Swaging, crimping and peening

[Chris Taylor 3Participant @christaylor3]

With help from the forum setting up my rotary table, I've finished making lots of non-standard Meccano pinions and I'm looking at making some larger gear wheels. Cutting the teeth on the gear discs and machining the bosses present no problems, but joining them together does. Are they pressed using a special die, or swaged or crimped? What sort of pressure and tool would be used, what profile should be turned on the boss? Could it be done in a mini-mill etc.? Any advice would be very welcome. I have thought of using a miniature collet but I would prefer to do it the Meccano way.

[Chris Taylor 3Participant @christaylor3]

[Tim StevensParticipant @timstevens64731]

As many of us (including me) cannot remember what is special about the Meccano Way, you might get more helpful responses if you could kindly remind us. A picture, perhaps?

Regards, Tim

[MuzzerParticipant @muzzer]

Surely you can't have forgotten these? Crummy image, apologies. Swaged over using some sort of single operation press tool I expect?

[BazyleParticipant @bazyle]

I think Chris does not know what the Meccano Way is, hence asking. I have some Meccano gear wheels that rotate on their bush but mostly they are still firm. I have never taken one apart but would expect to make a number of nicks, or 'keyways' in the edge of the hole in the plate embryo gear and then press/stamp the end of the bush over with sufficient force to extrude some metal into these keys to hold it.

[Tim StevensParticipant @timstevens64731]

In that case, it might be a solution to make the flange a bit wider than normal, and use soft solder to hold the boss to the gear. The larger area will add strength as it all has to shear at once. At the same time, no softening or distorting of the gear due to heat or bashing.

If I understand you …

Cheers, Tim

[SillyOldDufferModerator @sillyoldduffer]

Small Meccano gears appear to be solid. Muzzer's photo shows how the larger sizes are made. I had some old gears with loose bosses and managed to restore them with a peening hammer. I'm sure they would have been pressed in the factory with a die shaped to neatly turn the edge of a rim left on the boss. Wouldn't be difficult to turn on a lathe, mild-steel be OK for light use. More pressure than I would care to put on a mini-mill, but easily done in a vice I would think. Can anyone advise about annealing?

Dave

[Chris Taylor 3Participant @christaylor3]

Dave, as you say, the small gears are all machined from solid, which is what I've been doing recently. What you suggest with a die and vice is the way I've been thinking, but I think it would need a jig to keep the gear disc perpendicular to the boss axis, the gear discs would be about 1/16th thick and up to 3" in diameter. The bosses are 3/8" diameter.

[Anonymous]

Looking at my old Meccano gears they look like Muzzer's picture, but not as neat. There is some evidence of rotary action on the central boss. The edges of the boss where it has been folded over are showing signs of cracking, and the cracks are not radial. So I'd suggest they used some sort of rotary swaging. Whatever method was used the bush would need to be pretty ductile.

I wouldn't use my Bridgeport mill to attempt swaging a gear like the Meccano one. I think you'd need a proper arbor press or flypress.

Andrew

[Neil WyattModerator @neilwyatt]

A small version of the eye tool at the top of this photo might do the job, if the brass was annealed first.

Neil

Edited By Neil Wyatt on 04/09/2017 19:02:07

[SillyOldDufferModerator @sillyoldduffer]

Posted by Chris Taylor 3 on 04/09/2017 18:48:08:

… but I think it would need a jig to keep the gear disc perpendicular to the boss axis, …

I'd try glue first. It only needs to hold the disc in position on the boss long enough to press the swage. My main worry is squeezing the brass so that it flows rather than splits. It may need to be softened first and then the whole gear re-hardened afterwards. I've never tried heat treating brass, so let's hope an expert turns up!

Dave

[Tim RoweParticipant @timrowe83142]

Chris
​The process for fixing is called rotary riveting. Google it to see how it works. Basically it combines spinning with pressure. We used to make a range of stainless steel yacht fittings where spacers or small shafts were fixed to side plates. The action which is akin to a wobble keeps the material moving and prevents cracking due to work hardening. It is extremely quick and the geometry of the parts is very simple.
​The tool is a bit more complicate but if you have a standard size boss you only need one set of dies.

