Gallery, Projects and General > How do I??

Indexable insert holder, machining steps

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Mike K:
I saw this in an issue of Machinist's Workshop (Apr/May 2011) and was confused about the steps the author took.  It's a pretty standard indexable insert holder.  The work is a square bar with a pocket machined into a corner and a threaded hole to mount the insert.  The screw hole is 6-32 and is on center with the end mill (3/8") path.

The author's steps:
1. Locate screw hole.
2. Center drill about 0.1" deep.
3. Mill the pocket.
4. Return to the hole; drill through and tap.

I'm not as experienced as most and don't understand why the hole wasn't finished first before milling the pocket.  It seems like the author added an unnecessary step by having to return to finish the hole?

chipenter:
I think he set zero at the centre of the pocket , I have made holders and always drilled the hole last with the insert in place just to be certain .

Muzzerboy:
There are various ways you could do this but I guess it made sense to the operator.

Drilling after milling might reduce stresses on the milling cutter it might otherwise see as it transitioned over the drilled hole. But as the spot drill hole would have been milled away, it's not obvious what purpose it (spot drill operation) served in the first place.

Mike K:
Okay, thanks.  I was just curious.

PekkaNF:
There are several methods that I have been reading, these I have considered

1: Mill the pocket and then locate the screw hole using the insert (you need a little offset to draw the insert into pocket or it will not be stable.

I made latest holder using mostly these instructions:


2: Or you could use some CAD/CNC to locake the features, bit like this:


Pekka

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