Countersinking brass - what drill bit?

[David Mack]

I have bought some brass mushroom vents for Belfast and some brass M5 countersunk machine screws to fix them down with. However I find that the countersunk holes in the mushroom vent bottom flange are too shallow for the screw heads to fit neatly. So I need to drill out them out. I am struggling to find what sort of drill bit to use. The requirement is for a 90 degree countersink, drilled out to a top diameter of 11.2mm (in the existing 5mm holes). All of the countersink bits in the usual places seem to be carbon steel for use in wood, and I can't imagine they will last long if used in brass.

Any suggestions for what sort of bit I need and where to get it?

 

Thanks.

[MtB]

1 minute ago, David Mack said:

I have bought some brass mushroom vents for Belfast and some brass M5 countersunk machine screws to fix them down with. However I find that the countersunk holes in the mushroom vent bottom flange are too shallow for the screw heads to fit neatly. So I need to drill out them out. I am struggling to find what sort of drill bit to use. The requirement is for a 90 degree countersink, drilled out to a top diameter of 11.2mm (in the existing 5mm holes). All of the countersink bits in the usual places seem to be carbon steel for use in wood, and I can't imagine they will last long if used in brass.

Any suggestions for what sort of bit I need and where to get it?

 

Thanks.

 

answering obliquely in true internet style, drill bits are not suitable for countersinking as they have a much shallower angle. 120 degrees springs to mind rather than the 90 degrees of a countersink bit. 

 

How about these or similar?

 

https://www.ebay.co.uk/itm/HSS-COUNTERSINK-3-PC-BIT-SET-FOR-STEEL-SND-HARD-METALS-10MM-12MM-16MM-S78/282638842555?epid=2255182755&hash=item41ce967abb:g:03IAAOxyi-ZTYYh~

 

 

 

 

 

OR... use domed headed brass screws!

 

 

[ditchcrawler]

I find the problem with them is to stop them chattering and making a bumpy surface

 

[David Mack]

7 minutes ago, Mike the Boilerman said:

 

answering obliquely in true internet style, drill bits are not suitable for countersinking as they have a much shallower angle. 120 degrees springs to mind rather than the 90 degrees of a countersink bit. 

 

How about these or similar?

 

https://www.ebay.co.uk/itm/HSS-COUNTERSINK-3-PC-BIT-SET-FOR-STEEL-SND-HARD-METALS-10MM-12MM-16MM-S78/282638842555?epid=2255182755&hash=item41ce967abb:g:03IAAOxyi-ZTYYh~

 

 

 

 

 

OR... use domed headed brass screws!

 

 

 

Thanks Mike. Yes, I want 90 degree countersinks, not ordinary drill bits. The Screwfix offerings all say suitable for wood only (unless I pay £45 for a Makita set of 6). But I've just seen that Toolstation do a set of 3 similar to your ebay suggestion for £7.44 that claim to be suitable for steel and hard metals. https://www.toolstation.com/hss-countersink-set/p18880

[MtB]

6 minutes ago, ditchcrawler said:

I find the problem with them is to stop them chattering and making a bumpy surface

 

 

Good point, but surely the same will happen using a twin flute drill as a countersink anyway.

 

A bigger problem will prolly be the very short shank. 

 

 

[David Mack]

6 minutes ago, ditchcrawler said:

I find the problem with them is to stop them chattering and making a bumpy surface

 

Yes I'm a bit nervous about that.  Apparently, in wood at least, the answer to that problem is to drill the countersink first and then the hole.

https://www.popularwoodworking.com/american-woodworker-blog/smooth-silk-perfect-countersink/

 

But not sure if that works in metal, and anyway my mushroom vents already have the holes drilled (with inadequate countersinks).

[MtB]

 

Another approach would be to 'sharpen' a 10mm twist drill freehand to 90 degrees, using a bench grinder.

 

A third approach would be to turn yourself some nice wooden mushrooms  

[David Mack]

5 minutes ago, David Mack said:

 

Thanks Mike. Yes, I want 90 degree countersinks, not ordinary drill bits. The Screwfix offerings all say suitable for wood only (unless I pay £45 for a Makita set of 6). But I've just seen that Toolstation do a set of 3 similar to your ebay suggestion for £7.44 that claim to be suitable for steel and hard metals. https://www.toolstation.com/hss-countersink-set/p18880

 

The reviews on Toolstation's website vary from

 

"Poor quality. I bought these for aluminium work they remained sharp for around 6 holes"

 

to

 

"I have used one of the countersink bits to countersink 384 holes in 5mm stainless steel and this bit is still functional "

 

So i really don't know if they're any good!

 

[Jen-in-Wellies]

7 minutes ago, David Mack said:

The Screwfix offerings all say suitable for wood only

I've used this one from Screwfix successfully on brass without it blunting, despite it saying wood only. High Speed Steel.

