Myford ML10 Fine Feed Gearing Help

[messy457Participant @messy457]

Hello Everyone,

What’s the finest power feeds I can achieve with this machine, what gearing is required and what gears where?

I’ve got a 0.2mm radius polished carbide insert designed for aluminium and some 2011 aluminium on the way for testing.

I’m giving it the best chance I can to get a great finish.

[messy457Participant @messy457]

I know you can do the 25, 65, 20, 70, 20, 75 for a .0037. However, how do you work out the optimal for best finish and speed?

I’d assume there’s an equation for nose radius and feed so the nose goes over itself or is slower always better?

[BazyleParticipant @bazyle]

I guess you can calculate it but most people just try it and see what happens. With HSS don’t forget the oil. Don’t know about carbide as some say it is important to be taking a proper cut at supersonic speed not skimming half a thou like you can with HSS.

[bernard towersParticipant @bernardtowers37738]

If you use the ground carbide inserts you can take fine cuts but feed rate has to be quite high. I often use RCMT06 ground inserts for a finish cut and it amazes me how high the feed rate has to be.

[Howard LewisParticipant @howardlewis46836]

The normal technique for setting a fine feed is to arrange the changewheels to give the largest possible reduction ratio between spindle and Leadscrew.

Something along the lines of 25:75/20:80. With a 8 tpi Leadscrew, this would give a feed rate of 0.0104″ per rev, which seems a bit high.

Personally, I would be aiming for something nearer 0.004″/rev, if possible, which means using the smallest ones as drivers, and the largest as driven

On a mini lathe with a 16 tpi leadscrew, for instance, 20:80/20:80 gives 0.0043″/rev.

HTH

Howard

[mgnbukParticipant @mgnbuk]

Was there a fine feed cluster gear available for the ML10 ?

These were available for the ML7 (Part number A1974) and Super 7 (Part number A1974A) but I don’t have any info on the ML10.

Bradley’s Myford series 7 Manual (page 86 in my copy) describes the ML7 fine feed cluster gear as being 12 / 25 teeth & the Super 7 version as 12 / 30 teeth, giving a fine feed down to 0.0018″/rev when used in place of the standard cluster gear on the tumbler reverse pin. Both are shown on the Myford spares site, though are a bit spendy.

I’m pretty certain I have one of each that were bought many years ago & not used. IIRC I bought the ML7 version in error from an ME Exhibition & the S7 one from Myford Beeston Spares counter. If I can find them, one or both could be available for rather less than the current price.

Nigel B.

[Martin of WickParticipant @martinofwick]

Was there a fine feed cluster gear available for the ML10 ?

Simple answer – No.

Not sure if it is possible to get some larger change gears and configure the following spindle 25/80 x20/85 x20/90 x0.125

That would get you about .002 thou, but may not be possible, reasons of fit, mesh etc etc

 

[Michael GilliganParticipant @michaelgilligan61133]

Might be time to consider putting a stepper motor on one end or t’other of the lead-screw.

MichaelG.

[Martin of WickParticipant @martinofwick]

I think he means a stepper motor + spindle encoder + driver + arduino and software (or other magic box arrangement for integrating spindle and leadscrew).

Unless you are able to tell the speed of a rotating leadscrew just by looking at it.

[Michael GilliganParticipant @michaelgilligan61133]

Oh for pity’s sake !

We’re talking about a Fine Feed … it just needs a stepper and a very simple driver.

MichaelG.

.

Edit: __ or you could use a windscreen wiper motor, or employ a young lad  to turn a handle.

[BazyleParticipant @bazyle]

If you have access to a 3D printer you can make a cluster gear of your choosing, perhaps with prime number teeth to spread the wear.

[Michael Gilligan]

On Michael Gilligan Said:

Oh for pity’s sake !

We’re talking about a Fine Feed … it just needs a stepper and a very simple driver.

MichaelG.

.

Edit: __ or you could use a windscreen wiper motor, or employ a young lad  to turn a handle.

Exactly, it would also avoid a lot of fiddling about when you want to swap back to screwcutting

[Martin of WickParticipant @martinofwick]

I tend to prefer simple solutions when they are available.

To answer the OP original question regarding finish using  a 0.2mm radius cutter, or .008 thou, the included ML10 change gear set 25/65 20/70 20/75 gives an advance of .004 which should provide adequate finish for Al. Wider tip inserts are available. As are larger change gears. If higher finishes are required I would use a HSS cutter ground to give an angled shearing cut.

The great benefit of change gears is they provide the quickest, simplest way to link the leadscrew speed to the spindle speed, which an independent leadscrew drive does not. Once change gears are set up a consistent feed is available at any spindle speed.

If the ‘electric carving knife’ type solution is required, motorise the leadscrew no problem, you just have to make sure that for each job you know the spindle rpm, then calculate the required feed per rev and then fiddle about setting the leadscrew rotation to provide that feed using the  ‘simple driver’. Simples!

