1542Re: [mlathemods] Re: worn out bed
- Mar 14, 2006In reply, I would have to mention that I have no experience whatsoever of South Bend Lathes. I referred to 9x20 lathes being ones with hardened beds- and I quite correct in making a direct relationship there.Going back to 9x20 lathes and I assume the worn lathe, the intention of a hardened bed is to reduce wear.
However, wear on unhardened other parts would be greater than that found on the hardened parts.
Unless, my own wear like that of the South Bends of over 70 years has missed something vital????
Let us return to where the information is- and if my memory holds out a little while longer- to South Bends. The information is in Edward Connelly in Machine Tool Reconditioning- and it is still the definitive book.The definitive book on alignment is still Schlesinger's Limits. On both, there must be slight improvements and additions over the years- but we go back to them!
Schlesinger gives details of tests which are static, bench tests.
There is no question of what does a lathe show when it is running. Our tyro must go back to fundamentals and check his lathe- and determine to his own satisfaction what he demands from what is a cheapo lathe. If he is unsatisfied with what he has acquired, then he must go through each part and make the corrections according to Connelly.
I may sound pedantic and all manner of things, but that is what Classical machine tool construction and repair demanded and demands!
Let us turn to- what I expect! Not what is there- but wetting my finger and guessing. To all intents and purposes, I would expect the lathe NOT to be worn. It ain't 70 years old- or even 7. I would be surprised if it was pre-owned and it will have been made on precision equipment- far more accurate than in many machine shops of today, all that will be out of spec is alignment and gibs.
It suggests that there was something suspect with spindle bearings- which improved after parting off operations. This frankly is utter tosh, BS or whatever modern expression one finds.
Maybe, I should add that I have been there before. My two penn'orth is already in Model Engineers Workshop on a Myford ML7 and earlier on a Pools Major- probably a 70 year old one.
Today, there is a ML7 which has just had its bed Blancharded and a Super 7 B which is also receiving some TLC.
The rebuilding of both lathes is following the foregoing comments- but I am saving a lot of time in the use of a tool and cutter grinder to remove the slight wear since perhaps 1946.
I apologise for the lengthy reply but hot air and theory don't mend an inaccurate lathe- and I must now get on with my pair!
My kind regards
----- Original Message -----
Sent: Wednesday, March 15, 2006 1:33 AM
Subject: [mlathemods] Re: worn out bed
--- In firstname.lastname@example.org, "johann_ohnesorg" <bigdukeone@...>
>those are some good points, Johann; in searching other forums I've
learned that grinding is the usual method, but the surface grinder to
which I have access may not have a long enough bed; may have to try
planing it; in reply to Norman, I haven't seen any reference to
South Bend having hardended beds on their lathes in the 1930's and
the various dents and dings on the ways from 70 years of use would
certainly refute your contention
> Hy there,
> Scraping off 0.013" on the whole length of the bed will drive you
> nuts, try the planer, measure twice and cut once.
> Be careful with the holddowns, I once watched a guy shaping a small
> lathe bed. He flipped it over on a pair of 1-2-3 blocks, cut the
> stands to equal height with the shaper and then, he flipped it back
> over again.
> This makes setup easier. He used holddowns in the middle of the bed
> the cross braces (4 or 5 equally spread over the whole length) and
> small jacks underneath to push the bed up again.
> If this does not work (don´t hesitate, you got a few more cuts to
> it right...), junk the bed and buy a new one. Cut the 90° guide in
> same setup. Try to match the saddle by equal cuts to the left and
> right of the bed. Don´t forget you have to shorten the cut by a
> of 0,707 if you cut in a 45°angle. To see what you do, make a sketch
> which is scale 10:1 and the try to draw and measure toolfeeds and
> angles. Please do this in advance.
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