This may or may not be of interest to any No.O owners but I sometimes use the little dividing head on my 2 horsepowered mill. Handy for delicate jobs but there's the risk of exposing its Achilles Heel, the single 3/8 BSW bolt that fixes the head to its supporting bracket.

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I'm not sure that this weakness applies to the original head as my bracket is home made and made in two parts, both from 4E cast iron. Homemade because the only original parts are the headstock casting, the division plates and the spindle nose protector. So, I decided to do something about that Heel a couple of days ago.

After setting the head's spindle parallel with the mill table with the aid of a ground saw arbor mounted in the spindle and a 0.0005" dial indicator, I carefully drilled a 1/4" diameter hole through the bracket and to a depth of 5/16" into the thickest section of the head's casting, 45 degrees below the horizontal centreline. I could not ream the hole because the Sutton reamer I have has a starting taper that would have left the hole in the casting both tapered and undersize.

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Then I made a pin to fit the hole with a knurled head matching the knurls on the head I made fifteen years ago.

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To prevent the loss of the pin I cut a 2mm wide slot in it and for its retention I modified a 3/16 BSW socket set screw to suit. The tapped hole in the casting is only partially tapped allowing the tightening of the set screw.

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This simple modification will hopefully allow me to use the Hercus head with more confidence than previously.

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BT
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