I would like to add low rider bosses onto a steel fork using silver solder. I have seen the external ones that mount on the front of the fork. The other fork I have has the bosses in the side, which puts them in shear. I think that is good for durability.

In the side type bosses there is a hole on the opposite side, the inner side, of the fork.
What does this inner side fitting do? Is the bolt that mounts the pannier supposed to pass all the way through to reduce the bending moment on the outer boss?

In some cases the inside hole is just there to clearance passage of the tap.

If you have some meat in the drop area, you can sometimes go right through the end of the fork blade, and through brass, and drops steel. Very sturdy.

I don't think I've seen any bosses long enough to go all the way through. It is significantly easier to make a boss that has a through hole. There are bosses that are closed on the inner end if that's what you want.

I may not have been clear that these are the bosses that are mid way down the blade. Lower ones on the dropouts are no problem. On my touring fork I use now there is no bottom on the boss, you can thread a long bolt all the way to the other side. It's the hole on the other side that I don't get. It has a round boss in it, but I am not sure if it's threaded, will have to check.

For that application, silver solder some bottle inserts. One side only. If you want super stout, you should shoot for 6mm stuff. But if you want normal spec the water bottle mounts are fine.

We used these for low-rider mounts at Trek. They go all the way through the blade, but are just a simple unthreaded tube with a shoulder:

Now that I think about it, they may have put those there so you could put a nut on the end for safety. .??

Yup.

I doubt that would help. Locktite is useful the removable kind, or iodine. When you tighten the nut you would be torquing the bolt open, it should already be tensioned against the rack.

I like loctite a lot. They have a new version, like plumbers Teflon tape, but for opposite results.

I use nylock nuts on a lot of the rack mount points. They won't fall off even if loose.

is it ok to add some questions to this thread to keep the info in one place, easyer to search?

I have two bikes w steel forks, good quality early 90`s mtbs w rigid fork. I guess silver soldering is nescesary to make it strong enough? I know there is the bottlecage "crimp" ones that is pressed w a tool or qr axel but is it going to stay in place? I know there are many types of glue that could keep them in place, but i guess getting it to the right place could be a problem. I am thinking of putting the tlong type used on seatstays for ataching racks and put them on the rear edge of the fork to avoid drilling. No framebuilders around here so I have to trust a local welder.

Second queation, more tricky: I have two 20" wheel bikes, one folder one minivelo. I want to use lowriders on at least one of them, BF Tikit style. Problem is both is alu fork bikes (at least there is no response from a strong magnet, and frames are alu). Is there a safe way to do it on alu forks? I could of course buy a new fork w bosses already in it. Suggestions?

You can't use water bottle bosses, they are too weak and could easily pull out. The silver solder and proper boss, plus a hole cover(those diamond shaped ones) will hold up. Note that a thin walled bladed fork from an old road bike is not always strong enough for. The hole and the heat can weaken the blades.

Many aluminum frames for touring have steel forks for strength. Be careful!

Ok, thank you. I`ll be careful!

The old bike is a Scott Boulder MTB, not a roadbike. Maybe I`ll get a replacement fork w the bosses to use when I want to use lowriders.

Guess I`ll leave one of the alu bikes as it is and buy a new fork with the proper bosses already on for the 20" folder.

These would be rivnuts (or called rivet nuts or nutserts) and okay for bidon mounts on the main frame triangle. Installation requires a hole much larger than the bolt, you wouldn't want to make that big a hole in your fork. Somebody else has already invented the 'face plant'.

You will find lowrider racks purpose-built for forks with the bolt-through mounts, the Tubus Duo is an example.

If you look at some of the lowrider racks available you'll notice that most manufacturers either sell brackets with the rack or separately that allow the rack to be used on a fork with no midpoint braze-ons. Most of these brackets are basically U-bolts and plates, or some other bolt on clamp. So as long as you have clearance there should be something useful for even 20" forks.