ML7 toolpost - Turns Under Load

Hi Nigel,

My original Myford spanner sits directly above the lathe though I do sometimes suffer from 'bench blindness' and can't see it in front of me in the lathe tray!

I constantly move my toolpost when machining depending on specific tools - to have a pin would be really detrimental to me in the manner in which I work. Apart from experiencing the doming effect and dealing with it as said I have had no issues.

Your reference to surface grinding brought a smile (?) though - the one thing I really miss about not going to work is the Jones and Shipman 1400

Ramon

All, I’m not sure why there’s so much confusion about the spring. I’ve explained multiple times now that it wasn’t fitted during use, and why I temporarily fitted it for the contact tests.

There may be something in the observation about the spacers/washers under the handle. I had to make a spacer to get it to clear the tops of the q/r adjusters, and another washer to orientate the handle so I could actually lock it without any clashes. Clearly with direct contact I’d have one sliding interface at the top end, currently I’ve got three. I might try to eliminate the adjustment washer and then I’d be at two. If I can find a nut I might try that too, and reduce it to one, but I don’t really want another spanner hanging on the board. I’ve already got one permanently on the saddle lock bolt. I guess every little helps.

As Ramon says, I’m also constantly adjusting the angle of the tools, so a pin would only be if use for parting. Then again, parting was where I had the most issues.

Ill re-assemble any test it. I think enough is enough with this. Let’s face it, Skimming the casting by 0.003” must have made an improvrment.

Same toolpost here, I used to have a needle roller thrust bearing on top which helped. Installed it properly with the proper toolpost stud and it got worse, knurling and parting became impossible, blueing showed the contact area was OK, shimmed it with a sheet of paper and there was a large improvement.

Your reference to surface grinding brought a smile (?) though - the one thing I really miss about not going to work is the Jones and Shipman 1400

A bit bigger machine & easier to use than the Ingar RT612 all-manual surface grinder I had access to, Ramon.

A good work out cranking the table on larger pieces like the Super 7 cross slide, which I also tickled up at the time. I have one of the same model Ingar machines in the garage, bought from Ebay quite a while ago but not yet re-comissioned - one of the "retirement projects" I have aquired over the years when they became available.

Nigel B.

I re-fitted the top slide casting, and then found the locing lever that was with the lathe when I got it. Looks awful, but it works ok. I think I might revert to the Myford handle I bought, but turn another spacer. OK it will give another interface at the tp end, but I'm not sure it makes much difference.





Not tried parting off yet, but so far so good - seems solid.

Hi Nigel, I had a long period at work where I did an awful lot of surface and form grinding. I can't imagine having to weild the handles!! Like uoy say a good work out.

Our very old JS 1400 looked on it's last legs but was incredibly accurate. Common test after refacing the 24" chuck used to be grinding eight blocks set apart over it. Average error over the eight blocks after letting it spark out was .002-3mm.

Like you I made good of my time at work - milled and ground the table for my old Linley mill (amongst many other things

Regards - Ramon

DR,

You have made a lot of progress toward solving your problem.

It does not matter which handle you use, as long as it does not bottom out on the stud before securely clamping the Toolpost.. The object is to apply clamping force, to prevent the Toolpost from moving..

To that end, it may improve matters to ensure that all marking blue is removed, since you do want any possible form of lubricant to decrease the coefficient of friction between the Toolpost and the Top Slide

The Toolpost turns under load if the cutting force acting upon it exceed that provided by the clamping action.

This may be for a number of reasons: blunt tool. Tool mounted off centre, Excessive tool overhang, Excessive depth of cut; Excessive feed rate; or a combination of any of these. Only you will know which, if any, apply to your machine.

But do remember that it is a ML7 with a 3/4 hp single phase motor, not a 3 phase machine such as an 18" Edgwick with a 5 hp motor, or a 21" Dean Smith and Grace.with a 10 hp motor.

Happy swarf making!

Howatd

Thanks Howard,

Yes I've removed all the blue and re-assembled. So far so good - it seems solid enough.

My theory about the spacers under the locking handle is that the more interfaces you have under there (top of the block), the more chance you have of getting reduced friction at the top end. Despite the main contact patch being at the base, I'm assuming every little helps, and if there's maximum contact at the top, this might help.

I still have the original myford clamp, which is provided with a spherical washer under the nut, but unfortunately the nut itself is missing.

The Spherical Washer is a left over from the original Myford "lever" type tool clamp, which fitted onto the 7/16 BSF stud. It allowed the lever clamp to tip to "fit" a variety of sizes of tool shank or toolbit, as they were shimmed to bring the cutting edge to centre height.Some facility to keep the lever flat to the tool was provided by the adjustable foot at the other end of the lever..

Reduced friction between Handle and Toolpost is a good feature,since it means that the torque applied to the handle results in a greater clamp load between the Toolpost and Topslide. (If the Handle would not turn on the top, you could not apply any clamping! )

A screw thread is a means of applying a lot of force. Think of screw jacks on cars. (To my shame, I cracked a Cross Slide on the ML7 with an overtightened 1/4 BSF stud! )

Needle Roller thrust races are sold for some machjnes, specifically to reduce friction at this point.

