today but tomorrow I'll post some pics of the tricks I use to make setting the RT up very quick and accurate. The worst part is lifting it.


----------



## rick9345 (Jan 20, 2015)

zmotorsports said:


> I agree with confirming after setup.  I like the motto of trust but verify.  I trust my rotary table will be within a few thousands by using my adapter but then by throwing my test indicator on the quill and running it around the center hole I merely verified its accuracy or had to move it ever so slightly.  It is still much faster than setting up by test indicator alone in my opinion.
> 
> I have heard friends tell me that they hardly use their rotary table or hate to remove their vise from the mill table because of the time it takes to set them back up and dial back in.  I really don't understand that because after very little practice you can have a vise or rotary table dialed in rather quick.  I have just found the little trick I use helps me get there a bit faster.



Time? This is a hobby forum, it is what we do,to occupy our time.
Changing machine tool for the job is the practice to get better to expand my abilities.
When the effort becomes too much for me. it is not a hobby and time for me to get out.
I try too to make use of all the tooling,not avoid it.


----------



## Glenn_ca (Jan 20, 2015)

Holescreek said:


> Again, I appologize for questioning a new (to me) method, but I get an occasional visitor to my shop that will wonder why I'm using an indicator to tram a rotary table in when all I gotta do is eyeball a steel rule for parallelism to the table.
> 
> 
> 
> I'm out of time today but tomorrow I'll post some pics of the tricks I use to make setting the RT up very quick and accurate. The worst part is lifting it.



The steel rule is not being used to check parallelism to the table but to confirm that the centers are lined up accurately much the same way as you would use a rule to determine if your cutting tool is at the center point of the stock on the lathe, or at least that is the way it looks to me.


----------



## itsme_Bernie (Jan 20, 2015)

Great solution!

Tom G, a member here, also posted another solution to his YouTube "Tom's Techniques"

Bernie


----------



## atwatterkent (Jan 20, 2015)

My vote is for using a coaxial dial indicator. It's easy to set up and use and I believe it's the most accurate.


----------



## samthedog (Jan 21, 2015)

RandyM said:


> Instead of making the adapter I just use a center chucked in the spindle.



This is also the method I employ. As for the accuracy... a man on a galloping horse would never notice any inaccuracy in my work.

Paul.


----------



## RandyM (Jan 21, 2015)

rick9345 said:


> Time? This is a hobby forum, it is what we do,to occupy our time.
> Changing machine tool for the job is the practice to get better to expand my abilities.
> When the effort becomes too much for me. it is not a hobby and time for me to get out.
> I try too to make use of all the tooling,not avoid it.



Very well said.


----------



## ScrapMetal (Jan 21, 2015)

atwatterkent said:


> My vote is for using a coaxial dial indicator. It's easy to set up and use and I believe it's the most accurate.



That's the method that I use.

FWIW

-Ron


----------



## Holescreek (Jan 21, 2015)

rick9345 said:


> Time? This is a hobby forum, it is what we do,to occupy our time.
> Changing machine tool for the job is the practice to get better to expand my abilities.
> When the effort becomes too much for me. it is not a hobby and time for me to get out.
> I try too to make use of all the tooling,not avoid it.



I'd guess that there are many levels of "hobby machinist" and it takes time to step back and try to see things from each end of the spectrum.  At one end you have the beginners for whom figuring out the setup is the goal of the day and at the other end you have more advanced hobbyists for whom "setting up" robs them of the little time they can scrounge to complete a part of their project before they have to leave for their real job.

It takes a person with this understanding and some tact (mostly lacking in we old machinists) to applaud an effort and point out a simpler and/or more accurate method.  The majority of the time the simpler and/or more accurate method will work equally well for other setups and different machinery too, and using familiar methods leads to making less mistakes.  

I'm jealous of anyone for whom time is unimportant. It's the one commodity we can't buy when it runs out.


----------



## Chipper5783 (Jan 22, 2015)

atwatterkent said:


> My vote is for using a coaxial dial indicator. It's easy to set up and use and I believe it's the most accurate.



Like most things in life, and often the case in machining - there is more than one way to get the job done - depending on many different factors.

The coaxial dial works great - but the indicator I have takes up quite a bit of head room (my machine is small and I'm often battling insufficent head room).  Of course various other dial arrangements.  I like Osborne's Manuever (see Google for explanations) - I first saw it in one of G Lautard's books, is also good (very simple, need only an edge finder, the component diameter and access to the OD of what you're centering over).


----------

