Myford ML7

[prepman]

Well, I'm certainly not above making schoolboy mistakes, because that's what I am at the lathe, a schoolboy.

I had decided to cut this thread using the method shown in THIS VIDEO because it made sense to me that there would be less stress, and therefore less risk of twisting, if only one side of the lathe tool was cutting after the fine feed with the top slide.

If this is wrong, I'm afraid I'll have to ask for a bit more explanation, because it's not quite clear to me from the above ....

By the way, I had previously assumed that I was going straight into the workpiece at a 90° angle with the right chisel ....

Have a nice day

Carsten

--

Just looked at my Myford and now understand why you are confused. There's no datum mark on the side and scaled to 45 only, so you can't use it to dial in the angle. Neither did the man in the video. He used the profile gauge.

On the Colchester there is. It goes to 90. Set at ~60.5 degrees = 29.5 Metric

 

[25.4_mechanic]

BTW on purist pont (not one I rigidly follow) The cross-slide is set to slightly less than the 1/2 thread angle 1/2 deg. Think it's to ensure it cleans the trailing edge. So 29.5 and 27 or some such

The rear of the tool is relieved to not cut. Shown exagerated.

Forgive my ignorance, but a moment ago I thought I had understood.

Sooo, if we go by these pictures ....

... I should reduce the angle on the scale from 30° to 29.5°, i.e. point the top slide less steeply at the workpiece, but a little flatter. Correct?

This would ensure that I only cut on the side of the tool to which I feed in the Z-direction. Correct?

Turn your topslide to 90 degs and then subtract the 29.5 from it.

What?

When I put the top slide parallel to the bed, my scale shows 0°. From this position I can move the top slide 45° further towards the workpiece or I can move the top slide 45° away from the workpiece - but then I am already behind the end of the workpiece ....


Carsten

--

 

[Seadog]

Turn the compound so that it at right angles to the workpiece. Then back it off 29.5°

 

[prepman]

Turn the compound so that it at right angles to the workpiece. Then back it off 29.5°

You can't on the ML7. The gradients aren't there. In fact the dial fouls the cross-slide.

 

[prepman]

Forgive my ignorance, but a moment ago I thought I had understood.

Sooo, if we go by these pictures ....

View attachment 325371


... I should reduce the angle on the scale from 30° to 29.5°, i.e. point the top slide less steeply at the workpiece, but a little flatter. Correct?

This would ensure that I only cut on the side of the tool to which I feed in the Z-direction. Correct?



What?

When I put the top slide parallel to the bed, my scale shows 0°. From this position I can move the top slide 45° further towards the workpiece or I can move the top slide 45° away from the workpiece - but then I am already behind the end of the workpiece ....


Carsten

--

Because I rarely use the ML7 except for small work, I'm working from memory which ain't that good anymore. You can't use the scale as it exceeds the 45 deg limits. The man in video didn't use it although he did refer to it in passing. Pic 1 ML7 size part form insert. Whit I think? Pic 2 approximate angle you'll need.
Pic Gradients are over the side and my dial is fouling topslide.

 

[25.4_mechanic]

There's no datum mark on the side and scaled to 45 only,

I have a very faint line that you can see in the pictures and that I always refer to.

The question remains: 29.5° or 30.5° with my setup on the ML7 as shown?

Carsten

--

 

[prepman]

I have a very faint line that you can see in the pictures and that I always refer to.

View attachment 325396

The question remains: 29.5° or 30.5° with my setup on the ML7 as shown?

Carsten

--

No.... you need 60.5 for metric (60) and 62 for Whit (55), (if I've got 0.5 deg in the correct way round) the scale goes to 45 so you can to add to that by making another mark(s) at extra points. If you set the slide to zero and use the scale to find the extra degrees and make another mark(s) (centre punch?), then dial your 45 to that and voila!

 

[25.4_mechanic]

This Old Tony has a very good video on threading on the lathe.

He's very entertaining too.

Thanks!

That guy is funny and informative - I'll watch more of his videos I guess.

No.... you need 60.5 for metric (60) and 62 for Whit (55), (if I've got 0.5 deg in the correct way round) the scale goes to 45 so you can to add to that by making another mark(s) at extra points. If you set the slide to zero and use the scale to find the extra degrees and make another mark(s) (centre punch?), then dial your 45 to that and voila!

