E.I.S., Pinetown and T.I.Chalmers, Kew, Johannesburg.
For a machine upgrade from old, worn, cast iron parts with no bushes – to 21st century engineering with hard metal bearings and split lead screw thread holders and double thrust bearings:-
The machining materials and time cost a miserly R2000 , but when we come to fit the M24 metric fine threaded bar (looks like cut threads not rolled threads – but, now, not so sure), the 225mm long threaded bar entered the machine block by 45mm before it jammed.
Since we had cut the internal threads in the block in a lathe, followed by cleaning-out these threads with an M24 x 1.5 tap, slitting the block to enable us to adjust the thread backlash, then re-tapping the thread to clean-out the burrs from the slitting saw, it seemed strange to have this problem at all.
However, not discouraged, we make another block (a day and half later) and find the same problem – thread stuck at 45mm penetration.
Belatedly, we examine the threaded bar under magnifying glass and find that the thread was 1.509mm pitch instead of 1.500. (We’ve since cut the whole item, thread included on the lathe – now working fine – but were PRESUMING THAT IT WOULD BE CHEAPER AND QUICKER TO BUY THE THREADED BAR AND MACHINE IT TO SUIT.
Now for the WHINGE, notwithstanding the cost of the (2) blocks and machining them twice, the local vendor,
EIS declined to refund our money (+/- R300) for the bar “because we had cut it up and he couldn’t sell short lengths of bar” and admitted that they do experience thread creep on “long nut” installations, but would only credit us if the manufacturer, T & I Chalmers, would be willing to credit them – a matter we understand was declined.
So, guys, beware from whom you buy materials
If you’re using “long nuts” (or die blocks), buy cut thread bar, not rolled thread bar
Or, simply machine the parts yourselves :- IT’S CHEAPER THAT BEING SCREWED (pun).
Is this Man known to you?