Tooling size for myford ml7?

[HopperParticipant @hopper]

Mine spins at 800+ according to a digital tacho i hooked up to it once. But has a 1hp motor with non standard A section pulley so has been 'souped up' at some point.

I had the old Drummond M Type geared up to 970 rpm for a long time and the white metal bearings did ok. Wouldnt want to go much faster though. I ended up dropping it back to 800 because it gave more useful lower speeds for what i used it for.

640 does sound a bit slow. It was a more leisurely world back then!

IIRC the standard ML7 motor pulley was quite small.maybe about 1-1/8" or something tiny like that.. So speed is easily bumped up with a larger pulley. 

Edited By Hopper on 12/05/2020 09:39:47

[SillyOldDufferModerator @sillyoldduffer]

Hi Shaun,

Part of the fun is learning the ropes!

An ML7 in good condition is a decent machine, but – like all machines – has to be used within it's limitations. Not serious in practice but the lathe was designed 80 years ago towards the end of an era when HSS tools dominated.

Lathes made before about 1900 were designed to cut with Carbon Steel tools. As Carbon Steels soften at about 200°C, early lathes are spindly affairs that cut rather slowly. No point in putting fast powerful motors on them because their bearings can't take the speed, and their frames bend. But, used slowly they produce accurate work.

Circa 1900, HSS hit the streets. HSS cuts without softening up to about 500°C, and can be worked 5 times faster than Carbon Steel, so 20th Century Lathes designed for HSS are much stiffer, heavier and powerful. During the 1930's it was found that carbides outperform HSS, and today's industrial machines are monsters, removing metal up to 30 times faster than HSS, and able to cut very hard materials. An ML7 isn't in this class, nor does it need to be! It's a precision machine, think scalpel rather than axe, used to make accurate parts rather than hack metal at maximum speed. Power – ¼HP is a bit low, ⅓HP reasonable, ½HP plenty and ¾HP over the top. Substitute patience and skill for brute force!

HSS can be sharpened on an ordinary bench-grinder. Mostly these are sold with grey wheels, coarse on one side, fine on the other, which is fine. Being a clumsy oaf, I'm not good at it, but grinding HSS just needs practice. Carbide inserts are an alternative; you can get HSS inserts, but the sharp carbide intended for non-ferrous metals works well on steel at ML7 speeds. They're available in bewildering variety, but the types sold by hobby suppliers are a good place to start. Inserts remove the need to sharpen, and I value their easy convenience. (About 80%)

Generally easier to get good finish with HSS because it can be sharpened. Carbide likes to cut blunt, and it produces an excellent finish when used to specification. But this is too much for most hobby machines, making it necessary to experiment sometimes.

Experts prefer to buy blanks and particular tools rather than sets, but I found a set to be a good way to start. With hindsight, a tangential toolholder is attractive, and Eccentric's Diamond Type comes with a jig to simplify sharpening even more.

Perhaps the best book on lathes available is Sparey's The Amateur's Lathe. Written in the 1950s, when the ML7 was new, the only disadvantage is it doesn't cover developments like carbide inserts. Highly recommended!

As you suggest, not all QTCP are well-made. My main objection though is value for money. First there's the tool-post itself, then the holders. I'd need 8 or 9 at about £20 each. Say £200, which is a lot of money compared with a handful of shims, especially as I don't change tools much. I've got better things to spend the money on, but others find them indispensable. Not necessary for a beginner, maybe later.

Dave

[Shaun BelcherParticipant @shaunbelcher81617]

Posted by SillyOldDuffer on 12/05/2020 11:01:49:

Hi Shaun,

Part of the fun is learning the ropes!

An ML7 in good condition is a decent machine, but – like all machines – has to be used within it's limitations. Not serious in practice but the lathe was designed 80 years ago towards the end of an era when HSS tools dominated.

Lathes made before about 1900 were designed to cut with Carbon Steel tools. As Carbon Steels soften at about 200°C, early lathes are spindly affairs that cut rather slowly. No point in putting fast powerful motors on them because their bearings can't take the speed, and their frames bend. But, used slowly they produce accurate work.

Circa 1900, HSS hit the streets. HSS cuts without softening up to about 500°C, and can be worked 5 times faster than Carbon Steel, so 20th Century Lathes designed for HSS are much stiffer, heavier and powerful. During the 1930's it was found that carbides outperform HSS, and today's industrial machines are monsters, removing metal up to 30 times faster than HSS, and able to cut very hard materials. An ML7 isn't in this class, nor does it need to be! It's a precision machine, think scalpel rather than axe, used to make accurate parts rather than hack metal at maximum speed. Power – ¼HP is a bit low, ⅓HP reasonable, ½HP plenty and ¾HP over the top. Substitute patience and skill for brute force!

HSS can be sharpened on an ordinary bench-grinder. Mostly these are sold with grey wheels, coarse on one side, fine on the other, which is fine. Being a clumsy oaf, I'm not good at it, but grinding HSS just needs practice. Carbide inserts are an alternative; you can get HSS inserts, but the sharp carbide intended for non-ferrous metals works well on steel at ML7 speeds. They're available in bewildering variety, but the types sold by hobby suppliers are a good place to start. Inserts remove the need to sharpen, and I value their easy convenience. (About 80%)

Generally easier to get good finish with HSS because it can be sharpened. Carbide likes to cut blunt, and it produces an excellent finish when used to specification. But this is too much for most hobby machines, making it necessary to experiment sometimes.

