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Enlarging holes in piano hinges

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Teejay

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I have about 30 holes that need enlarging to allow the screws to sit correctly (flush). I've tried using my pillar drill with a fence behind and lining it up but I'm ending up with triangular or otherwise ugly holes and I really want this project finished nicely.

Can anyone please give me some tips on this?
 

Sheffield Tony

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Might a step drill work ? Do the holes themselves need to be bigger, or a deeper countersink ? That might do a tidier job.
 

J-G

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Teejay":r5vnr0ot said:
I have about 30 holes that need enlarging to allow the screws to sit correctly (flush). I've tried using my pillar drill with a fence behind and lining it up but I'm ending up with triangular or otherwise ugly holes and I really want this project finished nicely.
Why not use the correct size screws?
 

Teejay

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It was from Toolstation and I bought the screws that someone in the reviews said went with it.
 

Mike Jordan

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It's not easy to find a decent supplier of piano hinge in my experience, most of the countersinking for the screws is inadequate. My answer is to use a countersink rather than try to drill out the holes. It's a long and tedious job that shouldn't be necessary.
 

Teejay

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There are so many different types of countersink, which do you use for this job?
 

Teejay

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RobinBHM":370i9klk said:
Teejay":370i9klk said:
It was from Toolstation and I bought the screws that someone in the reviews said went with it.
There are special small head 3mm screws available

https://www.ironmongerydirect.co.uk/pro ... 200-864101
Thanks for the link. Toolstation sell very similar screws but they are brass coloured rather than silver, so wouldn't match the Nickel plated colour of the piano hinge.


In relation to that countersink, one of the reviews said it snapped within 30 seconds of use on stainless steel.
 

ColeyS1

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Stainless is hard compared to normal steel

Sent from my SM-G960F using Tapatalk
 

Mike Jordan

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Stainless will work harden immediately if the cutting tool is not very sharp. Cutting fluid may help but it's a difficult job.
 

AES

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Rather than getting the correct screws, if you MUST increase the CS size on your piano hinge I'd suggest using a centre drill (otherwise known as a Slocombe - presumably a Mr. Slocombe invented them, dunno).

If you're not familiar, image a VERY short twist drill with a normal drill point at EACH end, separated by a centre body with a much larger diameter than the drill part. They come in sizes which are numbered and there is a defined relationship between the diameter of drill part and the centre body. You'll have to try different numbers to get a drill part which suits your hinge (without enlarging the hole itself) but which will give you a bigger countersink without encroaching too much on the hinge line itself (or on the edge of the strip) - holes bored into piano hinges that are too big and spill out over the edge of the strip (or graunching onto the hinge barrel itself) are not only structurally unsound but also look horrid!

You can find the diameter/number details out by consulting the online table available at (amongst others), Arc Eurotrade, whose details are on the sticky at the top of this General Metal Working section.

The reason why I suggest a Slocombe is that being very short but with a thick centre body they are very rigid (their basic purpose is to bore centre "pips" into bars, etc on the lathe). They are also VERY sharp which is ideal for SS.

If you go this route, be careful of SS work hardening while drilling and countersinking, as said above. To overcome this you need a rigid countersink bit to prevent chatter, VERY sharp, slow speed, quite heavy feed - ALL of which suggest the Slocombe (although that's not its original purpose), plus LOTS of coolant. If you need to stop machining before you've finished countersinking be sure to allow the job to cool before starting again, and as above, expect the job to be even tougher than first time. But take it carefully as above and it IS doable. At a pinch you could try this in a hand-held drill, but a pillar drill is by far and away the best solution.

But as already said above, an even better solution is to get the correct size screws - it's VERY easy to ruin a piano hinge by graunching the hinge barrel or running off the edge of the strip!

HTH
 

Teejay

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Thanks for your replies, I have learned a lot. I didn't know that metal could harden when heated up by being drilled.

It explains why I managed two or three holes relatively well and then after that it just got messy!

I've ordered different size screws and hope that some of them will be suitable.

Thanks for the links.

By the way, I do have some of those drill bits you described that you put in a lathe!
 

AES

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Pleased the answers helped Teejay.

As you've discovered, work hardening happens quite a lot on some metals, especially stainless and aluminium! Just how much it hardens depends mainly on the alloy composition (applies to both stainless and ali - you'll hardly ever come across pure ali, it's normally alloyed with at least one other metal during manufacture - and stainless alloy "mixtures" vary an awful lot). So what actually happens depends on the alloy you've got in your hand, plus its dimensions (especially cross-sectional area), plus how hot you make it.

All of which is just "nice to know" really, as the practical result when handling either of these is just to remember "as I work it, it'll most likely get harder". So that means use: not too high a speed - commensurate with the hole diameter of course - a pretty heavy feed - e.g. good constant down force on the pillar drill handle - lots of coolant - and a SHARP drill/countersink. That's all there is to it really.

And BTW, even if you don't have a lathe, hang on to your Slocombes, they quite useful for a lot of things other than their originally designed purpose.

But back to piano hinges - getting screws to fit the existing countersunk holes is definitely your best bet IMO, especially if the item you're making is to be on show. Please D.A.M. H.I.K. that it's all too easy to completely ruin the look of a piano hinge!
 
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