Make a square plate round with your rotary table

[BobWarfield]

Today I spent about 3 hours in the shop making a square plate round with my rotary table. The most important discovery I made is that this is nature's way of telling me I need to buy a bigger lathe!

I wanted to pass along some more minor lessons. First, getting your part on the rotary table and concentric with its rotation. I used a technique I learned for dialing in a 4-jaw chuck:

1) Put an indicator on your part and spin the part 1 revolution. While spinning, note the high point and the low point. You can see these marked "H" and "L" on my hub:

I used my plunger-type indicator to be sure I had plenty of range of motion.

2) Mark the point midway between "H" and "L" and rotate the indicator bezel to zero at that point. You can see the point marked "0" in the photo above.

3) Now line up each pair of jaws (Not the individual jaws, so we're doing 2 not 4 operations here) with the indicator and move the opposing jaws until the indicator reads 0.

You're now lined up!

I did this a second time with my more sensitive Interapid DTI and Indicol just to be sure I was dead on:

Note the second set of markings. Now I had the hub lined up, so I mounted the square plate to the hub:

And a big ugly plate it was too...

 

[BobWarfield]

And now I proceeded to take shallow cuts to make the circle:

You'll note I started outside the proper radius so I had some material to experiment on. I was glad I did. Lots of things problematic with this operation. First the plate wants to ring and chatter. It isn't all that thick, and it is only supported in the middle. That meant I needed to experiment quite a lot with feeds and speeds. Ultimately, I got those corners cut off, but I decided my big corncob gave the most stable cutting action:

I'm not entirely sure why, other than that it is a big old solid cutter and could be happier at slower feeds and speeds. Cutting the edge was easier than the slot too, but even edge cutting with the smaller cutters wasn't as smooth.

And here we are trial fitting to the motor:

It starts to look like I will eventually get a disc sander built! Yay!

Next step is I want to balance that disc rather than just slapping it on the motor and firing her up. Once I have it balanced and spinning nicely on the motor, I can touch up the edge and deburr easily with some sandpaper wrapped over a file.

Cheers,

BW

PS Note the contents of that little white bucket. Those are some nice crowned wheels from the original belt/disc sander. I will use them to make a 2x72" belt grinder like the knife making crowd likes.

 

[jgarrett]

Bob, My 4J and RT look very much like that. How are you attaching the chuck to to RT?
Thanks,
Julian G.

 

[BobWarfield]

Through bolts.

There's a nice through bolt setup on this page: http://www.finelinehair.com/home/RF_mill_accessories.htm

He went that way because the chuck was as big as the rotab. I did mine in a hurry so I could get on with the project, so I haven't countersunk yet as he has. It was dead easy. I got my Chuck from Shars and it was a nice piece of cast iron--very easy to drill the through holes.

Another alternative is to make a plate:

That saves you drilling the chuck.

Cheers,

BW

 

[jgarrett]

Thanks, Love learning all of this neat stuff...I am trying to compile a book with all of it stored for reference.
The markings on the chuck look exactly like the one I got from LMS but I could not find a suitable back plate from SHARS.
Post a pic of the sander when complete.
Thanks,
Julian G.

 

[deere_x475guy]

Thanks, Love learning all of this neat stuff...I am trying to compile a book with all of it stored for reference.
The markings on the chuck look exactly like the one I got from LMS but I could not find a suitable back plate from SHARS.
Post a pic of the sander when complete.
Thanks,
Julian G.

Julian I started a reference book when I started into this hobby. It's been a real time saver to just pick it up and find what I need. I have all the articles indexed and sticky tabs on the stuff I go to often.

 

[raym 11]

Bob,
thanks for the 'micro-Tools' site. Looks like I can get an adapted head for my taig mill giving me the capability of using the ER-16 tooling currently used on my full sized Grizzly mill.
Ray M