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2.05mm or #45?

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Bazyle13/12/2018 23:11:04
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Posted by Vic on 13/12/2018 22:59:14:

Yes that makes sense. I’ve not had any problems though with the 2.05mm drill I’d been using until I snapped it! laugh

Can't you regrind the remains on the shank and/or sit the broken off bit into a holder?

Hopper14/12/2018 00:49:45
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Tubal Cain's chart in ME Handbook recommends 2.2mm drill for 2.5mm thread.

Vic15/12/2018 18:39:16
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I’ve ordered the Workshop Practice book.

The drill bits arrived today. I wouldn’t normally measure them but I did today just for you guys. laugh they were:

2.05 1

2.06 2

2.07 4

2.075 1

2.08 2

So any of them will do. I measured one of them with a M&W mic and also with a Mitutyo so I’m reasonably confident of shank size. How well they’re sharpened is another matter but I’m sure they’ll be fine.

Hopper16/12/2018 05:34:46
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Posted by Vic on 15/12/2018 18:39:16:...

...so I’m reasonably confident of shank size. ...

No point in measuring shank size. The shank, and first parts of the flutes, are made to be smaller diameter than the tip, for clearance. Maybe more meaningful to measure the tip diameter. But the size of hole depends also on how the tip is sharpened. If it's a bit off-centre, the resulting hole will be slightly larger than the tip diameter, as is usually the case.

colin hawes16/12/2018 09:53:36
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Normally a 2.1 drill would be used for M2.5 thread as there is likely to be slight deformation of most materials as well as the cutting action and that extra 0.05 mm allows for that. Colin

mechman4816/12/2018 17:12:11
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Posted by Hopper on 16/12/2018 05:34:46:

Posted by Vic on 15/12/2018 18:39:16:...

...so I’m reasonably confident of shank size. ...

No point in measuring shank size. The shank, and first parts of the flutes, are made to be smaller diameter than the tip, for clearance. Maybe more meaningful to measure the tip diameter. But the size of hole depends also on how the tip is sharpened. If it's a bit off-centre, the resulting hole will be slightly larger than the tip diameter, as is usually the case.

+1 … Also take note that often the drill bit can run eccentric on many of these small bits … bent! … I tend to use one size less for small drills like these... 2.1 etc.

George.

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