Removing Cherry Max rivets:

[jcbarker]

To those that have QB fuselages and wings you will be installing a lot of Cherry Max rivets for the LCP remediation. They are a legal direct replacement for driven rivets. However, they do require special attention and technique. As such, if you are at all like me, you will make a mistake and need to remove a rivet. There's a lot of advice out there. Some of it not clear or contradictory so I went to the source, Cherry Aerospace and found they had a very good video on how to properly remove a Cherry Max rivet. The example is a CS rivet but the only difference is the universal head rivet head needs to be ground down about half it's height before continuing as per the video. I uses an abrasive wheel on a dremel for this. Here's the link to the video:
https://www.cherryaerospace.com/product/video/rivetremoval

 

[TASEsq]

To those that have QB fuselages and wings you will be installing a lot of Cherry Max rivets for the LCP remediation. They are a legal direct replacement for driven rivets. However, they do require special attention and technique. As such, if you are at all like me, you will make a mistake and need to remove a rivet. There's a lot of advice out there. Some of it not clear or contradictory so I went to the source, Cherry Aerospace and found they had a very good video on how to properly remove a Cherry Max rivet. The example is a CS rivet but the only difference is the universal head rivet head needs to be ground down about half it's height before continuing as per the video. I uses an abrasive wheel on a dremel for this. Here's the link to the video:
https://www.cherryaerospace.com/product/video/rivetremoval
View attachment 67561

I’ve removed a few bad ones so far, and I learned that this video is ok from an overview but misses a small point.

There is a tiny steel locking “clip/ring” which holds the mandrel from falling out (the steel mandrel gives all the strength to the cherry).

In most cases where you are drilling out a rivet, it’s because it hasn’t set properly - meaning a lot of the time this steel collar hasn’t engaged the mandrel.

It’s easy to know - get a tiny punch, smaller than the mandrel, and tap. If the mandrel moves, then the locking collar isn’t set. This is what is depicted in the video. You can just tap the mandrel all the way out. The little steel locking ring will either fall out, or you can easily pry it out. In the video they seem to use an centre drill to remove it. With the mandrel and locking ring out, you’ve got a soft aluminium rivet, with a pre drilled guide hole you can drill out normally.

In fact, as a quality check I tapped on every cherry I set to make sure the mandrel was locked. If it wasn’t, then the most likely case was the wrong cherry was used. I’ve had few times where Van’s sent me cherries in a bag labelled with the wrong length. You can zoom in and read the fine print on the head.

If you wanted to remove a perfectly set rivet where the mandrel is locked - that’s a whole other headache. Then the head needs to be ground to remove some mandrel and allow the locking collar to come out. I’ve not had any experience with that - I’ve only ever removed the bad ones thankfully.

I’ve also only removed the flush ones - why do you need to grind the head to half the height? or is that only if the mandrel is locked?

YMMV!

29-14 -> 16: Riveting of Side Skins to Fuselage (Forward of Spars)

A Build Log detailing the build of a Vans RV-14

tasrv14.blogspot.com

 

[cvairwerks]

Having drilled out lots of MS90353/MS90354 blind rivets, which are the mil-spec, high strength version of a Cherry Max. using a grinder on the head should be your absolute last resort. Simply use a #40 or a #30 to center drill the pin until below the lock collar depth, and then move up a size or two, until you either completely remove the collar or it comes free. It takes higher than normal pressure on the bit while you are drilling and lower rpms. If you are really paranoid, switch to carbide or cobalt 40's or 30's for the pilot hole. If you mess up and over speed the bit and harden the area where you are starting the pilot hole, a light sanding with a disk on a die grinder will fix that.

One of the hardest things we had to teach the new kids on the line, was that drilling out the steel shanks and lock rings didn't require max rpms on the drill and it was faster overall to start with a pilot hole and bring it up.

 

[Bandera]

I picked up a tool from ATS just for drilling cherrymax rivets. It grips the outer edge and allows you to drill the center without walking off. It works great if you have plenty of room for access.

 

[rsultzbach]

I drilled out quite a few Cherrymax rivets and I used a small piece of aluminum sheet maybe just slightly larger than a rivet checking tool. I drilled a hole in the sheet that just fit over the rivet head perimeter. I taped this shield to the web of the wing spar. With this shield in place I used a conical grinding stone with my Dremel tool with the point used to grind out the locking collar of the rivet. Then, I used a small previously broken punch ground to a blunt point to drive the center mandrel out of the Cherrymax. When the mandrel moved it was easy to drive it out with a regular 3/32 punch. Then just drill out the rivet using the hole where the mandrel was which guides your drill bit like a pilot hole.

This shield technique protected the web whenever a punch or drill slipped giving me a chance to react and stop before nicking a part unintentionally. YMMV