ML7 - Zeroing the Topslide?

All, what’s the best way of setting the ML7 topslide to zero degrees, ie parallel with the bed?

Thanks.

Since it doesn't have a flat face you can't simply put a DTI against the side and travel the carriage.

You might simply turn a part with it and measure the diameters both ends.

For everyday use I know the 'end' of mine is 'square' enough to be run up against the chuck jaws or a parallel between them.

If it's 'critical' I'd clock it against a test bar.

Indeed - hence the question!

Is there a way of doing it with the topslide removed (exposing the dovetails) rather than messing about turning test pieces every time it’s adjusted?

I’m surprised there isn’t a zero degree dowel pin as standard.

Thanks.

Could the topslide be removed, and set up so that a datum could be milled along one side?

I’ll see what mine’s like. Thanks.

Standard correct answer is to use a decent quality test bar in the spindle taper, fix an indicator to the top slide so it touches the bar and traverse it back and forth. Adjust the cross slide angle until the indicator reading doesn't change during traverse.

Alternative is to turn a temporary test bar held in chuck or collet and use the same procedure.

Turning two collars using the topslide or turning a bar and checking the diameter is the same all the way along is, theoretically, subject to various errors and is not necessarily reliable. Whether the errors could be relevant in practice is a whole other matter. If the lathe and work holding device are in decent nick probably not for folk like us. Whatever its a total faff.

Adequate test bars aren't silly expensive and make this sort of thing easy. It is important to first verify that the lathe bed is in line with the spindle by traversing the saddle. If the bed is out of line you have problems.

Could run the indicator along the extended tailstock barrel. On a Myford it will probably not be dead nuts true but setting for the same taper readings as given by traversing the saddle will work well enough. Some creativity in mounting the indicator will be needed.

My opinion follows that of Big Den who taught me basic lathe work at RARDE and reckoned setting a topside parallel to teh bed was a "bloody stupid thing to do" as it unnecessarily multiplied the chances of error.

Clive

I don't understand that statement - what's the point of having a 0.001" graduated dial on a topslide if you're not sure exactly where the axis is pointing?

I'm doing work that doesn't protrude too far from the chuck, and need accurate longitudinal measurements/cuts. Surely the topslide dial is far easier to use for this kind of thing than the saddle leadscrew? How else are you supposed to do work like that when there's no room to easily get measuring equipment in to the job? At my current skill level, I think using the top slide dial - with a parallel top slide - would give by far the lowest chance of error.

Trouble with having the topslide set parallel is it's always in the way of the tailstock. When I had an ML7 I made a leadscrew handwheel, now I've got a dro so I have the topslide set around about 30 degrees out of the way.

Adequate suggestions have been forthcoming, your call. You must remember to lock the saddle if using the top slide as proposed. Dowels wear as do their respective holes therefore of dubious benefit, not to mention increased production costs.

Robert Butler

Yep, cut withe carriage and then adjust the top slide so it follows the part without cutting or diverging.

Simple way is to not use it for anything accurate.🙂 Mine only gets used for things like threading and turning short tapers - or sometimes cutting up to a shoulder where a tiny bit of alignment doesn’t matter for that few tenths of a mm cut. Most of the time it is jammed at the end of its travel, so no errors from the gibs.

Remember, the lathe will cut best when the cutter is directly over the cross slide dovetails, not hanging out as far as it will reach (unless really necessary).

I can see why Myford are now making them with all machined surfaces, so easy you just stick a magnetic mounted Dti on some part of the lathe and run the saddle up and down.

I use mine all the time to know how much of a cut I have put on or to position the tool as the saddle handwheel is not accurate and you are guessing anything much less than 10thou.

Tailstock not really a problem on mine but may be on a Myford as as I think the Doc is wanting to use this to position an internal groove then tailstock is not needed and would only be a problem when it's support is needed which may only be 10% or less of your total time using the lathe so hardly "always"

+1 - on an ML if you don't have a leadscrew handwheel or read-out then parallel topslide is by far the easiest way of establishing distances along the bed for small components.

..just a shame the dials are so b****y awful..

Edited By DiogenesII on 14/03/2023 07:18:54

Might I suggest a variable bed stop instead of fa****g about with the compound slide?

