Rivet Holes - How Big

[Borntoolate]

I tend to too closely match my rivet holes to my rivet size. Or, due to heat expansion when punching, I overestimate the hole size while hot. End result is I often have difficulty getting a hot rivet ro fit easily but not too easily into the cold, possibly shrunken hole. How do you personally fit your rivets to your hole so that it can readily be inserted hot and then properly headed without being too sloppy. Or perhaps I am trying too hard since a hot hammered rivet should probably fill an oversized hole within reason. Looking for guidance or a rule of thumb on this?

It's very annoying to have to go through getting a rivet installed with several heats, rivets getting stuck, bent, needing be ground to fit or otherwise causing various bits of Re-work. I have done several of these and I just keep tripping myself up.

[dablacksmith]

i generally rivet cold...... or at least start rivets cold then heat to finish....

[Borntoolate]

My thinking is I want to either let the rivet shrink for a tighter hold due to cooling or, in the case of tongs, I don't want a lot of excess heat in my tongs such that they can distort when you work them back and forth to get movement after riveting. So I didn't think riveting both hole and rivet hot would be good.

So, in either case it seems a hot rivet in a cold hole would be best... But that's just my thinking.

In the case of tongs perhaps cold rivet cold hole would be ok.

[Pat Roy]

I might be taking the easy route, but generally I put a cold rivet in a cold hot and heat the end with my O/A torch and hammer it. The rivet fits loose enough to get in the hole and the heat and hammer expand it some. IF the two pieces have to move relative to each other then you have to work them a bit.

[Bentiron1946]

Since most of my riveting was for decorative purposes only and not structural in nature it was done with cold rivets. I had an old book from the 1870's on boiler making and steam piping design but I gave it one of the young men that came to work for our company that was having a hard time with his engineers test with some thermodynamics problems. It had a table in it for the relationship between the drilled hole in steel boiler plate and the size of rivets. If you ever see some of the photos of them building the Empire State Building you will see that the rivets slide easily into the pre-drilled holes in the "I" beams and then the fellows went to town with the riveting hammer to set it. As the rivet cools it draws the steel together very tightly. For me however I would only back the the rivet on the anvil and if very large heat the head to facilitate the spreading of the head, rarely did I use a rivet for structural integrity. I found that a large nail worked very well for most of my rivets but I also made an awful lot of 1/4", 3/8" and 1/2" ones also. If I were doing it now my son would call my work somewhat Ork in nature.

[bigfootnampa]

The late Grant Sarver has said that he riveted his tongs cold... now that man set a few rivets... so I've been doing mine that way too, with good results. I do usually slightly taper them on one end to aid starting into the hole.

[Backwoods Blacksmith]

^{After having sloppy fits from punching holes I went to drilled holes the same size as the rivit and then heat the end to be formed then using a round peen and then a rivit set. If for tongs and the joint is tight, heat the rivit head to red and then work the tongs until cool. This works for me.}

[John B]

Rivet holes how big?
Depends on what you are rivetting, and what the rivet is made of, (some are more malleable than others), there is a place for both hot and cold rivetting,

Make or sort your rivet to be used, then punch or drill your hole to have a loose fit, this will vary on size of rivets (Small rivet proportionally less than large rivets, in each case they should fit easily with not too much slop)

If you punch your holes, try your rivet (cold) in them (when hot as you punch them), should be a loose fit, and easy to put in place.

Bought rivets are softer than forged rivets

Some forged rivets may not be round (especially if a swage is not used to finish them), which is why you should make them first and punch the hole to fit


A lot of problems associated with rivetting and getting poor results are in the technique,

Correct length for rivetting (One and a half times stock diameter)

Lots of light blows all around to mushroom the end(s), will help stop splitting the edges, this problem is minimised when using heated rivets, heavier blows to finish and use on snap.

Holes to be deburred if drilled, ensuring a good mating surface.

Use of rivet set and snap for domed heads and supporting during heading


Hot rivets will swell to fit the punched holes (as in tongs or dividers) and should be eased if a moving joint is required as you are working them.
It also used to be the practice to put a groove or slot in one half of the items to be joined on the outside, and under the rivetted part of the head (closing the joint) to secure the rivet allowing one arm to pivot independantly on the rivet (axle)

[beth]

john - could you explain that last bit again please about the groove ? im not clear...

[bigfootnampa]

Beth; John is simply referring to the practice of "keying" the rivet head... a notch or groove is created next to the rivet hole which the rivet head will smoosh into as the rivet is set and then that rivet will not revolve against that surface. So for tongs as example one leg of the tongs would be "keyed" and the other leg would be left free to rotate around the rivet. I usually do NOT do this personally. It is something that can be particularly useful though when you want to freeze the rivet in place altogether as in using a single rivet to attach a coat hook for example. A simple way is to use an old star drill to nick 4 notches around the rivet hole before setting the rivet... for something like a coat hook you'd want to "key" BOTH sides of the rivet hole to stop rotation completely.

