Old Brown and Sharpe Rotary Table Help Please

Janderso

Jeff Anderson
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Hi,
I was inspired recently to add a hold down or clamping fixture to my 10" Rotary Table.
The center hole is not a Morse Taper, just a hole.
In an effort to clamp a piece on the table, I would like to add an aluminum plate but I am not sure the best way to go about this.
Obviously to expedite table centering I would like to cut a standard taper of some sort to dial in center spindle on the Bridgeport Mill.
Based on this type of table, what would you do or what have you done to achieve my goals?
Thanks for the help.
JeffIMG_1161[1].JPGIMG_1162[1].JPG
 
I would just make a snug fitting plug to fit the RT hole, making sure it is tall enough to also index tight into the fixture plate. Hold the whole mess down to the RT with recessed SHCSs and t-nuts. Drill and tap the fixture plate as required to fit your jobs. This is assuming the round hole in the middle of the RT is precision placed, not just a rough hole.
 
No, it's Brown and Sharpe precision. The table is very tight, It turns fairly smooth with no discernible lateral movement.
Using your idea, would you think chucking a 3/8 piece of tool steel in a 3/8 collet to extend and line up the bushing?
I could ream a 3/8 hole in the center of the bushing.
Am I on the right track?
 
My other point, that I did not write, about using the table as is, is that putting in a Morse taper accurately concentric and square to the table top and bottom is not a trivial thing to do with typical home shop equipment. And, once it is wrong, it will be annoying from then on.

Yes, lining it up with a dowel pin or other known accurate locating pin would be fine, though it can move sideways and still go in the hole, so you still need to be careful when using it. A loose quill has slop when unlocked, and how accurately is the head trammed, how concentric is the collet to the spindle, etc., all matter, at least for fussy work. Also, the bushing you make will need to be accurately concentric and parallel.

Honestly, I use a very simple method for most work. My RT has a MT3 taper in the center. I have an extra drill arbor that fits the hole. I put an accurate rod with an accurate and coaxial 60 degree point on it in a collet, and then move the table around until the 60 degree point falls neatly into the center hole on the Jacobs taper end of the arbor. Done in short order. For fussier work, I use a Noga holder:
http://www.noga.com/Products/Centering/Centering Universal Holders/NF1018/Centering_NF_holder_3|fs|8"_-_NF1018
1537888862496.png
and a tenths indicator to center the hole to the spindle.
 
Just turn up a plug with a center drilled in it. As Bob says, use a 60 degree point and locate from that. I do exactly the same as Bob !
Works for me...
 
No, it's Brown and Sharpe precision. The table is very tight, It turns fairly smooth with no discernible lateral movement.
Using your idea, would you think chucking a 3/8 piece of tool steel in a 3/8 collet to extend and line up the bushing?
I could ream a 3/8 hole in the center of the bushing.
Am I on the right track?

I've got a 10" table with the same type of hole in the center I made a plug with a lip to go into the hole and put a dowel pin hole in the middle.

Stu
 
I have a 12" RT with a 1" cylindrical hole in the center. I made a threaded plug to engage a 4" three jaw chuck from my 6 x 18 lathe. The plug has an internal 3/8-16 thread as well. On the back side of the RT, I mounted a close fitting plate which is threaded for 3/8-16. I screwed a stud from my clamping set into the plate and thread the chuck onto the stud. The chuck is now centered on the RT to the limits of runout on the chuck. It is easily removable if I need to clamp to the table.

My 6" Tormach 4th axis RT also has a cylindrical indexing hole at the center. The 5" three jaw chuck is mounted on a special backing plate which references the hole and is clamped to the table using the table tee slots.
 
I've got a 10" table with the same type of hole in the center I made a plug with a lip to go into the hole and put a dowel pin hole in the middle.

Stu

Stu,
You use the dowel pin to line up the spindle? To center the table?
Bob, I agree with you. The morse Taper is not in my box of tools:)
I have a way or two forward now.
Thank you.
 
Stu,
You use the dowel pin to line up the spindle? To center the table?
Bob, I agree with you. The morse Taper is not in my box of tools:)
I have a way or two forward now.
Thank you.

Dual purpose, I can use the dowel pin to align the table under the spindle and also use the hole to align the part (if it has a hole at the center of rotation).
 
though it can move sideways and still go in the hole
Bob,
Could you please elaborate on your statement?
I can see some play due to lack of rigidity from the spindle and collet and length of the alignment pin to the table cavity.
 
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