Cutting left hand threds on a Myford ML7

Steve, it should be the same either way as the 18T is used as an idler (the fact that it's not 20 is not a problem, it could really have any amount of teeth and you would get the same ratio).

For instance, if you have a 20 tooth gear followed by an idler and a 100 tooth gear, the ratio will always be 5:1 irrespective of the number of teeth on the idler.

Any charts you have for RH will be fine for LH cutting. If you get bored, you can download my gear calc at

this will calculate any oddball ratios not on the charts.

DOH! Your right its obvious - it doesn't matter what the gear sizes are between the spindle and cluster gears - I wish I had thought about it more before asking.

Nice program though! beats my spreadsheet calculator.

Steve

---------------------------------------------------------- Steve Randall G8KHW snipped-for-privacy@btinternet.com UKRA #1072 Level 2

You are correct, but the error is insignificant.

Steve R.

Rubbish! There is no error significant or otherwise!

As Duncan pointed out the 18 tooth wheel is an idler and could be any size since its only purpose is to reverse the direction of drive and its size on the centre distances dictated by the physical design

Cheers Brian

If you have one tumbler gear that has two less teeth in the gear train

***there has to be a difference***! The error is divided by the rest of the train. This came up in Model Engineer in the 1970s. Someone from Myfords said that there was indeed an error, but it was insignificant, and was done to make the headstock more compact. If you calculate the numerical ratio from the spindle to the leadscrew for each tumbler gear, you will see a slight difference.

Steve R.

since its only

distances dictated

"Udie" wrote

Driver turns idler ratio D / I

Idler turns output ratio I / O

overall ratio = ( D / I ) x ( I / O ) = D / O

overall ratio is independent of the number of teeth on the idler.

-- Jonathan

Barnes's theorem; for every foolproof device there is a fool greater than the proof.

To reply remove AT

Was it an April 1st issue?

-- Steve Blackmore

No doubt Gareth will advise us that you should quote gear ratios in decibels.

Is this guy bein Pig Ignorant or do we have another Troll trying to wind us all up?

Cheers Brian

I don't think the first post was being ignorant just a case of being confused which is understandable.

The reply from Udie is total and utter bollocks. First off, if there was a difference of two teeth it would be far more than an ***insignificant difference*** Secondly after the recent posts between Chris with his brand new top of the range Myford Con-is-sewer and Myfords themselves I'd tent to disregard anything they say. If they can't sent a machine out with the right gear train on then they perhaps don't understand the reasoning behind all this.

I can post the calculations if anyone wants them and they work out exactly equal, either way. I can't see where Myfords can get this ***insignificant difference*** from. Their premises are quite sheltered so it can't be the wind and they aren't on a hill so gravity doesn't come into it..................................

-- Regards,

John Stevenson Nottingham, England.

Well, I may be mistaken on this, but there was some issue with a small screwcutting error. It may just be my faulty memory. After two bouts of cancer and attendant treatments, my memory does sometimes act up! The key will be in the tooth count of the cluster gear. My workshop is partly flooded at the moment, but I will count the teeth ASAP. If I am wrong I will admit to it! I never troll.

It has been over 20 years since there has been a need to cut a left-hand thread on my ML7! By the way, it was one of the first to have adjustable micrometer collars on the feed screws, and is a changewheel lathe.

it..................................

Steve, I am sympathize with you for your health problems, particularly as it must have robbed of many happy workshop hours.

I am glad you are not a troll, but you will be doubtless aware the "Unnamed One" has been raising a lot of blood pressure in this group, which is of course his sole motivation.

On the question of the Myford Tumbler Reverse (or any other one in the last 100 or so years), the only relevant gears are the Spindle Gear and the Cluster Gear. The other two gears are idler gears and do no effect the overall ratio which is exactly One to One in either position of the quadrant. On my Super Seven these are both 30 tooth hence

1:1. The idler gears have 30 and 28 teeth respectively but since they are only idler gears do not need to be considered in calculating the overall ratio.

I am sure that all the members in the group will join me in wishing you "happy swarf making".

Best Regards Brian

A very fair description of Mr.Stevenson. I am glad that I am not the only one who found his _PERSISTENT_ childish outbursts to be like a troll. I agree that his sole motivation is to raise blood pressure, and his unremitting campaign has been successful in that pursuit.

Let's keep this NG to what it is intended for, technical discussion upon matters to our mutual benefit. There is never any need for personal remarks, nor to lower the tone with the language of the gutter.

"Unnamed One" has been

The "Unamed One" could not possibly apply to John Stevenson as he always uses his full name and has valid email address. I was referring to you who never gives your name nor a valid email address.

Love and kisses Brian

On Tue, 11 Nov 2003 16:10:40 +0000, Ryan Breai wrote: GO AWAY IDIOT

Then you are mistaken. I am not a troll.

There is noth> > A very fair description of Mr.Stevenson. I am glad that I am not

Only raise a laugh. And at your expense Mr Lyon.

-- Regards,

John Stevenson Nottingham, England.

I must admit that I thoroughly enjoyed the beginning of the Blackgates castings saga, most entertaining! However the penny eventually dropped and I realised that it was just a massive advertising scam for Blackgates products. I then lost interest. However I did visit their web site and looked at their products, terms and conditions...etc. which I found most interesting so I guess the objective was achieved.

I do hate these modern advertising techniques, although I have to admit that they are effective. I prefer the traditional method of saying I bought the following products from company X and found them very good and their service friendly and efficient...etc. , but then I guess that I am just old fashioned

Cheers Brian

castings saga, most

products from

Brian, I understand that enquiries at London Zoo have also benefited from the recent "advertising" scam ;-)