Suggested method of machinng

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Joined: Sat Apr 29, 2017 8:11 pm

Re: Suggested method of machinng

Post by charkmandler » Tue Jan 01, 2019 6:05 pm

A late reply due to family illness. In the end I was unable to get any rectangular bar stock of the specified material that wouldn't have needed a fair bit of milling to size and deemed that it would be faster to make from circular material. I used a 3mm profiling tool that had a small radius (can't remember spec) on each side and turned as one and then parted off. I then made a jig to hold the parts to mill off each side 10 at a time. The surface finish doesn't look great but were actually pretty smooth when running a nail across the surface - I am pleased as EN8 isn't the nicest to turn. All turned to within a .0005" tolerance with only one wasted due to brain fade. Photo is of the parts bagged up (parts still have milling swart on them) as somehow I lost the other photos.
I did have an odd occurrence in the middle of the run. For the first 9 parts the DRO remained accurate with the turned diameter, but for the next 6 parts each diameter was about .006" more than the reading and the last cut. This then took time with more measuring / checking. I changed the tool insert after this happened with 3 parts and still got the same moving reading for the next 3. After this had been happening for 6 parts I got consistent readings and diameters (just as for the first 9) for the remainder of the run.
Nothing changed through the whole run and I used the same tool throughout so did not remove it from the holder - odd.

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Re: Suggested method of machinng

Post by pete » Tue Jan 01, 2019 8:04 pm

If ALL the lathes assembly was unquestionably tight from the carriage to the tool tip during that run of parts then I'd suspect a loose component holding your dro scale or reader head if you were seeing inconsistent readings and results. If it's a decent dro proven in the past it can be trusted then somethings obviously not quite correct.

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Joined: Sat Apr 29, 2017 8:11 pm

Re: Suggested method of machinng

Post by charkmandler » Fri Jan 04, 2019 2:52 pm

DRO is good and continues to be. I'm really at a loss as I have not had the problem since and have been on the lookout. Hopefully, just one of those things.

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Re: Suggested method of machinng

Post by Harold_V » Fri Jan 04, 2019 4:53 pm

This experience is one where one would have been wise to compare the DRO against the screw. It would reveal whether it was the DRO, or not.

Wise people talk because they have something to say. Fools talk because they have to say something.

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