Silicon bronze running in cast iron?

I’m currently busy refurbishing an old Singer K29-1 cobbler’s sewing machine.

This particular one was made in 1913 and although still working admirably for a machine of it’s venerable age, some of the parts are near, at or beyond the end of their working life.

Some small, heavy wear parts are still available for these machines (via college-sewing.co.uk), but most of the major parts currently to be purchased are for the later 29K-71 model machine and are not backwards compatible to the older K29-1.

In particular, the needle bar for this machine is no longer available. The needle bar currently in my machine, although working well enough, does have some wear.

In use, the needle bar runs vertically in a simple up-and-down sliding motion (no rotations) within the sewing machine head which is made of cast iron. There is very little side loading, if any, on the bar, most of the force being directed straight downwards. The usual speed that one uses the machine at is on the order of 100 reciprocations (stitches) per minute, but often far, far slower. The bore in which this bar moves is oiled daily.

I’m thinking that I could build up the few small areas with the worst wear using my TIG welder, laying down a thin layering of silicon bronze which I would then smooth file and stone out even with the rest.

Please note that since I cannot afford the potential risk of distorting the needle bar by adding on steel filler, I am choosing for an application of silicon bronze (at lower heat input) for building up the surface.

My question:

Will I run into any performance or wear issues running that little bit of bronze surfacing against cast iron under these conditions?

Edited By Ignatz on 18/12/2018 14:00:16

Edited By Ignatz on 18/12/2018 14:01:03

Ignatz,

Is it at all possible for you to run a test to simulate the wearing surfaces you propose to bring together to see how they perform in practice?

Steels run well against cast iron, I think you are on your own with bronze of any description in combination with CI

Regards

Brian

Sadly, I don't have anything that would allow me to simulate a test... certainly not one of long enough duration to be of any use before I have to make a proper decision and finish the repair.

As I stated, I have no way of replacing the part should I mess it up, otherwise, building up the steel surface would seem to be best.

It is also true that I have read (concerning clockworks) that where steel axles turn in brass bushings, it tends to be the steel that wears rather than the brass, since the oxides and dirts from the running imbed themselves in the brass and then work on the steel.

Another approach would be to try to locally raise the surface that is worn, perhaps by prick punching. I once had that done (in a different way) for a set of old, loose pistons in a '52 Triumph motorcycle. The mechanic chucked them in the lathe and lightly knurled them (below the piston ring area) to make up for the wear. When I asked him if it would last he told me that it worked quite well, especially since the knurled area tended to retain a better film of oil.

Edited By Ignatz on 18/12/2018 15:18:41

Another suggestion would be to hard chrome the worn surface. It would then need grinding back to the correct size.

Brian

+1 for hard chrome and grind back, I wouldn't be surprised if TIG deposit of bronze caused distortion. If there isn't already a centre in one end put one in first, use a fixed steady to ensure concentricity

Ignatz,

I have an image in mind of a round bar carrying the needle moving in a guide hole.

• Is the needle carrier, for want of a better word, a hardened item? Heating of any kind would be likely to induce distortion I think, and the risk of cracking.
• Do you have the option of building up the CI bit of this machine instead? Boring and bushing come to mind
• Metal spraying is a possible but rather specialised recovery and one you would have to get done for you I imagine
• There was a cold build up method I read about some years ago on the lines of a plastic putty that could be used to rebuild worn lathe beds, but sadly I cannot recall any details to pass on.
• Which just leaves plating as suggested as perhaps your best option, or simply make a copy of the needle bar as a replacement item if that is even realistic.

I'm sorry I can't think of any other suggestions.

Regards

Brian

Here are some pictures to illustrate the repair in question:

This is the old Singer 29K-1 cobbler's sewing machine. Singer made thousands and thousands of these in various models. The same form of sewing machine is still produced by companies to this day.

That arm on top works in a see-sawing way, driven by a camway in the rear by the handwheel, driving the needle bar up and down at the nose end of the machine. None of your high speed stuff here.

The cast head of the machine with the needle bar lying next to it.

The needle bar out in full view. It looks simple enough, but there is no way for me to replicate this part, most especially because there is an off-center hole in it, running end for end through which the thread passes.

Here at the top end is the area of most wear. This is where the needle bar is pushed slightly away from the top arm during each cycle. The machine works, it does sew, but I'ld be happier filling in that bit of wear.

