small counterbores

[tony bastickParticipant @tonybastick78554]

Hi all, does anybody know where you can get good quality (not cheap far easten rubbish) small counterbores in BA sizes, i know you could get them years ago but not seen any recently.Thanks Tony

[tony bastickParticipant @tonybastick78554]

[tony bastickParticipant @tonybastick78554]

Hi again, should have said that they are for metal cutting not wood.Tony

[Jeff DaymanParticipant @jeffdayman43397]

Hi Tony,

I can't help with a source to buy BA c'bores ready made, but offer a couple of alternate methods which might work for you.

– use the closest size throwaway slot drill or end mill to the desired hole to make the c'bore, after drilling the screw clearance hole.

-make your own c'bore cutter from drill rod/silver steel. I have made some small cutters by milling cutting flutes on the end of some drill rod, after drilling a central pilot hole. I turned a separate piece of rod to act as the pilot and have secured them with loctite or with setscrew if cutter is large enough. After hardening the cutter, the flutes are sharpened with a small stone.

JD

Edited By Jeff Dayman on 14/04/2013 13:22:44

[Michael GilliganParticipant @michaelgilligan61133]

Tony,

I have just seen some on ebay

seller:dhstoolsupplycoltd2004

MichaelG.

[David LittlewoodParticipant @davidlittlewood51847]

Tony,

I don't recall seeing any counterbores specifically for BA sizes, though I have not searched for them very hard.

I would go along with Jeff's suggestion about the slot drills – though you need to make sure they are configured for plunge cutting. Four flute end mills generally are not; two flute slot drills and (most) three flute disposable cutters are. I find that many commercial counterbores are rather too large for the sizes they are marked for; metric ones give much too much space for the heads of capscrews, it just makes a gap for swarf. I find I get better results using the correct size of slot drill.

I bought a set of counterbores from Tracy Tools about 20 years ago which have served quite well in the smaller sizes; they work better than slot drills in doing couterbores in delicate items (such as O gauge coupling rods) as the pilot helps to stop the part bending under cutting forces. Don't know if they still do them. Bear in mind if the pilot is too small you can often pad it out with a bit of tubing for such delicate work; if it's too big you are stuck.

David

Edited By David Littlewood on 23/04/2013 22:55:32

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 23/04/2013 22:41:27:

Tony,

I have just seen some on ebay

seller:dhstoolsupplycoltd2004

MichaelG.

.

Only three sizes listed, but they are "Robert Charles" and new.

…  also see here

MichaelG.

Edited By Michael Gilligan on 23/04/2013 23:46:10

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

When doing counterboring in a milling machine where there can be good guidance and location of cutters counterbores can be formed using :

Almost any kind of end mill/slot drill since there is normally an existing centre hole in work to clear centre part of cutter .

A simple boring bar type cutter in a boring head – can usually be done in one cut .

DIY cutters consisting of an axial toolbit offset by required amount in plain bar holder .

This also works :

Drill a normal hole to counterbore depth . Use a normal drill ground flat on end and with some reasonable cutting eges ground in just to finish the flat bottom .

Regards ,

Michael Williams .

PS: It has to be said that many people use a normal drill for counterboring in the rougher end of industry – the difference between an actually flat narrow annular land and a slightly conical one is not great and bigger cap screws just scrape their own seating when tightened down anyway .

[John McNamaraParticipant @johnmcnamara74883]

Hi All

Google:

Image Counterbore

**LINK**

This link looked promising Not BA But small You could make your own BA pilots?

**LINK**

Cheers

John

[Brian WoodParticipant @brianwood45127]

Hello Tony,

I wanted to cut some the other day to house M6 cap head screws in steel. The mill was already set up with another job on it, so I used the bench drill holding a 10mm diameter 4 flute end mill.

Before other readers shout 'foul and it will chatter' I opened the mouth of the hole to 11mm with a drill to leave a shallow countersink. Then the end mill went in without any trouble at all, cutting it's own location as it went. The end result looks very neat, with a nicely deburred edge to the hole.

I am the first to admit that straight plunge cutting using a bench drill holding an end mill is bound to chatter and the end result will be oversize. This might be a way out for you using little end mills suited to BA sizes. Do clamp the job to the table so that it can't move.

Brian.

[Author]

Posts