Re: Linkage repair on a brass locomotive


Daniel A. Mitchell
 

Due to the tiny size of the rivets used in HO valve-gear, the tools needed to set them are mostly available only from the suppliers of such rivets. That’s Bowser (ex Kemtron), maybe PSC, and someone mentioned some european (German?) supplier. Others?

Similar tools (not necessarily rivet-sets) are also available from commercial jeweler’s suppliers. Some of these are useful as a PART of the rivet-heading process. Ideally, using a proper rivet-set, the entire rolling operation can be done in one application. Note that my personal experience is the the heads form better with repeated light impacts rather than one big smash. However, the result can be achieved using several different tools applied in the proper order, such as …

1) a tapered tool like a center punch used to start the flare of the rivet, to perhaps 45 degrees

2) a ball-shaped tool to continure the flare out to perhaps 90 degrees. A small bearing-ball works well here. A Jeweler's “dapping” punch works well here if you can find a really small one.


3) a punch with a cup-shaped hollow tip to continue the roll well past 90 degrees. Jewelers use such “bezel-stone setting punches" for setting jewels. Watchmaker’s use such punches for setting small bearings … I have several varieties. Often these come with a small frame to hold the punches in alignment with a setting anvil.


The simple hand-tool set is not very expensive. The watchmaker’s set with alignment frame, etc., is quite expensive. How much of such work do you expect to do? Simple, cheaper tools will usually work even if they louse-up sometimes. How many blank rivets can you buy for the cost of the watchmaker’s setting device? Hundreds at least.

This is careful, fussy work for sure. It takes proper technique, experience, a good rivet blank, and some luck. Ideally the rivet can be flared and rolled without cracking it. That’s not always possible. Sometimes the rivets are too hard and brittle making a proper roll impossible. Such rivets are made of brass, copper, and steel. The softer the better. If the new head cracks examine it under strong magnification … you’ll have to decide if it looks good enough. If it’s mostly rolled over it’ll work … these little things are NOT highly stressed. If it’s rather squashed flat with several cracks, it’ll likely fail. Often it’ll take more than one try to get it acceptable.

If one has a small lathe the job becomes easier since you can make your own rivets and the tools to set them. They are not complicated.

Dan Mitchell
==========


On Jan 30, 2019, at 10:28 PM, Bryian Sones via Groups.Io <bryian.sones@...> wrote:

Dan,

With all that said. I assume there might be better tools available than others. Do you have any suggestion on where to get the best tool for this and which to buy? 
Also, thank you to everyone for the input. There are really good suggestions and advice.


Thank you,

Bryian Sones
Union Pacific Prototype Modeler
Murrieta, CA


On Wednesday, January 30, 2019 12:03 PM, Daniel A. Mitchell <danmitch@...> wrote:


Good advice.

When setting such a rivet one wants to roll the hollow end over into a bead rather like a doubled-over sock. You do not want to just squash it flat. Flattening it may work, but will usually crack the rivet’s new head, and weaken the rivet. This is why rivet-set tools are made.

<tubular_set.gif>

They form the new head with a smooth sort-of “rolling-over” action (no true rotary motion is involved). Lacking a rivet-set of the correct size, a reasonable alternative is to carefully expand the rivet just a bit with a countersink or other pointed / tapered tool, then work the edge outward and down with a small jeweler’s ball-peen hammer. It’s not as good as using a proper rivet-set, but can be quite satisfactory.

As an aside, this is the same idea as rolling in boiler tubes in a tube-sheet. Here the much larger tubes ARE actually rolled into form with a rotary-roller tool driven by a large air or electric drill. As the tool rotates inside the hollow tube it forces the metal outward then bends and stretches it back over itself forming a bead.

<universal-combo-bead copy.png>

Such a tool would be great for hollow rivets too, but for HO valve gear the parts would be microscopic!

Dan Mitchell
==========
On Jan 30, 2019, at 11:09 AM, Edward <edb8391@...> wrote:

I would also like to add that when setting such a rivet to join moving parts, that it not be set too tight.
If set and too tight, the rivet should be removed and the job done over.
Trying to work a tight joint to free it up could damage the rivet 's upset.
Binding might also cause the moving parts to possibly fail at some point. 
Putting a thin piece of paper or similar removable material between the moving parts before riveting may help avoid the issue.

Ed Bommer
.



<tubular_set.gif><universal-combo-bead copy.png>

Join main@RealSTMFC.groups.io to automatically receive all group messages.