MEW 205; Lathe levelling

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MEW 205; Lathe levelling

This topic has 4 replies, 4 voices, and was last updated 14 September 2013 at 16:13 by Howard Lewis.

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12 September 2013 at 15:09 #129440
Erik Christiansen
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@erikchristiansen31905
As a machine installer, I'm a beginner, but have found that lathe levelling was very wortwhile, and dead simple to do. My (AL-1000) 3/4 tonne Taiwanese lathe doesn't seem to be as rigid as David Fenner finds on p56 of MEW 205 – fortunately, I think, in retrospect. It wouldn't turn as precisely parallel as a "toolroom quality" lathe should, even after tweaking the tailstock alignment. My heart sank when I measured 0.48 mm (0.019&quot twist in 1160 mm of bed length, using a spirit level with laser shining on a wall 5.8m away. How was I ever going to straighten that out?

A chinese machine level, with each division equal to 0.02 mm in a metre, was not too expensive. It resolves 0.0027 mm (.0001&quot across the 133 mm shears on my lathe. With its help, and a jacking screw in one leg of the machine stand, I now have the bed ends parallel, with a bit of twist in the middle, amounting to 5 scale divisions (0.1 mm in 1 m = 0.013 mm across the 133 mm bed). That's half a thou in the old money, and it'll have to do.

I made no attempt to make the machine level, just parallel, which is all that is needed, I figure. Packing was placed under one end of the level, to make it read level at one end of the bed when sitting on the flat top of the cross-slide. Winding the saddle to the other end, the screw was adjusted for the same reading. Bed ends parallel – job done. (Ten minutes to fiddle suitable packing, since one thicknes of newspaper sent if off-scale. Then five minutes to level the machine, cranking back and forth a few times to check how much the other end had moved, after waiting for the bubble to settle. A few degrees of screw rotation are more than enough for the final adjustment.)

It's a very nice machine now. But I figure I'll give it a quick check summer and winter in the first year, to see how much it has moved, even though it's on a steel stand on a thick reinforced concrete floor.
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12 September 2013 at 15:09 #38196
Erik Christiansen
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@erikchristiansen31905
12 September 2013 at 20:42 #129474
Sub Mandrel
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@submandrel
Welcome to the forum Erik,

Very brave of you to dive in and raise this thorny and controversial topic again!

Neil
13 September 2013 at 13:32 #129513
OuBallie
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@ouballie
Had no problem leveling my BH600G, but I was fortunate in that the previous owner has used studs in the two turrets, with nuts rop and bottom to raise and lower the machine.

Double nuts top and bottom of course to lock the height, with no faffing around searching for packing.

I recommend this method without hesitation.

Photos if anyone is interested.

Geoff – I need to 'Calm down'
14 September 2013 at 16:13 #129679
Howard Lewis
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@howardlewis46836
My lathe is an Engineers Tool Room BL12-24, very similar to the Warco BH600, or the Chester Craftsman.

It sits on 6 off 1/2 UNF x 20 tpi setscrews. (They started life as bolts but have been threaded all the way down).

With nuts above and below levelling is pretty easy.

My previous Myford 7 was a nightmare to level, as the slightest change of torque on a mounting screw, even when apparently "solid", would send the bubble off on its travels. (There are better ways of spending an evening)

My level is machined from a College Engineering casting, fitted with the most sensitive vial ( 1 div = 0.005" over 12" (0.417mm over 1 Metre) that they offer. It was checked out and adjusted on a surface table in the Calibration Room of the Standards Room at work.

End to end level does not concern me particularly, since it is unlikely to affect parallelism of the work, but twist in the bed does.

With the BL12-24, the most sensitive fixings were the two immediatly behind the chuck, but being able to lock the upper nuts against the lower ones, a 20tpi thread gave a fairly fine adjustment, since one flat produces a movement of 0.0083 inches (0.217mm) in round figures.

Using a level on a Lathe with a vee bedway can be difficult if suitable parallels are not available. In which case, if posible use the level on the top surface of the cross slide.

My method was to adjust at one end only.

With an alignment bar that was within 0.0005 over 12", the tailstock was aligned across the bed.

Needless to say, the gib strips should be adjusted so that slack does not interfere with any of the readings.

It pays to be patient, checking and rechecking, at each end, after each small adjustment, until any twist has been eliminated.

So the only thing likely to result in tapered worki is if the tailstock centre is above or below the headstock centre.

If it is below, it may be possible to shim the tailstock higher. If above, some delicate scraping or machining might bring things back into line (but beware of the tailstock barrel no longer being parallel to the bedways!

Howard
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