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Spotting drill or centre drill

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Former Member11/02/2022 10:28:23
1085 forum posts

[This posting has been removed]

Emgee11/02/2022 10:44:57
2426 forum posts
290 photos

I would usually drill through both clamped plates with the tapping drill, then use a clearance drill on 1 plate.

Emgee

Thor 🇳🇴11/02/2022 10:52:56
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1627 forum posts
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I too drill through both plates with the tapping drill, then clearance drill. For starting the tapping drill I first use a spotting drill (using the dials on the milling table handwheels to place the spotting drill), then the tapping drill.

Thor

Former Member11/02/2022 10:59:59
1085 forum posts

[This posting has been removed]

Emgee11/02/2022 11:08:20
2426 forum posts
290 photos

I would spot it with a drill the same size as the existing hole, only needs a light touch to give a point for the spot or centre drill to use.

Emgee

magpie11/02/2022 11:09:04
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494 forum posts
98 photos

Spotting drill.

Hopper11/02/2022 11:31:19
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6391 forum posts
334 photos

I use the same size drill as the existing hole, so its a nice tight fit when I drill the start of the hole in the other plate, gets the new hole nice and central. Just sink the drill in to the edges of the tip, then change to the tapping size drill or pilot drill if you are going to use one. I don't bother with a centre drill or spotting drill in this instance as the larger drill has already provided the starting divot in the bottom plate.

John Baron11/02/2022 11:54:14
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520 forum posts
194 photos
Posted by Hopper on 11/02/2022 11:31:19:

I use the same size drill as the existing hole, so its a nice tight fit when I drill the start of the hole in the other plate, gets the new hole nice and central. Just sink the drill in to the edges of the tip, then change to the tapping size drill or pilot drill if you are going to use one. I don't bother with a centre drill or spotting drill in this instance as the larger drill has already provided the starting divot in the bottom plate.

Exactly what I do ! Saves time and you end up with an accurately drilled hole.

Derek Lane11/02/2022 12:47:49
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759 forum posts
171 photos

If you by chance have a set of transfer punches use them

JasonB11/02/2022 12:55:53
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Moderator
22744 forum posts
2653 photos
1 articles

I'd do them separately using the DRO to set out the holes. Spot and clearance size in one plate. Spot and tapping size in the other and while it's on the mill use that to also guide the tap perfectly perpendicular

Missed the edit, if I did not know the hole ctrs then use a spotting drill if I have one that fits existing hole if not use a drill bit of the same size to transfer onto the undrilled material.

Edited By JasonB on 11/02/2022 12:58:09

larry phelan 112/02/2022 16:59:58
1180 forum posts
15 photos

Hi Br

I thought you made it perfectly clear.

Must be missing something ?surprise

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