ML7 toolpost - Turns Under Load

Is the threaded post a larger diameter at the bottom than the threaded part ? If so are you sure that the tool post block is not clamping against the step on the post rather than the top of the top slide ?

Les.

Rod, my assumption about the grub screws was because their holes are orientated such that when the toolpost stud is pushed up, the o/d of it’s lower flange (with the anti-rotation pin) bisects the holes. The holes are fully threaded such that each grub screw simultaneously engages with the top part of the casting (by about 8mm) and lower down with the casting and the stud flange. This means that the grub screws , whether by accident or design, prevent the pin from moving down. Surely the ratchet would be a one-time fitment, and you’d just clean any swarf out of the holes as a routine part of fitting?

Not saying your wrong at all, just that it seems an elaborate way of just blocking some holes against swarf. Why not just drill and tap the holes through the top 8mm face and thread that? Seems like an unnecessary step in production to fit the stud before drilling and tapping, and presumably need special tooling to drill and tap so close to the stud.

Thanks Les, the stud is parallel sided.

Thanks all. I think it’s a flatness/friction issue. I’ll re-check with some blue as Jason suggested. I was pretty sure it was flat, but clearly something is wrong. Might try the aluminium washer too.

Dr GMJN

Hmm... perhaps I was being rather dogmatic, sorry about that.

Perhaps Myford changed the design from time to time.

On my 1980s vintage Super Seven the grub screws are only 1/4" long and they do not engage with the flange of the toolpost. The exploded parts diagram of my handbook gives the Part Number for the grubscrews as MY2811 and specifies them as 1/4" x 2 BA, and as i have had this lathe from new I am sure they are original.

The ratchet of my 4 way toolholder came with 1/2" long countersunk head screws and instructions to remove the grub screws and use the longer screws to secure the ratchet. The ratchet is 1/4" thick so the longer screws also do not engage with the flange of the toolpost.

I also have a 1960s(I think) vintage ML7 which has had many owners and the grub screws on that are missing altogether, but the toolpost seems quite firmly fixed. I can't find the handbook but the arrangement seems very similar to the Super 7.

Or perhaps

If your grub screws are longer and do engage with the flange, I wonder if this is a modification done by a previous owner perhaps because he/she had lost the original grub screws or perhaps because the toolpost had become loose- otherwise I can see no need for the pin to prevent rotation of the flange/ post. The pin is shown clearly as Part Number 75/1411 on the exploded diagram of the Super 7 so I think it is fairly certain that the pin is intended to be there.

What do you think?

Rod

Rod, I don’t know. There is an ML7 toolpost modification video on YouTube, and the post flange looks to be drilled exactly like mine. My assumption was they’d separated the rotation constraint (pin) and the vertical constraint (screw threads) so as to avoid loading the grub screws such that they might try to ‘cam’ out of their holes under rotation of the flange. May well be wrong. On mine I had to tap the post out with a hammer. The entire inside of the casting along with the flange appeared to have been painted great after assembly. The paint flaked off the interface on disassembly.

ETA my ML7 is 1966. I doubt very much that the post would ever have dropped on its own. It took a decent few whacks with a copper hammer to loosen it.

Edited By Dr_GMJN on 11/11/2020 22:44:33

The toolpost on my lathe clicks in and locks in any one of four positions.

I thought all toolposts were like that ??

Dr GMJN

Bit of a mystery then.

It sounds very much as if your lathe's toolpost has not been disturbed or loose since the lathe was built and painted so it's not clear why anyone would feel the need to modify it's fixings. Perhaps some Myfords were built like that.

When I thought your toolpost might have become loose and then been fixed it occurred to me that perhaps the toolpost was not secured precisely vertically and that might lead somehow to the the loosening toolblock. That now seems unlikely, but perhaps worth checking anyway?

Good luck with the lathe anyway, they are good solid machines of their type and size and with reasonable care they outlast several generations of users.

I have never heard of one like Larry's and I can't think why that would be useful, unless Larry is referring to what we might think of as a tool block or holder rather than the post (It's only a bolt really) on which the block or holder rotates. Perhaps Larry will explain.

Rod

My lathe has a sort of dog clutch under the toolpost:

In conjunction with a mating plate under the 4-way toolpost it allows one to index the toolpost every 9°. It's a really useful feature:

• When parting off I know the toolpost is perpendicular to the lathe axis without needing to measure and the tool is not going to move whatever the cut.
• For non-critical chamfers it's easy to lock the tool at a convenient, but repeatable, angle
• When reseting the tool from chamfering, accurate positions on the dials are maintained, at least to a thou or so

Andrew

The one I made while at school for my Unimat had a similar arrangement to Larry, The 4-way post sits on a plate that has 4 shallow holes, the post has a hole with a chamfered and sprung pin so as you turn the post round (one direction only) the pin will index it 90deg.

The Multifix type being discussed elsewhere have a similar arrangement to Andrews and I have also see a ratchet type arrangement that has a sprung pin coming in from the side.

My ML7 with a 4 way toolpost had a 4 tooth ratchet attached to the Top Slide into which a spring loaded pawl (Mounted horizontally, from memory, within the body of the 4 way toolpost ) engaged to prevent rotation.

Howard

I think we may have a confusion of terminology here.

Myford call the bolt on which their 4 way toolholder (or quickchange toolholder block) rotate the "Toolpost". It is fixed into the topslide casting, and it's really just a pivot, plus a way of securing the actual toolholder once it has been rotated.