[beth]

nice one big foot - i can visualise that lovely. .very useful :)

[MOblacksmith0530]

I do all my tongs as bigfoot has said I have a star drill that I gtound the end flat on.

[Rich Hale]

I hot punch holes, alittle bit over size but not alot,,I do not measure them I kjust use a punch the right size. (if that makes any sense) I cut the rivet to length and put it in the cold hole and then cold form both ends of the head just enough to not fall out in the forge. I then form ends with a ball pein. I do nto worry about deforeming reings from working them open and closed as I let them cool more before that. I work them at a dull red or black heat back and forth as they cool down. I like the way they fit and work. And again I have to repeat my mantra: the first 50 or 100 are the hardest. Any thing we do with metal wew simply cannot expect the first few to come out like they do later on when we have learned how.

[John B]

Beth; John is simply referring to the practice of "keying" the rivet head... a notch or groove is created next to the rivet hole which the rivet head will smoosh into as the rivet is set and then that rivet will not revolve against that surface. So for tongs as example one leg of the tongs would be "keyed" and the other leg would be left free to rotate around the rivet. I usually do NOT do this personally. It is something that can be particularly useful though when you want to freeze the rivet in place altogether as in using a single rivet to attach a coat hook for example. A simple way is to use an old star drill to nick 4 notches around the rivet hole before setting the rivet... for something like a coat hook you'd want to "key" BOTH sides of the rivet hole to stop rotation completely.

To stop rotation completely, use a square rivet in a square hole

[Francis Trez Cole]

when making tongs I put in the rivet cold and heat the tongs and rivet at the same time. not had any problems punching is great but if you can drill it is more accurate.

[Frank Turley]

On occasion, I've run across an old pair of tongs which freeze up occasionally in use. The jaws refuse to open or close. So I got upset and banged the tongs against the anvil, and they loosened! Then, usually withing five minutes, they would lock up again. Dang! I banged them against the anvil again, loosening them. Being curious, I took the tongs apart and found the rivet shank was bent and was rotating. When it rotated in use, it would hit a certain place to lock the tongs. I replaced the rivet with a new one which had the keyed head on one side, as described above. I used a cold chisel to indent the perifery of the hole. In this manner, I now had a straight shanked rivet which would not turn around.

We don't know the history of old tongs. I wondered how the rivet could have got bent in the first place. Perhaps it was run over by a jeep, for all I knew. Sometimes tongs get too near the fire and a red heat in the rivet area could cause problems.

Francis Whitaker told me that he always drilled the holes cold before using a hot rivet. Tongs should have enough slop that the bottom rein falls open easily to the fingertips.

[bigfootnampa]

John I agree about the square rivets... double "keying" is a quick way and less effort but not as good for sure. It does have the advantage of easier alignment as you have to have the square holes aligned for the square rivets whereas the "keyed" rivets can rotate until you set them down.

[John B]

If you put your square rivet in hot, you can tweak any slight misalignment before final clenching whilst the rivet is still hot

[Alan Evans]

Like John B says it depends on the circumstance.

The way I would go about solving the OP's dilemma of how big to make the hole for a hot rivet is back to first principles. Heat up the rivet you want to use and measure its diameter. If your work piece is to be cold when riveted do a similar experiment and measure the hot hole to see how much your hole will shrink and then drift the actual hole to size to compensate. I have found that most of the time you can predict the outcome very accurately provided you are consistent in your process. Wierd things happen to visual heat assessment when the sun comes around and shines in the door!

If I am using the rivet as a pivot for tongs etc then I want good bearing surfaces, so I tend to drill and used a slide fit rivet, put a healthy chamfer on the end, rivet cold with the flat hammer, heat the whole joint and quench while working the reins. The quench and wiggle seems to give just the right tolerance without slop.

I found that if you use the ball pein to mushroom the end ,thats all it does, it does not upset the shank to fit the hole. Much stronger to use the flat of the hammer, the chamfer does two things it transfers the energy/movement further down the shank and prevents the splitting mentioned by John B. The other bad thing I found using the ball pein is that invariably I would bruise the surrounding area, which looked amateurish even if I was getting paid for it!

The disadvantage of too big a hole for the rivet is probably the cause of Franks bent rivet tongs, some of my old tongs were so well worn that at some time in their life the rivet had been replaced in a hurry with the wrong size and similar bends occurred. I have to confess to driving over a set with my forklift the other day which made a useful set for working around corners!

I used to use rivet snaps/sets to try and make matching round heads, but after a few years I decided that for aesthetic and philosophic reasons that a hand hammered head was more appropriate for most of my work. I either leave it from the flat hammer or after setting with the flat hammer, use a flat head punch to give a 5 clout facetted head, or when in frilly mode decorate with ball and centre punch to make flowery things.

Edited April 28, 2012 by blackersmith

[beth]

blacker - the flowery things sound nice ;)