# Fixture Plate for Rotary Table



## firemaker76 (Oct 24, 2022)

I finally got around to finishing a fixture plate for my 8" rotary table.  This turned out to be a little more involved than I was anticipating, but it was well worth it and I learned a lot.
I started with a piece of 8.250" diameter x 1.250" ductile cast iron and chucked it up in my lathe.
I faced the first side and turned it to a diameter of 8" x .800" thick.  Then I flipped it in the chuck jaws.  This gave me a nice, square face to sit up against the jaws of the chuck to be able to machine the other side. 
With the material now turned down to finished diameter and length, I bored a 1.0713" hole through the middle.  This hole will mate up to the 1.0708" OD feature on a setup tool that I built to serve two purposes.....#1-to center my rotary table to the quill of my mill vía the MT3 taper, and #2-to center the fixture plate on the rotary table.  I ended up with a bore .0005" over that of the setup tool. 
I then set up the plate on the mill and indicated off of the bore to find center.  With my X and Y axis zeroed, I drilled the mounting holes that would attach it to the rotary table. One of the feautures I wanted to have, was a relatively easy way to align the mounting bolts perfectly parallel and zero with the X axis at any given time.  This would be especially useful, if (for whatever reason) I needed to remove the plate from the mill, unexpectedly, and then be able to set it up exactly where it was before.  After a little brainstroming, I came up with an idea.  The mounting holes would have a secondary purpose - a way to locate them using a precision pin.  Step one was to drill undersized .367" holes that I then reamed to .375".  These holes were drilled exactly 3.625" from center of the fixture plate at 0, 90, 180 and 270 degrees.  Secondly, I parted off a 1" piece of .375" 01 tool steel in my lathe that would be used as the locating pin.  Now if I ever wanted to align the fixture plate to the X or Y axis of my mill, I could center the rotary table, mount and center the fixture plate, zero the quill in both axis, adjust the quill to 3.625" from center and then (using the .375" locating pin in the quill) rotate my rotary table slightly until the pin just slipped into the mounting hole and then lock it all down.
With the precision holes drilled, I then used a 9/16" endmill to stepdrill the holes .375" deep. These would allow the mounting holes to sit just below flush of the fixture plate. 
I initially engraved light grooves along the X and Y axis and was going to attempt to mill circular grooves at several different diameters, but this didn't work on the mill like I wanted. With the ability to remove and reinstall the plate on my mill to the same location (which now would pay off), I decided to put it back in my lathe and turn the circular grooves.  I turned .015" deep grooves at 2", 4" and 6" diameter. Now back to the mill it went.
At this point I decided that the I wanted the previously engraved lines along the X and Y axis to serve a better purpose.....to center and hold round stock.  So, using a 1/16" endmill, I milled .0625" deep grooves and then milled a nice 45 degree chamfer along the edges.
Next I drilled 76 holes using a #7 drill bit at .750" centers, added .030" chamfers and tapped them 1/4"-20.

***Note to self....never use a carbide tap to thread 76 holes in 3/4" cast iron, because when it snaps off inside the hole because you didn't adjust your new tapping head correctly, you will spend a good amount of time (if you're lucky enough to succussfully remove it) trying to chip it out piece by piece to save your project. Ask me how I know LOL!***

With all holes drilled and tapped, I then flipped the plate over, located the center and mounting holes, and then chamfered all holes.
After this project, I had to do a complete wipe- down of my lathe and mill to clean off all the graphite powder that had covered everything. It is terribly dirty material to machine.

Thanks for looking everybody, and Happy Machining!!!!


----------



## davidpbest (Oct 24, 2022)

Very nicely done.  Curious where you purchased the cast iron.


----------



## Janderso (Oct 24, 2022)

Looks really good.
You will find that plate to be very handy.
Unfortunately, in my case, there never seems to be a threaded hole where you need one.


----------



## firemaker76 (Oct 24, 2022)

davidpbest said:


> Very nicely done.  Curious where you purchased the cast iron.


Hi there David,
Thank you very much.  I got that piece of cast iron from McMaster Carr (part #8588T25).


----------



## firemaker76 (Oct 24, 2022)

Janderso said:


> Looks really good.
> You will find that plate to be very handy.
> Unfortunately, in my case, there never seems to be a threaded hole where you need one.


Thank you sir.  I ran into quite a few situations already trying to build parts, where this would have saved me lots of time, so I think it will prove very useful.


