Author Topic: Countersinking ? (Read 11443 times)

picclock · « **on:** August 05, 2011, 10:33:29 AM »

Hi

I have two types of countersinking bits, the 'normal' rose bit and the newer design which just uses the edge of a hole to do the cutting.

(See http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Deburring)

I seem to be having trouble with both as I use larger sizes. The normal rose type bits seem to judder and try to create holes with straight sides (like a pentagon or hexagon).

So I thought I'd try the type with the hole. I do not understand how these are supposed to work

On the one I bought the shaft is fitted eccentrically to the cutting head. This puts very high sideways loads on the mill head as it cuts and you can see the chuck moving eccentrically as the tool cuts.

Is the shaft supposed to be eccentric to the cutting head ?. Is this what makes it function?

Does anyone know how to stop the rose bits juddering as they get to larger diameters ?

Any other hints or info from successful countersinker's most welcome.

Best Regards

picclock

Jasonb · « **Reply #1 on:** August 05, 2011, 11:29:09 AM »

Slowest speed possible, cutting fluid and there is the old trick of putting a bit of emery cloth over the hole and then cutting the CSK, not tried it myself as I don't want the abrasive near the machine.

Jason

DaveH · « **Reply #2 on:** August 05, 2011, 12:58:39 PM »

Picclock,

I second Jason,

you may have to turn it by hand to finish. In a tap wrench.
No idea about the emery cloth - never done that.

As for the one with the hole in I've never used one, but what you say does seem a little odd.

DaveH

jim · « **Reply #3 on:** August 05, 2011, 02:25:50 PM »

them with the hole in have been about for at least 30 years!

i prefer a rose, i just give the cutting edge a rub with a stone to dull it slighty, it stops it grabbing and chattering

slow is the way to go

Lew_Merrick_PE · « **Reply #4 on:** August 05, 2011, 04:51:07 PM »

Picclock,

The "cross-drill" type countersinks used to be known as "Weldon" countersinks. They are not easy to be accurate with (unless you have the type that seems to have disappeared from the market that have a micrometer stop-collar on them), but they are easier to use with hand-drills. I have been using single-flute countersinks for any operation requiring precision for several years now. Use them at very slow speed, feed them carefully, and keep heavy oil over the whole thing and you will like the results!

Over at http://www.scribd.com/Lew%20Merrick you will find a document Countersunk Fastener Hole Considerations that has quite a bit of information you may find helpful.

Jonny · « **Reply #5 on:** August 05, 2011, 05:45:28 PM »

Experiment with the spindle speeds and feed rate, of which i get a feel for whats happening.
Assume the work piece is clamped rigid and no other movement any where? There again can be done quite easilly holding by hand.

Whats happening is the cutter is momentarilly cutting then job or cutter flexes and so on. I rarely get this with using drills to countersink csk screws, 4 flutes would be better. Once it has started its hard to rectify. 9 times out of 10 with aluminiums i run at max cap 1250 rpm, just get the feed right.

krv3000 · « **Reply #6 on:** August 05, 2011, 07:21:06 PM »

HI this may sawnd daft but have you got the right countersinking tool I have no experince with the hole type countersinking tool but the three fased cuting type ones I yoused all the time on all sorts of metels the key thing is speed if in dawt start off slow with plenty of cuting oil you say you have a rose type ? dus it have more than three cuting fayses if so this type is for wood this is a pic of the type that i youse

picclock · « **Reply #7 on:** August 06, 2011, 02:49:49 AM »

I have both types of rose bit, 5 flute and 3 flute. I'm countersinking the parts in a mill, so fairly rigid. Material is steel, they don't tend to misbehave in softer metals like aluminium. Its always with larger sizes, say above M6.

This seems to be an ongoing issue for me.

@KRV3000
I saw those at RDG but they are no different to the ones I have. Do you make large countersinks in steel ? I was quite tempted to get a set as the sizes seem to correspond to metric cap screw sizes. At the moment I use a larger countersink bit which means the hole shape is a cone, however for the first 0.8mm of, say an M8 screw it would be better if the sides were parallel, easily achieved by using a bit with the correct outside diameter.

@ Lew_Merrick
I've never come across a single flute countersink bit before, but I think it may well reduce or solve the problem. I'll have to get hold of one to try. Precision is what I'm aiming for so this may resolve the issues I have.

@jasonB

The emery cloth trick may work but after the cloth has worn through you have hard abrasive dust between the tool and the work. I can't imagine this being good for the tool or anything else it gets on.

Many thanks for your helpful comments and ideas.

Best Regards

picclock

Lew_Merrick_PE · « **Reply #8 on:** August 06, 2011, 12:12:23 PM »

Quote from: picclock on August 06, 2011, 02:49:49 AM

@ Lew_Merrick
I've never come across a single flute countersink bit before, but I think it may well reduce or solve the problem. I'll have to get hold of one to try. Precision is what I'm aiming for so this may resolve the issues I have.

Take a look at http://www.use-enco.com/CGI/INPDFF?PMPAGE=65&PARTPG=INLMK32 for a single flute countersink. I have no idea about vendors on your side of the pond, but they have been a standard-off-the-shelf item in the U.S. since (at least) the late-1960's. I had a set of 7-flute countersinks I was given as an apprentice were wonderful -- but they finally dulled to non-recoverable condition about 1980. I spent an inordinate amount of $$$ trying to replace them (the flute form was NFG) before I settled on the single-flute type. The HSS variety are easy to "touch-up" the cutting edge which I find to be a tremendous advantage.