[John ReeseParticipant @johnreese12848]

Posted by Tim Rowe 4 on 04/09/2017 19:18:21:

Chris
​The process for fixing is called rotary riveting. Google it to see how it works. Basically it combines spinning with pressure. We used to make a range of stainless steel yacht fittings where spacers or small shafts were fixed to side plates. The action which is akin to a wobble keeps the material moving and prevents cracking due to work hardening. It is extremely quick and the geometry of the parts is very simple.
​The tool is a bit more complicate but if you have a standard size boss you only need one set of dies.

Do you think a rotary broach with the proper tooling would work?

[HopperParticipant @hopper]

Loctite would be the modern way of doing it, I reckon.

If not, a riveting punch for a hollow rivet might do the job.

Edited By Hopper on 05/09/2017 01:11:40

[Ian S CParticipant @iansc]

A number of years ago I made some 1 inch Meccano pulleys, that needed a 2 piece die to form the shape of the V in the two halves of the pulley, then I rivited the hub into the wheel. Made most in brass, and when I ran out of that used galvanised iron sheet.

Ian S C

[Chris Taylor 3Participant @christaylor3]

Tim, is that process called orbital rivetting where the punch rotates at an angle to the vertical?

[Tim RoweParticipant @timrowe83142]

John – Not really. Chris has it where the punch rotates at an angle to the vertical. The best analogy I can think of is a spinning top where the point stays in one place but the main body orbits creating the angle. The beauty of the system is that no heavy presses are necessary. We used standard drill presses.

​This was in a production environment with many thousand operations per day. In a home workshop I would probably take the Loctite option or even very thin super-glue applied after a very light peen.

[Michael GilliganParticipant @michaelgilligan61133]

Chris,

If you want to reproduce the visual detail of the Meccano fixing, without the specialist machinery that Tim mentioned … have a look at Figure 9 in Laurie Penman's article here: **LINK**

http://www.awci.com/wp-content/uploads/ht/March2012.pdf

[wow, that took some finding]

Watchmakers often just use the staking tool; but for clock [and Meccano] sizes, this ^^^  is much more appropriate.

MichaelG.

.

For reference, here's Roger Smith using the Staking Tool:   https://m.youtube.com/watch?v=J_bQu8D3Tdg

 

Edited By Michael Gilligan on 05/09/2017 11:19:42

[speelwerkParticipant @speelwerk]

In musical box governors hardened-tempered steel pinions needs to be fitted very securely on to the their brass wheels. For that the part of the pinion that is pressed in too the bore of the wheel is larger in diameter, 0.5 mm or more. The turned down teeth of the pinion that is pressed in the wheel act as cutters. Everything needs to be lined up square and the pinion centered with a bush and pressed into the wheel with a staking tool or a press if you have larger wheels, a vice is not accurate enough. After that the pinion is riveted on the otherside to make the fit definitive. Most important is that everything is as square and accurate as possible and the brass wheel has good support. Niko.

Edited By speelwerk on 05/09/2017 11:59:51

[Martin CargillParticipant @martincargill50290]

Oh this is about attaching gears……….I thought it was related to preparation for a night out!

[SillyOldDufferModerator @sillyoldduffer]

I couldn't find a damaged Meccano gear to investigate but this is what the boss hole in a 3" pulley looks like:

You can see that the hole isn't round, it has eight lobes cut into the inner circumference.

Other than the lobes being about 3/16" in diameter, I couldn't work out the Imperial base. Hence the dimensions are in mm. Apologies to Meccano purists for using metric and also to anyone offended by my drawing package suggesting I can measure accurately to 0.0001mm! Please read about 9mm, about 2.4mm and about 8.4mm. ±0.02mm

Dave

Edited By SillyOldDuffer on 05/09/2017 14:42:52

[Chris Taylor 3Participant @christaylor3]

Thanks to everyone for all the advice and ideas so far, this website https://www.orbitform.com/assembly-processes-services/orbital-riveting-and-forming/ gives a really good description of the orbital rivetting process, although it may not be the way Meccano did things at Binns Road. The attraction is the 80% reduction in the pressure needed over a simple press but I think trying to use a mill drill might be a bit ambitious. I think the shape of the hole described by Dave would help to lock the part onto the brass boss in terms of resisting rotation and maybe the "rivet" part is instrumental in maintaining the alignment perpendiculat to the boss axis. I think some experimentation is needed!

