Countersinking large holes

[JayRS4]

I`ve come across a job that requires several 16mm holes to be countersunk. Not quite sure why, i`ve personally never come across bolts of that size with a countersunk head. Can anyone shed light on how I go about doing it? Thanking muchly, Jay

 

[Paul.]

A big countersink bit is what you need!, or maybe grind a large drill at 90deg if the job wont stand the cost, M16 csk screws are quite common

 

[JayRS4]

Thanks Paul, i`ll have a google and see if I can find a supplier for such a thing. Not sure if the job will pay for it, or if i`ll have any use for it after, way out of the size range of what I normally deal with.

 

[Paul.]

The head diameter of an M16 Csk socket screw is 29.6mm just so you know what size to look for,

 

[JayRS4]

Thanks again, I found 30 and 50mm ones on weldmets site, but only for mag drills (which I dont have) and 45 odd quid each, might have to farm out that bit, tad annoying.

 

[wyn]

We use the type of countersink with a pilot, in work (pic below) ...you seem to get less chater on materials that are a bit hard going. I should imagine they are a bit pricey though.

 

[Hitch]

Ive never had much sucess with csks in mag drills, even on slower speeds.

Radial drill on autofeed is the way
As Paul said, they are fairly common for us that deal with that size stuff all the time.

Ours usualy come from J&L, but they are not cheap if you want ones that cut.

If its only a few, and profit wont stretch to it, see if you can get a twist drill and sharpen it up to 90degs. Its easy to get carried away doing it that way though, so check the depth regulalry.

 

[brightspark]

theres a set if 3 on ebay biggest being threquarter inch hss . type in countersinks 4th down the list £1.99 starting u should get em 4 a song

 

[Welderpaul]

theres a set if 3 on ebay biggest being threquarter inch hss . type in countersinks 4th down the list £1.99 starting u should get em 4 a song

£1.99? My moneys on em being crap!
£40-odd quid last one i bought - still going strong!

We've not had any problems using countersinks in mag drills. CSK fixings in structural stuff are a nightmare though.
CSK holes no good for the podger

 

[Paul.]

3/4" isn't big enough anyway, £40 plus is about right for a decent one, dormer or starret, even a small 1/2" one is over a tenner

 

[brightspark]

£1.99? My moneys on em being crap!
£40-odd quid last one i bought - still going strong!

We've not had any problems using countersinks in mag drills. CSK fixings in structural stuff are a nightmare though.
CSK holes no good for the podger

not everythings crap on e bay the only thing is the size isnt big enough i bought a brand new. starret dial gauge for 6 quid of e bay brand new it wasnt crap and its still going strong

 

[Welderpaul]

£1.99? effectively unbranded? Crap

Might buy a set for the laugh. See how good/crap they are

Agree that there can be decent stuff on there.

 

[brightspark]

£1.99? effectively unbranded? Crap

Might buy a set for the laugh. See how good/crap they are

Agree that there can be decent stuff on there.

it says pan american on em mind u it says india on tires but it dont mean there made there

 

[Ratty]

There is this one on ebay - 30mm, under £25 with postage..or make them an offer.
Or a 27mm at less than half that.

Or you could buy a really good one then sell it afterwards on ebay...given the stupidity of some buyers you'll probably get your money back!

 

[Welderpaul]

The Kennametal one is a top make. Good price. Shame no picture though.

 

[Ratty]

The Kennametal one is a top make. Good price. Shame no picture though.

Fancy - didn't know that, another name to add to my back-brain. There is a little picture in his listings.

 

[the artfull-codger]

countersinking bits

I have made my own for years & frequently use them on aluminium as well which is notorious for building up on the cutting edge, all you do is get a drillbit
the diameter you require ( if it's been snapped it doesn't matter) grind it to 90degrees & sharpen it like a normal drillbit, THEN the secret is to round off one of the cutting edges so that only one edge cuts & the other guides, if it's too large for your chuck you just turn the shank down to fit,hss drill shanks are soft enough to machine. Snapped /shortened drillbits are more rigid than full size ones.

 

[Pete.]

I've seen countersinks where you turn a cone in some annealed tool steel, bore a hole into the cone at an angle, then harden it. The sides of the hole provide the cutting edge and they don't chatter as they have no flute. Work great in aluminium.

 

[JayRS4]

Aren`t they deburers Pete? I could be wrong, never used one, i have my own bad habits.

 

[Pete.]

They would make a good de-burring tool. I found some on a yank site:

http://www.technologylk.com/_CS618S/crl-weldon-countersink-set.htm?