Bluechip · « **Reply #9 on:** August 06, 2011, 12:21:22 PM »

Quote from: Lew_Merrick_PE on August 06, 2011, 12:12:23 PM

Quote from: picclock on August 06, 2011, 02:49:49 AM
@ Lew_Merrick
I've never come across a single flute countersink bit before, but I think it may well reduce or solve the problem. I'll have to get hold of one to try. Precision is what I'm aiming for so this may resolve the issues I have.

Take a look at http://www.use-enco.com/CGI/INPDFF?PMPAGE=65&PARTPG=INLMK32 for a single flute countersink. I have no idea about vendors on your side of the pond, but they have been a standard-off-the-shelf item in the U.S. since (at least) the late-1960's. I had a set of 7-flute countersinks I was given as an apprentice were wonderful -- but they finally dulled to non-recoverable condition about 1980. I spent an inordinate amount of $$$ trying to replace them (the flute form was NFG) before I settled on the single-flute type. The HSS variety are easy to "touch-up" the cutting edge which I find to be a tremendous advantage.

Solid carbide items are available here, I had one, and promptly broke it.

However, in it's brief life it did seem effective.

Here is one UK source.

http://www.drill-service.co.uk/Product.asp?Parent=060080040000&Tool=31

I might add the one I destroyed was NOT sourced from this supplier !!!

BC

DaveH · « **Reply #10 on:** August 06, 2011, 01:42:22 PM »

Quote from: Bluechip on August 06, 2011, 12:21:22 PM

I had one, and promptly broke it.

However, in it's brief life it did seem effective.

BC

No sorry, one should not laugh

DaveH

Bluechip · « **Reply #11 on:** August 06, 2011, 03:09:02 PM »

Quote

No sorry, one should not laugh

DaveH

No, one shouldn't. So, I didn't ..
My own fault anyway. CI casting. I knew damned well it had a chilled spot as I had just drilled a 5/16" hole in it.

Just poked it with the Csk. and KERRPLINK ...

Ah well. It was nice while it lasted ...

BC

krv3000 · « **Reply #12 on:** August 06, 2011, 05:29:45 PM »

HI right i have sum pics for you I dont have a mill at the moment but i did this m8 countersink on me piller drill I went a bit to deep I jus dun this one for you on the lathe its a m8 in justa bit of scrap and ther is a pic of the type yoused for wood enjoy

krv3000 · « **Reply #13 on:** August 06, 2011, 05:31:26 PM »

ups mist it off

AdeV · « **Reply #14 on:** August 08, 2011, 06:39:05 AM »

The way I was "taught" to countersink, using a 3-flute tool, was to switch the machine on, then off, and peck the tool in using just the remaining momentum to cut the countersink (this is on a Bridgeport machine). As a technique, it works well, so long as you don't need a deep countersink (it gets a bit tedious, all that flicking the machine on & off).

As others have said; slow slower slowest... decent amount of lube (you don't need to go nuts), and don't put too much downward pressure on - enough to keep it cutting, but don't hang off the handle with all your bodyweight...

I have cut some square countersinks in my time, usually due to using too much speed I feel.

dickda1 · « **Reply #15 on:** August 08, 2011, 12:09:01 PM »

AdeV,

I'll give your method a try. Counterboring works for me, but I almost always get a bit of chatter with countersinks.

-Dick

Miner · « **Reply #16 on:** August 21, 2011, 01:55:34 PM »

The standard rule when chatter becomes a problem is to lower the rpm and/or up the feed rate. On a drill press for example you sometimes need to lean on the downfeed spider a lot more than one would think. You want a heavy feed to force the tool to cut.

Pete

johnbaz · « **Reply #17 on:** September 17, 2011, 03:46:44 PM »

Hi all

I presume that everyone knows that countersinks have to have an odd amount of cutters to truley countersink (well, a nice round countersink anyhow)
If you try countersinking with a twist drill (just the two cutting edges), it comes out like a pentagon- can anyone say why this happens???

We were told this in metalwork years and years ago (I went to skool wiv Robin Hood

) but never told the logic behind it??

Cheers, John

Rob.Wilson · « **Reply #18 on:** September 17, 2011, 05:04:39 PM »

Close John

Not an odd number of cutting edges ,,,its the space between them that should differ , so the cutting edges are not equally spaces , this stops the rise and fall affect you see as chatter .

Two cutting edges will give you a triangle ,as with a drill bit ,,,its always one more side than cutting edge ,,, cant remember why

Rob

Russell Nash · « **Reply #19 on:** September 17, 2011, 05:29:19 PM »

Back when I was a toolmaker, I re-sharpened all of these designs. Our company didn't make countersinks, but sharpening them was so easy it turned a good profit.

The countersinks with the big hole (I long ago forgot the proper name) isn't on the shaft eccentrically. It is made with relief behind the cutting edge. The arc behind the edge has a smaller radius than the tool itself. Once it gets all the way around it does make the tool look funny.

My milling experience was long before my grinding, so I have nothing from the user's end to add.

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Author Topic: Countersinking ? (Read 11443 times)

Rob.Wilson