The last 3-4 posts seem to be referring to what Myford call " toolholders" rather than the pivot bolt itself - which Myford calls a "Toolpost". Most of this thread has been dealing with a Myford lathe problem so we have been conversing in "Myfordspeak"

I think that's right, and hopefully a bit clearer!

Rod

I took the words "tool post block" to mean the four way toolpost, as did several others it seems, judged by the comments on the ratchet wheel under the toolpost.

Sadly, I have seen two instances of Myford fourway tool posts being sold without the ratchet wheel, spring and pawl.

Which is what it seems has happened to the OP.

For what little comfort it may be my far eastern lathe has a positive stop system to resit cutting forces. BUT if the Toolpost, rather than the Top Slide, is set at angle for, say, a quick and nasty narrow chamfer, it does not move if clamped securely.

Lacking the ratchet and pawl, may I suggest checking that the clamp is not bottoming out and limiting the applied force, on the 7/16" stud and nut?

A few minutes checking and modifying may improve matters, as long as 0.250" a side cuts with a high feed rate, and a blunt tool, are not being attempted. It is a ML7 not a 21" Dean Smith and Grace.

Howard

Edited By Howard Lewis on 12/11/2020 17:46:28

Andrew,

That's exactly what I'd be looking for: Allows solid location, but also allows some incremental rotation to orient tools to clear existing part geometry or tailstock centres or whatever. Never seen one for an ML7 though.

Thanks.

Rod,

Actually no, you're right: I stripped it all down again just now, and the grub screw holes in the casting are drilled and tapped as I said, through the depth of the face and partially on the counterbore interface, but the tool post "spigot" flange is NOT threaded. So I was wrong - the grub screws play no part in securing the spigot either axially or in rotation.

Apologies - the frequency at which what I thought I remembered is at odds reality is definitely increasing.

So this might explain things better

Toolpost in-situ:



Removed:



I wonder if the unused hole was meant for a locking pin? There's obviously no corresponding hole in the casting, and unless there was an array of holes, I'd be stuck with a limited number of positions, which isn't really what I want.

So as suggested I applied some blue, and clamped it down (without turning it). Seems like it's only conatcting over a small area:





Strange becasue I can't get either part to rock on the surface plate. Maybe there's some pull-up effect going on when it's tightened.

I guess back to the wet and dry...

Not sure why the photos are rotated at random.

Ah, a QCT, but a pretty badly battered combination.

The fact that cutting forces move it says that the clamping force between the Tool Holder and the Top Slide is insufficient.

Given the condition of the surfaces, that is not surprising, since the contact areas are greatly reduced.

Ideally, both surfaces should be ground or machined to clean up and get rid of the damage.

The least that I would try to do is to strip the Top Slide (Being Cast Iron ) and machine the surface flat to get rid of the dents. If the central bush is proud, that will also get rid of it standing proud.

If you don't have a mill. with some ingenuity, you could possibly mount the Top, Slide on a Faceplate, or possibly even in the 4 jaw, and machine it flat again. But it must be clocked level,as far as you can, given the deep indentations.

Maybe carefully gluing a shim to it,l to cover the many dents may help clocking?

Once clocked level, you take light cuts with a slow feed, with a HSS tool until the surface is acceptably clean.

Being cast iron, it will be a dirty job. Place a magnet beneath some newspaper under the chuck in the hope of collecting some of the swarf.

The Tool Holder may be hardened , in which case you have a long time to spend grinding it flat on emery on a surface plate.

Does that bush around the central post stand proud of the Top Slide, even by a thou or two? If it does, it may be bearing a lot of the clamping force applied by the handle.

If you do want, or cannot restore the surfaces, you will have to resort to bodge methods.

Even if you have to use a grinding point in a Dremel, it might be worth putting a chamfer around the hole in the tool holder, to prevent any interference.

Failing that, you could interpose some thin soft material (Copper, Brass or Aluminium shim ) between the Top Slide and the Tool Holder. Hopefully, being soft, when clamped it will be deformed to fill the many indentations in both. But having undamaged faces would be preferable.

In the past, someone has neglected and abused the machine, and you have to deal with that to have it behave as it should..

However you go about it, the centre height of the tool will, need to,be reset, either to take account of the Tool, Holder being lowered by the remachining processes, or raised by the shim interposed between the scored and dented surfaces.

Which method are going to adopt?

Hopefully, after all the hard work, you will have moved it from a total sow's ear nearer to being a silk purse.

Howard

Thanks Howard. It’s actually only the casting that’s pitted - the tool holder is pretty much perfect (I bought it when I got the lathe). It looks bad because the blue has transferred all the casting imperfections, that’s all.

There’s no bush to stand proud - the column doesn’t rotate. What you’re seeing is where the chamfer around the toolpost hole hasn’t transferred any Blue to the casting around the pin.

The tool holders are knurled for height adjustment, and locked with a caphead bolt. I routinely adjust tool heights if I change insert types or if I have to swap tools and have run out of holders.

I’ve got a mini mill, so I’ll probably fly-cut the cast surface and be done with it.

Strange because I can't get either part to rock on the surface plate. Maybe there's some pull-up effect going on when it's tightened.

Can't help thinking that the post might not be straight. Is it better without the top sleeve washer ?

I have identical QCTP blocks used on my Super 7 and ML7 lathes. Mine do not rotate under load even on my homebuilt topslides (GHT retracting etc) so it must be down to the poor surface on the OP's topslide. Clamping nut does need to be tight.

With the OP's topslide bolted to an angle plate, it might be possible to flycut a decent surface using his lathe, or indeed his mini mill..

Edited By KWIL on 13/11/2020 10:50:50