This is the bottom end of the needle bar. The lower screw secures the needle. You will notice a fine groove in the metal across that flat area. This has been worn into the steel by the passage of thread over time. At least here I feel comfortable putting in two or three tiny 'spots' of metal with the TIG welder to fill it in without causing undue harm. For an idea of actual size: those rather damaged screwheads on the top right in the picture are only 3mm in diameter. Micro surgery time.

The hard chroming sounds interesting, but probably beyond the worth of the part and machine being repaired. This old thing is only worth about £100 and I'm pretty much fixing it up to get a few extra years of service out of it for my own use.

It must also be admitted that the machine was working when I disassembled it. I simply wish to put it back into the best possible condition in order to serve. But at a certain price point, it probably pays better to search out another old-timer in slightly better shape.

How about opening the hole to allow use of a DU bushing?

https://www.ggbearings.com/en/products/metal-polymer/du

I suggest the DU because it is metal backed and can be press fit into the housing.

How much is it worn and how much is the bore worn? Little ponit in making up the shaft by so little if the other part is worn far worse. A bit like a spec of sawdust and a plank in the eye....

Edited By not done it yet on 18/12/2018 17:38:26

Having seen it and the degree of actual wear in over 100 years, I would leave it as it is, especially as you say it works.

Regards

Brian

The heaviest wear on the part measures a loss of 0.003" of metal. I'm assuming there must also be a slight loss of material from the cast iron bore as well, but I haven't measured that. In any case, haven't the machine tools available to do anything at all with that cast iron head

The wear on the needle bar does permit a bit more 'wiggle' than I'ld like, but considering that it is held under a bit of spring tension (in the direction of the wear) when connected to the top arm of the machine this may be of less concern than I'm fearing. The real test will be when the machine is reassembled and I start sewing with it again.

Brian, having examined some of the other parts removed from the sewing machine head, I'm of the opnion that they were certainly replaced at least one time in this machine's 100+ year existance. That said, I'm thinking that putting the needle bar back in service as is would certainly work. Also, the machine is so simple to disassemble that even if I chose to do something more drastic to the bar, it would be out and in my hands again in less than fifteen minutes.

Also, the machine normally runs lubricated with household sewing machine oil. Considering the wear on the needle bar, I might be better off lubricating this part of the machine with something heavier like #68 way oil.

Edited By Ignatz on 19/12/2018 09:24:00

Ignatz,

Having slept on it I am relieved to hear you are going to do nothing about trying to correct the wear. That I hope includes not doing any welding in the thread exit groove it has worn for itself to the degree of polish and fit it is comfortable with.

Any messing there must surely leave a surface that will cause thread breakages and be a thorough nuisance

We watched a recorded craft programme on TV last night filmed in Northampton at a shoe and boot museum, they had Singer machines just like yours in use stitching the soles onto shoes. It was difficult to see if there was any slop in the action but I'm willing to bet there was in all the various pivot points and in the coupling from the cantilever frame onto the needle bar. They also demonstrated a Goodyear machine which runs round a shoe in seconds

A nice piece of history for you to have and use.

Regards

Brian

Deleted, double entry

Edited By Brian Wood on 19/12/2018 11:43:28

take it to a local engineers and get a price for metalspraying and turning to size?

My brother uses 29K's he has three of them, known in the trade as "boot patchers".

deleted double entry

Edited By Phil Whitley on 19/12/2018 22:27:09

If its working why bother. Is the needle striking the needle plate , presser foot or looper? If not I would leave alone. Just my 2d

Just a note to all. I finished the refurbishment of the old sewing machine. It is now back together and working like a champ.

In the end, I elected not to try to resurface that needle bar with an application of silicon bronze. However, I did spot-fill that worn groove using my TIG torch after which I filed it down flat with some miniature die files. That spotting process with the TIG torch was so quick that the bar suffered no heat distortion whatsoever.

It should be mentioned that I DID use the bronze surfacing technique on two other parts of the sewing machine. There, however, the parts do not move at the same speed. Also, they are more easily fixed and/or remachined if so required.

Here you can see the needle bar with the replacement check spring in place..

Thanks again to all for the suggestions and opinions.

Hello Ignatz,

Nice job on the slot especially, as you know I had my misgivings about that but the result looks very well

Regards

Brian