Quote:
Originally Posted by fintubi
Ed,
The tap drill for M6 is 5mm (0.197), which is larger than the major diameter of a 10-24 internal thread (0.190). Therefore drilling to tap at M6 should leave a clean hole with no compromised material at the crest of the tapped female M6 threads.
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You have a 0.007" diameter difference and a 0.0035" difference per side. This is small. I would definitely consider just using a 5mm reamer to bring the hole on size for tapping and forget the drilling idea. Even jobber length drills in a mill do not produce the precise sizing the reamer alternative does. With as little material as you have to work with there is no room for a whoops.
You can find a 5mm reamer at McMaster-Carr, click here =>
5mm Reamer.
BTW still use a drill press or mill for a straight precise 5mm hole. If you use a mill do not forget the head is movable and may have been moved by the last guy who used the mill. That means you need to zero the mill before reaming the hole.
Ed
p.s. To do this job correctly you should use a mill. Use a gauge pin that matches the ID of the original screw hole to locate the true bolt hole center. Make sure your mill has a digital read out for the x-y position of the table. I have an Excel spreadsheet that will give you the x-y co-ordinates for each of the six holes. If you go this route and need the spreadsheet send me an email and I'll send it to you. The forum has my email address and will allow you to email me. I will send you the Excel spreadsheet. It is very intutive and will work up to some large number of holes, providing you accurate x-y coordinates, out to as many decimal places as you wish.
p.p.s. I just remembered, the Moto Lita PCD is not evenly spaced holes. I have a document with the correct x-y positioning coordinates for the unequally spaced holes. Same offer, email me for a copy.