# 10” Brown and Sharpe Rotary Table Cacraficial Mounting Plate



## Janderso (Oct 29, 2018)

We are encouraged to post projects. Ok, here goes.
I found this piece of 6061 aluminum plate, 10.5” square, 1” thick. I was convinced to leave it square to increase clamping options.
I used my Bridgeport and the Asian boring kit. The center pilot hole came out perfect with about .001-.002” slip fit.
I don’t know if I should put a random threaded hole pattern or let the project dictate.
The next step is to figure out an accurate way to retain the plate. Centering slots or something like that. The standard t nuts will not allow repeatability.
The first pics are the additional challenge of mounting my Bison, 3 jaw 4” chuck.
I don’t think I have the talent to drill and tap the center of the centering pin with the required accuracy.
I was toying with removing the backing plate, but how to secure it?
There are four drilled and tapped holes I could use but it would need to be pretty darn perfect.
(Edit, I just noticed the typo in the title, what a bozo)


----------



## Cadillac (Oct 29, 2018)

Looks like good progress there. To mount the 4” chuck is easy don’t be intimidated. Find the center of the rotary table with the plate already installed on it. After you find center you will need to move half the diameter of the chuck mounting holes. You have a three hole mount on chuck so your index will be 120*. Find out the chuck hole mounting diameter and your there. Looks good


----------



## Janderso (Oct 29, 2018)

You make it sound simple. 
Your way does make sense.
Thanks


----------



## Janderso (Oct 29, 2018)

Mr. Cadillac,
Thinking this through, my first though was to slot the 120* holes for indexing. But, how would I secure the Chuck once it was centered?
It has to be mounted from the back on center. Just thinking out loud.


----------



## silverhawk (Oct 29, 2018)

Janderso said:


> Mr. Cadillac,
> Thinking this through, my first though was to slot the 120* holes for indexing. But, how would I secure the Chuck once it was centered?
> It has to be mounted from the back on center. Just thinking out loud.



While that is true, Cadillac has the right idea. You start the holes on this side while mounted, then you can countersink them after removing the plate.

Install the chuck to the plate, and then install the plate to the rotary table. As you tighten it down onto the rotary, you index the plate back into place.


----------



## Janderso (Oct 29, 2018)

"Install the chuck to the plate, and then install the plate to the rotary table. As you tighten it down onto the rotary, you index the plate back into place. "

So, you are saying to remove the 1.250" centering pin? There is no indexing with the pin installed.
With it removed, I will have indexing options for the work and/or the chuck. I just need to make sure the fastening system I come up with for the plate to the table is robust.
Am I following?
This is not simple for me. I want it to be right the first time.


----------



## benmychree (Oct 29, 2018)

Mighty fine looking chuck you have there!


----------



## silverhawk (Oct 29, 2018)

Janderso said:


> "Install the chuck to the plate, and then install the plate to the rotary table. As you tighten it down onto the rotary, you index the plate back into place. "
> 
> So, you are saying to remove the 1.250" centering pin? There is no indexing with the pin installed.
> With it removed, I will have indexing options for the work and/or the chuck. I just need to make sure the fastening system I come up with for the plate to the table is robust.
> ...



The centering pin should help. My concern would be recent earring it, and of you use the pin, it should be dead nuts on, as long as the pin was clean when you started and remains clean when you reinstall. No chips or oils.


----------



## Janderso (Oct 29, 2018)

benmychree said:


> Mighty fine looking chuck you have there!



I do agree sir!
I took it apart to clean and lube, it is smooth as glass.
Thanks again John!
I hate to take the backing plate off but it seems the only way to mount it on the rotary table.
I'll get it. Bob has been great with advice and pointers.


----------



## Janderso (Oct 29, 2018)

""My concern would be recent earring it ""
Mister Silverhawk, I really want to hear your advice, what did you mean to say?


----------



## Bob Korves (Oct 29, 2018)

Jeff, first fit the plate to the chuck so it is located rigidly.  Tight fitting round (or square or whatever) steel pins to fit the narrow portions of the t-slots below the plate along with the centering pin you made will effectively make the tooling plate an integral part of the RT.  Do that first.  Try to have the plate fitting on the center pin tighter than the .001-.002" clearance you mentioned.  Not only will it be less accurate if it has play, it will also be less rigid, which can cause chatter when using it.  Make everything fit tight and snug.


----------



## silverhawk (Oct 29, 2018)

Janderso said:


> ""My concern would be recent earring it ""
> Mister Silverhawk, I really want to hear your advice, what did you mean to say?



What Bob and others have said. I can't believe I messed that up, but I meant re-centering, not recent earring. (Sigh)


----------



## Janderso (Oct 30, 2018)

One of the guys at work has a set of transfer pins. I am thinking that would be a good way to center the chuck and mark for drilling.
Bob, I mentioned .001-.002” because the plate fits snug over the pin.
I turned it to .001 for clearance, it’s tight but can be moved on and off with a bit of wiggling.
I see what you mean about, everything tight, chatter creeps in at every opportunity I have found.
(Edit) Bob, I’m glad you mentioned the round or square locating pins for the plate to table fit.
I was heading off a different direction.


----------

