Model Engine Maker

Help! => Specific Engine Help => Topic started by: Davis2x1 on March 30, 2015, 06:35:05 PM

Post by: Davis2x1 on March 30, 2015, 06:35:05 PM
New Member saying hello to all,

I need some advice on cutting an internal  7/64 radius on the end of my rivet setting tool. Will a tool bit ground to that radius cut into the end of the 3/8 dia. bar?? Working on my first mode,l a PM Research vertical boiler. thanks for any help.

Post by: Jasonb on March 30, 2015, 06:42:57 PM
The common way to do it is to use the end of a drill to make a shallow indent in the end of yout tool then heat it upto red heat, place a 7/32" ball bearing in teh recess and give it a whack with a hammer.

You could turn a half circle on the end of some 7/32" drill rod (silver steel) then mill to half thickness to make a ball nosed "D" bit then harden that and use to cut the shape into the tool.

I think Stan has a thread on his PM boiler that showes how he made the tools
Post by: Arbalest on March 30, 2015, 08:31:55 PM
I used a burr to make an eye punch, not sure what sizes are available though.
Post by: Davis2x1 on March 30, 2015, 10:22:49 PM

I read that thread start to finish. Talks a lot about the riveting. He shows his tools but does not describe the method of fabrication.

I have a lot of extra bits.  I'll try shaping one to make the cut. I have a Sherlne radius tool but have not figured out how to use it, and if it will go down to the required size.

Post by: mklotz on March 30, 2015, 10:42:36 PM
A 7/32" ball end mill would be perfect.  I'll bet the more commonly available (and future usable) 1/4" ball mill would work just fine.
Post by: Jasonb on March 31, 2015, 07:43:56 AM
Strictly speaking a 7/64" radius is not quite right as the head may measure 7/32" across but they are not actually a half circle. Probably needs to be a 1/4" ball or milling cutter and only taken 3/32" deep

MAybe Marv would be kind enough to work out the dia given the following data (1/8" rivit size)
Post by: Dan Rowe on March 31, 2015, 03:14:59 PM
The BS 641 rules for rivets are the diameter of the head is 1.75D and the height of the head is .75D where D = the shank diameter.

So if you draw a rivet head for a unit 1 diameter shank the diameter of the circle forming the head works out to be 1.77D.

If the rivet shank is 1/8" then 1.77 times that is 0.22" . That makes a 7/32 ball mill the closest fractional choice.

I usually simplify the rule to 2D for the ball mill and make the bucker or dolly and the punch so the factory head fits with just a tiny amount sticking out so the bucker does not leave marks on the finish work.

Also note that BS 641 states the set allowance is 1.429D. I use 1.5D for the set allowance and drill a hole the size of the shank in a piece of stock 1.5 times the shank diameter or 3/16" thick for a 1/8" rivet.


Post by: sshire on March 31, 2015, 05:56:01 PM
I chucked the W-1 drill rod in a 5C collet. " ball end mill in the tailstock chuck.
Worked perfectly for the PMR boiler.
Post by: mklotz on March 31, 2015, 06:16:07 PM
I chucked the W-1 drill rod in a 5C collet. " ball end mill in the tailstock chuck.
Worked perfectly for the PMR boiler.

It's hard to remember (don't you hate it when that happens?) but that sounds like exactly what I did when I built mine.
Post by: Dan Rowe on March 31, 2015, 07:38:31 PM
Of all the helpful folks answering this question how many have had a rivet not quite form correctly or lean over to one side a bit?

I use two tools to make a rivet head. The one that looks like the head is the finish tool and it matches the bucker needed to support the factory head.

The first set tool is made with an end mill the same diameter as the rivet shank or D. I use a center cutting end mill and go in 1.2D deep. Then I use a countersink tool or spot drill to make a small internal chamfer. Now when this tool is used first it will bottom out in the tool and form a small cone at the base of the rivet to match the chamfer on the end of the tool. (this tool will usually stick on but gently rocking it will release it)

The rivet is formed at the base FIRST and is much less likely to lean over with the finish tool.

The length of the rivet or the set allowance I use I use is 1.5D, so as I mentioned I use a piece of stock drilled to make a cutting guide for the rivet to get the correct length to form the head.

To make the finish tool and bucker I use a ball mill 2D in diameter or for a 1/8" rivet use a 1/4" ball mill.

My system is from "Model Boilers and Boiler Making" by K.N. Harris only I simplified the it to two tools not 3 liked he used.

