What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Question about countersinking CS4-4 rivets on page 09-02

L

Lee Jordan

Member
Something appears odd with the countersinking I'm doing for the CS4-4 rivets. I've done the countersinking for the 426 rivets and they all went well, but the CS4 rivet is a pop-rivet with the counter sunk head and I'm wondering if they "fit" differently then the 426?

As I'm machining the hole everything starts out great, but as I approach the correct depth for the pop rivet to sit flush I get a loud screeching from the MCS tool and then I see that the hole in the flange is starting to become enlarged. And I still need to go deeper because the CS4 Rivet is not sitting flush.

About the time I get the rivet to sit flush, the hole "appears" too big because I can move the rivet around.

I'm using the #30 CS bit for these #30 holes. Is that the correct tool?

Thanks,
Lee
 
The CS4-4 rivet has a 120 degree head. The AD426 rivet has a 100 degree head. You should have a #30x120 deg countersink bit. Bet that is what you are experiencing.

When I asked on the forum if a 120 dimple die was required for the RV12, the consensus was no. The 100 degree dimple die was OK when you dimple for the CS4-4 rivet.

When the microstop screeches, I have found that the bit is wandering in an enlarged hole. Try pressing down on the collar with your left hand to keep the microstop centered in the hole while applying vertical pressure on the drill.

Hope that helps.
 
Last edited:
Try adding a little WD-40 or cutting oil to your work piece, and slowing down the speed of the drill. Go to a slower speed on the drill.

Also, when it starts to squeel try slightly tipping the micro stop cage just a little, you might not be square to the hole. It takes practice and adjustment.
 
I totally missed the fact that the CS4 has a 120 degree cut. I'm thinking now that because I was using the 100 degree bit that I was drilling too deep, as the bit goes deeper (past it's designed cutting depth) it starts to enlarge the original hole which lets the bit wander in the hole and starts the screeching.

Now it looks like I need to order a new HS-1202 fwd spar. I have eight holes in the flange that appear too big on the backside. The rivet looks and sits great from the countersunk side, but the size of the holes has me worried. Better safe then sorry.

Thanks for the advice Marty and Larry,

Lee
 
Call Van's Technical Support Monday (maybe they are closed) or Tuesday. Discuss your problem and get their advice. Then make your decision on a new part. You can always e-mail photo of the part with the rivet next to the hole to give them an idea of the enlarged hole. Good luck.

This won't be the first part you may have to re-order.
 
CS info is hard to find

There had been a post on this forum about those CS4-4 rivets but I remember no reference or link to an official source. A web search turns up several posts in the VAF forums regarding this rivet http://www.vansairforce.com/community/showthread.php?t=38558, but I have not found a standard describing this type of rivet in detail on the web. Does anyone know where to look?
The 6th Editon of Standard Aircraft Handbook included with the kit does not have the information, but it is 10 years old and probably due for a new edition.

Tony
 
Hi Tony,

I asked this question on the forums and I think Mel responded with the following,
here is the information I wrote down. I was looking for the same information on the rivet angle. You can find the specs in the Aircraft Spruce catalog.

Cherry commercial rivets

BSP-43 will sub for Van's LP4-3
BSP-44 will sub for Van's LP4-4
BSC-44 will sub for Van's CS4-4
 
Lee Jordan said:
I'm thinking now that because I was using the 100 degree bit that I was drilling too deep, as the bit goes deeper (past it's designed cutting depth) it starts to enlarge the original hole which lets the bit wander in the hole and starts the screeching.
Click to expand...

Lee...

? #23) How do I machine countersink the sub spar assembly?
Answer: Make sure to use the 1/8" (#30) 120 degree countersink. Practice on scrap aluminum first. Hold the stop with one hand against the aluminum to keep the stop from spinning, while drilling with the other hand. One author recommends using a lower speed and higher pressure than drilling, not to exceed 2500 rpm. Whatever combination of speed and pressure used, the goal is to avoid chattering which will result in an uneven surface and irregular depth. If the pilot reaches the back wall of the aluminum, the bit can chatter. If the pilot reaches the back wall of the spar, a shim can be used behind the spar to center the pilot. A drop of machine oil may extend the life of the countersink bit. It is important to maintain the angle once you start drilling and avoid "wobbling." If the drill is not perpendicular to the hole, it will appear eccentric. Just clear the loose aluminum, reset the angle and drill again. Once the depth was set on the practice aluminum, I took a 2X4 and essentially match drilled three holes into the 2X4 near the center. I then enlarged the center hole in the 2X4. I clamped the 2X4 to the EAA table and cleco-ed the sub spar assembly to the 2X4. I then countersunk the hole over the enlarged hole in the 2X4. I did need to drill a few "sets" of holes to accomodate the variable spacing in the flanges and the ends of the flanges. Be aware that both the lock nut AND/OR the plastic stop can become loose and contribute to irregular depths.

Hope that helps,
Jeff
 
120 degree cutter

I bought one of the 120 degree cutters and I suggest you practice on a pc of scrap first. It removes a lot of material fast. I use my electric drill for counter sinking as I can control the speed, and drill very slowly. After a few seconds, I stop and stick a rivet in the hole to check it!!! I think it's the best way. Also, the head of the rivet can sit on the surface as long as the tapered part under the head is in the counter sink. The head is flush and I have had no interferance so far.

Bill
 
Same problem

I used the correct countersink, but am still getting the holes starting to enlarge before the rivet head is quite flush. How critical is the hole size, or put another way, how critical is it that the full depth of the head is completely flush with the surface?

Cheers...Keith
 
I'm doing all the countersinking with a doubler. For the stabilator spar flanges I initially match drill an angle of aluminium to the spar, thereafter I countersink. Due too the doubler the bit will not wander. This also worked for the CS4-4 with a 120 bit.

FP23032009A0001S.jpg


The doubler is the VS spar that I ruined due too an aggressive bench grinder.
Positive effect is that I have some scrap aluminum to practice.
 
Last edited:
Hi Guys, I too countersunk the stabilator spars and web with a 100 degree countersink, instead of the correct 120 degree countersink to suit CS4-4. As a result because the material is only about .045" thick the holes are almost knife edge at the smallest diameter. I guess I too will be emailing Vans to find a solution/buy new parts. Has anyone asked Vans the same question? What was the response? Anyway.... back to the shop. Thanks in advance.... Marcus.
 
Time to refresh this thread

Faced with the infamous CS4-4 countersinking issue on page 09-02 of the Stabilator instructions, it took me a while to clarify and dig out this thread which contains a mine of information. Some good follow-up too on some builders Blogs (Schmetterling and Marty's RV-12). Too bad all this has not been integrated in the instruction book, it would save time and aggravation. As we have more and more newbies builders (like me) as opposed to the expert "bleeding edge" builders of the first two years, there is a need to make all information accumulated by these early builders more easily accessible. May be some sticky posts?
 
You must log in or register to reply here.
Back
Top