 

Jen

[WotEver]

21 minutes ago, Jen-in-Wellies said:

I've used this one from Screwfix successfully on brass without it blunting, despite it saying wood only. High Speed Steel.

 

Jen

Good reviews for that too. This one bears posting here:

 

I used this to countersink 20 x 6mm holes in 8mm mild steel and it was as sharp at the end as it was at the start. Problem is people no-longer are educated or skilled enough to understand- speeds, feeds and cooling when using cutters. If you force this into even soft pine on the fastest speed and with the most pressure you will overheat and destroy it within a hole or two. When countersinking steel you need slow speeds and ideally a lubricant or cutting fluid and it will last no problem. If you get it so hot its turns blue then you have destroyed it and you may as well throw it away

[ditchcrawler]

24 minutes ago, David Mack said:

 

The reviews on Toolstation's website vary from

 

"Poor quality. I bought these for aluminium work they remained sharp for around 6 holes"

 

to

 

"I have used one of the countersink bits to countersink 384 holes in 5mm stainless steel and this bit is still functional "

 

So i really don't know if they're any good!

 

Maybe one used a good cutting compound and one didnt

[MtB]

5 minutes ago, ditchcrawler said:

Maybe one used a good cutting compound and one didnt

 

Maybe one used a bloody awful cutting compound and one didn't!

 

[RLWP]

These are HSS, so they'll cut metal

 

https://www.ebay.co.uk/itm/6-x-Durable-90-Degree-Hss-Chamfer-Cutter-Bit-Chamfering-Countersink-Drill-Bits/263960624733

 

Richard

[jonathanA]

Brass is softer than even the cheapest Chinese steel so just use any old counter sink bit you have lying around just don’t expect it to be any good for cabinet making afterwards 

 

although I’m surprised you’re having to bother for 5mm machine screws I usually only have to increase the countersink when I upgrade to 6mm 

 

I’d recommend stainless Allen ( hex socket) screws rather than brass slotted screws 

[RLWP]

Just now, jonathanA said:

 

I’d recommend stainless Allen ( hex socket) screws rather than brass slotted screws 

Where's your sense of adventure? Why miss out on all the fun of shearing the head (or half the head) off by trying to get the slots to line up...

[ditchcrawler]

Just now, RLWP said:

  by trying to get the slots to line up...

Do people still do that

[jonathanA]

True and brass is easy to drill out too.... 

[RLWP]

2 minutes ago, ditchcrawler said:

Do people still do that

Well, some do - me for instance

 

Sometimes even with Philips head screws

 

I must get out more...

Edited March 31, 2019 by RLWP

[WotEver]

12 minutes ago, RLWP said:

Well, some do - me for instance

Me too. Light switches, socket outlets, hinges... anything really. 

[TheBiscuits]

37 minutes ago, RLWP said:

Well, some do - me for instance

 

Sometimes even with Philips head screws

 

I must get out more...

Torx is the way forward here ...

[Tonka]

Drill for brass have a different cutting angle to drills for steel. I remember the father in law having sets marked and shouting at you if you got it wrong 

[Ray T]

11 hours ago, RLWP said:

Well, some do - me for instance

 

Sometimes even with Philips head screws

 

I must get out more...

When Mr. RLWP came to work on my gear box a while ago now, it was noticed that some of the slots in some dome head screws in the cabin were all at different angles. Not only that but they were not aligned fore- aft with the boat!

By the next visit they were! 

 

Edited April 1, 2019 by Ray T

[alan_fincher]

11 hours ago, RLWP said:

Where's your sense of adventure? Why miss out on all the fun of shearing the head (or half the head) off by trying to get the slots to line up...

 

11 hours ago, ditchcrawler said:

Do people still do that

 

When Brinklow Boat Services manufactured us an excellent Northwich style pigeon box for Sickle, they didn't have glasses for the ports that go onto them.

 

Simon had to be persuaded that I would be able to fit them myself to an adequate standard before they would let me off the premisis, and I was shown an example of how lined up the slots should be.  I'm sure they have subsequently seen my efforts, and I'm relieved not to have been chastised for an inadequate job.

 

They were less than complementary about the Warwickshire Fly manufactured box on Flamingo.  Although the slots line up on the bolts, it is apparently ruined by them being too small a size!

[Stilllearning]

11 hours ago, RLWP said:

Well, some do - me for instance

 

Sometimes even with Philips head screws

 

I must get out more...

I do as well, it looks good and  if no one else ever notices, so what.

[Taslim]

1 hour ago, Stilllearning said:

I do as well, it looks good and  if no one else ever notices, so what.

I think that no one notices when they do line up but when the don't line up.......