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Old 04-04-2018, 01:21 PM   #1
bobs7-62steamair
 
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Default Brass Ball drill & Tap fixture

Here is a fixture I have built and used successfully to drill & Tap a .500 inch diameter Brass Ball used in Fly ball Governor construction. I ball end milled a cavity in a piece of 1" CRS and drilled & Tapped 4 holding screws at 90 degrees. You need to ball mill the cavity about .030 to .050 inch deeper than the mid point on the ball to successfully hold it in the fixture. The brass screws have a portion of the tip turned down to minor diameter and smoothed to grip the ball without scaring or damage. Locking nuts are provided to maintain the pressure on the ball during turning. Don't need a lots of tightening to hold the ball in place for drill and tapping, of course you can over do here and scar the brass with a brass screw if excess pressure is applied. Tap was a 5-40 tapped about .400 deep. Balls came out without a scratch!


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Old 04-04-2018, 06:25 PM   #2
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When I needed to drill balls for my last project's governor I found I could just hold them in the chuck jaws. But as you said, I didn't have to tighten the jaws much at all for drilling and tapping.


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Old 04-05-2018, 11:01 AM   #3
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Very nice, but a bit OTT for what needs to be done.

I drill softened ball bearings by just holding them in either a 3 or 4 jaw self centring chuck, but for tricky bits like glass balls, I tend to use my collet chuck, a better control of pressure on the part.

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Old 04-07-2018, 01:23 PM   #4
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I too just use a Collet Chuck ;-)
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Old 04-08-2018, 11:50 AM   #5
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It's nice to see a catspaw chuck again and it is still is a useful( and cheap) way to hold irregular pieces for machining.

Laughingly to a younger generation- it was forerunner to both the self centring and independent chucks..

And then some poor sad benighted soul called Keats 'Invented' a variation called the Keats plate.

Oh dear, oh dear!

Norm
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Old 04-08-2018, 01:10 PM   #6
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There is very little new in this game Norman.

I read lots of old books dating to the turn of the 20th century and just a little later, and see things today that are just updated versions of tooling or techniques.

Most of this very good information and techniques have been lost over time. If only people would do a little more readin, most of the questions asked on here could be eliminated.

John
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Old 04-09-2018, 10:35 AM   #7
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Quote:
Originally Posted by Blogwitch View Post
If only people would do a little more reading, most of the questions asked on here could be eliminated.
In a previous life, I used to teach engineering. I ended up feeling that most of the role of the lecturer was to give the students confidence that, given a little application, their effort would be rewarded and that they'd grow in competence. Some of that involved choosing reading for them; something I thought was at the right level, with perhaps some extra guidance around sticky bits or outright errors in the text. A lot of what I recommended was written a long time ago, although most is still in print. That's what I get from forums like this - 'I've done this before, and I found xxx useful. Watch out for the errors in yyy drawing'.
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Old 04-09-2018, 03:32 PM   #8
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I hope people come here for information. The way the path to the answers gets sometimes wanders.. This is only the stepping stone but the journey is most interesting.
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Old 04-09-2018, 07:06 PM   #9
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Don't get the wrong idea, I have to make one like Bobs for my lathe.

Just that I will be fitting it on the other end of the spindle, just like gunsmiths do to keep the material running straight while it goes through the spindle to the chuck, which is also usually a cat chuck, to get the barrel perfectly on centre.
I just don't like wobbly material sticking out the back of my spindle.


John


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