New Myford Owner with Problems!!!

[Richard Bartholomew 3Participant @richardbartholomew3]

Hi everyone, I have just bought a beautifully preserved ML4 which is missing some parts.  Am working on those issues, but one key piece of info I am seeking advice on is that the twin-gear Cluster which operates the backgear has been lost!   The twin-gear cluster on the Spindle (Mandrel) has teeth totals of 54 and 20, and my query is this:  MUST the operating Backgear lever cluster match EXACTLY these teeth numbers , or might some other combination be just as effective as long as “Meshing” distances are the same??? Lord knows how easy/difficult it may be to source such ‘old’ parts, but don’t want to limit any options if more than one combination could work.

Over to you all please? Any advice welcomed,

Richard

 

[BazyleParticipant @bazyle]

The backgear layshaft will have a different number of teeth but they must be in the correct proportions to ensure the centre to centre distance is correct both ends. Read about ‘diametric pitch’ to understand the concept behind gear teeth sizes and how that makes it easy to calculate gear sizes.

[Martin of WickParticipant @martinofwick]

Determine the DP of the gears you have.

measure the approximate centre distance from the back gear cluster shaft to mid tooth distance of each of two gears on the spindle and calculate gear teeth using the DP calculated in step 1.

Or find a manual on line/ ask on google myford forum.

[Brian WoodParticipant @brianwood45127]

Richard.

The ML4 bull wheel with the 1 inch bore on the lathe spindle, also called the mandrel, was 65 teeth and in cast iron. These wheels often have broken teeth. From memory, the second gear, probably 20 teeth, was in steel and secured to the cluster pulley set that ran on the lathe spindle.

The other part of the back gear was on the swinging cluster that could be brought into mesh with these two gears to give a reduction through the set of able 7:1, that may not be exact

You should be able to measure the centre to centre distance mandrel to swinging cluster an, all divided d use the formulae in Ivan Law’s book on gear cutting WPS 17

The relevant ones are Centre to Centre distance, in inches, is PD of gear 1 x PD of gear 2, all divided by 2.

PD = Pitch circle Diameter measured in inches and sum of PDs of two mating gears is 2x the centre distances between them

I have a few new bull wheels to Myford spec if you are in need of a replacement

Regards   Brian

[SillyOldDufferModerator @sillyoldduffer]

Um, depends on what you do with the lathe.

Exact ratios don’t matter when set-up to do a fine feed, that is pulling the cutter slowly and steadily along the work to get a good finish.

Correct ratios matter when thread cutting!  Close as possible to get the correct turns per inch or pitch, otherwise nuts won’t screw onto bolts without jambing.

Best answer is to find a correct spare if you can, because sooner or later you will need to cut threads.  Parts from scrap Myfords pop up fairly often on ebay etc.   Or someone here might have what you need.  Luck of the draw stuff, so keep looking.

3D-printing opens many doors.   Rather than looking for original metal gears, find the specification and print plastic ones!  Won’t last as long as metal, but serviceable.  I don’t know what gears where provided (how many, number of teeth, diametric pitch etc),  but I’m sure somebody does.   If all else fails proceed to lathes.co.uk and cough up for the manual!   Then a friend with a printer or a commercial  firm can be sent the model.

Also possible to buy new metal gears of the correct gear profile and modify the bore and keyway to fit.  This firm is an example.

Dave

 

[jim1956Participant @jim1956]

>  MUST the operating Backgear lever cluster match EXACTLY these teeth numbers , or might some other combination be just as effective as long as “Meshing” distances are the same??

 

With Myford gears you can just work with tooth count.  My backgear was 25T-60T

but I could have replaced this with a 35T – 50T or a 30T – 55T.  Obviously the backgear ratio would have reduced but the centre to centre distance would be the same.

