What are the pitfalls of attempting to wind a pocket watch main spring by hand, without the special tool.

For only an occasional mainspring job, is it really necessary to obtain the winding tool?

Paul

It may not be necessary, but it sure makes life a whole lot easier.

For me, it is a lot cleaner, requires a lot less handling of the barrel and spring (less risk), and is a lot faster. I feel like I have a lot more control and can keep the angles and stresses on the spring more in line with the design loads.

Hand packing a spring takes a lot of finesse not to kink or twist the spring as it goes in and also requires a ton of focus not to loose control of the barrel and have it whiz across the room...

Spring winders have a bit of a learning curve in learning how to get the rotation correct on the first try... it's one of those upside and backwards things.

The steepest part of the learning curve for me was how much abuse the tongue will take in shaping it to catch the post on the winder. I actually find it easier to make the first wrap on the winder stem before putting the spring in the winder barrel, keep tension to keep the hole on the post as I slide the stem in to the handle of the winder barrel... then I don't have to risk shaping the tongue to work for the winder and suffer a set back fitting the arbor because I've made the circle too small.

Then the next discipline is getting proficient at anchoring the post on a T-end in the hole in the barrel and getting it to stay there when the spring is pushed out of the winder in to the barrel. If the post jumps the hole... start over... the flag type will catch when they rotate around to the detente... the T-ends have to be right before the cap goes on or it will either distort the cap, the barrel, push the cap off, ruin the T...

Practice, practice, practice.

One word about winding a mainspring by hand, don't.

I have done this a time or two. It is a pretty neat experience dodging the mainspring barrel as the spring uncoils in your hand, not to mention the dents in the drywall It also will cause the mainspring to get out of round and turn into a cone so I would recommend against hand winding. If you have nothing else … then you need to get something else