Post by: Steamer5 on March 31, 2015, 09:54:36 PM
Hi guys,
 I knew putting off doing anything more than thinking about a riveting tool would pay off! I saw a reference on the model engineer forum from a guy doing major work on a motor bike, he had built a hydraulic rivet closer for doing 3/16 rivet. Now WHEN I get round to doing the frames on my loco that's the size I'm using. So after hunting around I found a hydraulic cable crimper to do the job. Sketched up the parts that need to be made & had number 1 son do some stress analysis for me, the design failed miserably!
So the questions are......
          has anybody got some design ideas on a closer "head" "C" shaped,
          has anybody used the rivet snaps that are available for the commercial hand & hydraulic closer,
          and last but no means least hows the best / easiest way to shorten rivets up to say 1/4"....when these more the 1 or 10. I have an idea on this but would be greatful of any other thoughts.

Oh the 3/16" rivers are steel, the 3/32" are stainless, just to make thinks a bit harder!

Cheers Kerrin

Post by: Jasonb on April 01, 2015, 07:56:20 AM
Rob Wilson over on Madmodder has a nice squeezer thats a reinforced "C" shape with hydralic ram on one end and holder for the dolly on the other. A lot of the traction engine builders just use a hydralic press with a simple holder to keep the set in place above the rivit. Another option is to modify the end of an SDS+ chisel and use it in a drill, like this

If you have a bandsaw then a simple clamp like a set of stocks can be made to hold several rivits at a time and saw off the excess

I've not found the need to use the cone shaped set on rivits 1/8" or less I just cut off teh excess and go straight at then with the snap, soon get the hang of it and with over a 1000 rivits in my traction engine I had enough practice!
Post by: Steamer5 on April 01, 2015, 10:01:19 AM
Hi Jason,
 Thanks for the info, I'll go have a look at the links. Yes Ive got a bandsaw, best tool in the shop......well most used. Do you do anything to clean up the cut ends, or do you find that on removing from the plate that the ends are ok enough to push through the metal to be riveted & closed?

On the hydraulic press, I can see how the traction boys can do it, figured that loco frames may be a bit more of issue, have to think about that some more?

Cutting rivets by must be able to crush walnuts with 2 figures  :lolb: do you use side cutters or end cutting ones?

Cheers Kerrin
Post by: Jasonb on April 01, 2015, 10:44:01 AM
Just quick rub with a file if there are any burrs to remove, does not need to be a perfect end.

I would have thought your frames would be easier than trying to get a press into an assembled traction engine wheel

I just nip then off with a small pair of bolt croppers, I have a pair that are about 8-9" long and easily go through 1/8" steel/iron rivits. 1/16" can be done with side/end cutters.

Found this pic of a simple jig to cut them in a bandsaw


This is what you really need

Post by: Davis2x1 on April 01, 2015, 03:46:41 PM

Thanks for all the tips, comments, links and old photos. This forum is great!!

I finally figured out how to use my Sherline radius cutter. The small radius required a tiny tip on the tool bit but it works. I used the formula for calculation a cord of a partial circle to determine the diameter of the rim of the cut.

The formula is 2 x square root of h x (2r-h).  The radius called for is 7/64 with a depth of 3/32. Using the formula I calculated the "surface" diameter to be 0.2165. I now cut down until I reach the required diameter. All is well. There two other tools have straight bores to start the rivet set and prevent the aforementioned rivet tipping.

As a young boy in Chicago I would love to watch the steel erectors set hot rivets. Out of the heater, thrown to the catcher, set in place and bucked home with a pneumatic hammer. The hot rivet would be forged into any gap in the hole and when it cooled it would shrink to provide a very tight, sturdy connection.

Best Regards to those "across the pond" and "down under".

Dave, Retired Mechanical Engineer
Post by: Steamer5 on April 02, 2015, 11:10:27 AM
Hi Jason,
 Thanks for the info re shortening rivets, the bandsaw idea looks good, guess those are a bit bigger than 3/16". Yep that rivet press will do the job, now I wonder if the architect made the roof truss design string enuff......
 I think I found Robs rivet press, the pictures don't come up, sounds like it would do the trick.
 I hope I didn't derail your thread to much, you didnt by any chance take a picture or two of you making the rivet snap by any chance? Making an internal radius that size must of been fun. Thanks for the calculation filed for latter use!

Cheers kerrin