Hi
Maybe you guys can help me with this! By the book the shop head is supposed to be 1.5 times wider than the rivet when driven correctly. Well if you have over driven it, how much is to much. Is there a percentage of leeway? I just can not find any info that tells me if you have driven the shop head to much and when it needs to be drilled out.
Thanks in advanced!
Riveting
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Spike
- Chief Rivet Banger
- Posts: 4013
- Joined: Thu Oct 14, 2004 8:40 pm
- Location: Baltimore, MD
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Airman good question. There is also a minimum thickness for the shop head of a driven rivet. Your rivet is still fine as long as your shop head has the minimum thickness. Whats considered unacceptable is when the shop head is either too thin or doesnt have enough surface area. Think of both recommended dimensions as minimum dimensions.
Make sense?
-- John
Make sense?
-- John
http://www.rivetbangers.com - Now integrating web and mail!
Current Build: 2 years into a beautiful little girl
Current Build: 2 years into a beautiful little girl
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4kilo
- RB's First
- Posts: 227
- Joined: Mon Nov 08, 2004 10:32 am
- Location: GPM (Grand Prairie, Texas)
- Contact:
What Spike said: you need to have both a minimum diameter and a minimum thickness for your shop head. A set of gages like those sold by Avery is the best way to make sure your rivets meet both requirements.
Pat
Pat
RV-8
N804PT - IO-360, Hartzell blended airfoil, GRT dual Horizon I & EIS, TruTrak ADI Pilot II
Flying - 950 hours!
N804PT - IO-360, Hartzell blended airfoil, GRT dual Horizon I & EIS, TruTrak ADI Pilot II
Flying - 950 hours!
I agree completely with Mikey. That is the same philosophy that I have taken to the construction of my plane.arffguy wrote:If the rivets are on a line of about 20 or 30 in a row then leave it as is and move on. If it is a bracket that is held on by three rivets then I get a little more picky. Just my two cents. Oh yeah. Get the gauges from Avery too.
Mikey
RV6 wings
Ron
RV-9A
N379RV - Registered!
90965
RV-9A
N379RV - Registered!
90965
Hi
Thanks again for the responses; I agree when you are looking at only 2 or 3 rivets you need to take a closer look at the rivets. I have been using a digital caliper to check my rivets for now. But again, if you are banging rivets, I can not see how you can get them perfect every time. All the books and literature shows a picture of what an over hit rivet looks like, but there is no specific #'s or percentage that you can go over. Say you have a rivet that is 0.094 in diameter, and you know your length is good. That means the diameter of a good shop head should be 0.141. Now lets say your at .151 or .161 is that to much. Is there any lea way?
Maybe I am looking too much into it!
Thanks Guys
Airman
Thanks again for the responses; I agree when you are looking at only 2 or 3 rivets you need to take a closer look at the rivets. I have been using a digital caliper to check my rivets for now. But again, if you are banging rivets, I can not see how you can get them perfect every time. All the books and literature shows a picture of what an over hit rivet looks like, but there is no specific #'s or percentage that you can go over. Say you have a rivet that is 0.094 in diameter, and you know your length is good. That means the diameter of a good shop head should be 0.141. Now lets say your at .151 or .161 is that to much. Is there any lea way?
Maybe I am looking too much into it!
Thanks Guys
Airman
RV9A
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Spike
- Chief Rivet Banger
- Posts: 4013
- Joined: Thu Oct 14, 2004 8:40 pm
- Location: Baltimore, MD
- Contact:
You are looking at it too much. Remember, were talking minimum width (surface area) and minimum thickness. If your rivet is 5 feet wide and has the minimum thickness then that rivet should be strong enough 
Get the picture?
Get the picture?http://www.rivetbangers.com - Now integrating web and mail!
Current Build: 2 years into a beautiful little girl
Current Build: 2 years into a beautiful little girl
Yes, get the set of rivet gauges from Avery. There is a rivet gauge that checks the length of rivet protruding from the work piece. The part the forms the shop head. If this is the correct length, it seems that the rivet can only be sqeezed to the correct thickness and shophead height because it work-hardens at that point and becomes difficult to squeeze further. That gauge is basically a small rectangle of thick aluminum with notches on each corner. The notches are numbered with the rivet sizes. I.E. 3, 4, 5, etc. You stick the rivet through the hole, and holding it firmly, tight against the job, you then measure using the notch. You run the correct notch up to the protruding rivet shank and if it will not pass over the rivet, the size is OK. If it protrudes excessively, you must trim the rivet down to slightly over the notch height. The other set of gauges are just little tabs with drilled holes in one end. These tabs are also numbered with a rivet diameter number on each one. You attempt to put the drilled hole in the tab over the shop head. If it will slip over the squeezed shop head, then the rivet needs to be squeezed a bit more. On the other end of the tab is another notch. You then attempt to pass the notch in the tab over the shop head. If it slides over the shophead, you have overdriven the rivet. If it catches, then it is OK. So there are the two criteria for the shophead, the diameter is measured by the drilled hole, and the height is measured by the notch in the tab.
