ML7 toolpost - Turns Under Load

Yes, the unused hole is for a locking pin, you would need to drill and ream a matching hole in the topslide.

Your local garagiste will know someone who skims cylinder heads. My local chap has a surface grinder and does little jobs like this for not a lot of folding currency/

Thanks Duncan.

Is there anything particulary wrong about fly cutting it? I can do that myself on the mill - it's only a small area, and seems pretty straightforward on cast iron?

Dr GMJN

No problem, not always easy to see inside these smaller assemblies.

I use a Myford QCTH on both my Super 7 and ML7 sometimes and they do not rotate unexpectedly. I don't use a locking pin. I don't remember one being supplied by Myford with the QCTH, or a pin being mentioned in the literature, though I understand they are used on some lathes.

If you can re-surface the topslide surface, and the toolblock if needed, I think you will find that there will be enough friction to resist unwanted rotation in normal use.

A pin is all very well, and would definately prevent rotation but I think I would find it restrictive, sometimes I need to rotate the block just a little to get the tool into an odd corner.

Rod

Thanks Rod. Yes, I’d rather retain the infinite adjustability. I wonder if roughening you the underside of the block might help? Just abrading the surface with some coarse wet and dry on a surface plate?

With fly cutting it's very easy to leave the surface concave if the mill isn't trammed perfectly. Personally I'd use a smaller endmill, say 10-13mm, run nice and fast. It should be as quick as flycutting, the finish might not look as pristine but will probably be just as smooth and the overall flatness will be significantly better if there is any out of tram.

Neil

Posted by Ramon Wilson on 10/11/2020 18:58:29:

If so bolt the topslide to your mill table, lock the gib and using a small cutter say 6mm-1/4" touch on in the centre area around the bolt hole and take very fine skims off until the milled area is all over - personally I would not use a fly cutter - despite the appearance of overlapped machining marks the face will be much flatter than if the fly cutter isn't perfectly true.

Been there, said that Neil

Flycutting is an easy way out, does give you a nice finish if the tool is right but does not, as you say, give you a perfectly flat surface. Possibly good enough for this instance but if it's on the mill why not carry out the job in a manner to ensure it is.

Ramon

If you must use the flycutter then take multiple passes with a small 5-6mm stepover which will eliminate any dishing caused by being out of tram.

Dr DMJN

I don't think I would try the abrasive paper, except perhaps as a very temporary expedient on just the block to see if it improves the grip. It seems to be the topslide surface which really needs improving. It takes a lot of rubbing to remove even a very few thou and some of those marks look quite deep. There is every chance of rounding the surface as you rub back and forth, especially so with the toplide which is an ungainly, unbalanced lump. An old timer would file and then scrape the cast iron surface flat to the surface plate, but that takes practice and more skill than most of us amateurs will ever have.

As you have a mill, it would be safer to mill back to a good surface as discussed in the last few posts. Or take up Duncan's idea and locate someone with a surface grinder.

Rod

I can mill it no problem, I assumed previous advice given on the 10V machining thread (back in May!) was to use fly cutting for flat surfaces like the box bed edges, sole plate and valve chest parts. I got a fly cutter and it seemed to work very well. Didn’t appreciate it could give a dished surface. Thinking more I guess that’s right. I must have been lucky, and/or trimmed the mill right, because it cut consistently over an area. In fact with some light clean up and a polish, I could wring the valve chest parts together and they’d stick. Much smaller areas though.

Anyway, Ill mill it, as you say less chance of flatness error.

Dr GMJN

Just a last thought.

Don't take off more metal from the topslide than is essential get a flat surface! The topslide needs to be stiff enough to resist the pull of the toolpost. A few marks left in the surface will not matter any more than the tapped holes for the grubscrews.

Rod

Thanks Rod, I’ll do it tomorrow - just enough off that shows some machining over the area.

Hello Doc, You may be interested in seeing this

I rebuilt this boiler some time back and fitted a new dome bush. Despite being careful it was not true to the vertical so had to be faced. As you can see, in order to get this as flat as possible I used a new 6mm FC3 cutter and stepped over taking the final cut in both directions

The dome that fits atop has a 2 mm Viton O ring for a seal so when I pressure tested it at 100psi and it seeped at this joint losing about 5 lbs pressure over 10 mins or so I felt the O ring groove may have been cut a tad too deep.

When I removed the dome to redress this I was surprised to find I had not fitted the O ring at all - the metal to metal surface taking that pressure and fundamentaly holding.

As said before the machining marks do not/may not look as cosmetic as a flycut surface but you can be sure that it is flat If the surface needs to be flat off the machine then this is much the better option. Stepping a fly cutter over as Jason suggests may be an option but it rather defeats the idea to my mind

Regards - Ramon

Edited By Ramon Wilson on 13/11/2020 22:52:31

The topslide surface on my ML7 is pitted almost identical to this and does not move under heavy loads. (.100" deep cut under power feed, parting, etc.) Although, I did give the surface a few licks with flat file to get rid of the slight raised up centre area that the clamping bolt had caused over the years. The pits themselves will not cause slipping. If anything, the edges might even provide a bit of extra grip! So when milling, don't try to remove all the pits. Just get the surface flat all across in general.

Im not sure if the pitting is from years of corrosion or if Myford did not machine all the orginal casting roughness away in the interest of leaving the top slide as thick as possible for maximum strength. So remove the bare minimum of metal required to get machining marks across the full width of the surface and don't bother trying to remove all those pit marks.

