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Runout drilling 2mm hole

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Chris Trice11/11/2017 02:05:26
975 forum posts
2 photos

Gently tap the drill shaft near to the collet as it's rotating. I find this often seats everything where it should be before tightening it a little more. In theory, it shouldn't make a difference. In practice, it often does.

Chris Trice11/11/2017 02:11:13
975 forum posts
2 photos

... or use the tail end of a boring tool and advance it until it just touches the shaft of the drill near the collet in the same way that you can use a boring bar to steady a drill bit to drill centrally without resorting to a centre drill. Again, in theory it shouldn't make a difference but in practice it sometimes does.

JasonB11/11/2017 07:25:03
12675 forum posts
1147 photos
Posted by Men Ifr on 10/11/2017 23:01:07:
Posted by JasonB on 10/11/2017 18:31:48:

90p seems very cheap for a spotting drill, save yourself more hasle and get a decent one, I usually use the KEO ones.


Try searching "engineering supplies" as machine shop is more an American term.

This is whet I was looking at:



That is not a spotting drill, this is not tried the sherwood but as you were looking at Cromewll's I used one of theirs to link to.

This is a KEO one though they are imperial, don't be put off by ythe photos they actually ;look like the Cromwell ones at 1/8" x 1.25"

Edited By JasonB on 11/11/2017 07:30:52

Men Ifr14/11/2017 17:33:02
73 forum posts

The ER20 collets arrived from RDG and to my dismay the 2mm hole does not look to be in the centre of the collet (where the split lines cross) this is what I could see with the chinese one I had before. - Maybe it is my imagination but I don't think so. They do seem to be machined/ground though and the chinese ones aren't but you can also see some manufacturing errors.

Anyway 1st test I check the run-out setup the same as the video I posted earlier and I get 0.045 - so only slightly better than the Chinese one.

I'll go and measure some-more and re-check the collet holder in case that's a long way out...

What's the consesus on oil on the collet and tightening torque - I'm giving a reasonable nip with a 300mm spanner I may try a few 'tightnesses' and see if things seem to get better or worse.

Only 1 more thing - I'm using a drill bit and measuring on the shank, I'm assuming that should be a reasonable method. - also it means this is likely the best possible result as the run-out is likely to get worse further away from the collet (i.e. at a drill bit tip where it actually matters...)




Edited By Men Ifr on 14/11/2017 17:33:52

Emgee14/11/2017 19:02:22
785 forum posts
170 photos

Wonder if you are using a drill shank the same size as the maximum collet capacity and not oversize.
Don't expect a 2mm collet to close less than 1.5mm and retain any good concentricity, 1.5-1.0mm collets are available.

My collet tapers and threads get a very light coat of oil before fitting the tool.


Men Ifr14/11/2017 19:47:43
73 forum posts

Typically I've been measuring like for like i.e. 2mm collet 2mm drill bit shank.

I've been getting 0.045 - 0.07 across the set so far. I'll ring them in the morning to see what they say.

I ordered a drill chuck plus abour at the same time - I'll measure that - I wouldn't expect it to be more accurate but given the poor results from the collets you never know.

The other possibility is even through I can measure the collet holder at + 0.01 maybe the way it holds the collets makes them inaccurate..?

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