milldrill tilting fix

[Chris TriceParticipant @christrice43267]

Joegib is right. The only way to be sure is to swing the device through 180 degrees and compare measurements in which case you may as well use just a single dial. For the two clock version to be reliable, the collet has to be a perfect fit in the spindle and the shaft of the device a perfect fit in the collet. Even the tiniest error which would normally be acceptable would be multiplied many times because of the distance between the two measuring points.

[Sub MandrelParticipant @submandrel]

It is interesting how geometry can work with us or against us.

Assuming a 100mm (8&quot radius circle for the indicator, a one-degree error in the spindle alignment gives us a deflection of 3.5mm (1/8&quot As we can easily measure to 1/100 of this, we cal correct the spindle angle very accurately. with 0.02mm difference between the sides, the error is 0.005 of a degree.

Obviously if the error over the 200mm diameter is 0.02mm, then across a 10mm cutter it is 1/200 of that – only .0001mm – tiny and less than the flex in a very rigid machine.

As the 'dual tramming machines' have measuring points about 100mm from the spindle nose, they inmtoduce an error at the measurement point equivalent to the runout at 100mm from the holder.

If held in a collet chuck with an accuracy in the region of 0.02mm runout at 100mm, they wil roughly triple the error in the system , about 0.0003mm across the 10mm cutter.

If you hold the trammer in a drill chuck with could have 0.2mm runout at 100mm the runout across our 10mm cutter is still only 0.0011mm.

Perhaps the real message here is that we may be congratulating oursleves on getting our mill heads perfectly aligned, when what we should be doing is giving more attention to good rigid setups, accurate toolholders and sharp tools.

…and here endeth the sermon!

Neil

[Brian WoodParticipant @brianwood45127]

And there speaks a wise man!!!

Brian

[Douglas JohnstonParticipant @douglasjohnston98463]

I stand by my previous post, the accuracy of the collet or chuck is irrelevant if the tool is set up the way I mentioned.

Doug

[Sub MandrelParticipant @submandrel]

I think Doug is right, but only if both DTIs are set up on the same block in the same place and teh arrangement is trued in this way every time it is used..

Neil

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