Stop.
Did you take into consideration that my toolpost is positioned so that I can set my turning tool perpendicular to the workpiece?

I will reconstruct this now and take pictures, then I will come back and it should only be 0.5° one way or the other ....

Carsten

--

 

[Pete.]

If you want a mark to line up 60degrees for threading simply put a scratch or pencil mark next to the 30 degree on the scale and swing the compound round so the OTHER 30 degree mark (or 30.5) lines up with your scratch.

 

[25.4_mechanic]

No.... you need 60.5 for metric (60) and 62 for Whit (55), (if I've got 0.5 deg in the correct way round) the scale goes to 45 so you can to add to that by making another mark(s) at extra points. If you set the slide to zero and use the scale to find the extra degrees and make another mark(s) (centre punch?), then dial your 45 to that and voila!

If you want a mark to line up 60degrees for threading simply put a scratch or pencil mark next to the 30 degree on the scale and swing the compound round so the OTHER 30 degree mark (or 30.5) lines up with your scratch.

The aim is to turn a small handle for the new central nut for the QCTP.
The thread should be M8x1.25.

First I turn the rod round and clean and down to 8mm.
In doing so, the tool is aligned perpendicular to the workpiece, the top slide is parallel to the bed, the scale shows 0°:

In the last recommended video on the subject, the author presents the required adjustment like this:

What strikes me now when I look at this picture again, however, is that the value the OM does show here does not represent a 29.5° angle either, it looks like more than an angle bisector, i.e. more than 45° ... mhhh ... that looks more like ~60° region to me ....


So this one would be 90° for me, the top slide is exactly aligned perpendicular to the workpiece, I have no way to clamp and nobody needs the parallel adjustment levers of which none can work in this position anyway:

Now I can try to turn the top slide back until I find the first clamping possibility, i.e. to bring the bottom slot into alignment with a T-slot underneath.
That would be about here:

And if the truth should indeed be 90° - 29.5° = 60.5°, then I could make something in the unguided vicinity .... if I'm able to measure it correctly ...

But I have my doubts: if I were to approach the workpiece so steeply, I would not be able to reach the target at all. Instead of gently widening the valley of the thread and thereby only loading one of the cutting edges of the tool, I would, on the contrary, be approaching the workpiece far too steeply and only aiming for depth.

Since the thread flank angle is 60°, i.e. the mountain, the valley is also 60°:

Accordingly, as I understand it, it would be nonsensical to feed with anything steeper than about half the opening angle. This is the only way to push the desired cutting edge of the tool towards the new, opposite lying flank that is still in the process of being created.

And we are back to the question: 30.5° or 29.5°?

Help me, I can't explain it to myself any other way .... Thanks


Carsten

--

 

[25.4_mechanic]

Additional question:
Since I don't have an original Myford four-jaw chuck, but this much too small one with jaws that are no longer completely intact ....
... Up to what size can I clamp on a four-jaw chuck (or any chuck for that matter)?

Many thanks in advance

Carsten

--

 

[brightspark]

my ml7 came with a 6 inch 4 jaw chuck and a 4 inch 3 jaw from new

 

[25.4_mechanic]

my ml7 came with a 6 inch 4 jaw chuck and a 4 inch 3 jaw from new

Then this should be approved (perhaps only not necessarily up to the peak speed?)!
Or does it mean that a four-jaw chuck has a better balance intrinsically?

Thank you very much.

Carsten

--

 

[Lewis_RX8]

Then this should be approved (perhaps only not necessarily up to the peak speed?)!

Thank you very much.

Carsten

--

Most big chucks will have their speed rating stamped into them or in a manual somewhere , Big clanky old 4 jaws for example probably wont be rated to spin over 800rpm

 

[25.4_mechanic]

Big clanky old 4 jaws for example probably wont be rated to spin over 800rpm

Thank you, Lewis!

Carsten

--

 

[Pete.]

The aim is to turn a small handle for the new central nut for the QCTP.
The thread should be M8x1.25.

