Counter Sink Chattering

No, it's not talking to me but my toaster does has attitude. But I digress. My counter sink is now chattering. Is this from getting dull? I am using by hand. I have tried going slow, fast, Boelube paste and last but not least Boelube liquid. I am still getting chatter. Can the counter sinks be sharpened? Can I sharpen them, if so how? I dont want to ruin them any more if they aren't made to sharpened.
Thanks in adVANce.

I've rarely gotten zero chatter from my fluted deburrerer (er...), and every once in a while I've had some chatter in the fluted countersinks. Certainly if the guide hole is too big or elongated, or if the guide hole was enlarged by countersinking through the other side, chatter happens.

I recently acquired a coupla single-hole countersinks, both guided and unguided, and they do a slick job of deburring and countersinking without chattering at all. They do, however, tend to want to bite into the metal pretty quickly, so if you get some I advise experimentation first - I use 'em by hand for deburring with great success. I use only the single-holers for countersinking now, but rather than nice, thin, gently long peels of Al, I get a stiff, conical chunk as soon as the countersink touches the metal...but I get a shiny, gorgeous countersink. If I didn't use a countersink stop cage, I have a feeling I'd end up with a 3/8" hole through the metal in 20 milliseconds.

I got the guided one-hole 'sinks from Avery, and unguided ones for deburring from McMaster (don't forget to get the correct angle!).

Backup strip/hole

You probably just need a backup strip/hole behind what you're countersinking. As the countersink cutter goes deeper through the material, there's less material stabilizing the pilot. Just need something to stabilize the pilot and I'll bet all the chatter will go away.

)_( Dan
RV-7 N714D
http://www.rvproject.com

Almost always, countersinking should be done at low speed. That's why Van's recommends using an low speed but high torque rechargeable drill. I would second the couple of other comments above as well.

Alan Erickson said:

I recently acquired a coupla single-hole countersinks, both guided and unguided, and they do a slick job of deburring and countersinking without chattering at all. They do, however, tend to want to bite into the metal pretty quickly, so if you get some I advise experimentation first - I use 'em by hand for deburring with great success. I use only the single-holers for countersinking now, but rather than nice, thin, gently long peels of Al, I get a stiff, conical chunk as soon as the countersink touches the metal...but I get a shiny, gorgeous countersink. If I didn't use a countersink stop cage, I have a feeling I'd end up with a 3/8" hole through the metal in 20 milliseconds.

Click to expand...

I did not like the result I got from the single hole countersink. With mine, that stiff conical chunk of aluminum would curl over, stick in the hole, and leave a deep 3/8" circular gouge in the aluminum around the countersink. Boelube seemed to help a little, but it still happened on every third hole or so.

PJ
40032.

Dan is right

Most of the countersinking on the RV is in metal which is too thin for the countersink pilot to nest in adequately. I used a chunk of .125 with a couple #40 and #30 holes in it to hold behind the material with a couple fingers as I countersunk spars and flanges.

Bruce
-9

Use a Countersink Cage and it will help a bunch.

What I am counter sinking is the inspection cover nut plate holes on the bottom of the wing skins .025. I did "back it up"(thanks Dan) and that I think it did make a big difference. But I just tried only one real quick before getting out of the shop for the day. Should I drill out the ones that had rough edges in the hole from my mistake/chatter? I did squeeze a couple rivets in those holes. They were rough holes. Can't use a cage. I wish I could.
Again, Thanks in adVANce.

Terry

again, use NAS1097AD3 rivets with nutplates

Use NAS1097AD3-3.5 rivets when attaching nutplates to anything less than .040" thick stock. Trust me, it's so much easier. And you don't have to countersink as deep, since the NAS1097AD3 has a much smaller head than the AN426AD3.

Just give it a few turns with your deburring tool and it's good to go. Save yourself the hassle.

Besides, trying to use AN426AD3 rivets on anything thinner than .032" or so means the countersink bottoms out through the material -- undesirable at best.

See my previous post on this topic (I seem to state these same words at least once a month because new builders don't know this stuff off the bat) here on this thread:

http://www.vansairforce.com/community/showthread.php?t=2125&highlight=NAS1097AD3

)_( Dan
RV-7 N714D
http://www.rvproject.com

dimpling steel

Because dimpling those nutplates imposes more stress on your dimple dies. Could bend the pilot, could snap it off. Probably won't, but I didn't want to risk that. Plus, when you go to rivet the nutplate on, there's not really enough of a "dimple" to accommodate the dimpled skin, and you often get slight misalignment. I did actually dimple a few nutplates on my empennage early on until I learned better.

)_( Dan

My stupid question of the day. Why doesn't Van's just ship pre-dimpled nutplates? It's not like they are that rare or anything. And while we're on the topic of nutplates, why doesn't Van's use MS numbers for theirs? They look like the exact same part (I inventoried my Emp. hardare today).

they're expensive

Last I checked, pre-dimpled nutplates were much more expensive. I assume that's why Van's doesn't bother with them.

)_( Dan

Yeah they are probably about twice the cost, but in the grand scheme of things, thats probably less than $50 throughout the whole airframe. (at least of the parts that need um) I'll probably end up buying them seperately anyway.