[SillyOldDufferModerator @sillyoldduffer]

Posted by Chris Taylor 3 on 05/09/2017 15:15:25:

…

I think some experimentation is needed!

 

Me too!

I turned a 3/8" diameter brass boss with a 4.1mm through hole and a 1.5mm deep step to form the swage. The diameter of the step was cut to be slightly larger than the boss hole's minimum diameter, ie an interference fit with the inner side of the lobes.

I used an odd bit of junk box steel to support the rear of the pulley and eased the boss into the hole with a 4" vice:

Then I made a 1/2" diameter mild steel die with a 4.1mm pin to fit inside the brass boss:

And squeezed the whole lot in my vice as hard as I could by hand:

Results not very exciting. Although the boss is firmly fixed, and the pulley is at a right angle to the boss, it's not obvious that any swaging has taken place. Actually the diameter of boss is 0.1mm bigger, so the brass has deformed slightly. Hitting the die with a 2lb lump hammer increases the diameter by about 0.1mm per whack BUT the rear face of the boss got damaged and the pulley moved off axis. Not good.

I conclude that the brass would have to be softened before this approach might work, and that using a hammer is likely to distort the gear. At least in my unskilled hands it does!

Now I'm off to investigate annealing.

Please let me know if you find a way of doing this Chris – I'm interested in making non-standard Meccano parts too.

Dave

 

Edited By SillyOldDuffer on 05/09/2017 15:59:36

[Chris Taylor 3Participant @christaylor3]

Dave, just another thought or two. Looking at the boss you tuned, if it had been a bit longer to protude more and then undercut so that the section you pressed was thinner, would it not deform more easily in a straight press or with a profiled die, or even better with a rotating die that folded over the brass as it was pressed. This brings me back to the orbital rivetting process – I can see how this would produce the finish required.

[Jeff DaymanParticipant @jeffdayman43397]

Many years ago when I worked for a large American controls firm many cam packs for timing various switches had cam plates sandwiched around a central brass or die cast hub. These were staked in place to hold everything together. Many cam plates had a central hole with 4 semicircles cut around it just like the Meccano pulley shown.

The stake tool for these ops was not a plain punch / brute force. Sometimes one stake op was done, with a punch having chisel-like angled features and sometimes an angled ring which displaced metal sideways into the 4 semicircles. Sometimes after this op a second stake would be done with a punch having a rounded groove, to displace the flange out and down to grab the cam plates better. Another type of stake tool had 4 round punches to hit the outer rim of a bushing in a plate to push the metal down and outward to hold the plate over the bush. In this type of stake tool the centreline of the punches was on the joint circle of the two parts. The punches' ends were angled down and out to direct the metal flow.

We also staked bushings into 3 mm plates for water valves, before soft soldering to seal them. These stakes were radial chisel marks around the bush OD, displacing metal sideways into the plate.

Almost all staking involved angled faces in the punches and dies to move the metal sideways and down with a vertical punching action, or tools to do a rolled flange action. We had a fleet of literally hundreds of Denison electric pump / hydraulic cylinder one and two ton presses to do these ops. These were clean, accurate, quiet presses that people could use for a full shift without fatigue.

Staking was once a very common assembly method for metal parts but has fallen by the wayside in the last number of years due to alternate materials like injection moulded plastics, and alternate processes such as snap fits, glues and heat staking being used for the type of assys that used to be staked metal work.

I'd bet that Meccano did most of their hubs exactly the way my old firm did, with staking tools in some sort of press, displacing metal with angled features / rings on the punches. JD

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