Myford quick-change gearbox

[sparky mikeParticipant @sparkymike]

Can anyone explain the workings of the Myford quick change gearbox. I assume that the large external gear drives the input shaft. How does the box connect to the leadscrew shaft? How do the layshaft gears transmit the power from input shaft to leadscrew? I have downloaded the gearbox manual, but it does not show the drive path in various gears.It does not quite make sense to me at the moment, but no doubt it does work somehow !!

Mike.

[sparky mikeParticipant @sparkymike]

[KWILParticipant @kwil]

If you look closely the gears are in an increasing number of teeth and you merely shift an intermediate gear along the shaft picking up in order. The lever on the top switches between various clutch drives. Easier when you have one in front of you.

[sparky mikeParticipant @sparkymike]

I now know why the operation of the box seems impossible. It turns out by looking at other box photos that are for sale, that mine is different !! On my box, the lead screw does not pass through the box, but ends in a blind hole in the right hand side of the casting. The drive is taken from the other shafts by three gears that are on the right hand face, outside the box , where there is also an alloy cover, which in my case is missing. I am now wondering how many more parts are different to the normal box ?

Mike.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Mike,

Is your gearbox a 'made in Beeston' box? It would be helpful (and interesting) if you could create an album here and upload a couple of photos to it.

Laurence Sparey designed a Q/C gearbox for the ML7 and drawings for it were sold by the ME Plans service at one time. I've also heard of a gearbox kit being sold by one of the third party accessory firms, can't remember which one. Maybe your box is one of those.

If your box WAS made by Beeston Myford, maybe it is an experimental prototype that 'escaped' from the factory.

Best regards,

Swarf, Mostly!

[John Stevenson 1Participant @johnstevenson1]

You have the early Myford box, later ones had the leadscrew go inside and did not have the drive train on the right.

See here.

**LINK**

John S.

[sparky mikeParticipant @sparkymike]

Hi John,

Yes that is the one. Certainly had me mystified ,as I could not figure out how the lead screw got through the box, going by the later manual !! If most of the parts for the early box are the same as the later one, I stand a chance of getting this one back in one piece. On the picture on Tony's lathe site, I believe that one of the gears on the right hand end of the box is just an idler and is held on to the end of the nine gear shaft by a washer and screw. If I could find out the number of teeth on the two corresponding gears, then the idler could be worked out from those.

I don't know how many early type boxes were made, but the serial number on my box is OC 1802 or possibly QC ****

Mike.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Mike,

Mystery solved!

John, thanks for that link. I've browsed the Lathes site a lot but I must have missed that page. I had encountered references to early boxes having unhardened gears but I'd always assumed that the layout of the gear-trains was the same for both early and later boxes.

Thanks again,

Best regards,

Swarf, Mostly!

[David LittlewoodParticipant @davidlittlewood51847]

The third party box mentioned by swarf could have been the kit marketed by Hemingway:

**LINK**

David

[sparky mikeParticipant @sparkymike]

If the internal gears are the same on both boxes, then the same gearing must be employed to take the drive from the layshaft to leadscrew in either type of box or else the screw cutting will not be correct. Admittedly, the two driving gears could have more or less teeth, as long as the ratio was the same.(The idler gear as said before does not matter as long as it fills the gap and meshes correctly.

Perhaps someone can tell me how many teeth are on the gears in question in one of the later gear-boxes. At least this will be a start and something to go on. (Unfortunately, the pictures of the gearing on Tony's site are not sharp enough to cound the teeth on the right hand end of the box.)

The electric motor has been stripped and cleaned and checked out and is now in primer. I will have this part working before the lathe is anywhere near ready !!

Mike.

[John Stevenson 1Participant @johnstevenson1]

Mike, do you have any of the gears ?

Failing that you can count the top one easily, I make it 18 T

If you can now measure centre to centre on the holes for the other two gears it will be easy to work out what gears are needed.

John S.

[sparky mikeParticipant @sparkymike]

Hi John,

No I don't have any of the gears on the right hand side of the box. However I also make the top gear 18. The middle is debateable at 32T and the leadscrew possibly 20T. Tony at lathes uk does the manual for the early box, so I have emailed him with a view to buying it. Could save a bit of time in the long run.

