Drilling out a CherryMax rivet

[William Slaughter]

Due to a particularly boneheaded mistake, I find myself needing to drill out the CR3212-4-6 rivets used to attach the flap brace to the rear spar of a quickbuild RV-8 wing. I would really appreciate any tips on technique from anyone who has actually done this successfully, as I simply cannot afford to booger up the rear spar on a finished wing. Thanks.

[Pmerems]

I have drilled out cherrymax before but it has been some time since I last did it.

First drive out the mandrel, drill the head off and then drive the body out with a punch. If the hole is oversized, order an oversized cherrymax.

Not much different then any other blind rivet.

Paul

[penguin]

Unless you really, really have to I would leave it in.

- If possible drive out the stem using a punch and someone backing up behind. If not ...
- Drill out the stem to break the lock (not easy as stem is steel and hard, try to get a good center pop, and not to slip off, use some thing smaller than rivet dia), punch out the remaining stem, then pry out what is left of the locking collar.
- Now drill out the rivet as normal

http://www.textronfasteningsystems.c...C1005-0805.pdf for cherry locks, and
http://www.textronfasteningsystems.c...42-5M-1003.pdf for cherrymax

A CR3212 is a cherrymax, but that book does not have anything on removal. A cherrylock is basically the same as a cherrymax, except it needs a special pulling tool. The little washer on top of a cherrymax allows them to be pulled with a regular pop rivet plier.

Pete

[svanarts]

The way I remove Cherry Max rivets is to:

1) CAREFULLY grind down the head of the rivet until you have ground past the steel lock collar
2) puch out the mandrel
3) drill the remaining portion of the head off, then puch the rest of the rivet out.

Make sure you really can't workaround the bonehead mistake. I've been able to most of the time. Not always.

[penguin]

Originally Posted by svanarts

The way I remove Cherry Max rivets is to:

1) CAREFULLY grind down the head of the rivet until you have ground past the steel lock collar

Yeah, but these are countersunk so not very easy to grind out.

Pete

[cytoxin]

pop the center out. drill only deep enpough to snap the head off. i did 2 of these yeserday and the second one was a dog. make sure you get the mandrel out or deep enough that you can drill to the shank, if not the drill will walk off of the mandrel and reeeeeeeeealy cause you grief. you can dig a little with a very small pointed punch to get the collar out if need be. just make sure its out.

[William Slaughter]

Ok guys, thanks. I think I'll pull a test rivet in some scrap to practice on. Wish me luck!

[svanarts]

Good plan and good luck.

Regarding grinding CS cherymax rivets; they do tend to sit a little proud so it's not that difficult with a keen eye and steady hand and small grinding wheel and nerves of steel and....and...and...

[Jconard]

I just punch the mandrel out and then drill done the hole with a #41 bit. It wil stop when it hits the lock, and then hit it with a punch again, it will knock the end off.

This is for the countersunk.

I tell you, I have my doubts about these rivets until I had to remove one. They are not going anywhere in service!

[AndrewTR30]

Do the cherrymax rivets neet the special nose to be set or can I use the regular rivet puller used for LP4's and such?