Odd bolt size

I did say friction conditions, for that very reason!

Often torque settings are qualified by specifying the lubrication, or otherwise of the fastener and its threads. Presumably after having investigated the results from a particular combination of materials and lubrication.

If you want to know the clamp load applied, use a load cell, strain gauge the components being clamped, or after some experimentation, tighten the bolt to give a known extension.

Forgot to mention Pilgrim nuts for large fasteners!

The ultimate is probably tightening until the fastener just goes into yield, and takes a small, permanent extension.

This is a most efficient use of a fastener, and should produce consistent tensile loads.

I found that W range fasteners, into cast iron, would give consistent results, lubricated with soluble oil (Which we deliberately varied between 5 and 20% concentrations ).

For a variety of reasons, it took six months before simultaneous yield tightening of 32 fasteners was considered safe to be allowed in high volume production. Thereafter problems were almost unknown, and gasket failures dropped to zero.

Howard

Edited By Howard Lewis on 27/09/2023 16:54:17

Obviating needing two spanner sets for servicing machinery is one thing, but the flanged bolts sold nominally as building components seem to be a law unto themselves, heavily tapered and not the normal A-F size for the ISO-M Coarse thread.

While I've yet to identify properly the nut on my ML7's rear tool-post's main stud!

The taper is the draft angle of the forging, to allow the product to be removed from the die, for the same reason that castings have a draft angle on internal and external faces.

Because of the age of the design (1947 saw the ML7 launched ) the fastener on the Myford is likely to be a BSF size. The stud for the front too[post is 7/16 BSF, from memory, so ithe rear one is likely to be something similar with a Whit form thread.

Howard

Edited By Howard Lewis on 29/09/2023 21:55:43

My Gipsy Queen engine has metric threads with imperial widths across the nut and bolt heads. That threw me for a while.

Howard -

Forging draught angle. I appreciate that, but it is rather larger on these building-trade fixings than on most nuts and bolts. There is also a rather generous fillet with the flange.

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My Myford's rear tool post is of modern manufacture, and the nut on the main Tee-bolt always has me searching for the right spanner. The two small ones on the base flange do seem to be of BSF size.

It is the nut size that is awkward. The thread does not really matter.

Obvious solution: make all the accessory fastenings compatible with the original machine, with as few different sizes as possible!

It can be frustrating when a machine contains mixed thread forms, or hybrid hardware. Whilst it may have suited the original manufacturer, knowing what is needed for servicing can be a nightmare.

If the nut on the rear toolp;ost is not of Whit size, it could be mounted in a 4 jaw and faced down to a suitable size.

An ex navy cha\p that I was mentoring showed me a nut that he had made, as a test piece, since only a lathe was allowed to be used.,

Howard

I'm not clear what facing the nut will achieve other than making thinner, unless you mean facing each facet to give a smaller across-flats size.

It would be easier to make a new nut from BSW-size hexagon bar, or full-diameter round and mill it hexagonal to size.

If of course I don't have a suitable nut anyway, lurking in the come-in-handy "stock" !

You do not face the ends of the nut, you face the raw material to produce a hexagon.

IF no hexagon bar of a suitable size is available.

Remember, 100 miles out to sea you may have to be innovative, and ships do not always carry a milling machine.

The drilling and screwcutting, or tapping can come later.

Once thre faces have been faced, at 60 degrees to each other, they can be be used as a datum to face the opposite side.

So if you have a nut of a size for which no spanner is available, each face can be machined to produce a size across flats for the tools available.

Ah, I see! I was wondering how you'd hold the workpiece on a lathe to do that, then twigged that if you drill and tap it first you can hold it on a nut and bolt to use that as a makeshift spin-indexer on an angle-plate.

I have done something like that to drill pairs of holes at 60º from each other in the ends of three rods, to make a triangular framework a bit like a Toblerone slice.