When using your squeezer, you can adjust the squeeze compression depth by turning the shank. Close the squeezer handles together and you will see the adjustment shank with some flats on it. Use a small open end wrench to turn the shank if necessary. Once you get the height set properly by checking the shophead with the gauge, you can carry on squeezing without checking for many,many rivets because the squeezer will give you the same depth on each rivet when the material thickness is constant.
Hope that is some help.
Cheers, Pete
When using your squeezer, you can adjust the squeeze compression depth by turning the shank. Close the squeezer handles together and you will see the adjustment shank with some flats on it. Use a small open end wrench to turn the shank if necessary. Once you get the height set properly by checking the shophead with the gauge, you can carry on squeezing without checking for many,many rivets because the squeezer will give you the same depth on each rivet when the material thickness is constant.
Hope that is some help.
Cheers, Pete
Peter Marshall
Newbie RV-8 builder.
You wanna draw, ....against the fastest rivet gun in the West??? LOL
Newbie RV-8 builder.
You wanna draw, ....against the fastest rivet gun in the West??? LOL
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Guest
Rivet gauges
OK, everybody says get the gages from Avery--everybody but me.
There is a newer gage you should check out first:
http://clearairtools.com/Merchant2/merc ... y_Code=NEW
This is a pretty slick little gage & it does a lot more than the Avery gage (which I have), for only $4 or $5 more.
Richard Scott
RV9A Wings
There is a newer gage you should check out first:
http://clearairtools.com/Merchant2/merc ... y_Code=NEW
This is a pretty slick little gage & it does a lot more than the Avery gage (which I have), for only $4 or $5 more.
Richard Scott
RV9A Wings
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Spike
- Chief Rivet Banger
- Posts: 4013
- Joined: Thu Oct 14, 2004 8:40 pm
- Location: Baltimore, MD
- Contact:
Pretty slick Richard!!
http://www.rivetbangers.com - Now integrating web and mail!
Current Build: 2 years into a beautiful little girl
Current Build: 2 years into a beautiful little girl
Just letting you guys know you can also get the new gages at Aircraft Spruce, here http://www.aircraftspruce.com/catalog/t ... reader.php
RV9A
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David
Rivets on Production Aircraft
I had this same concern on my rivest. So I looked at the Cessna Aerobat that I am renting now, and I saw many rivets that were overdriven. And the tail has not come off yet. So it should be OK.
Riveting
When considering whether to remove an overdriven or too short rivet, you also need to consider what damage you might cause to the rivet hole. In many case you may be better off leaving a rivet that does not meet the specs rather than drill it out and risk messing up the hole. A new rivet in an oversized hole may be worse than the original rivet. Or you may have to drill out to the next size and use an oops rivet.
As someone mentioned, take a look at a production plane and you will see a lot of rivets that you would probably redo if it was yours. If they didn't see a problem with them, why should you?
As always, use your best judgement, and do what makes you feel good.
As someone mentioned, take a look at a production plane and you will see a lot of rivets that you would probably redo if it was yours. If they didn't see a problem with them, why should you?
As always, use your best judgement, and do what makes you feel good.
Paul Trotter
RV-8 82080 Finish Kit
N801PT
RV-8 82080 Finish Kit
N801PT
Rivets, Riveting, & Tolerances
A builder finished his left wing and began on the right wing. He used the same techniques on the right wing that he used on the left wing. The dimple dies were the same, the drill bits were of the same size and manufacturer, and the rivet types and sizes were the same. However, the finished rivets on the right wing had a distinctly different appearance to his discriminating eye (J) than the rivets on the left wing. After all of his painstaking attention to detail, that’s enough to cause this builder more than a little turmoil.
What has this builder done wrong? Probably nothing at all.
Welcome to the World of Tolerances.
Let’s take a look, step by step, at the building process and closely examine some of the details.
