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By thetyreman
#1231454
I have a nice fisch countersink bit and would like to know if I can safely use it on a brass hinge to enlarge the countersink, I bought some no6 solid brass screws and they are 6.6mm and the hinge countersink is around 6mm, I want the screws to be below the surface by a fraction of a millimtere in this case, for a tool chest. Just don't want to damage the bit because they are expensive, should I get a special drill bit just for metal? advice would be appreciated,

cheers,

Ben.
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By CHJ
#1231456
Is the bit HSS? If it is then no problem on brass as it will happily cut mild steel.

Make sure you have suitable brass or ali. backing to the hinge rather than wood else you may just dish the counter sink rather than cutting it.
By AES
#1231462
+1. AND do it in your pillar drill so you can set the depth stop to get the depth/dia of the countersink accurate, so a really nice just under flush for those screw heads. Should look very nice (& if the screws are slot heads and you really want to go for broke, make sure the slots all line up!).
By phil.p
#1231467
If your hinge is fitted perfectly you can hold it in place and use the countersink to mark the screw holes - the drill then follows the hollow in the centre.
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By ED65
#1231479
I just had a quick look online and it does seem the Fisch countersink will be HSS. They make a selection Ben, which style is it out of curiosity?

But even if a countersink is carbon steel it should still have no problem taking just a hair off brass. If a rose countersink blunts slightly in the process it can be touched up fairly easily with some gentle file work or with a slipstone. IME many cheaper modern countersinks would benefit from this anyway!
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By ED65
#1231480
AES wrote:AND do it in your pillar drill so you can set the depth stop to get the depth/dia of the countersink accurate...

+1. An alternative that can work is to use a hand drill and count handle revolutions.

AES wrote:(& if the screws are slot heads and you really want to go for broke, make sure the slots all line up!).

I loved "clocked" screws as they're now frequently referred to (apologies if this is an Americanism, I wouldn't want to help in spreading it if it is) but I've gone off the idea a bit after reading how it nearly invariably means some of the screws aren't fully tightened, or requires some to be modified so they can be.
By novocaine
#1231481
if you start the screw in the same orientation using a pilot hole it should finish in approximately the same orientation. :D

what sort of countersink is it? if it's multifluted then go easy and set you speed and feed it very very gently. single flute is a bit more forgiving.

if you are using a pillar drill, set each one centered with the drill off then clamp the hinge down tight, any movement will show and look terrible.
a decent depth stop is a must for identical holes.

if you aren't sure, you could lap the top of the brass screws instead to bring them down to just shy of 6mm, it's only taking 0.3mm of the head.
By AES
#1231488
ED65 wrote, QUOTE: I loved "clocked" screws as they're now frequently referred to (apologies if this is an Americanism, I wouldn't want to help in spreading it if it is) but I've gone off the idea a bit after reading how it nearly invariably means some of the screws aren't fully tightened, or requires some to be modified so they can be. UNQUOTE:

Never heard that term before, but as I believe a lot of clockmakers do do that, I guess it's a good term, American or not. BTW, I saw a recent TV programme where 4 different old railway passenger carriages were renovated, and they did that on one of them (I can't remember if it was Queen Victoria's carriage or a Pullman) so that all the brass screws were "clocked". Looked really good when pointed out on the programme.

If you do find that the screw slots don't line up when correctly tightened (as they're solid brass screws you "must" drill a pilot hole, which should help with that, as already said) then after driving the screws almost home you can remove them, insert a matchstick stump, then re-tighten them until they are fully home with the slots all aligned. I only did that once but it worked fine.

HTH
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By thetyreman
#1231507
yes it's HSS, and I don't have a pillar drill, should I screw the hinge into a block of scrap wood whilst enlarging the hole? I plan on using a regular power drill and I also have a spare hinge that I'm using to do the testing on. I was worried it might blunt the countersink because it's my main one I use for wood as well, but sounds like it'll be fine, should I use some oil on the metal or not bother?

this is the exact bit I'm using, the 5-13mm version. https://www.axminster.co.uk/fisch-quick ... k-ax947361
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By Eric The Viking
#1231577
Do a sanity check before you start: will the countersink still clear the middle of the hinge (where the pin is), when it's opened up the hole a bit?

I have attacked a fairly manky old countersink with a grinder (no lathe, sadly), so it's narrower. It was for one specific project, but comes in handy more often than I expected. Axminster used to sell a set of three "snail-shell" countersinks, and the smallest of those was fairly dinky. They have two advantages: a clean cut with almost no chatter nor wandering, and the ability to cut going backwards.

Personally, I'd thin the screw head slightly, even if you can enlarge the countersink in the hinge. This is because the cone of the screw head usually doesn't finish with a sharp edge where it meets the flat top of the screw. If you take off the tiny lip, it will sit more neatly in the hinge. But you also have to remember to use a slightly narrower screwdriver too.
By xy mosian
#1231579
thetyreman wrote: I bought some no6 solid brass screws and they are 6.6mm and the hinge countersink is around 6mm, ...

I bet the hinge is for number 5 woodscrews, about the only place where non-even number screws are used I believe.
xy
By AES
#1231580
I think what EtV said, QUOTE: ..... But you also have to remember to use a slightly narrower screwdriver too. UNQUOTE makes good sense, especially IF enlarging the C/S diameter ends up hitting (or very close to) the hinge pin. Been there, done that, and "the T shirt" looks awful.

As we're only taking about three tenths of a mm, taking a bit off the screw heads MAY be the better option, but as we're dealing with brass screws and "the look" here, then if you go the thinner head route I'd suggest taking a suitable screwdriver and "attacking" it with a smooth file to make sure it sits snugly in what's left of the slot - a slip during final tightening will look awful (on either the hinge and/or on the wood).

HTH

A piccie when done perhaps ???

Edit for P.S. What xy mosian has just said makes good sense too - I'm no expert but it's quite likely those brass screws are an "odd" gauge (much simpler here "on the Continent" where there's no screw gauge sizes, just lengths n diameters in mm).