The formula for diameter is toothcount+2 / diametric pitch (20 for Myford)

25/60 is 1.35 +3.1   35/50 is 1.85+2.6  both adding to 4.45

Just using toothcount can be handy for working out if something will fit on the banjo, on my older Randa (which uses Myford gears) the largest I can fit from top to leadscrew is a 50T -65T adding to 115.  It’s easy to then see that with a 40T in one position a 75T will fit in the other.

Regards

Jim

[Julie AnnParticipant @julieann]

The centre to centre distance for two spurs gears is the sum of the two pitch circle diameters (PCD).

PCD = toothcount/DP

The formula:

(toothcount+2)/DP

gives the outside diameter (OD) of the gear. The centre to centre distance is not given by the sum of the ODs as the teeth on one gear extend beyond the OD of the other gear.

Julie

[duncan webster 1Participant @duncanwebster1]

The centre distance is the sum of the pcds/2

Backgear ratio won’t affect screwcutting as that is driven direct off spindle

A bigger problem is pressure angle of the gears, some lathes use 14.5 degrees (I think) whereas modern gears tend to be 20

[Howard LewisParticipant @howardlewis46836]

Back Gear will not give a fine feed. It reduces the speed of the Spindle by about 1:6, by the double reduction. Since the Spindle is rotating more slowly, the feed will be slower, but still in the same ratio set by the changewheel train.

The gears are likely to be 20 DP, and if you measure the pinion, and bull wheel on the Spindle, and the centre distance of the back gear spindle from the Spindle, the tooth counts and the centre distance can be used to calculate the tooth counts of the gears on the layshaft.

The OD of the gears might enable you to calculate the tooth counts. ID in inches = (Tooth count + 2)/20, rather than  counting teeth.

It might then be possible to make a back gear shaft, carrying gears from a later 7 Series machine.

(The gears are the same 20 DP and 5/8″ bore, but will need to be keyed to the shaft in some way).

HTH

Howard

[Charles LamontParticipant @charleslamont71117]

I feel sorry for Richard, given the amount of confusion, misinformation, irrelevance, and failure to RTFQ in some of the above posts, fortunately corrected by others.

[BazyleParticipant @bazyle]

Indeed Charles. I hope the OP will do a little research and learn to understand gears a little and not give up in despair. Growing up with Meccano is so useful.
Anyway lets try again.
You have a large gear on the spindle (bullwheel) of 54 teeth. Imagine you mesh that with one of 25. Now add the two together giving you 79. The small gear you already have on the spindle of 20 must be meshed with a gear that give the same total, so you need 79-20 = 59. The two pairs must add up to the same total to keep the centre to centre distance equal.
However 59 is admittedly a bit of an unlikely number to get hold of but 60 is a favourite so that would dictate your sum to be 60+20 = 80. So go back to your initial pair and calculate 80-54 = 26. Would that be easier to find perhaps? You can go round this loop finding the combinations that will work.

However in a day or so someone who actually has an ML4 will check theirs and tell you the original parts. I think I saw some on ebay recently.

[Lee RogersParticipant @leerogers95060]

There is a very good group on Facebook that might be able to help with finding the required spares for you.

Drummond/Myford lathe owners and enthusiasts . I know that many have an aversion to FB but this is a decent friendly group and many lathes have gone back into use with their help. ML4s are not rare and there are plenty of spare parts out there .

[Richard Bartholomew 3Participant @richardbartholomew3]

Wow!!! Gentlemen what a multi-layered response!  Hugely helpful and – as someone mentioned politely! – a LOT to take in and process.

I will go back and re-count the teeth on the two on the cluster that’s on the Mandrel, and start to make some estimate as to what to consider for possiblities of acquiring a replacement for the top cluster so as to get the Backgear to operate.

All good fun, and this will keep me out of mischief for a good while!

Regards and thanks to all,

Richard(ps; As  Bazyle used in his text -ie: the letters ‘OP’ – – not quite sure what that referred to but  it inadvertantly could stand for ‘Old Person’ , and that’s definately on the ball!!)

 

[Charles LamontParticipant @charleslamont71117]

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