1. Van’s prepunches the kits to fractional sizes. Therefore, the hole for a 3/32 rivet is prepunched to 3/32 fractional (.0938) and the hole for a 1/8” rivet is prepunched to 1/8” fractional (.1250). A #40 drill bit is sized to .0980 and a #30 drill bit is sized to .1285. Assuming that the CNC punch is new and sharp, the 3/32 hole is .0042 undersized and the 1/8” hole is .0035 undersized when compared to ideal finished dimensions, i.e., #40 and #30.
2. DRILL BITS: True American Manufactured NAS 907-J Cobalt Drill Bits are heavy duty, 135 Degree Split Point, M-42 Cobalt Jobbers Length Drill bits manufactured to a Rockwell C of 66-67.5 and held to a diameter tolerance of +/- .003. Other drill bits are manufactured to different tolerances.
3. REAMERS: Aerospace quality reamers are typically held to tolerances of + .0002/-0.
4. RIVETS: Below is a MilSpec label off of a package of MS20426 B 5-7 rivets. These are the softer “B” rivets (5056 Aluminum Alloy) with a Shear Rating of 24,000 lbs. per square inch compared to the Shear Rating of 30,000 lbs. per square inch for the “AD” rivets used in RV construction. Nevertheless, the specifications are typical.
Of interest to us are the following tolerances:
A. Fastener Length: .022”
B. Shank Diameter: .004”
C. Head Major Diameter: .008”
D. Grip Length: .020”
E. Countersink Angle: 99.5 Degrees Minimum & 100.5 Degrees Maximum
ASSUMPTIONS: We’re assuming that the thickness of the same parts on both wings is the same. We’re also assuming that the builder is using the same stainless steel dimple dies and that the pilots for those dimple dies are #40 and #30 respectively.
THE WORK: When a rivet is set, the material first flows to fill the hole and then the shop head (bucktail) is formed. Given all these tolerances, what then is under the builder’s control?
What is under the builder’s control is to final size the hole as precisely as possible and to correctly prepare it for the dimpling/riveting process. Several things can affect this:
A builder is either going to drill a prepunched hole to final size or they are going to ream the hole to final size. Both operations are going to be done with hand tools. Therefore, the likelihood of drilling or reaming a hole exactly perpendicular to the work surface is minimal. However, a drill bit is designed to cut through solids. The first thing it wants to do is grab and twist as it finds material to cut. In our scenario, at best the builder would be using the outer .002 of each end of the drill bit to final size the hole. A reamer is designed to final size existing holes and is the proper tool to use. A reamer is also held to much tighter tolerances than a drill bit.
If a hole is not deburred there is a chance that the parts will not fit flush against each other. A portion of the rivet will flow to fill that tiny gap and it can later become a “working” rivet. If a builder deburrs a hole too much it leaves knife-edges on both sides of the material. With the quality of current kits a builder should ensure they are “deburring” as opposed to “removing material”.
If a hole is not final sized to the diameter of the pilot on the dimple dies, the pilot is then forced to expand the material to size. This can cause microscopic cracking in the material.
If working in close tolerance or blind areas, a builder can use drill bushings of various types to ensure that the hole is drilled perpendicular to the work pieces.
SUMMARY:
One of the most attractive features about building your own aircraft is that you can build it “your” way, but we’ve never met a builder yet who didn’t want to do it to the best of their ability. However, there are a great many things a builder does not have control over, but may or may not understand. In looking at all the possible combinations of tolerances above, each meeting “the specifications”, one begins to understand this. Having factual knowledge of a process can only enable a builder to make better-informed decisions regarding their work.
The MilSpec tolerances for preparing a hole and installing solid rivets can be found on at least two(2) builder’s web sites:
Gil Alexander
http://www.flash.net/~gila/
Dan Checkoway
http://www.rvproject.com/
It’s very revealing just how much latitude a builder has.
Blue Skies!
What has this builder done wrong? Probably nothing at all.
Welcome to the World of Tolerances.
Let’s take a look, step by step, at the building process and closely examine some of the details.
1. Van’s prepunches the kits to fractional sizes. Therefore, the hole for a 3/32 rivet is prepunched to 3/32 fractional (.0938) and the hole for a 1/8” rivet is prepunched to 1/8” fractional (.1250). A #40 drill bit is sized to .0980 and a #30 drill bit is sized to .1285. Assuming that the CNC punch is new and sharp, the 3/32 hole is .0042 undersized and the 1/8” hole is .0035 undersized when compared to ideal finished dimensions, i.e., #40 and #30.
2. DRILL BITS: True American Manufactured NAS 907-J Cobalt Drill Bits are heavy duty, 135 Degree Split Point, M-42 Cobalt Jobbers Length Drill bits manufactured to a Rockwell C of 66-67.5 and held to a diameter tolerance of +/- .003. Other drill bits are manufactured to different tolerances.
