Hard turning, finishing the part.

P. Waller

Brass
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A month ago a 2" + dia. bar of D2 turned up, I faced it to 110 1/4" long and drilled and tapped the ends 5/8-11, the threaded end is for hanging it in a vacuum furnace for hardening I am told.
It was then straightened and centerless ground to 1.999 +-.0005, the grinder nailed it. It is now 62C Rockwell scale hardness as well.


My job is to turn one end to 1.437" +-.001" diameter X 7" long and the other end to 1.500 +- .001" diameter X 5" long. The company that hardened it earned their money as it is every bit of 60 Rc

Due to length I had to turn it in a steady rest over a cats head and a live tail stock center, one of the advantages of having a tapped hole in each end is that one may screw a common hex head bolt in it and create a new center.

I chose a 135 Deg. insert shape to clear the center using a Sumitomo hard turning insert that I believe is cermet, unless parting to center I set the tool height with a ruler, this will probably cause many hobbyists a good deal of chagrin, this lathe is 11 7/16 from the ways to the center of the spindle.

Made a spindle guide to keep the part from flailing around at the back of the machine from nylon, this does the job of what many call a "spider".

It looks like this in use

Hard turning leaves a beautiful finish even when roughing, tomorrow morning the finishing cut will be completed and I will have to nearly double the spindle speed for this as the diameter is now smaller.
Roughed at 200 SFM, .020" DOC and .008 IPR, this is conservative, will spin it at 300 FPM, .005" DOC and a .004" IPR feed which should work nicely, this would be about 700 RPM
 
You sure that not a CBN insert. I never seen Cermet coated just CBN.


Sent from my iPhone using Tapatalk
 
You sure that not a CBN insert. I never seen Cermet coated just CBN.


Sent from my iPhone using Tapatalk
I believe it is CBN, it has about 1/4 the mass of carbide.
Worked a charm and the turning was finished this morning. As mentioned the key way is SEP (Someone Elses Problem)

Turning looked like so, I would have kept the camera on it longer but the hot chips were out to get me so only a 2 second video.
https://photos.smugmug.com/My-First-Gallery/i-5R5q99h/0/1b738faa/640/21video[1]-640.mp4
 
Had a cnc lathe running a lengthy program unattended so I drilled rough holes in the parts for the next job.
I made a How To video, I dislike the constant chatter prevalent in most How To ytube videos so this has no narration.

How to a Drill 1 5/16" hole through 3" of Mild Steel

1 Buy a used 60 year old WS turret lathe with a 25 HP spindle motor (-:
2 Place drill in turret position
3 Place saw cut blanks in chuck, the chuck must have serrated hard jaws and be very tight or it will push the part through the chuck
4 Turn spindle on
5 Engage turret feed and coolant
6 Sit down for 5 minutes or go and do something else, repeat 32 times
No spot drill, no pilot hole and no pecking required, drill straight through.
 
Finished just in time today, the chips wanted revenge and were leaving the machine.
Many look forward to "making chips" I look forward to the day when I never make another chip. I loathe them in every possible way.


For anyone that has never used such a machine, the blue frame and tube is part of it.
The round unpainted part is a back rest, a "spider" chuck with its own bearings and 4 set screws to hold the stock bars. The entire tube and back rest will slide along the round bar ways and advance the stock for the next part using a hydraulic cylinder.
One may load 20 Ft. lengths of 5" diameter rounds and advance them against a stop held in a turret position.
 
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That is one very nasty looking snake of a "chip." Be careful out there!

[Hill Street Blues]
 
That is one very nasty looking snake of a "chip." Be careful out there!

[Hill Street Blues]
They were out to get me today, after 30 years of killing metals Chipnet has become sentient and is fighting back, the outcome is uncertain.
 
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