# Self Centring Drill Bits



## custard (30 Jun 2012)

What's the view on using self centring drill bits for installing butt hinges on small cabinets and boxes? 

I can pretty much guarantee the location and depth of the hinge mortice to 0.1mm, but every now and again I'll get a hinge that's fractionally displaced, and I'm pretty sure it's due to an off-centre screw/pilot hole. 

Do self centring drill bits guarantee real precision, or are they just a "close enough is good enough" convenience for larger door butt hinges?


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## MattMoore (30 Jun 2012)

I use one regularly for hinges, jigs etc, as long as the drill is plumb it will be very well centred. I would spend a bit of money to get the better quality ones rather than the very chap ones that are out there. my set are trend ones fwiw.

Sent from my Desire HD using Tapatalk 2


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## custard (30 Jun 2012)

Thanks Matt, I'll give the Trend No 6 and No 8 sizes a go. 

You make a good point about keeping the drill bit plumb, I remember reading an account of David Charlesworth going to extraordinary lengths to guarantee drill accuracy on a wooden hinge joint he was making, he set up his drill press using a dial test indicator to ensure it was absolutely vertical. I'm not sure I want to go quite that far but you're right, it's pointless being centred if you're not also plumb.


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## bugbear (2 Jul 2012)

custard":2f747l7t said:


> What's the view on using self centring drill bits for installing butt hinges on small cabinets and boxes?
> 
> I can pretty much guarantee the location and depth of the hinge mortice to 0.1mm, but every now and again I'll get a hinge that's fractionally displaced, and I'm pretty sure it's due to an off-centre screw/pilot hole.
> 
> Do self centring drill bits guarantee real precision, or are they just a "close enough is good enough" convenience for larger door butt hinges?



Twist bits will follow grain to some extent. The self-centring bits not only start off in the right place, but are HELD there for the duration of the drilling process.

BugBear


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## custard (2 Jul 2012)

bugbear":12r7oekg said:


> custard":12r7oekg said:
> 
> 
> > What's the view on using self centring drill bits for installing butt hinges on small cabinets and boxes?
> ...



Very good point. 

Wish I could find a good quality smaller self centring bit, the smallest Trend self centring bit is 5/64" (2mm) for a No 6 screw in hardwood. I'd like a 1.5mm or 1.6mm pilot hole for a No 3 or 4 screw in hardwood, but so far haven't found anything. Does anyone have any suggestions?


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## Racers (3 Jul 2012)

Hi,

You can use a bigger one to form a depression on the centre of the hole and use it to locate a smaller drill bit, it’s what I do.

Pete


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## custard (4 Jul 2012)

Racers":61yc46md said:


> Hi,
> 
> You can use a bigger one to form a depression on the centre of the hole and use it to locate a smaller drill bit, it’s what I do.
> 
> Pete



What a cracking suggestion! Thanks for that.


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## Jacob (4 Jul 2012)

custard":3chptorp said:


> Racers":3chptorp said:
> 
> 
> > Hi,
> ...


Or just use a bradawl, a nail, a centre punch etc just like everybody else! For tiny no2 screws (and for scratching lines/points in general) I use a dart (as in the board game). No feathers - can tap the end with a pin hammer.


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## bugbear (4 Jul 2012)

Racers":3r5c306p said:


> Hi,
> 
> You can use a bigger one to form a depression on the centre of the hole and use it to locate a smaller drill bit, it’s what I do.
> 
> Pete



It's a good system for marking, but doesn't give the "guide DURING drilling" behaviour that I pointed out.

(BTW, you might be entertained by the female counterpart of these drills, an engineering gadget called a "bell punch")

BugBear


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## custard (4 Jul 2012)

bugbear":18kzg6zc said:


> Racers":18kzg6zc said:
> 
> 
> > Hi,
> ...



Damn! You're right, although if it's precisely marked then a box at least could go on the drill press. 

Nine times out of ten my hinges work out fine, but I can't quite get the process 100% bomb proof.


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## bugbear (5 Jul 2012)

custard":1iyhqlvo said:


> Nine times out of ten my hinges work out fine, but I can't quite get the process 100% bomb proof.



Hmm. Do you always use the same (model/size) hinges?

If so you could make a metal drilling guide. A piece of steel at least as big as a hinge (probably bigger for ease of handling and/or clamping) with holes in it with the correct locations and size.

Then "just" drill through the holes. This would locate and maintain the position of the drill.

BugBear


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## Racers (5 Jul 2012)

Hi, BB

The problem could be with the manifacture of the hinge, an accurate guide might cause more errors.


Pete


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## bugbear (5 Jul 2012)

Racers":1jz3vyq5 said:


> Hi, BB
> 
> The problem could be with the manifacture of the hinge, an accurate guide might cause more errors.
> 
> ...



Hadn't thought of that - fair point.

BugBear


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