Myford quick-change gearbox

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

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 !!

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.

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

Myford gears 20 DP 14.5 degrees pressure angle

The Guard bolts directly to the left hand side of the gearbox with two fixings, there will be a space between the bed end and the Guard. The single stud which is located in the rear of left hand end of the bed takes a stud with nuts and washers (2 of each).Adjust the nut positions to clamp the guard between the two nuts with washers placed against either side of the guard. Try not to force the guard into any form of misalignment. ie before tighhtening move nuts lightly into place by hand only, then nip tight.

K

Hi Kwil,

The guard on my lathe bolts directly on the rear of the lathe bed with three 1/4 BSF bolts . There is a tapped hole in the rear face of the gearbox, but as this is in the area of a cutout in the guard I don't see that it can be used. I have taken a few more photos and the link is below.

I will also upload the rest of the photos, so a photographic record of the entire process will be on Flickr.

**LINK**

Mike.

I have now had a chance to upload some more photos right from the start. About 29 pictures so far and counting!!

Link below.

**LINK**

Edited By sparky mike on 31/07/2012 11:00:52

A further question re. missing parts. The detent plunger or ball which engages with the quadrant is missing from the lid. The grub screw is there but nothing else. I was thinking of turning up a plunger with a counterbore in the grub screw end, to take a small compression spring. Would this be correct ?

I have now made the drill jig out of 1/2" thick steel strip, so I can now drill the securing holes for the box in the lathe bed. Slow progress, but at least some progress !!

Mike.

A bit more progress.

Jim of Latheparts.co came to the rescue and supplied me with the layshaft and dog clutch gears, so the inside of the box is nearly complete apart from the first 16T gear in the cluster set.

That gear, according to the manual, has a taper pin, but the rest are on one long keyway. I can only think of two reasons for this. (A) The pin acts as a safety pin in the event of a gear lock-up.. (B) Perhaps having a full length keyway would weaken the shaft at that point.

The lathe bed is now drilled to take the top two bolts for the gearbox and the Myford grey paint has arrived.

Mike.

This post is mainly addressed to Dennis, who is in posession of most of the correct facts.

I now have all the internal parts, bar one 16T gear from the main cluster bank, but this is on Myford's website, so I should be ok for that.

Now to re-cap, the right hand gears are 18T, 30T and 18T. I will have to get them specially made as at the moment as they are not available.

The 24/30T tumbler gear should be a 12/30T gear. Correct? I ask this as the tumbler gear as fitted to my lathe is a 20/30T, which is neither one nor the other, and the small gear is removeable and keyed , but I can't see a 12T fitting the same keyed shaft as the keyway would ,in my opinion break through the gear at the base line of the teeth. However the Tumbler gear on Myford's site (A 1974A/1 may well interchange which would solve the problem. The 20T gear is damaged anyway, so it has to be changed before long.

The detent pin is missing from the box lid and I would welcome any details of pin and spring so that I can turn something up to fit.

Now that I have the layshaft and gears, I can understand how the box functions and I will post some pictures with a "flow chart" later when I get a bit of spare time. As dennis points out I do have some way to go yet, but I am getting there,one piece at a time !!

Mike.

Mike,

Not Dennis but can help a bit. the early box, yours, needs the 12/30T gear which is a one piece gear as you have guessed correctly that a key will break thru.

You say you need the 18T, 30T and 18T as they are specials but can you use a standard 30T bushed out to suit.

I accept the 18T's might not be as easy to get.

Hi John,

I believe the 30T needs a boss, but now you mention it, I think this gear , being an idler might not need the boss/set screw to anchor it as there is the large washer and screw on the end of the shaft to do just that,, so it might be possible to just bore out a standard change wheel gear and turn up a spacer /boss to fit the gap.

These things are always so much easier when you have a complete item by your side. !!

There is however a very good company in Derbyshire, who make this type of gear, with or without the boss and they will also do specials to order.

Mike.

Mike, If you are talking about HPC make sure you tell them it's 14.5 degrees pressure angle as all thier stock gears are 20 degrees.

Also make certain you are sitting down first.

John S.

Hi John,

I had not realised about the pressure angle difference, but as the chain of three gears are on their own on the right side of the box, could they be in 20 degree mode.?

Is there a "for and against " for the different angles?

Mike.

Mike, yes no reason why not as this is a complete train.

20 degrees is better but Myfords got stuck on 14.5 like a lot of lathe manufacturers because of legacy issues.

In which case the HPC gears are reasonably priced for off the shelf items, it's just the specials you need to have a lottery win for.

I have uploaded a photo with captions to explain in simple terms how the gearbox functions. A sort of flow chart diagram. Note: this is the early box. Later boxes have the output shaft extended through the box to the left and not the right hand side.

Link below. Mike.

**LINK**

Well I have at last I now have the three gears for the right hand end of the early box.

These are 18 teeth for the small gears and 30 for the large gear.

Size is 20DP. They were stock size gears from HPC , but I have had to adjust the length of the boss and width of teeth to suit this job. The gears are very good quality and the machineability of the steels that they used is very good. I had HPC machine the keyway for the top small gear, but that was only around £4 or 5 pounds extra.

**LINK**