How Critical is Blind Rivet Length?

[minuteman62-64]

Getting ready to do some work that will involve blind rivet installation. I've purchased a bunch of rivets (from Amazon, btw) with a specified grip range from 0.126" - 0.250". Most of my fastening will fall within this range. However, there will be a few that will fasten parts with an aggregate thickness of about 0.094" - about 1/32" below the lower grip range of the rivets I've ordered.

I'd like to avoid building up a big inventory of blind rivets. Any problem with using the longer rivets to fasten the thinner materials? My understanding from my reading is that if the rivets are too long (within reason) I should be OK - just may have to do a second pull to break the mandrel.

Appreciate any sage advice.

 

[jigngrub]

Re: How Critical is Blind Rivet Length?

You should be ok, experiment on some scrap if you have any.

The problem with blind rivets that're too long is that the mandrel will break off above the top of the rivet leaving a sharp nub, but these can be filed down if that happens. You can also use a piece of scrap to thicken up your material with 3 pieces instead of 2 giving you better chance of the mandrel breaking off inside the rivet instead above the top of it.

 

[Watermann]

Re: How Critical is Blind Rivet Length?

If you have access to the backside of the project, just get a little box of aluminum blind rivet washers to back your rivet. It would look way more tidy that way.

 

[joed]

Re: How Critical is Blind Rivet Length?

I have in the past when I needed a few shorter rivets pulled the pin out and filed down the rivet to make it shorter. Push the pin back in and rivet away.

 

[jigngrub]

Re: How Critical is Blind Rivet Length?

I have in the past when I needed a few shorter rivets pulled the pin out and filed down the rivet to make it shorter. Push the pin back in and rivet away.

What???

 

[minuteman62-64]

Re: How Critical is Blind Rivet Length?

I have in the past when I needed a few shorter rivets pulled the pin out and filed down the rivet to make it shorter. Push the pin back in and rivet away.

I'll be using closed-end rivets - won't work.

Appears the way to go is (1) test on sample of thinner assembly; and, (2) if a problem, bring up thickness with washer or a backing plate (I'll have access to the back side).

 

[90stingray]

Re: How Critical is Blind Rivet Length?

If you have access to back side, then why not buck a solid rivet? Blind rivets are just that... when you don't have access to both sides.

 

[minuteman62-64]

Re: How Critical is Blind Rivet Length?

If you have access to back side, then why not buck a solid rivet? Blind rivets are just that... when you don't have access to both sides.

I've done solid rivets before - in iron and copper, but not aluminum. It just seems so much easier to pop a blind rivet and will be just as effective for what I'm doing. Besides, I'll get to use my new air operated blind rivet tool

 

[Watermann]

Re: How Critical is Blind Rivet Length?

I've done solid rivets before - in iron and copper, but not aluminum. It just seems so much easier to pop a blind rivet and will be just as effective for what I'm doing. Besides, I'll get to use my new air operated blind rivet tool

Now your talking! I got my new HF 1/4" air riveter and it works great, it's so easy now with just the pull of the trigger.

 

[ssobol]

Re: How Critical is Blind Rivet Length?

Getting ready to do some work that will involve blind rivet installation. I've purchased a bunch of rivets (from Amazon, btw) with a specified grip range from 0.126" - 0.250". Most of my fastening will fall within this range. However, there will be a few that will fasten parts with an aggregate thickness of about 0.094" - about 1/32" below the lower grip range of the rivets I've ordered.

I'd like to avoid building up a big inventory of blind rivets. Any problem with using the longer rivets to fasten the thinner materials? My understanding from my reading is that if the rivets are too long (within reason) I should be OK - just may have to do a second pull to break the mandrel.

Appreciate any sage advice.

Blind rivets have a certain working depth (length). The rivet is designed to shear in that range when the force on the mandrel builds up. A rivet works by both expanding in width and shortening in length to mechanically bond to work pieces together. If the rivet is too long, the mandrel will shear before the rivet has fully collapsed bringing the work pieces together. Do to the expansion of the rivet body this may hold the pieces together well enough if the loads are not high. In this situation it is possible for the pieces to become loosely held together by the rivet, sort of like if a bolt is not tight.

If the rivet is too short, the blind head may not form fully before the mandrel breaks because the head is trying to form inside the material hole. Depending on the material, this formation of the head inside the material will often damage or enlarge the rivet hole and may simply pull the mandrel straight through the rivet body. This can also result in a bond that can separate under stress.

Depending on the expected stress loads and the materials involved you may get away with using the wrong size rivets.

Pardon the lecture.

 

[Scott Danforth]

Re: How Critical is Blind Rivet Length?

between the different grip lengths and different materials, I must have at least 30 different containers of rivets. while you can back up the rivet with a washer, I like to use the correct grip length when working blind

 

[minuteman62-64]

Re: How Critical is Blind Rivet Length?

Blind rivets have a certain working depth (length). The rivet is designed to shear in that range when the force on the mandrel builds up. A rivet works by both expanding in width and shortening in length to mechanically bond to work pieces together. If the rivet is too long, the mandrel will shear before the rivet has fully collapsed bringing the work pieces together. Do to the expansion of the rivet body this may hold the pieces together well enough if the loads are not high. In this situation it is possible for the pieces to become loosely held together by the rivet, sort of like if a bolt is not tight.

If the rivet is too short, the blind head may not form fully before the mandrel breaks because the head is trying to form inside the material hole. Depending on the material, this formation of the head inside the material will often damage or enlarge the rivet hole and may simply pull the mandrel straight through the rivet body. This can also result in a bond that can separate under stress.

Depending on the expected stress loads and the materials involved you may get away with using the wrong size rivets.

Pardon the lecture.

It's not a lecture, it's education Anyways, back to my original question - which re-phrased would be: "what's the tolerance in the grip range of blind rivets" or something like that. In my case, my rivets have a specified minimum grip range of 0.126". I want to rivet an assembly with a thickness of 0.125". Is that 0.001" difference going to result in the kind of problems you describe?

 

[ssobol]

Re: How Critical is Blind Rivet Length?

It's not a lecture, it's education Anyways, back to my original question - which re-phrased would be: "what's the tolerance in the grip range of blind rivets" or something like that. In my case, my rivets have a specified minimum grip range of 0.126". I want to rivet an assembly with a thickness of 0.125". Is that 0.001" difference going to result in the kind of problems you describe?

Probably not, but it will kind of depend on what you are riveting together and what kind of loads are going to be on the riveted joint. In high load or high vibration situations you may have the joint start to work loose.

 

[minuteman62-64]

Re: How Critical is Blind Rivet Length?

OK, I'm convinced. I just went on-line and ordered a batch of the next size down. So, I'll build up an inventory - maybe I can open a store