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  1. #1
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    Default Hercus Dividing Head runout

    Bob asked me to do some measurements of the TIR of my dividing head. It was actually a lot more than I expected. Rather than simply emailing them to him I wondered if other members may have similar heads and may benefit from the info. The spindle was simply spun by hand to achieve the readings. There wasn't a lot of movement within the bearings at each position and the runout seems to be in the spindle itself. Pictures basically tell all.

    Pete






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  3. #2
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    Default

    I do not have a Hercus dividing head. But if I read the DTI correctly, what you have there is only 0.015mm runout on the inner taper. Many older good brand name lathe had a spindle runout specification of 0.02mm or better. Your 0.015 would pass for the inspection certificate, and that is for a brand new and unused machine. Of course, the same tolerance then also applies 200 or 300mm down a test bar seated in the spindle taper, and for the registration flange behind the threads measured both axial and radial.

    By the way, looks like your dividing head has grease nipples. Have you tried to grease these before doing the test? If the error became smaller right after greasing, that would be a sign of slop in the bearings. If it stays the same, the error is more likely to be spindle tolerance.

    Chris

  4. #3
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    Default

    Chris I think they're actually oil nipples.

    Pete

  5. #4
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    Default

    The "bearings" are simply the bored holes in the casting. I'll go up to the shed and slip a DTI down the throat of mine and file a report.BT

  6. #5
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    Default Nothing conclusive.

    I'd say the bore in my spindle isn't concentric.( remember, this is home made ) Measured half way down the taper, there is 0.0006" runout. At the spindle nose it's 0.0009" With my horizontal mill arbor installed I have a reading of 0.005" at the outer end, about ten inches from the spindle nose. Installed in the ARL, there is 0.001" TIR at the end, but this could well be a case of cancelling errors. I installed a Schaublin 3C collet in the nose adaptor and measured the runout on a new Presto cutter shank. First try resulted in 0.0009" TIR. With the adapter repositioned, the reading was reduced to 0.0005" ?

    The bottom line is that the dividing head will suffice for machininig bolt heads. If accuracy is required I will use the Schaublin dividing head. Funnily enough though, I did use the Hercus head to make a part when I repaired the Schaublin's damaged handwheel.

    It would be interesting Pete, to find out what sort of reading you might have if you installed your arbor in the factory spindle.

    BT

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