Experts prefer to buy blanks and particular tools rather than sets, but I found a set to be a good way to start. With hindsight, a tangential toolholder is attractive, and Eccentric's Diamond Type comes with a jig to simplify sharpening even more.

Perhaps the best book on lathes available is Sparey's The Amateur's Lathe. Written in the 1950s, when the ML7 was new, the only disadvantage is it doesn't cover developments like carbide inserts. Highly recommended!

As you suggest, not all QTCP are well-made. My main objection though is value for money. First there's the tool-post itself, then the holders. I'd need 8 or 9 at about £20 each. Say £200, which is a lot of money compared with a handful of shims, especially as I don't change tools much. I've got better things to spend the money on, but others find them indispensable. Not necessary for a beginner, maybe later.

Dave

 

Thanks for that info.

I may well just use the lathe without a fancy QCTP for now anyway.

I have just finished machining a new feedscrew for my lathe today, using the cheap chinese carbide tools off ebay, they didnt do the greatest job and I had to improvise with shims(see photos!) but considering this, im still quite impressed with the finish.

I had to change tooling about 3 times, the parting tool i bought was supposed to have had the correct holder for an ML7, but it still needed heaps of shimming. This is the parting tool ive got, it seems to have a nice sharp carbide blade that has not gone blunt, but it takes ages to cut a part off!

I still really dont know alot about the different types of tooling, im really still learning at this stage.

I did have trouble making too deep cuts, probably taking off about 1-2mm max in one pass is about the most it can handle. Also it would also seem to slip rather than cut at times leaving uneven surface (see photo) I wasnt making a very deep cut when this happened, so not sure what was going on here.

All in all the finished part seems OK considering. Will be great to get some decent tooling anyway.

Edited By Shaun Belcher on 12/05/2020 12:29:00

[Robert ButlerParticipant @robertbutler92161]

Perhaps the packing was an issue and the speed range for a Super 7 and an ML 7 is NOT the same!!!! Robert Butler

[HopperParticipant @hopper]

Came up pretty good for your first job. Finish is probably a factor of those brazed carbide tools not ideal for brass and job sticking out of the chuck a bit too far.

You should get yourself one of these LINK

It's the best aid to machining in the old Myfords that money can buy. Worth its weight in gold.

[Shaun BelcherParticipant @shaunbelcher81617]

Posted by Hopper on 12/05/2020 23:46:24:

Came up pretty good for your first job. Finish is probably a factor of those brazed carbide tools not ideal for brass and job sticking out of the chuck a bit too far.

You should get yourself one of these LINK

It's the best aid to machining in the old Myfords that money can buy. Worth its weight in gold.

I wondered about that, my main concern was if there was play or wear on the bushings, i couldnt feel any movement out of it, so think thats OK, I was hoping I could have used the tailstock on this, but where I was cutting didnt allow the tailstock to reach.

I think I will definitely grab some HSS tooling soon.

I have seen that book thrown around quite a bit on here, so I may as well get a copy.

I have been recently given a couple of books titled "Newnes complete lathework" volumes one and two, they look well written, probably published in the 1950s or 1960s, dont see any date anywhere, but would be around the right period when myfords were popular.

It mentions some interesting materials for cutting tools such as stellite alloy.

[Allen NorrisParticipant @allennorris97892]

Reference above to the Eccentric tangential tool prompts me to enquire which size tool holder people have found most suited to the ML7 with the standard clamp down tool post? The Eccentric website refers to measuring the centre height to base of tool post height which as referred to above is around 15-16mm. Eccentric seem to do a 16mm and also a 12mm. Would I be correct to assume that thicker would be better as it would be more rigid? I can see that 16 might be ‘too close’ for comfort and that 12 mm might therefore be preferable but does anyone have any experience to share?

I had also wondered whether one should just stick to 8mm as per the normal HSS tooling but other than the possibility that such a tool would fit in a QCTP should one decide to go down that route at a later date I can’t really see any advantage to doing so. Any thought please?

Thanks Allen

[V8EngParticipant @v8eng]

I do not have a QCTP so cannot help on that but I do find that most tools need some spacers on the standard toolpost unless you have the optional Boat type tool set.

The Maximum speed of a factory fresh ML7 was 1280 RPM when fitted with the 2 speed 3/4 HP motor and Tri Leva attachment.

Please excuse the picture quality (or lack of).

Edited By V8Eng on 13/05/2020 11:21:07

[Michael GilliganParticipant @michaelgilligan61133]

Posted by V8Eng on 13/05/2020 11:19:28:

[…]

The Maximum speed of a factory fresh ML7 was 1280 RPM when fitted with the 2 speed 3/4 HP motor and Tri Leva attachment.

[…]

.

That’s creeping-up nicely from the 1000 mentioned on lathes.co.uk

MichaelG.

[Nick Clarke 3Participant @nickclarke3]

Posted by Michael Gilligan on 13/05/2020 18:53:33:

Posted by V8Eng on 13/05/2020 11:19:28:

[…]

The Maximum speed of a factory fresh ML7 was 1280 RPM when fitted with the 2 speed 3/4 HP motor and Tri Leva attachment.

[…]

.

That’s creeping-up nicely from the 1000 mentioned on lathes.co.uk

MichaelG.

And if such a thing as a 2 speed 60Hz motor existed in the US it would go up to 1570 rpm?

[Shaun BelcherParticipant @shaunbelcher81617]

Thats interesting to know.

Do you know if the newer models with bronze bushings can handle higher RPM than the older white metal bushings?

[Author]

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