----------



## buffdan (Oct 24, 2022)

Great idea, thanks for sharing


----------



## IamNotImportant (Oct 24, 2022)

Love it!


----------



## firemaker76 (Oct 24, 2022)

buffdan said:


> Great idea, thanks for sharing


Thank you!


----------



## firemaker76 (Oct 24, 2022)

IamNotImportant said:


> Love it!


Thank you!


----------



## extropic (Oct 24, 2022)

Very nice EVERYTHING.    

Please describe what purchased part (MT3) you used to make your 'setup  tool'.


----------



## firemaker76 (Oct 24, 2022)

extropic said:


> Very nice EVERYTHING.
> 
> Please describe what purchased part (MT3) you used to make your 'setup  tool'.


Thanks very much,
For the setup tool, I bought a 3MT shank with 1/2"-20 threaded end off of Amazon.  Then I chucked up a 3" piece of .750" (Heat Treated) 4140 in my lathe and drilled and tapped the end 1/2"-20 to mate up to the 3MT shank. Once the 4140 rod was secured onto the shank, I used a 3MT to 5MT adapter so I could pop it into the 5MT spindle of my headstock and then turned it between centers with a live center on the tailstock end.  This way, when I turned the 4140 down to size, it would be concentric with the 3MT shank.  At this point, I turned the end 2" section of the 4140 down to .500" so it could be inserted into a 1/2" R8 collet on my mill.  This setup tool was originally built as the shaft in my "Tailstock Tap and Die Holder" post, but luckily for me, my rotary table uses the same #3 Morse Taper...basically one tool for two applications.

Thanks for looking!


----------



## Cheeseking (Oct 24, 2022)

Very nice project love all the photos.
Cast iron is so nice to machine too bad it makes such a nasty mess 


Sent from my iPhone using Tapatalk


----------



## firemaker76 (Oct 24, 2022)

Cheeseking said:


> Very nice project love all the photos.
> Cast iron is so nice to machine too bad it makes such a nasty mess
> 
> 
> Sent from my iPhone using Tapatalk


Thank you sir,
I couldn't agree more.  I love machining it, but I hate the cleanup after.


----------



## Just for fun (Oct 25, 2022)

Very nice work, and very nice clear photos to go along with it.


----------



## firemaker76 (Oct 25, 2022)

Thanks for the support Tim!


----------



## Norseman C.B. (Oct 25, 2022)

Nice work  !!..............


----------



## firemaker76 (Oct 25, 2022)

Norseman C.B. said:


> Nice work  !!..............


Thank you


----------



## Janderso (Oct 26, 2022)

firemaker76 said:


> I finally got around to finishing a fixture plate for my 8" rotary table.  This turned out to be a little more involved than I was anticipating, but it was well worth it and I learned a lot.
> I started with a piece of 8.250" diameter x 1.250" ductile cast iron and chucked it up in my lathe.
> I faced the first side and turned it to a diameter of 8" x .800" thick.  Then I flipped it in the chuck jaws.  This gave me a nice, square face to sit up against the jaws of the chuck to be able to machine the other side.
> With the material now turned down to finished diameter and length, I bored a 1.0713" hole through the middle.  This hole will mate up to the 1.0708" OD feature on a setup tool that I built to serve two purposes.....#1-to center my rotary table to the quill of my mill vía the MT3 taper, and #2-to center the fixture plate on the rotary table.  I ended up with a bore .0005" over that of the setup tool.
> ...


You mentioned you had a good cleaning to do.
I bet, your mill looks brand new. Cast iron is fun to machine but boy is it messy.
Beautiful job sir.
Say, are the brass nuts on an eccentric screw?
I just watched Click Spring’s video on this subject. He is an amazing machinist and clock maker.


----------



## firemaker76 (Oct 26, 2022)

Janderso said:


> You mentioned you had a good cleaning to do.
> I bet, your mill looks brand new. Cast iron is fun to machine but boy is it messy.
> Beautiful job sir.
> Say, are the brass nuts on an eccentric screw?
> I just watched Click Spring’s video on this subject. He is an amazing machinist and clock maker.


Thank you sir.  
Yes, those are on an eccentric screw.  I actually just bought those to use on low profile setups specifically for that fixture plate.  They are the Mitee-Bite brand and seem to work really well.


----------

