How to fix a hex collet block I milled?

[JoeLee]

I have a rotary table but it doesn't run perfectly true.
What does go off the end of the hex bar mean? One end will be in the center located on the draw nut and the other end will be in a center hole I put in the 1/2" shaft that's in the collet.

What I mean is to grind the entire length of the bar your wheel needs to go past each end. What ever you chose for hold downs are going to have to be set past each end of the bar by several inches. From what I can see you have a round shoulder followed by a hex on one end. Are you going to stop before that ?

Which model T&C grinder do you have ??

JL....................

[challenger]

What I mean is to grind the entire length of the bar your wheel needs to go past each end. What ever you chose for hold downs are going to have to be set past each end of the bar by several inches. From what I can see you have a round shoulder followed by a hex on one end. Are you going to stop before that ?

Which model T&C grinder do you have ??

JL....................

It's a B600 unit.
I'm going to use a set of centers I have for the grinder and get as close as I can to the draw nut. The collet end will have plenty of room to allow the wheel to go past.
This is how I'm thinking of for the milling.
The parallels will need to be shimmed as a milled face is going on the bottom.

[JoeLee]

The B600 is the smaller model, but should have enough table travel to cover the bar.
The set up in the mill looks like it should work but you accuracy is at the mercy of the hex nut being centered, symmetrical and at the same center height on both ends.

JL............

[JoeLee]

I have a rotary table but it doesn't run perfectly true.
What does go off the end of the hex bar mean? One end will be in the center located on the draw nut and the other end will be in a center hole I put in the 1/2" shaft that's in the collet.

How do you mean it doesn't run true?? Like the chuck isn't centered ??

JL.....................

[Paul Alciatore]

If you have an indexing device, but it has too much run-out (off center error) then you can just use it for generating an accurate, 60 degree angle. Use it as an accurate, protractor scale by mounting a piece of straight stock cross-wise on it and then moving it 60 degrees. Sit the indexer on the table and use a parallel to support the piece of stock while you tighten it on the indexer's spindle. You will want it to be sticking out one side so it can be rotated by that 60 degrees.

Then:
1. Mount your bad hex between centers on the mill table.

2. Start with the lowest side - the one that is closest to the center line. With it on top, take a skimming as described below.

3. Devise a method of locking/clamping it at an angle once it is mounted. Make two of these clamps so that you can clamp one end and mill half of one side flat. Then attach the other clamp on the newly milled end before removing the first one.

4. Remove the first clamp and then mill the other half with the depth of cut exactly the same.

5. Use your indexing device/protractor to move that freshly cut side to 60 degrees from the table. That should be 120 degrees from your first cut. Now repeat #3 and #4 above to get that second side to match the first one.

6. Repeat #5 to get a third side accurately cut.

7. Set your improvised protractor for 30 degrees and use it to set for a fourth side.

8. Then back to 60 degrees for the fifth and sixth sides.

[challenger]

How do you mean it doesn't run true?? Like the chuck isn't centered ??

JL.....................

It's a low budget Palmgren/Craftsman unit and isn't flat. It runs +-. 005" in 360 degree rotation.

[754]

Mount something on the Palmgren and grind or mill it true.

[challenger]

Mount something on the Palmgren and grind or mill it true.

I'm sure you have to know it isn't as simple as that right?

[oxford]

I’m not familiar with the 3c collet but the block looks really long. Any reason for that?

[J Tiers]

I’m not familiar with the 3c collet but the block looks really long. Any reason for that?

3C is almost the same as a 3AT. Used on Southbend. Almost 2 3/4" long, and 5/8 diameter approx. The block looks about 2x longer than needed, to me.

[Mcgyver]

I've spent a lot of shop existence in "must make everything myself" phase, great for learning (and concluding you need every machine under the sun)

Now, I'm more in the "get on with it phase". Without the right tools to quickly and accurately cut the hex, I'd be looking at a foot of cold rolled for $25-30. https://www.mcmaster.com/hex-stock/

[challenger]

3C is almost the same as a 3AT. Used on Southbend. Almost 2 3/4" long, and 5/8 diameter approx. The block looks about 2x longer than needed, to me.

It is longer than I'd like. That's because I'm using a drawbar/nut from the little vertical head I have for my Burke horizontal mill.

[J Tiers]

Make one!

Check the pic in your other thread that discusses the block.