And unless you only ever cut one pitch of thread, you will always have to faff about swapping change gears for screw cutting, and if that is too onerous a task for you, then the best solution would be a fully electronic leadscrew implementation.

 

[messy457Participant @messy457]

Morning,

From what I’ve read half nose radius seems to be the sweet spot between speed and finish just trying to get opinions.

I thought the slowest gear ration made sense but again just confirming as very new.

In regards to stepper motors and printing gears I do have the understanding and printer to do such a thing however, like to keep this as “stock” as possible. Plan is to get a more substantial lathe down the line in which I’ll modify as plan on keeping that long term. Got a Harrison M250 in the works if all goes well.

[Michael Gilligan]

On Michael Gilligan Said:

Might be time to consider

Well those five innocent words prompted more reaction than I expected

… Wow.

MichaelG

[HowiParticipant @howi]

i have had a simple electronic leadscrew fitted for a few years now. it is purely for altering feed rate as it does not have a spindle decode, but uses a simple spindle rev counter fed into an Arduino. The change gears and banjo have been removed which makes the lathe much quieter when running but can be replaced if I ever needed to cut large threads (highly unlikely but the option is there.

Metric and imperial is available with 0.02mm being the slowest feed rate, using change gears the minimum feed rate was 0.08mm.

The banjo and change wheels sit on a shelf gathering dust!

 

[SillyOldDufferModerator @sillyoldduffer]

Noting that the Myford ML10 isn’t famous for producing poor finish as a result of an inadequate set of change gears, I suggest there’s a simpler answer – technique!

My favourite lathe book is Sparey’s “The Amateur’s Lathe”.  Chapter 6 contains many wise words on lathe tools, including this diagram showing how to get a good finish by setting a sharp knife tool up with a rubbing action:

If the knife point is presented conventionally at 90° to the work, it cuts rapidly, which is ideal for roughing out, but may leave a poor finish such as a faint spiral in an obviously torn surface. Sparey’s answer is to present the knife to the job obliquely on the final pass so the knife rubs as much as it cuts.  Finish is improved by setting the cutter to have a pronounced burnishing action.  Rubbing tends to flatten the spiral peak into the spiral valley whilst also polishing over tears and smudges.  Job done!

Poor choice of steel may be an issue.  Ordinary mild-steel is popular because it’s cheap and readily available.  Unfortunately it’s intended for structural work and doesn’t machine particularly well.  As ordinary mild-steel often tears and smears rather than cut cleanly, it’s better to cough up for a free-cutting steel like EN1a-Pb whenever a good finish is needed.

Same principle applies with carbide – not their intended purpose, but a gently applied large radius blunt insert tends to burnish whilst cutting.

Try it and see.  Though ML10’s fine feed is a little coarse, I don’t believe Myford got the design so wrong that it’s necessary to buy new gears, or to fit an ELS.

Dave

 

 

[Martin of WickParticipant @martinofwick]

Howi,

I’m amazed – and does it cut threads accurately and repeatably?

When you say ‘a simple spindle rev counter’  how simple?   Just a hall effect sensor  (would not have thought that would be precise enough). Or do you really mean a relatively sophisticated rev counter but not an actual encoder.

 

[bernard towersParticipant @bernardtowers37738]

Personally I use 0.4 radius for finishing and 0.2 for roughing. Or what has been said earlier try a skiving tool.

[bernard towers]

On bernard towers Said:

Personally I use 0.4 radius for finishing and 0.2 for roughing. Or what has been said earlier try a skiving tool.

On Martin of Wick Said:

Howi,

I’m amazed – and does it cut threads accurately and repeatably?

When you say ‘a simple spindle rev counter’  how simple?   Just a hall effect sensor  (would not have thought that would be precise enough). Or do you really mean a relatively sophisticated rev counter but not an actual encoder.

 

while in theory it will cut threads, i would be reluctant to try. The problem is that when cutting the lathe spindle will slow down due to the limited power on our small lathes.

A hall effect sensor is attached to the spindle to act as a rev counter and fed into the arduino.

From there it is a simple bit of maths to work out the leadscrew speed based on stepper steps and ratio of stepper reductioin to leadscrew.

The display shows imperial or metric feeds/threads and has forward/off/back control.

The stepper I have used is probably more powerful than it need to be and is coupled to the leadscrew via a toothed belt system,

It was based on an idea I found on the internet which I modified quite a bit, but essentially is still a SIMPLE ELS, but it works for me

[duncan webster 1Participant @duncanwebster1]

It’s fairly easy to arrange an ‘electronic gearbox’ to keep leadscrew speed some set ratio of spindle speed, which is what I suspect Howi has. It is much more difficult to keep them in synch so you can screwcut. Swapping a gear train between different Tpi is much less faff than swapping from fine feed to screwcut, and the lathe is a lot quieter without all those exposed gears whirling around

[Author]

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