Cabinet Rigidity (Myford ML7)

[Nigel Graham 2Participant @nigelgraham2]

The lathe is a fairly early ML7 I bought in rather bare condition quite some years ago and have slowly treated to accessories including a proper Myford cabinet and raising-block set.

This evening I set about clocking a work-piece to run true on the faceplate, from a turned step already on its large-diameter periphery.

I admit my generic DTI clamp-stand is a bit of a lash-up – none of the holes in the commercially-made clamps seem properly to fit any rod diameters as we know them… Jim.

Nevertheless it works. I clamped the magnetic stand to a cleaned area of the chip tray and chivvied the plunger against the work.

Then leaned back slightly while holding the tray wall. This produced quite a large movement on the dial!

Surprised, I gently pressed my fingers onto the floor of the tray near the magnet, as if testing a newly-baked sponge-cake, and the clock registered nearly 0.005″ movement.

I moved the upper arms and indicator from the stand to the tool-post to complete the setting, but this is concerning.

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How rigid is the cabinet, and what effect might it have on a lathe we think have correctly levelled on it?

Or am I worrying needlessly by having “tested” an area of sheet-metal that is not itself structural? Also there was probably a large radius-magnifying effect ‘twixt pressure point on the tray and DTI plunger on the work-piece. Might there quite naturally be a slight void between the thin tray material and the stand proper, and was I simply springing that?

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My lathe cabinet stands with packing under its feet on a solid concrete floor, but is not screwed down.

[Don CoxParticipant @doncox80133]

Are the bolts which hold the lathe down good and tight following the adjustments to level the support blocks?  What you are describing suggests that the tray and the stand top have a gap between them which needs squeezing up.

[HopperParticipant @hopper]

Never clamp your magnetic base to the chip tray. The tray is thin, very flexible sheet steel and will always flex too much to give a reliable reading. Always clamp magnetic base to the lathe bed ways if possible. Second choice to the cross slide (locked). Third choice is toolpost (cross slide and topslide locked).

The chip tray sits on top of the main stand, so rigidity of the stand itself is a separate issue. Stand can be rigid as a brick outhouse but the thin tray sat on top will still flex. Myford stands are probably not perfectly rigid but they have been functioning acceptably since 1946 and many a fine model engine and more produced using them. So no need to stress about that.

 

[DiogenesParticipant @diogenes]

^^This, exactly..

..also be wary of resting arms on the tailstock, etc., whilst craning over to try and see what’s happening..

[noel shelleyParticipant @noelshelley55608]

Why on earth would you clock from the tray that is only there to catch swarf Etc ? The tray is thin sheet metal that will flex at the first chance. A good magnet, wipped so there is no swarf Etc under it, a clean bed and as short arms as can be will all help to reduce error. The best place as Hopper has said is the bed. If the same result was got from leaning on the bed then I would worry.  Good Luck . Noel.

[duncan webster 1Participant @duncanwebster1]

Slight digression, I made the stand for my ML7 to the same height as Myford and found it too low, gave me backache. I eventually put 6″ square timber under it, which was a great improvement. I find having the cross slide handle level with your belly button about right

[HopperParticipant @hopper]

Yes cross slide handle in line with the elbow is about right, and that’s about in line with the average belly button I believe! (Depending on how much beer one drinks perhaps?)

Not sure of the original Myford stand height. I made my bench to my usual standard of 1 metre, ie 39 inches. Then there is another 2 inches of risers under the lathe, which it really needed. I am 6’1″ (185cm) tall. It is very comfortable. Have put in full days many times with no back ache.

I have a rubber mat about 1/2″ thick on the floor, one honeycombed with circular holes all over it, made for use in restaurant kitchens etc. The swarf falls in the holes and so you are not crunching around on it all day long. Very nice on the feet and the back on a long day at the dials.

[Dave HalfordParticipant @davehalford22513]

Nigel,

If you levelled the lathe by taking cuts and packing between lathe bed and stand or stand to floor then any flex has already been allowed for.