Mike.

[sparky mikeParticipant @sparkymike]

I have now had a chance to measure the gear centers. It is 1 3/16" either side of the center gear.

If my calculations are correct, the top gear 18T (if that is correct size) , would measure around .956" over the top of the teeth. As the hole centers are equal, it would make sense that the small leadscrew gear is also 18T. If that is correct, then all that is needed is to select an idler gear for the center position that meshes correctly with the two smaller gears. Any comments welcome.!!

See photos on link below. There are some before and after pictures of the lathe bed. It is only in primer at the moment, but it is looking a lot better than when I purchased it. The slides are covered in masking tape while it is being painted.

**LINK**

[John Stevenson 1Participant @johnstevenson1]

1 3/16" =1.1875 take away half of the PCD of an 18T gear at 0.450 and you are left with 0.7375

Muktiply this by two and you get 1.475 which doesn't match up to any gear.

Now if we do the sums again with a centre distance of 1.200" which is only a bit bigger and probably more correct we get 1.200 – 0.450 = 0.75 x 2 = 1.5" which equates to a standard 30 tooth gear.

Try measuring again a bit more accurately and I'm sure you will get 1.200"

John S.

[sparky mikeParticipant @sparkymike]

Hi John,

I will find some rods to fit the bores and measure with a micrometer.

Mike.

[Alan Worland 1Participant @alanworland1]

Mike,

I have the same box as yours and just been out to remove cover and I counted 18 tooth gears either side of a 30 tooth idler – hope this helps

My box is s/n QC 2268 and is mounted on bed s/n K16170 and was purchased assembled by Myfprd 30/3/1951

I think the internals are the same as I had a broken gear (20 tooth I believe) and obtained a replacement from Myford – and to be honest I didn't even realise I had the early box till I read your post!

I guess you could obtain the correct tooth gears fromm a screwcutting geartrain and adapt?

Alan

[sparky mikeParticipant @sparkymike]

Hi John,

Now re-measured and they came to 1.203 and 1.180.

However, Alan has kindly posted the gear details above so I can now find some blank gears and bore them out to suit. Possibly some of the stock Myford gears will fit or adapt. The 18 teeth gears will need the keyways, but I think that the idler gear has a plain shaft.

Mike.

[DMRParticipant @dmr]

Mike,

You are not getting the full story. So before you get in too deep……
In no particular order:
1. The last gearbox of the type you have was Serial No. QC (for Quick Change) 2500. QC2501 was the first "modern" one.
2. It is thought that many early gearboxes were retrofitted in the factory with hardened cogs, but no records were kept. Also quite possibly from some point before QC1950, hardened cogs were fitted as standard.
3. The leadscrew on your none-gearboxed machine has quite probably got a different plain diameter at the headstock end, as in smaller than what you require.
It must fit the hole in the gearbox casting closely for obvious reasons.
4. It is somewhat trickier to align the gearbox with the leadscrew, but it must be done and done carefully or the hole in the casting for the leadscrew becomes worn. The "modern" box is almost self aligning as it goes right through, but it still needs doing.
5. To align the gearbox properly, you need a spacer strip between the gearbox and the top two fixing screws along the bed shear. It is just a flat strip with two holes in, but I have no idea what the thickness is. That is a left over from the earlier ML7 fitting.
6. Your gearbox runs at half the speed of the "modern box" to cut the same thread. That is to say, your output gearing at the right hand end is 1:1, whereas the modern box is 2:1 at the left hand end. There is no chance of you altering the principle to be the same as a modern one as you won't make it fit!
7. A consequence of this that you also need a 12/30T FINE FEED TUMBLER GEAR A1974A/1 as it is termed on the Myford/RDG website to drive the standard fixed quadrant geartrain. The modern box uses 24T/30T and hence does not have to be a combo cog.
8. Do not try and use the Myford modern screw cutting details as in a later manual as you will end up with a times 2 factor as above, but you can do far better none imperial threads than the earlier Myford tables.

9. The guts of the boxes are identical and interchangeable apart from the shaft differences of course

Think that's it.

You have some way to go to get going.

