Similar to how I was taught to use T gauges. But we were taught to rock the T gauge from side to side a little before dragging it through to make sure it was situated across the very largest part of the circle. Getting within .001" is easy enough, especially if you are doing it all the time. Would take a lot of careful practice to get down to a tenth.

I much prefer ball gauges on anything under about half an inch.

I see the builders around here fit a large locked-on wheel clamp, like a parking infringement "boot", to their trailers when left unhitched and unattended on site etc. Might be worth engineering something of the sort.

Steel is going to flex rather than crack when subjected to the forces of the taper on the OD of the collets being forced home by the nut. Definitely go with steel.

Save your meehanite for a use where it is advantgeous: bushings, gears etc.

But if it is a 6 cylinder four stroke, you only want six sparks per two revolutions.

You can buy them ready made but are sized to go between the chuck and the arbor so you mught have to go a bit oversized on a collet holder. Easy enough to make if you have a mill. The shallower the taper they better they will work.

Edited By Hopper on 31/05/2023 09:15:47

Yes just a little bit tongue-in-cheek, but there is a lot of truth behind it, as you say. The British motorbike industry was another one that did exactly the same. Whole books have been written on its demise. But basically producing 1930s designs updated along the way a little bit until their demise in the 1970s. Thanks to short-sighted management still banging out cast-iron-cylindered, vibrating, pushrod twins with separate four speed gearboxes and kickstarters when the opposition had all alloy, overhead cam smooth four cylinders with five speeds and electric start, CV carbs and fresh styling. And levels of reliability unrivalled even today.

Then new Triumph came along 20 years later and proved British industry could do it, from the ground up once old traditions and old management practices were dead and buried. But they missed the boat to be the new Honda or Yamaha etc.

Myford launched the 7-Series in 1946 with the ML7 and later expanded it with the deluxe spec Super 7 -- the same basic machine with a few bells and whistles but steering carefully away from the suspect post-war fad of roller bearings that were looked down upon by the purist adherents to the bronze age. Having developed the ultimate lathe Myford saw no need for an ML9. "Progress is all very well, but it has been going on far too long," Mr Algernon Myford said when queried on the possibility by the press. That is why Myford is today the world's leading supplier of machine tools.

Try the advice several gave above of applying a steady pressure via either Brian Wood's suggestion of a plate captive behind the collet holder nut with jacking screws applying pressure, or a pair of wedges. Jack it/wedge it as hard as you dare and leave it overnight. Then in the morning, try adding a little more pressure if you can, and then try your impacting and heating/cooling etc again.

Chances are it will have popped off of its own accord before you get up in the morning. They quite often do that.

You don't need bronze bushes in such an application. Steel on steel would work just fine for a home use chop saw hinge. I would make the pivot blocks from square mild steel and bolt them in position to allow for final adjustment so you can set the saw up to cut dead square in all planes and to make sure the cutting disc is spot-on vertical. If you weld it all up you will be stuck with whatever alignment you weld it at.

Edited By Hopper on 31/05/2023 00:58:21

A rotary sleeve valve like that was tried on various motorcycles back in the 1920s but they could never maintain a good seal once the rotary sleeve and its housing in the cylinder head wore a bit. And being subject to hot corrosive exhaust gasses, wear was rapid.

The rocking valve on the old steam engine in the OP is more reminiscent of a Corliss type valve gear. Pretty neat to watch in action.

Ah yes. It seemed so long ago.... 200kg. My apologies. Spread over the full 3 metres length, not that great, especially if you put the heavier items near the ends. If the shelf is going to be the usual sort of 600 to 750mm wide, I wouild try three beams, one on the wall, one on the outer edge and one in the middle.

Easy enough to rough test before construction. Place your three beams together on the ground with a brick under each end. Stand two hefty blokes in the middle and observe the sag (of the beams, not the hefty blokes). I can't imagine two blokes sagging three 40x20x1.6 box sections overly much. (Provided they are oriented narrow side up. Laid flat they might bend a bit.)

