Member postings for Kiwi Bloke

Nah, don't like the wave washer. You'd still need to lock the nut. The wave washer does provide spring pre-load to the bearing pair, but it also destroys axial stiffness.

I'd rather forgotten about the other end... If you're driving this with a pulley, it can be screwed on (I'd assumed that, much earlier), and a plain locknut added. Don't rely on just a thread for accurate location of the pulley, though; it should be a snug fit on the plain section of the shaft, to ensure it runs true, and have a boss, outboard, which is threaded. This has the added advantage of getting the pulley as close to the tail bearing as possible.

Clive's comments above, about (partially) isolating the pulley from the shaft, is good stuff, and also applies to drilling machine quills, of course. But we're chasing simplicity, aren't we?

Edited By Kiwi Bloke on 25/07/2023 12:23:31

M7 Nyloc?

Nigel - my apologies. I now realise that my question would have appeared rude, had you thought it was aimed at you. It wasn't - it was semi-rhetorical, and aimed at the forum's readers in general. I agree with your comments above.

Do you ever get the impression that you're being watched, or are you just paranoid?

I suppose truly anonymous mass data collection is OK. What is worrying is that idiots or ideologists like politicians then make decisions based on a faulty understanding, or unreasonable selection, of the data. Most mass data collection, however, is far from anonymous - even though you might think you can hide from prying eyes.

OK, more simplification. Probably.

Make the 'nose nut' without the flange you've drawn, so that, when tightened, it sticks out say 3mm beyond the end of the housing. The nut's OD is threaded along its entire length (easier to machine), and it has a couple of axial holes on its exposed face, for a pin spanner. When boring and screw-cutting the housing, make the threaded section longer, then part off say 3 mm. This parted-off section then screws onto the exposed threads of the 'nose nut' (taking the place of your flange), locking it. You'll need to make a couple of pin spanners (or a C spanner for the locking nut, if its face is too skinny for spanner holes) to tighten the nuts. (Sorry for that complication). I can think of other locking strategies, but this one seems the most elegant - so far...

Looking good! And pretty pictures too. (Wish I could bring myself to re-learn CAD. I had an early version of TurboCAD - it drove me nuts. Ever since, it's been back to pencil & paper...).

I think the most challenging aspect of manufacture is getting the spacer-to-spindle fit right, if one is going for a snug fit in the hope that it will add rigidity. Perhaps someone could tell us how snug the fit has to be to be effective, for this geometry. I'd imagine that significant hoop stress has to be induced in the outer member, to effectively pre-load the inner, so it would need to be a press fit, which rather screws up the whole idea. The idea is more effective when the spindle is really skinny, and the spacer can increase the overall diameter a lot. It's probably an unnecessary gilding of the lilly here, because the spindle is of relatively large diameter already, and the spacer can't easily be much larger. Please can someone advise?

So, perhaps the spacer can be freed from its obligation to add stiffness, tolerances can be relaxed and simplification is achieved..

More simplification. If the spindle's 7.5 mm diameter section between the bearings is made only a little larger than the ID of the tail end bearing (say 7.1 mm), the dark green thrust washer (?) twixt spacer and inner track of tail bearing can be deleted. Also, I'd delete the groove in the shaft behind the nose bearing pack. If needed (and it looks unnecessary from your drawing, a small internal chamfer could be added to the spacer tube to clear the transition between spindle diameters here

Don't forget the pulley, the nut being outboard of it. Keep us posted!

Edited By Kiwi Bloke on 23/07/2023 23:56:38

Apologies, it's bed-time. I shouldn't post this late - nurse will be cross.

There may be some confusion about boring through the housing. There needs to be a step for the inner nose-end bearing's outer track to abut. You could have a loose, but well-fitting sleeve here, behind which is an internal circlip. The sleeve is so that the outer track abuts a reliably 'square' abutment, not a swash-plate. The tail-end bearing can have a smaller ID, so the spindle components can still be loaded from the nose end. But these complications aren't really that important. Loading the tail end bearing into the housing, with the spindle in place wouldn't be that difficult.

