Compound needs a better degree dial

[whydontu]

Simpler method? It’s aluminum. It has tapped mounting holes. Bolt it to a faceplate, center it. Trepan to <almost> cut through. Unbolt. Drill through the remaining web. Grab a coping saw and cut out the web. File to fit.

 

[Susquatch]

Simpler method? It’s aluminum. It has tapped mounting holes. Bolt it to a faceplate, center it. Trepan to <almost> cut through. Unbolt. Drill through the remaining web. Grab a coping saw and cut out the web. File to fit.

I like it! This has promise and if it works, it would save me from having to make a huge collet!

 

[RobinHood]

Bore pie jaws for a good fit. Insert part and machine carefully. It won’t distort and you can use the trepanned center on another project. If you are concerned with holding power, superglue the outside “ring” to the pie jaws. It won’t move.

 

[eotrfish]

You could also make a pot chuck like this - you only need 3 slits since you don't have a 6-jaw chuck

Turn the bore to the diameter of your part +.001" and hold the assembly in your 3J.





I made this specifically to trepan a thin part.

 

[thestelster]

Everyone is talking lathe, what about on the milling machine.
-hole saw or trepanning tool
-boring head
or rotary table

Clamp a sacrificial disc on top of your dial, like a sandwich. Or use crazy glue.

This way no marring of the numbered edge of the dial.

 

[historicalarms]

I would use a 4-jaw and center the piece perfectly in the jaws ( using light grip force and then glue to the chuck face with best glue i could find. Wife claims that "gorilla glue" the best that she has ever used.

Now re-clamp the 4 jaws to lightly hold and help alleviate the torsion of the cutting force on the glue

 

[Susquatch]

I made this specifically to trepan a thin part.

This is more or less the same as my thoughts but your design has a few improvements I like.

I am a fan of custom collets. I make them all the time. So it's quite natural for me to head down that path with this problem. I was gunna shoot for the same 1 thou fit but with only one slit. I reasoned that a really close fit didn't require distributed compression. Positioning the one slot halfway between two of the jaws would permit me to index the collet to ensure a perfect non-elliptical center in the degree ring. But I think three jaws isnt hard to do and would guarantee that outcome. It solves another problem I've been noodling too - how to bore the degree ring when it is sitting flat against the check jaws. I was going to make another ring for that purpose alone, but a collet like yours could have that feature integrated right into the collet itself.

A few other points for discussion.

1. Is it better to have the collet ears articulate about a central hub, or is it better to make the backplate solid but very thin at the outside inner corner and have the plate articulate like three ears around an inner outside rotation point - like bending just your finger tips but not your fingers to hold the degree collar. I wish I had modelling capabilities to evaluate this, but the old fashioned build and test works too.

2. The degree ring needs to be adjustable to calibrate it to my compound travel. Should the degree ring be a perfect fit to the plynth or should it have 3 or 6 points of contact that are deformed for installation and then released to hold or should I just use a few tiny grub screws?

I am gunna noodle all this for a while. But I need some plate anyway to make an indicator base for my lathe (yet another great lathe improvement project @Dabbler suggested). So I think I'll get a stock order in process right away.

New fresh ideas or improvements or even just discussion are still always welcome.

 

[Susquatch]

then glue to the chuck face with best glue i could find

This would work but has a problem for this application.

It doesn't provide a relief to cut the ring bore without also cutting the chuck face.

However, I like the idea of using the Jaws as backup for the glue.

 

[Susquatch]

I guess I should also confess a slight aversion to glue. The degree ring is anodized on the outside, front, and rear. I don't want to damage those surfaces if I can avoid it. So any glue I use must be easily and completely removed without damaging the anodized surface of the collar.

 

[Johnwa]

You could mount it on a faceplate with clamps on the OUTSIDE portion of the ring. That way you could trepan and bore in one setup. If you dread the thought of getting it centered on a FP, it could be mounted the same way on a metal plate mounted in a 4jaw.

 

[Susquatch]

it could be mounted the same way on a metal plate mounted in a 4jaw.

Unless I misunderstand you, that's my preferred approach till I hear or think of something better.

I have no fear of centering on a four jaw or a table. I have 40 plus years of getting that process down to an instinctive habit.

 

[PeterT]

Not directly related to topic but just so happen to have an angle block in the mill & took a picture to show a method to obtain or check an angle. DRO makes it very quick & easy. I have an indicator in the quill, touch down to register a value, say zero. Now null DRO X & Z to zero, retract quill. Move the table over to the other end of the block, any length will do. Touch DTI to same zero again, record new X & Z DRO values at that position. Angle = ArcTan(Y/X). Here I'm checking an offshore angle block (they're not that great actually) but it could just easily be a part to be machined, although fussier to set up to a target angle unless you can pivot on one corner. The same general principle can be used in a lathe on a cylindrical bar.

 

[Susquatch]

I have an indicator in the quill, touch down to register a value, say zero.

Since lots of guys don't have Z-Axis DRO, it is worth pointing out that your method only works if you use the same zero on the indicator. However, you can do the same thing with a plunge indicator instead of a dial test indicator and then use your X-Axis DRO and the plunge indicator readings to calculate the angle instead.

Those without any DRO at all can also use the table dials with a plunge indicator if they remember to take up the backlash in the same direction for both measurements.

 

[a smile]

哈哈！擦进去。

当我还能呼吸并发誓时，CNC永远不会碰我的车床。

Very determined!
Very old school!
I think, this is the right persistence!
But being as electronic as possible still makes it easier to use.

 

[a smile]

I want to know in what state do I use Angle apps that exceed +/ -60?

 

[Susquatch]

I want to know in what state do I use Angle apps that exceed +/ -60?

The translation isn't excellent but I think I know what you want to know.

29.5 degree threading is usually set as 60.5 on a compound.

Negative compound travels are always beyond 60. This is where the compound is rotated such that the crank is at the back of the lathe and the tool travels toward or away from the user.

For very large parts. Say you have a 12" lathe and an 11.5" disk but you need to work on the circumference or the back side. It isn't possible to do that without rotating the crank so it is at the rear of the cross-slide.

Just a few I've had to do.