I would be more suspicious of your Far Eastern-made aftermarket QC toolpost. As we saw in the other recent thread about the "precision ground" test bar that ran 0.04mm out of true when checked, a lot of this cheap Asian tooling is very hit and miss on the quality control. Sometimes it is ok. Sometimes it is not. So you always have to check it to be sure.

ON this one I would check that the bottom face of the toolpost is machined dead square to the hole up the middle for the clamping bolt. The blue off to one side in your pics indicates it might possibly be sitting at a slight angle. If the hole for the clamping stud is a tight fit and not drilled dead square, the whole block could be sititng a tad cockeyed.

To check it, after machining your topslide flat and reinstalling the clamping stud and checking it sits square to the machined surface, smear a thinner layer of bearing blue on the topslide and then slide the toolpost down over the clamping stud. Rotate it back and forth about an eighth of a turn a couple of times then slide it off. You should get a fairly even blue reading all round the base of the toolpost block. If its all over to one side, its sitting cockeyed.

Also, I would take a Dremel and chamfer the edge of the clamping stud hole in the toolpost block so it can not bind there. The other smaller holes look like they could use a chamfer too as one has a bit of flue around it like the edge is possibly burred a bit and riding up.

Edited By Hopper on 13/11/2020 23:43:27

Edited By Hopper on 13/11/2020 23:49:21

Well, well, this thread has taken an interesting turn. I thought about saying I wouldn't use a flycutter as it doesn't leave a really flat surface, instead I'd use a corner radius endmill and multiple passes. I didn't do so as I assumed I'd be howled down by the pro flycutter lobby. Strange how things turn out.

Andrew

.

How very strange ... I had always assumed that Myford faced that top surface in a lathe

... That would certainly be my approach !

It is perhaps a near-perfect example of the merit of Schlesinger's test-requirement, for a lathe to face flat or very slightly concave.

MichaelG.

If we look back to some of his first posts the Doc was getting ridging when machining a flat surface quite possibly due to nod of the mill, someone else suggested a flycutter to give a better finish. Doc then started to use this in his 10V thread as it gave the "best* finish" and as it was being used with an insert tool coped well with the chill in some of the castings that would have blunted an HSS mill quite quickly.

Now if there is nod in the machine that may still allow the flycutter to cut a flat surface if only used in one direction be it with a slight tilt a milling cutter particularly flat ended will still leave the steps. As the areas where something like a valve travels are only something like 3/8 x 5/8 even if the cut were concave it would be so small as to not be worth worrying about, the use of gaskets on the mating faces has taken care of any other possible concavity. I'll flycut valve faces on smaller engines but have used the multiple pass method on larger ones using an HSS cutter, just a case of what suits the job ad what the individual machine is capable of.

* Best probably being visual

I agree with Hopper that it does look like the toolpost is not sitting flat but could that also be due to the stud leaning at an angle due to many years or pulling on a spanner to tighten the nut? I would say do the blue test again when the stud is removed.

As for the marks on the surface again probably years of use with this type of clamp and off bits of packing, you can certainly see a ring of indents with deep ones at 9 & 12 o'clock where the screw opposite the tool has made the deepest indents

I took what I thought was the conensus, and got on with it.

First things first: I checked the perpendicularity of the post (threaded spigot) and I couldn't see any deviation when checked with a square.

So then I machined the face: 10mm diameter mill, with 2mm radii (the only radiussed one I've got I think). Overlaping cuts, with the final cut taken at the same setting but at 90 degrees.

I put a DTI in the spindle and rotated it to check flatness. Difficult to judge due to the roughness, but it was within a couple of thou indicated. The bottom face of the casting was clean, as was the mill table.

This is after the first, minimal, skim on touching the surface near the centre hole:



Then this is part way through the final skim - 0.002" lower than the intial cut:



And the final finish - I'd estimate -0.003" in total:



Tried putting blue on the face - all results are after applying hand pressure and turning back and forth by a few degrees:



This was the initial impression:



Another go with the block blued:



The with Felt-tip:





And finally with it clamped with a spring and rotated back and forth a few degrees:





I can't explain the inconsistency in patterns. The block certainly feels "floaty", not what I'd expect for full contact over that area. Maybe it's becasue the block is sucha smooth finish. It doesn't feel "right" to me.

Perhaps I should mill the block as well?

The hole through the block on my genuine Dickson toolpost is 5/8" fitting over a 7/16" pin. It is bored even bigger at the bottom, then there is a short top hat bush at the top to centralise it. Is your block a good fit on the pin? If so is the hole square to the base?

I'll post some photos after I've walked the dog and raked up the vast quantity of leaves in the back garden

There is blue on the end of that round pin in the foreground. It could be riding up on that.

But if it's not that, you could put some blue on your surface plate or a piece of glass and rub the toolpost on it and see if you get the same pattern of reading, ie tending to be on the one side only. If it shows up on both sides, then the problem is most likely the toolpost has the hole for the clamping stud drilled crooked and its a too close fit so is holding the toolpost cockeyed. Solution, if the toolpost is not hardened, would be to bore it out five or so thou bigger.

Also, check what's going on in this photo with the narrow ring of shiny metal in the middle of your blued surface around the hole where the clamping stud sticks up. Is that the result of metal-to-metal contact there that has displaced the blue? (It happens, thus making the highest of high spots look like low spots to the unsuspecting.) Seems odd. You should have a good chamfer in the bottom of the toolpost hole to clear this area without binding. So the blue should be consistent right up to the protruding stud with no shiny ring.

Edited By Hopper on 14/11/2020 12:52:17

Edited By Hopper on 14/11/2020 12:58:17