Time for bed...

The tail-end bearing's inner track is sandwiched between spacer tube and nut, so that's OK. The spindle is fully axially located at the nose end. The outer track of the tail-end bearing should be allowed to 'float' (a snug, sliding fit), to take care of possible thermal expansion. Andy_G's illustration of an O ring bearing on the outside of this track is good practice - it reduces the ability of the track to slowly walk around the bore of the housing.

Agreed that you can't fully assemble the spindle before assembly into the housing, but all the important bits can be in place, except pulley and nut, of course. I'd keep the nose bearing spacer, unless you're going to buy expensive matched pair bearings. Adjustability is good...

Talk to your bearing supplier about bearing seals. It's possible to get non-contact 'seals' that don't drag on the spindle. Conventional seals can add a surprising amount of drag. And oil is probably preferable to grease. (I think someone else said that, but I'm editing this now, and can't see previous posts...)

Having now re-read the whole thread properly, I'm conscious that I've essentially re-stated Duncan Webster's ideas, although perhaps with different emphasis. It wasn't my intention to steal his thunder. Just two (great?) minds thinkng alike (or suggesting standard solutions...).

It's heading towards being a really nifty, scalable spindle. Well worth your writing it up for MEW. It would raise the tone of the mag considerably...

{Edited: it's difficult to type with fists...)

Edited By Kiwi Bloke on 23/07/2023 11:55:06

Michael, you say your weighing device isn't calibrated. It may be worth making a standard or two, to calibrate it, perhaps from copper wire. It's generally of pretty high purity, so its density is known, and it's hard enough to allow its diameter to be measured accurately, whilst soft enough to straighten for length measurement.

You haven't mentioned the sensitivity of your weighing device. I've been impressed by the performance of the ultra-simple (see-saw) balances made for ammunition reloading. A friend and I reload with piddling target loads of 1.5 grains (about 0.097 g) of powder. Our scales' calibration agrees within about 0.006 g, and, whilst neither has been calibrated against a standard, they are remarkably consistent, with repeatable measurement. (Yeah, OK, in this case, they're acting more as comparators, but the point is that simple devices can perform quite well).

Not a criticism, but a suggestion...

The design can be simplified, removing one screw-cutting operation, and making the spindle itself simpler to machine.

Instead of a ring nut against the nose bearing inner track, a tubular spacer can be substituted, between the inner tracks of the inner nose bearing and the inner track of the tail-end bearing. Everything is tightened up by the tail-end nut. The tubular spacer should be a close fit to the spindle shaft, and will increase stiffness as a bonus.

Probably need a simple locking arrangement for the ring nut abutting the outer track of the outer nose bearing.

Steve - the comments in the thread you saw may have been mine. I've posted about the book before. I'm disappointed that the book was published in its present form; the manuscript should have been sent back for revision.

Yes, let's see your drawings. You can be assured of a barrage of critical comments. Some might be helpful...

I've now got Harprit Sandhu's book in front of me. I wish to correct and add to my comments above, to avoid doing the fellow a disservice, since my comments might appear to be wrongly rubbishing everything in the book.

His 'Basic Spindle' (Ch 3) is OK, if a matched back-to-back pair of bearings is used. Alternatively, with a shim between the inner races, preload can be adjusted. So that one's potentially OK, even with standard bearings.

His smaller MT2 spindle (Ch5) is not OK, because the inherent axial play in the nose bearing cannot be adjusted out.

Micro Spindle (Ch 6), 1.000 Diameter Spindle (Ch7) similar weakness, but worse - the spindle is only prevented from pulling out by friction or adhesive holding the outer race of the nose bearing. Same for Ch 11 spindle.

Ch 9 & 10's spindles rely on accurate dimensions of inner and outer race locations, and the inherent axial play in the bearings can't be adjusted, except by trial-and-error machining.