+1 on Brian's suggestions. Rather amazing that leaving a taper under tension like that for some hours, or even overnight, can often work wonders. I guess it is the reverse process of leaving it under drawbar tension for extended periods that created the bond in the first place. A bit impact added to the mix as suggested can often be the final straw that breaks it loose too.

Well, my curiosity got the better of me out in the shed this morning, so I had to set up and check old GHT's mathematics on the relatively little influence of tool or DTI height on a taper.

So I set up an MT2 centre between centres as shown below and using a dial gauge mounted solidly to the topslide by clamp, set the topslide to achieve a 0-0 reading along the MT2 taper, plunger set at centre height.

Then set the plunger 10 thou above centre. Result: Still got a 0-0 reading (on my .001" graduated gauge).

Set the plunger 30 thou above centre. Result: about half a thou of needle movement from one end to the other. Maybe as much as 3/4 of a thou on some passes. But closer to a half, I reckon.

Plunger 1/8" above centre, as in pics below. Result: About 2 or 3 thou of variation, end to end.

Conclusion: Old GHT was right. Unless you are waaay off centre height by say 1/8", it will not make a noticeable difference. Set to centre height by eyeball should be good enough for us bodgers. Also I reckon he was right about the concavity along the way being only one millionth of an inch. Certainly no sign of it by my crude 1 thou measuring device.

One thing I did notice is that the thou or less of necessary clearance on the topslide gibs, amplified by the leverage distance out to the dial gauge point, can give a different reading on the return pass than on the initial pass by a thou or two. So make all measurements starting at the tailstock end and ending at the headstock end, and disregard readings on the return pass so all slack is taken up in the same direction as cutting forces.

I always finish off such tapers with some emery cloth and oil to get a nice smooth finish without tool marks and find it is easy to "adjust" the taper by a thou or a fraction thereof in the process if needed for the very final fit. Usual method is to put felt pen marks along the length of the taper then fit a 2-3MT sleeve over it and rotate it about half a turn and back. The pen marks rub off on the high spots. Works better than gooey bearing blue for this.

Edited By Hopper on 30/05/2023 11:11:33

If you search Aliexpress for 8#-32 US coarse thread stainless steel hex socket flat counstersunk head screw bolt, you will find a pack of 10 screws for $1.26 with free delivery worldwide. Searching for 8-32 countersunk screws reveals a few more similar. Shipping will take some weeks at that price.

Depends entirely on what you plan to store on the shelf. A row of motorbike petrol tanks would be ok with one beam and a sheet of plywood attached to the wall of the shed. A row of truck gearboxes would need a lot more.

I would also just get the SC4, unless you have a specific special need for the smaller lathe eg watchmaking etc. You can always do a smaller job on a bigger lathe but not always vice versa.

Have a look on the lathes.co.uk website LINK Not parts for sale but might be useful info?

Edited By Hopper on 29/05/2023 11:59:15

See post above. About one millionth of an inch difference according to GH Thomas. I don;t think that is the source of your problem, unless you were a quarter of an inch below centre etc. .

Yes certainly AI functions in the same way as the human brain in some areas. But the key difference is AI (so far!) has no understanding of what it is doing. It has great powers of computation, that is calculation, at great speed, good memory capacity and the ability to search the web etc and bring a lot of stuff together but zero power of comprehension. It can write an essay on how a Myford lathe compares with a Sieg lathe as shown earlier in this thread. But it has no understanding of what a lathe is and even less of why anyone would care. So far, no great threat to the status quo.

Yet some of the world's leading AI experts are concerned for the future, so there must be potential for it to develop further. And so certainly bears watching. But I see their calls for limits or restraints or rules on its development as naive.Only the good guys will follow those rules and restraints. The criminals, and rogue regimes everywhere, will carry on regardless. Better we have first and not them.

Just remember to take your keys out before heating up your morning coffee in the microwave.