3. REAMERS: Aerospace quality reamers are typically held to tolerances of + .0002/-0.
4. RIVETS: Below is a MilSpec label off of a package of MS20426 B 5-7 rivets. These are the softer “B” rivets (5056 Aluminum Alloy) with a Shear Rating of 24,000 lbs. per square inch compared to the Shear Rating of 30,000 lbs. per square inch for the “AD” rivets used in RV construction. Nevertheless, the specifications are typical.
Of interest to us are the following tolerances:
A. Fastener Length: .022”
B. Shank Diameter: .004”
C. Head Major Diameter: .008”
D. Grip Length: .020”
E. Countersink Angle: 99.5 Degrees Minimum & 100.5 Degrees Maximum
ASSUMPTIONS: We’re assuming that the thickness of the same parts on both wings is the same. We’re also assuming that the builder is using the same stainless steel dimple dies and that the pilots for those dimple dies are #40 and #30 respectively.
THE WORK: When a rivet is set, the material first flows to fill the hole and then the shop head (bucktail) is formed. Given all these tolerances, what then is under the builder’s control?
What is under the builder’s control is to final size the hole as precisely as possible and to correctly prepare it for the dimpling/riveting process. Several things can affect this:
A builder is either going to drill a prepunched hole to final size or they are going to ream the hole to final size. Both operations are going to be done with hand tools. Therefore, the likelihood of drilling or reaming a hole exactly perpendicular to the work surface is minimal. However, a drill bit is designed to cut through solids. The first thing it wants to do is grab and twist as it finds material to cut. In our scenario, at best the builder would be using the outer .002 of each end of the drill bit to final size the hole. A reamer is designed to final size existing holes and is the proper tool to use. A reamer is also held to much tighter tolerances than a drill bit.
If a hole is not deburred there is a chance that the parts will not fit flush against each other. A portion of the rivet will flow to fill that tiny gap and it can later become a “working” rivet. If a builder deburrs a hole too much it leaves knife-edges on both sides of the material. With the quality of current kits a builder should ensure they are “deburring” as opposed to “removing material”.
If a hole is not final sized to the diameter of the pilot on the dimple dies, the pilot is then forced to expand the material to size. This can cause microscopic cracking in the material.
If working in close tolerance or blind areas, a builder can use drill bushings of various types to ensure that the hole is drilled perpendicular to the work pieces.
SUMMARY:
One of the most attractive features about building your own aircraft is that you can build it “your” way, but we’ve never met a builder yet who didn’t want to do it to the best of their ability. However, there are a great many things a builder does not have control over, but may or may not understand. In looking at all the possible combinations of tolerances above, each meeting “the specifications”, one begins to understand this. Having factual knowledge of a process can only enable a builder to make better-informed decisions regarding their work.
The MilSpec tolerances for preparing a hole and installing solid rivets can be found on at least two(2) builder’s web sites:
Gil Alexander
http://www.flash.net/~gila/
Dan Checkoway
http://www.rvproject.com/
It’s very revealing just how much latitude a builder has.
Blue Skies!
-
Spike
- Chief Rivet Banger
- Posts: 4013
- Joined: Thu Oct 14, 2004 8:40 pm
- Location: Baltimore, MD
- Contact:
Great info 
http://www.rivetbangers.com - Now integrating web and mail!
Current Build: 2 years into a beautiful little girl
Current Build: 2 years into a beautiful little girl
Intersting info .. I was just about to post a question about reaming vs. drilling. Tom mentioned last weekend that this was the preferred method for sizing the prepunched holes; anyone have any experience with this?
Also, is a dimple die a dimple die? I.e. are there some that are manufactured to closer tolerances than others? I notice when I hold mine together (mated) there is a VERY small amount of "play" between the two halves. I'm wondering if these are like a lot of things, made by one company then sold by many others under their brand (like Mani and I went to Harbor freight yesterday - got a drill press for 39$, on sale; we then went to Sears to look around and Craftsman was selling the exact same press with different stickers and different color knobs for over 100$).
Thomas
Also, is a dimple die a dimple die? I.e. are there some that are manufactured to closer tolerances than others? I notice when I hold mine together (mated) there is a VERY small amount of "play" between the two halves. I'm wondering if these are like a lot of things, made by one company then sold by many others under their brand (like Mani and I went to Harbor freight yesterday - got a drill press for 39$, on sale; we then went to Sears to look around and Craftsman was selling the exact same press with different stickers and different color knobs for over 100$).
Thomas