Shop built compression collet chuck

[precisionworks]

This chuck holds thin walled DOM tubing (.093") for boring or reaming. The 16 segmented slots provide equal pressure all the way around the tubing.

A short piece of aluminum solid round stock was used, 3.25" diameter, 3" long. Larger stock, like 4" or 5", would have been easier to mount to the face plate. With this diameter, the mounting holes are really close to the face plate hub, so three holes were spot faced & drilled, using the rotary table, at 120 deg spacing.

Three matching holes were drilled & tapped into the end of the aluminum stock. It was then bored out .001" larger than bushing diameter, with a step left inside the bore to locate the bushing. Then to the band saw to cut the slots.

The next step is to prep the OD of the bushing, by first setting tool height to center line using the shop built center height gage.

Then the bushing is mounted on an expanding mandrel for OD turning.

The boring bar is mounted and set to center line height +.010"

The final step (at this stage) is to bore the bushing. The bore measured 1.5550", and it needed to go to 1.562", so only .0035" had to be removed.

The chuck works really well, and maintains perfect centering of the bushings as they are bored.

 

[gadget_lover]

I think one more picture needed. The one that shows the DOM tubing in place with whatever clamping mechanism, while it's not spinning?

Daniel.

 

[precisionworks]

I noticed that too, and will post a "still" shot tomorrow. FWIW, the band clamp is an Ideal T-Bolt Standard Clamp 30010:

http://www.idealclamps.com/images2/products/f1/1270.pdf

 

[gadget_lover]

That's exactly what I expected... Well, actually I expected a hose clamp.


That looks real nice.


Daniel

 

[dom]

Excellent solution.
That is some real neat cutting with the bandsaw! Was it done by hand?

Cheers
Dom

 

[precisionworks]

Was it done by hand?

Dom,
The uncut part was secured to an 8" x 8" wood block, about a foot long. A 1/2" diameter lag bolt was used for attachment. The first cut was made, part was rotated 90 deg, and made the second cut. Part was rotated 45 deg for the third cut, another 90 deg for the fourth cut, etc., until all eight cuts were done, which produced the sixteen slots.

Band saw is the often seen Delta 14", running a bimetal Lennox blade, 4 tpi hook tooth profile, .025" thick, at "normal" wood cutting speed. With the coarse blade, work has to be fed slowly, but it does a nice job on aluminum up to about 1" thick.

 

[jhanko]

Nice project & pictures! +1 for one more pic showing the compression/clamping device...

 

[precisionworks]

Shown with T-bolt clamp, after boring a bushing. Grip is also secure enough for reaming. (This face plate is an eBay purchase, and had a nasty surface before a trip under the surface grinder - which made it better than new).

 

[wquiles]

Too cool

Question: Is the out-of-balance once it is running bad? Or just a small/minor vibration?

 

[precisionworks]

I also wondered about vibration, but found that the clamp caused no vibration that was detectable. If the weight of the clamp is figured as a percentage of the weight of the face plate plus chuck body (2 oz versus 56 oz) it's only 3.5% . If the clamp were larger or heavier, a counterweight would be needed.

 

[jhanko]

Have you considered using a split collar instead? I've seen them as big as 6" ID. The bolt on that clamp looks dangerous, just waiting to hit/snag something...

 

[precisionworks]

In fact, a split collar was my first thought. They don't provide 360 deg compression, unless they are bored to size and then split ... and the T-bolt was a quick, $5 solution.

The bolt on that clamp looks dangerous

I see what you mean, but it isn't a lot different from the jaws on a 3-jaw or 4-jaw chuck.

 

[dom]

Still impressive looking accuracy on your cuts for hand feeding -well done.

If the balance was real bad,then another clamp with the weight on the opposite side would fix it.
The collet looks much bigger than it actually is.

 

[Clark]

What an impressive project!

This week I tried to trim the neck of a 308 case necked down to 260 in a #3MT 3/8-1/2" collet in my Atlas lathe. The base of the case .470". That collet was not going to grip the case with the 5 foot pounds of torque I could put on the 3/8"-16 threaded rod draw bar. I had a brass door knob for a wheel to tighten the draw bar. I have the 11 piece set of collets, and never realized how inadequate my system was before now.
http://littlemachineshop.com/products/product_focus.php?Focus=Collets
I think I will go to a two draw bar system: door knob for standard sizes, and socket wrench for odd sizes.

 

[precisionworks]

If the balance was real bad,then another clamp with the weight on the opposite side would fix it.

Great idea ... especially since I had to buy 5 to get what was needed. I'll install the second one 180 deg from the first.

socket wrench for odd sizes.

Clamps are rated by tightening torque, and the T-bolt has the highest rating at 75.0 in-lb/8.5 Nm. Conventional worm gear band clamps are rated only half as much.

 

[tino_ale]

I agree the bolt looks very dangerous :sick2:

 

[precisionworks]

the bolt looks very dangerous

It only looks that way with the spindle stopped. At 1000 rpm, it is much less imposing:devil:

On a more serious note, there is no reason to ever have contact with the side of the chuck. Every operation is done in the bore, whether boring, polishing, or honing. Hands never get anywhere near the side or the clamp.

 

[StrikerDown]

It only looks that way with the spindle stopped. At 1000 rpm, it is much less imposing:devil:

On a more serious note, there is no reason to ever have contact with the side of the chuck. Every operation is done in the bore, whether boring, polishing, or honing. Hands never get anywhere near the side or the clamp.

If you turn the clamp around so the exposed bolt trails and the tapered side of the band leads it would be a little less likely to grab something getting a little too close, not that anything should be getting close

 

[precisionworks]

Seven bushings went to the honing shop today, all bored to 1.5625". The Sunnen hone took them out to between 1.5633" and 1.5634" (easy to do with a slow running, fine cutting hone).

As honed, still not smooth enough:

After a maroon Scotchbrite pad and a grey Scotchbrite pad:

Close up - from the hone:

After the nonwoven abrasive:

Off to the hard chrome shop they go

 

[gadget_lover]

I don't understand getting a super exact dimension ( between 1.5633" and 1.5634" ) and then using an abrasive pad to smooth it out.

Is the initial size just to keep them uniform?

Daniel