I simply adjust my bed stop and let it auto trip the long travel while under power feed. Good reprducibility as long as I stick to constant depth of cut and chuck speed (so constant feed rate).

Seems like myfords are much harder work than most others?

Like as not I'm doing it wrong because I'm self-taught, but it's unusual for me to not have the topslide parallel, and doing so hasn't caused me any problems. How does having the top-slide parallel to the bed multiply the chance of error?

Is it to do with the design of the lathe? From other posts it seems the Myford tailstock is more likely to collide than the hook-shaped type found on later lathes.

Dave

Agreed, the cheap and nasty die-cast index dials are just another example of the ML7 & ML7R deficiencies. I changed mine to friction dials that are still readily available from the new Myford but have risen in price quite a bit since I bought mine although, IMO, well worth the investment. BTW, despite my criticism of Myford design shortcomings,and there are more than just the dials that should have been corrected decades ago, but it was of British manufacture after all so no surprises there. I have an ML7R since enhanced to a Super 7 spec. and would not part with it for all the tea in China!

Edited By Chris Crew on 14/03/2023 08:48:50

At some point in the future at the editor's leisure, there will be an article in MEW on making your own quite simple resettable top and cross slide dials for the ML7. Absolutely worth their weight in gold. The best mod I have done on the ML7.

As for setting top slide and measuring lateral distances etc, I am big fan of the graduated carriage leadscrew handwheel. The drawback on the ML7 is disengaging the change gears to use the handwheel. So a lead screw dog clutch is in the works too, at some point when i get around to it. There was a handy design reprinted in MEW last month too, disengaging the gear on the end of the leadscrew which is good too.

Meanwhile, another way of doing it is set your topslide as best you can by lining up the machined straight front edge on it with the edge of the cross slide. Use the topslide to take the first roughing cut or two, but accurately up to the shoulder where you want it. Then take the finishing cut/s up to that shoulder using the carriage feed to ensure the diameter is parallel along the job.

I looked at drilling and reaming a dowel pin hole to keep the top slide set parallel when wanted but there is not a lot of meat there where it is easy to access so have not bothered.

To expand on Hopper's meanwhile method, I often use the topslide to measure up to a shoulder. The angle scale on the topslide can be set within 1 degree by eye. The cosine error is very, very small: Cos(1)=0.9999. So, over a 1" length, your actual length would be 1/10,000" short.

Rod

It depends what you are doing with the top slide, Lengths may have little error worth worrying about but thinking ahead of what Doc has to do on his Princess royal there may be a need to space out a series of grooves which would become deeper by upto 0.018" if there was 1deg error over 1" if feeding in the cross slide to the same depth for each.

Yes it can be done with the leadscrew if the nuts are left engaged etc but if you were spacing things like cylinder cooling fins and driving the grooving tool under power X feed that ain't going to work. Other options are a plunge type Dial Gauge with reasonable travel but a faff to set up on a regular basis

Doc asked "Could the topslide be removed, and set up so that a datum could be milled along one side?" I don't see why not. If it were set up on it's side on the mill and the edge of the dovetail clocked horizontal then you could skim one side either full width or just a strip wide enough to run the Dti against

Edited By JasonB on 14/03/2023 10:50:37

Thanks all.

Jason - yes, I'm thinking ahead to the flywheel grooves, and the grooves/rings in the eccentric components, as well as any number of other features where small steps or undercuts are needed.

Bearing in mind the question is specifically about the ML7:

Saddle leadscrew handwheel:

a) It's at the other end of the lathe to where I'm working, and very awkward to use for fine work. The scale isn't great either.

b) It needs disconnecting from the feed gearbox every time.

I don't see how that can be better than an accurately set top slide.

Saddle stop:

The ML7 doesn't have one. I have made one, but it's a simple device that requires measured shims to give accurate dimensions.

Again, I don't see how that can be better than an accurately set top slide, although it's worked fine for steps in longer jobs such as the crankshaft.

Clash with the tailstock:

I don't need the tailstock for any of the work I want to do, so a non-issue.

Dials:

I have already replaced the cast dials with re-settable items, so again it's a non-issue.