Whittling down round bar stock with emery paper.

I am making some half-shaft axles for a tricycle which are of nominal 12mm diameter.

First set I made were from plain old 12mm milt steel and I did not expect the round bar to be a precision piece of rolled steel and fit perfectly through the 28x12x8mm deep groove ball bearings of the outer axle-tube. I was not disappointed in this belief and no, the bearings would not slip along the length of the axle shaft.

What I did to make them work quite well was to mount them in my lathe chuck and a tailstock centre and run the lathe up while looping a piece of oiled emery cloth around the bar and traversing the entire length back and forth with frequent stops to check on progress with a bearing.

Soon enough the "slip-fit" I was looking for was achieved.

I have a concern that "mild-steel" just won't cut the mustard for this application and so I am replacing the mild-steel with Silver steel equivalents.

Now, I had expected this much more expensive bar stock to be produced, rolled & polished to a much tighter tolerance to 12mm than it appears to be, seeing as it is commonly used in gearboxes as layshafts. But No!

The bar is marked "Precision 12mm BS1407" which I believe is meant to be within tolerance by 0.00025" So I guess I got a piece that is on the high side and not the low side Ha! Ha!

Now Silver steel is a darned sight tougher than mild steel and the same trick is taking FOREVER.

Is there a better way of bringing such stock down so marginally that it fits the precision manufactured race of a bearing? It seems to me that taking a tool to it is overkill and will ruin the steel because it probably isn't even 0.00015" oversize. Is effectively "polishing it down" to size with emery cloth the only real way to do this? If it is the only way so be it, I just wondered if there was a better/easier and more "approved" way.

TIA.

Dan.

Not answering your question, I'm afraid, but I don't think silver steel would be the best choice for a half-shaft. Anyone else have an opinion?

Rob

For micron type whittling in the lathe I use that green grit paper

Its a situation where a proper micrometer would be a serious help

Fitments like that need time and patience because the surfaces must be thoroughly cleaned each time

Edited By Ady1 on 08/05/2023 17:37:24

Thanks Rob,

Folks suggested to me that 12mm mild steel would be "too soft" and liable to bending at the intersection of the exit from the outer axle-tube and the 2 bearings there. Normally for singe-sided wheel mounting on recumbent trikes we all use 12mm bolts of 8.8 hardness and over, and no-one has (to my knowledge) come unstuck.

I'm giving Silver steel a go because a German chap with a similar application has used it successfully.

All the commercial trikes with split rear axles have 12mm inner axle elements and this was the best I could think of.

Regards,

Dan.

Thanks Ady1,

I was intending to use my 100 grit standard Emery cloth and then polish with green polishing compound on a leather wad.

At the moment in the absence of a micrometer I am using a bearing itself as a go/no-go gauge and wherever it "stops" along the shaft I am reducing that spot a little extra it is still a snug-fit but passes.

Thanks for the response.

Dan.

Word of warning, be very careful hand holding cloth or paper around a spinning job. When it snatches, the hand goes with it. Think bruises, dislocated or broken fingers and the truly horrible de-gloving. This video shows a chap being pulled into a lathe...

Dave

I would have chosen EN16T or at a push EN24T if you can't get the 16T, Silver steel can be very brittle.

If you've as much a half-a-thou to remove, I'd start with a second-cut or finer flat file, swept foreward and sideways across the area of bar you're seeking to reduce, hoping for a decent surface. If you see tramlines developing, stop and go over to strips of emery looped over the end of the file to provide a flat abrading surface. Finger pressure's enough to hold the strip and provides a bit of a safety feature - though I can't remember experiencing a snatch that was in any way dangerous over a lot of years. Keep speeds and pressure moderate. Choose a final emery grit that'll get you a suitable finish.

Grade 12.9 cap screws, cap socket head screws, is a very good steel to make axials from.

Thanks Mick B1,

Fingertip pressure on the emery with an oil to prevent glazing of the cloth seems to have slow but OK results.
I will keep at it. Good info though the use of a flat file as a backing for the emery is a great idea.

Thanks,

Dan.

You could always take say 5thou off most of the length by turning and just leave the areas where the bearings go unturned and then emery them down to size which would be quicker than doing a whole long shaft

Edited By JasonB on 08/05/2023 19:32:31

Its hard to tell, but it looks to me that its actually his sleeve getting caught rather than the emery cloth, though he has kind of wrapped the emery round the bar and it might be that that snatched his sleeve.

Sobering stuff anyway. Also noticeable how long it takes in this kind of situation for people to figure out what to do - the first man on the scene grabs hold of the lad to stop him being drawn further into the machinery, but the second takes several seconds to stop the lathe - ideally you would always use the emergency stop button so that became the automatic reaction to stop the machine.

I would agree with Chris Evans, en16t or en24t, they are chrome moly and strong all round.

Danny

Trikit make tricycles and used to make rear axle conversions It may be worth asking the proprietor Geoff Booker [email protected] what material he uses.

HTH Dave

Thanks all for the help and advice.

All noted and very much appreciated.

On the issue of the 12mm Silver steel as an axle half-shaft, yes I agree silver steel may not be the best choice.

The commercial "QR axles" I have from Sturmey Archer are 12mm Stainless Steel.

Perhaps SS would have been a better option.

Yes - that was my immediate reaction: stainless-steel. (The printing-machine manufacturer for whom I worked for a time, used this for all manner of pins and spindles.)

However, if you examine commercially-made shafts you often notice them turned from slightly over-size steel so the critical areas can finished properly to size, and the intervening or end sections are turned down a little below to allow the bearings, etc to be assembled readily to their seatings.

And keep that emery-cloth well away from the lathe - for your safety but also its health!

Any chance of using a skiving tool as they will take off tenths, which you can do quite successfully if you compound is set to 5.5deg or so which will give you a ten to one ratio of bed travel to infeed.

There's plenty of old imperial micrometers in decent nick on ebay that do to 0.001 which is 0.025mm

I use an old moore and wright 965 which you can get for 10 to 15 on ebay

Has lapping been mentioned?

With a well set-up lathe and properly fettled tool bit, it is possible to take off a couple of 'tenths' (or less) at each pass. Lapping is a good idea, but very slow. A hand-held hone, such as those by Delapena (probably no longer made...) or, IIRC, a similar pattern by Bruce Engineering, is quicker. These three methods will ensure roundness, whereas filing and emery paper won't correct a lobed surface - common on centreless-ground stock.