Ch 12's spindle is potentially OK, but looks difficult to adjust - which would be required every time a cutter is changed.

Ch 13's spindle looks fine.

If you're chasing good surface finishes, you need to be able to get rid of all possible sources of unwanted movement...

Edited By Kiwi Bloke on 21/07/2023 02:53:32

Presumably, you'll have to grind the domed surface after hardening. In which case, an alternative might be to (weld) hard-face the ends, then form the domes.

As Howardt says, there's much to be found from bearing manufacturers, available online.

Beware Harprit Sandhu's book. His double taper roller bearing design is OK. All the others are, in my opinion, seriously flawed. Working from memory, most are designed with the outer races abutting shoulders in the housing, and the inner races separated by a spacer tube over the shaft. This is fine, provided you can machine the relevant axial abutment dimensions accurately, but it makes the design non-adjustable, for fine-tuning of axial preload. It should be obvious that this is important when using angular-contact bearings, but it's also important when deep-groove bearings are used. I think there are some designs where axial location must rely on friction fits or adhesive. look critically, before cutting metal!

The axial location of a spindle, and the axial stiffness of its bearings, is clearly of great importance. It's theoretically better for this to be taken care of by a pair of opposed bearings that are close together. If they are at either end of the spindle, its thermal expansion will alter the desired axial pre-load. Probably not a major problem for home machinists' spindles. If the bearing pair is at the 'business end', then you have two bearings sharing radial loads. Thus, designs tend to place bearing pairs at this end. In this case, the bearing at t'other end must be allowed to float axially.

You can get matched pairs of bearings, to be fitted back-to-back, which take care of the axial requirements, but you'll have a limited choice and need deep pockets.

Perhaps the easiest design is with a deep-groove bearing at each end, with the tail-end one spring-loaded in the direction of thrust. This is the headstock arrangement loved by Emco, in its small lathes, and works well, but is, of course, only axially stiff in one direction.

Be aware that there are different grades of bearing available (not counting junk from the East), and beware of the drag caused by rubber seals.

What could possibly be of any interest about the sex-lives of the over-60s? And has the strap-on sensor got anything to do with this subject?

The mind boggles...

Sorry, I can't point you in a specific direction, but when I've needed hydraulic seals (jack, tractor, pallet truck, etc.), I've just gone to the local hydraulic/pneumatic seal dealer (who may also be a bearing distributor). With luck, it'll be a standard size and configuration - and cheap.

Nice bit of kit, especially compared to the oriental stuff available here.

This might help... www.classic-british-car-jacks.uk/Lake_&_Elliot_Jacks_4.htm

Edited By Kiwi Bloke on 16/07/2023 07:09:55

Fingers aren't so much of a problem - you've got lots of spares. But, for goodness' sake, wear safety spectacles! If you get copper or a Cu alloy in your eye, it will wreak terrible damage, quite quickly.

Is it a coincidence that, as I write, the adjacent post - from Margaret - is titled 'Safety Gloves'?

The calories available for metabolism are those left over after our gut biome has taken its share. And the amount is reduced by many other effects, like transit time, intestinal health, etc., etc. What goes in certainly doesn't all get used. Stop counting calories - eat, drink, and be merry!

Well, you can do a bit of guesstimatology...

Estimate the mass of the element in the breaker that flies forwards to strike the chisel's backside; estimate this element's stroke. You know the number of cycles per second, so you can estimate the element's max. forwards velocity (unless the geometry of its driving mechanism is peculiar), so you can get an idea whether the given energy figure is reasonable.

You can also estimate the terminal speed of a lump hammer, and you know its mass, hence you can guesstimate its energy.

What you don't know is whether concrete yields better to very many little taps, or to Thor and his hammer, smiting it mightily. My money would be on Thor, but machines don't get tired.

Edited By Kiwi Bloke on 13/07/2023 10:30:11 (typing with fists again)

Edited By Kiwi Bloke on 13/07/2023 10:30:58