My advice would be, firstly ensure that the handle does not bottom out on the stud (Hopefully the ball handle is tapped 7/16 BSF right through, so that this problem does not arise. )

Then you turn up a spacer to a length that ensures that the Handle clears the adjusters on the Tool Holder, and so that the Handle, when tightly clamped does not over hang the work (3 o'clock to 6 o'clock would be my preference )

Or you can use washers under your current spacer.

CAVEAT Ensure sufficient thread engagement; Ideally at least 7/16" Too little thread engagement is likely to result in a stripped thread at some time, possibly with damage to the stud.

HTH

Howard.

Thanks Howard, that does make sense.

Yes, with the original spacer I made, the thread in the lever was fully engaged, but I needed an additional washer to get the handle to point away from the q/c gubbins. It was a bit rough, so instead of the washer I might incrementally shorten the spacer until it's right again.

I think I'm pretty much there now.

One advantage of using a nut and spanner is that that lump of a handle is absent.

I use a nut and an offset ring spanner, being a ring, you can leave it in place if you wish and at a suitable angle, again the ring misses the QC locking as well.

As Howard says, you just need good grip between the toolpost and the top slide. The width of the toolpost is four to five times the diameter of the clamping nut so the resistance to turning torque is overwhelmingly generated by the toolpost on the topslide.

The area of the toolpost reduces friction, however, so increase in clamping pressure from a thrust bearing or even a lightly lubricated washer to counteract this will bring greater gains than any slight loss of resistance to turning at the top.

Neil

Thanks Neil. Yes, understood.

I'm going to order a new Myford nut for the post, and put a washer under it. For the sake of a few quid I'll try it with the nut and spanner and see how I get on. I'm pretty sure that skimming the casting has cured the issue, irrespective of what the blueing suggested. Thinking about it, there had to be an improvement in grip (assuming no gross mis-alignments during machining. As others have said, my technique for using the blue was probably giving dodgy results anyway.

You can make one. (Far cheaper than "The genuine article" ) The end faces need to be square to the thread, and the thread should be at least 1D, ie, 7/16" long.

If you go for a hexagon nut and a ring spanner, you can apply a lot of torque, and huge clamp loads. Possibly sufficient to strip a thread if you really heave on it With a ring spanner 70 or 80 lb ft torque could be achieved, but not necessarily needed, to apply a huge clamp force. Probably enough to do damage.

The current ball handle that you have should be quite capable of providing sufficient clamping force.

An hour so ago, I was taking a 0.050" facing cut on 1" steel with a four way toolpost set at an angle, to provide clearance, with only the clamping force provided by manually tightening the toolpost handle . (No dowel or stop )

And there is no needle roller bearing between the handle and toolpost, but I do make sure that the handle is tight.

At over 80, my days as a Charles Atlas clone are way behind me!.

Reducing friction between handle and toolpost means that the handle turns more easily, so that, for a given applied torque, it goes slightly further down the thread, and so applies more clamp load.

You don't want to crack (or strip ) a nut, so no sledgehammer required

Howard

The original nut supplied with my S7 is a 'long' nut probably about 1-1/4 to 1-1/2 times longer than width AF. I still use the double open ender spanner that cam with the lathe and when it's not in it's place above the lathe usually lies in the tray.

I think it very unlikely that sufficient force could be applied to strip 7/16 BSF thread unless someone had absolutely no idea what they were doing - that would take a considerable force indeed. I really don't see Doc G in that league.

I have found a good indicator if things have been tightened a tad too much is that the topslide becomes distorted slightly and becomes slightly stiff to move. A retweak on the spanner cures that in quick order. This is usually when I use the original tool clamp (with spherical washer) to hold a knurling tool though.

Regards - Ramon

Thanks both - Ramon yes, the nut is very deep, I guess to reduce the chance of stripping, and/or give more thread engagement so it can be really leaned on. I'm not strong enough to strip a 7/16" thread - at least not without a very big lever and a lot less finesse!

Howard - I hear and appreciate what you're saying, and people will probably dismiss me as a bit odd, but I honestly have very little interest in making tools or nuts or whatever. I'm in this pretty much purely to make models. I've got other pastimes that are very time consuming, but have limited time! The cost of a tap and the time taken to make the nut would be way in excess of the £5 it's costing me to buy.

I even half considered buying a spindle turning handle yesterday, and only didn't becasue apparently it was too big for the ML7, so I'll have to make one.

Just to finalise this - I went with the suggestion of using a nut, and found some space to hang the spanner...





Seems solid now. Thanks all.

O K, you are a model maker, but sometimes you just HAVE to make tools or jigs.

If something fails at 7 pm on a Saturday evening, and you are desperate, you will make up a new nut, rather than wait until the middle of next week for the genuine article to arrive!

I have an awful lot of tee shirts!

Making a mandrel handle will probably provide a useful learning experience, as well as a useful tool. It may well save several broken taps or dies and scrap workpieces!

Go for it!

Howard