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-   -   Jagged Countersinks (https://vansairforce.net/community/showthread.php?t=146401)

s10sakota 02-05-2017 08:47 AM

Jagged Countersinks
 
I know I've seen a thread or two on this before, but the search didn't turn up the threads.

I am countersinking some holes in a piece of aluminum on a different airplane and they are coming out really jagged.

In the pic you will see the jagged hole, and the other hole I've smoothed out with the hand held debur tool.

But I've used the bit shown on the RV-7 and all the holes came out absolutely smooth and perfect.

What's going on now? Is the bit dull? I've tried high speed and low speed and the speed makes no difference. I've tried light pressure and high pressure and they all come out jagged. I can smooth them with the debur tool, but I'd rather them just come out smooth from the countersink tool!

Any thoughts?

Thanks


60av8tor 02-05-2017 08:53 AM

Generally when I've had chattering while counter sinking it has been when I'm not properly backing up the work piece. This allows the pilot to wander causing the results you're seeing.

s10sakota 02-05-2017 08:55 AM

I don't think that's the case here as I have two pieces of wood underneath the hole right up to the hole. So it's pretty solid under.

Marc Bourget 02-05-2017 09:36 AM

Advise you look at the cutting edges with a loupe or inspection microscope?

N427EF 02-05-2017 09:44 AM

Single flute
 
These single flute countersinks produced better results for me.
http://www.cleavelandtool.com/Single.../#.WJdVxlu8Zao

60av8tor 02-05-2017 10:02 AM

Quote:

Originally Posted by s10sakota (Post 1147756)
I don't think that's the case here as I have two pieces of wood underneath the hole right up to the hole. So it's pretty solid under.

You know, right after I posted that, I looked at your signature and assumed you had covered that base:D. If every hole does it with that cutter, I would guess the cutter...

David Paule 02-05-2017 10:37 AM

Quote:

Originally Posted by s10sakota (Post 1147756)
I don't think that's the case here as I have two pieces of wood underneath the hole right up to the hole. So it's pretty solid under.

Try a piece of 1/8" aluminum instead. That worked for me. I'd let the countersink go into the aluminum, which was thick enough that the pilot remained constrained.

I use a very low speed for countersinking. I use a Dewalt battery drill.

The 1/8" aluminum part had other holes in it so that I could cleco it to the work using adjacent holes.

Dave

60av8tor 02-05-2017 11:03 AM

Quote:

Originally Posted by David Paule (Post 1147782)
Try a piece of 1/8" aluminum instead. That worked for me. I'd let the countersink go into the aluminum, which was thick enough that the pilot remained constrained.

I use a very low speed for countersinking. I use a Dewalt battery drill.

The 1/8" aluminum part had other holes in it so that I could cleco it to the work using adjacent holes.

Dave

Same technique here - start very slowly and end fast once I know the cut has been initiated smoothly; always use the electric for this. Good call on using aluminum to back up the work. If countersinking a lot and using wood, I usually have to make a fresh hole fairly often as the hole quickly gets slightly enlarged and doesn't hold the pilot as well as necessary.

Steve Melton 02-05-2017 11:14 AM

Quote:

Originally Posted by N427EF (Post 1147771)
These single flute countersinks produced better results for me.
http://www.cleavelandtool.com/Single.../#.WJdVxlu8Zao

ditto, these worked much better for me.

you owe it to yourself to try one of these debur tools, you will never go back
http://www.cleavelandtool.com/Deburr.../#.WJds29QrKys

skylor 02-05-2017 11:19 AM

Chatter
 
Quote:

Originally Posted by s10sakota (Post 1147752)
I know I've seen a thread or two on this before, but the search didn't turn up the threads.

I am countersinking some holes in a piece of aluminum on a different airplane and they are coming out really jagged.

In the pic you will see the jagged hole, and the other hole I've smoothed out with the hand held debur tool.

But I've used the bit shown on the RV-7 and all the holes came out absolutely smooth and perfect.

What's going on now? Is the bit dull? I've tried high speed and low speed and the speed makes no difference. I've tried light pressure and high pressure and they all come out jagged. I can smooth them with the debur tool, but I'd rather them just come out smooth from the countersink tool!

Any thoughts?

Thanks


Chatter is often the result of a combination of too high of a tool speed combined with too little cutting pressure. If you are already backing up your work with a piece of metal or wood, match drilled and rigidly clamped, then I would suggest using more pressure on the drill. Also pull the cutter off of the hole as soon as it bottoms against the stop.

Skylor


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