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  #1  
Old 02-05-2017, 08:47 AM
s10sakota's Avatar
s10sakota s10sakota is offline
 
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Location: Westland, MI
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Default 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

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  #2  
Old 02-05-2017, 08:53 AM
60av8tor 60av8tor is offline
 
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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.
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  #3  
Old 02-05-2017, 08:55 AM
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s10sakota s10sakota is offline
 
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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.
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  #4  
Old 02-05-2017, 09:36 AM
Marc Bourget Marc Bourget is offline
 
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Advise you look at the cutting edges with a loupe or inspection microscope?
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  #5  
Old 02-05-2017, 09:44 AM
N427EF N427EF is offline
 
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Default Single flute

These single flute countersinks produced better results for me.
http://www.cleavelandtool.com/Single.../#.WJdVxlu8Zao
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  #6  
Old 02-05-2017, 10:02 AM
60av8tor 60av8tor is offline
 
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Quote:
Originally Posted by s10sakota View Post
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. If every hole does it with that cutter, I would guess the cutter...
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  #7  
Old 02-05-2017, 10:37 AM
David Paule David Paule is offline
 
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Quote:
Originally Posted by s10sakota View Post
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
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  #8  
Old 02-05-2017, 11:03 AM
60av8tor 60av8tor is offline
 
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Quote:
Originally Posted by David Paule View Post
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.
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  #9  
Old 02-05-2017, 11:14 AM
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Steve Melton Steve Melton is offline
 
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Quote:
Originally Posted by N427EF View Post
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
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Last edited by Steve Melton : 02-05-2017 at 11:21 AM.
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  #10  
Old 02-05-2017, 11:19 AM
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skylor skylor is offline
 
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Location: Southern California
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Default Chatter

Quote:
Originally Posted by s10sakota View Post
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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