[bernard towersParticipant @bernardtowers37738]

Isn’t the Myfortd stand supposed to be bolted down?

[bernard towers]

On bernard towers Said:

Isn’t the Myfortd stand supposed to be bolted down?

Possibly but mine is quite happy and stable sitting on adjustable feet on an uneven concrete floor.

Rod

[Howard LewisParticipant @howardlewis46836]

The essential for any measurent is rigidity.

A thin, flexible chip tray does not not meet that requirement.

As Hopper says, says site the magnetic base on the bedway, or the cross slide. Make sure that the gibs are not loose! Or make up a holder to be clamped on the toolpost.

Minimise the overhang of the clock from the pillar of the magnetic base, so that the structure is as stiff as possible.

Howard

[Nigel Graham 2Participant @nigelgraham2]

Thankyou very much, Chaps, for the reassurance!

After those antics with the chip-tray I did set the work with the indicator stand bars held in the tool-post.

The nature of the item meant a rather long reach for the indicator, the plunger having to contact a narrow ledge behind a large-diameter flange.

When I centred a part on the Harrison L5’s faceplate, with slightly similar access difficulties, I stuck the magnetic stand to a stout steel plate clamped to a shelf above and behind the lathe.

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I think my Midlands shopping-list will have to include better indicator mounting sets, if I can find any; and perhaps a lever-type indicator to complement the plunger ones I have. The collection of bits I have means nothing quite fits anything else, leading me having to improvise in odd ways at times when the work is awkward. Hence trying to use the chip-tray!

The magnet does not fit either lathe bed very well, but I am not sure it won’t always be a compromise. One option that’s just occurred to me – indeed as I wrote this – is to make a steel plate with a simple, quick clamp to fit both lathe beds, to give a big flat area for the magnet to cling to.

[DiogenesParticipant @diogenes]

..one of the most useful types of indicator holder for the ML is essentially a square-section ‘G’ clamp with holes on the sides and corners in which the ‘posts’ are held with set-screws….if I can’t find a picture online I’ll post one tomorrow..

[Nigel Graham 2Participant @nigelgraham2]

Thankyou Diogenes.

A bit of this lathe’s history.

I bought it c.2010, from a gentleman who had used it occasionally for making model aircraft parts, he told me, but apparently nothing very sophisticated because he had almost no tooling or accessories for it.

Including parting-tools, if the hacksaw-blade nicks in the edge of the back shear, near the chuck, are a clue. Though I think those might have been from a previous owner still, who had never mastered the mysteries of parting.

It was bolted to a massive wooden bench, via a cast-iron “chip-tray” that was clearly not intended for mounting any machine-tool, Myford or other, because it had no machined surfaces anywhere on it. It was just rough-cast  and painted. Luckily this unwitting abuse does not seem to have damaged the bed permanently, but must have strained it.

Over its years with me I have steadily equipped it, and the raising-blocks then cabinet / stand were almost the first purchases.

With its original 1ph motor the cabinet resonated powerfully enough to make me worry about disturbing my neighbour – though she had a terrible temper that often disturbed me! A Newton-Tesla 3p conversion not only enhanced using the machine, it also removed all that resonance, and the lathe runs very quietly indeed.

It latest birthday-present is a Hemingway Kits keyway slotter I have still to finish, but which is evidently designed to fit a Myford’s T-slotted cross-slide.

[HopperParticipant @hopper]

Hacksaw nicks seem to be standard on many hobby lathe beds from that era. Parting tools must have been expensive in those days!

[DiogenesParticipant @diogenes]

Nigel, apologies; got sidetracked by the rain yesterday..

A thing like this – if you can make it ‘square’ it makes it easier to drill extra holes should you need them in the future..

This one gets quite a lot of use too..

[HopperParticipant @hopper]

A 6″ long piece of 3/8″ square bar held in the toolpost with a dial indicator held to the end with a screw into a tapped hole can be pretty handy too.

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