Dennis

[sparky mikeParticipant @sparkymike]

Hi Dennis,

Many thanks for the in-depth information on the early box. I did not think it was going to be easy !! The lathe was picked up from an estate sale by the previous owners son. There is a slim chance that some of the missing parts are still at the same address so I am taking steps to check on that, now that I have a better idea what is not actually here !!

My lead screw is full length at the moment, but at some time in the past it looks like it was fitted to an early box, as now there is a thicker tube portion that might have been welded/brazed on to take it back to standard length. It can not have been used on my lathe with a box ,as there are no holes drilled and tapped on the side of the bed for the box fitting.

While on that subject point, I would like to drill the box fixing holes while the machine is stripped down. Does anyone have a drawing for the position of them ?

One part of the box I can't yet figure out. The smallest gear on the internal cluster is a 16 teeth gear. There is a cross hole in the shaft where this gear should be. Is this for lubrication , or is that single gear pinned? All the others are secured by a long key and they are all here. If you could explain how the drive is taken from the cluster gear shaft to the layshaft and also the purpose of the dog clutch, I will then have all the facts. (I hope !!)

One last question, should there be a ball and spring under the top cover to act as a detent for the quadrant. ? The small grub screw is present but no detent here.

Mike.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Mike,

Check your personal messages.

Best regards,

Swarf, Mostly!

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Mike,

Another thing,

It's quite common for ML7 leadscrews to have that coupling sleeve. I've heard it said that the securing cross-pin acts as a mechanical 'fuse' in case there's a lock-up anywhere.

Best regards,

Swarf, Mostly!

[KWILParticipant @kwil]

Sparky,

Yes there is a small spring and ball below that top plate grub screw to provide a detent on the A-B-C setting.

The holes along the front shear below the headstock. The left hand and rignt hand threaded holes which contain the headstock  "thrust screws" are 6.375" apart, the second from left is 1.1875" in and the third from left is 3.75" in. Both these holes are threaded 1/4" BSF on old lathes (M6 on later I believe). All holes are on a common horizontal centre line. There used to be a drilling template part no. A2754, I have one somewhere. The spacer shim was 1/32" I think, I would have to check this if someone else does not have a sure answer.

K

 

Edited By KWIL on 30/07/2012 11:57:44

[sparky mikeParticipant @sparkymike]

Hi Kwil,

Many thanks for that information. I can double check those dimensions on my lathe by fitting the quick change rear cover to the lathe and box and the holes in the box ought to line up with your dimensions.

As the three holes in the back end of the bed do not seem to be on a machined surface I might be inclined to fit a thin sheet of alloy between guard and bed to allow a bit of "give" as I don't want to crack the guard. Re. the shim at the rear of the box, I had guessed it was no more than 1/16".

One part of the gearbox just refused to budge when I tried to remove it. The part was 203 (Anchor pin A 3015) in the manual. I tried penetrating oil and then heat and eventually gave up, until today. I slipped a large tube and thick washer on the pin and replaced the end nut and used the nut as a puller and it extracted it easily. This tip may well help other Myford owners who wish to change the pin through wear etc. and no strip down of the actual box is needed although I think that the alloy rear guard would have to be removed first.

With all this information I have no excuse now, but to get on and fix it !!

[sparky mikeParticipant @sparkymike]

I now have to order the various missing gears.

I need to know what DP Myford gears are ?

I assume that they were imperial sizes in the 50's when the box was produced.?

I have lined up the gearbox casing with the lathe and guard and I find that there is a slight gap between the LH face of the box and the rear face of the guard. Is this correct. The gap is around 1/16" at a guess.

Mike.

[Alan Worland 1Participant @alanworland1]

Mike,

I dont seem to have a gap between the l/h side of the box and the guard? Measuring from the r/h side of the gearbox (not the alloy cover) to the l/h side of the gap in the bed I get 1.870 inches

Also I dont have a spacer fitted where it bolts to the bed? This doesn't seem to have caused any unusual wear anywhere which I thought would have been the case if it was supposed to be there?

I would have thought the gears would have been the same DP as the change gears on an 'unboxed' lathe (they look the same)

Alan

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