Workholding on the lathe

[Wongster]

Hi folks,

I'm planning right now to make an ER32 collet chuck that is to be bolted onto the spindle flange of the Proxxon PD400 lathe. The spindle flange is 100mm in diameter, has PCD of 83mm for the M6 mounting screws, and recess of 70mm in diameter. The mounting holes are threaded M6. The chucks are held on the flange by either 3 or 4 M6 screws (3 for 3 jaw chuck and 4 for 4 jaw) inserted from the front of the chucks.

I bought a pieces of mild steel round stock of slightly bigger than 100mm and of 42mm thick. Both sides were cut in a bandsaw and so are rather rough. There is also a layer of "skin" on the cylindrical face. Here is the piece:



I am wondering how I can hold it in the lathe to start squaring up the 2 faces and the side.

Here my thought after having a "chat" with andyf:
1) Drill 3 clearance hole for the M6 screws (PCD 83mm) with deep counterbores. Andy suggested drilling the holes and counterbores slightly bigger to allow wiggling room for the register recess to seat properly. The holes will be done on my little Sherline mill on a rotary table (if I've enough head room. Otherwise, wait for 8 weeks for the arrival of the Wabeco F1200).

2) Faced the other side and turn it down to fit into the 4 jaw chuck (my 4-jaw opens up to max of 100mm per the thin manual it came with, chuck jaws reversed).

3) Indicate in the turned portion in the 4 jaw chuck to turn off the rough surfaces and machine the register recess.

4) Flip the work around and bolt in on the spindle flange directly.

5) Reduce the diamter of a section of the workpiece for the nose. I should be very close to the head of the M6 capscrew.

6) Thread the nose for the ER32 Nut (M40 x 1.5) and bore the taper (this will be my biggest challenge).

7) Dance in joy before starting to test for run-out - to at least be happy for a moment that a job has been completed.

Would that be how you folks do this? Any other ways or improvements to make it simpler?

Regards,
Wong

[aametalmaster]

Well since i have made an ER40 collet chuck i would face one side and bolt it to whatever you are going to run it on and then finish the rest...Bob

[Wongster]

Thanks Bob.

I've been trying to figure out the part on facing the first side. The piece is a little big to go on my 4 jaw chuck at this moment. With the M6 screws coming from the front, the screw holes have to be made with deep counterbore so that I can still cut the face while holding it on the flange.

The question remains for me, if the rest of the steps are correct, is, would I be able to drill and counterbore the 3 holes on the PCD accurately enough. At 42mm thick, I have a problem drilling the counterbore. My longest endmill has not more than 25mm length of cut. Also, my current mills can only take up to 10mm diameter shank. So making the counterbore may require boring tool. I'll go source for one if that's the only way to go.

Regards,
Wong

[aametalmaster]

Well you could drill the center in the drillpress and turn it on an arbor that is chucked in the chuck and the other end of the arbor is held in a live center. Then turn a spigot that you can chuck up in your chuck. Then face the other side once its chucked up. Been there...Bob

[aametalmaster]

Look at this post for what i mean. But you will have to make a suitable arbor. Just my thoughts...Bob
http://www.metalworkingfun.com/showthread.php?tid=183

[DaveH]

Wong,

It seems your chucks are right on their limits. So Bob's idea with the arbour may be the way to go.

Picture it, do a couple of sketches how you would make it, see what you think.


DaveH

[Wongster]

Bob,
Thanks. I was reading your post before starting the thread. Thought of using the using the mounting holes to ensure all features are concentric to each other. I think my thought is flawed as I'll be drilling the holes slightly oversize.

I'll go through the your pics again tonight on my Notebook. iPhone screen too small.

How do you ensure that the hole on the middle is in the middle? I guess it is not very important as the turning ops will ensure the OD is concentric with it.

Regards,
Wong

[Wongster]

Dave,

I will. Good idea to do the sketches, though my drawing skill leaves a lots to be desired...

Looks like I'll be starting a thread (or rename this) on this project soon.

Regards,
Wong

[EdK]

Wong,

I have used this method to hold such items for machining. See attached sketch.

You can face the end and turn the diameter when it's mounted as shown. Then you can chuck it up in the 4-jaw and face the other end. I've also used an arbor as Bob suggested.

Ed

   

[Wongster]

Ed,

That's a good idea. Thank you.

Regards,
Wong