First I turn the rod round and clean and down to 8mm.
In doing so, the tool is aligned perpendicular to the workpiece, the top slide is parallel to the bed, the scale shows 0°:



View attachment 325414View attachment 325415


In the last recommended video on the subject, the author presents the required adjustment like this:

View attachment 325416

What strikes me now when I look at this picture again, however, is that the value the OM does show here does not represent a 29.5° angle either, it looks like more than an angle bisector, i.e. more than 45° ... mhhh ... that looks more like ~60° region to me ....


So this one would be 90° for me, the top slide is exactly aligned perpendicular to the workpiece, I have no way to clamp and nobody needs the parallel adjustment levers of which none can work in this position anyway:

View attachment 325426


Now I can try to turn the top slide back until I find the first clamping possibility, i.e. to bring the bottom slot into alignment with a T-slot underneath.
That would be about here:

View attachment 325427

And if the truth should indeed be 90° - 29.5° = 60.5°, then I could make something in the unguided vicinity .... if I'm able to measure it correctly ...

But I have my doubts: if I were to approach the workpiece so steeply, I would not be able to reach the target at all. Instead of gently widening the valley of the thread and thereby only loading one of the cutting edges of the tool, I would, on the contrary, be approaching the workpiece far too steeply and only aiming for depth.

Since the thread flank angle is 60°, i.e. the mountain, the valley is also 60°:

View attachment 325431


Accordingly, as I understand it, it would be nonsensical to feed with anything steeper than about half the opening angle. This is the only way to push the desired cutting edge of the tool towards the new, opposite lying flank that is still in the process of being created.

And we are back to the question: 30.5° or 29.5°?

View attachment 325432


Help me, I can't explain it to myself any other way .... Thanks


Carsten

--

What I mean is that you need to swing the compound through 60 degrees (or 60.5) but your scale only goes up to 45 so you have to think outside the box a little. Put a mark on the cross slide at the 30 degrees on the left (marked in green in the pic). Now if you swing the compound so that the 30 degrees on the right lines up withe your mark you have turned it through a measured 60 degrees.

 

[25.4_mechanic]

What I mean is that you need to swing the compound through 60 degrees (or 60.5) but your scale only goes up to 45 so you have to think outside the box a little. Put a mark on the cross slide at the 30 degrees on the left (marked in green in the pic). Now if you swi

Thank you very much, Pete,

That's what I thought you said, but I didn't think it could work ... but I was wrong, it worked the second time (just about) and that's how I'm cutting the thread now:

I didn't want to make a permanent mark yet, hence this red dot - so I don't know the exact angle at the moment - but that'll do for now.

It works great.

I can't say I've quite got the hang of the 60.5° yet, but I'm doing it that way now and eventually I'll understand why, it was counter-intuitive for me at first.

It's all good.

Thank you all.

Carsten

--

 

[Pete.]

If that steel bar is stainless you're going to be lucky to thread that successfully - I wouldn't even attempt that setup. Even mild steel is going to be a push without a follow rest with that amount of overhang.

 

[25.4_mechanic]

If that steel bar is stainless you're going to be lucky to thread that successfully - I wouldn't even attempt that setup. Even mild steel is going to be a push without a follow rest with that amount of overhang.

Thank you for your vigilance, Pete!

It is soft steel of 8mm and of course I tried to apply the running tip first, but unfortunately it didn't fit:

The overhang is 42mm and I am very, very patient.
I adjust the top slide by 0.05mm with each pass and they come in at an angle.

With back gear, without hurry.

When turning down (without additional support as well) I was actually so careful and patient at the end that I ended up with only 0.002mm deviation over 40mm.
I found that quite ok, for now.

Thank you,

Carsten

--

 

[prepman]

Thank you very much, Pete,

That's what I thought you said, but I didn't think it could work ... but I was wrong, it worked the second time (just about) and that's how I'm cutting the thread now:

View attachment 325451


I didn't want to make a permanent mark yet, hence this red dot - so I don't know the exact angle at the moment - but that'll do for now.

It works great.

I can't say I've quite got the hang of the 60.5° yet, but I'm doing it that way now and eventually I'll understand why, it was counter-intuitive for me at first.

It's all good.

Thank you all.

Carsten

--

Great!