Myford gearbox confusion

[Adrian 2Participant @adrian2]

[Adrian 2Participant @adrian2]

I am far from new to Myford lathes but have no experience of using their gearbox.

The two photos show the thread cutting chart. The blue plate is a 2001 lathe , the red is I believe a 2002 machine.

I was surprised to see the different TPI shown . Just an observation really.

Right, here comes my confusion. The Myford quick change handbook states that there are 48 English threads available for instant selection. The plate shows 24. The plate states "FOR FINE FEEDS REVERSE GEAR ON STUD 'A' "

Reversing the cluster gear on stud 'A' would double the threads available to 48 .

My question is, at what point on the chart is a thread considered to be fine and require reversing the cluster gear ?

The plate itself is clear enough about where to set the levers but not when to reverse the cluster gear.

I 'm overlooking the obvious I expect. I am looking forward to being enlightened.

Adrian.

[John Stevenson 1Participant @johnstevenson1]

The chart with the 23 tpi thread on it is for the North American market as its a common pipe thread whereas we use 19

[peak4Participant @peak4]

Adrian, the big numbers on the black background are for thread cutting and give TPI; if you reverse the gear for normal turning, read the feed rates per revolution on the smaller red/blue backgrounds.

The gear itself is held in place by a little gate, so you don't need tools to reverse it.

[Adrian 2Participant @adrian2]

Thanks John, that makes sense. I bought this lathe from the original owner in Canada. I would guess that is a standard made for export gearbox.

Adrian.

[Adrian 2Participant @adrian2]

Thanks peak4, I am beginning to see the light. Just been and had a play, makes sense now. That's 24 of the available threads where are the other 24 alluded to in the handbook ?

Adrian.

[Clive FosterParticipant @clivefoster55965]

Found a download of the handbook, **LINK** , which makes it all clear :-

"The Myford Quick Change Gearbox permits instant selection of 48 English threads and feeds without the necessity for setting up gear trains"

24 threads + 24 feeds = 48.

One of those doesn't read the way the writer intended it to be read things. Incredibly hard for a writer, or even a knowledgable checker, to proof read out 'cos you know exactly what you meant to say.

Clive.

[Adrian 2Participant @adrian2]

Thank you for the link Clive. I have the same literature. As you say the wording could have been better, and my reading and interpretation of it were incorrect.

All is made clear now. Thanks to everyone. You can find out anything here.

[Clive FosterParticipant @clivefoster55965]

Glad thats sorted Adrian.

Having made the same sort of foot (keyboard?) in mouth error myself a time or three before its perhaps easier to spot and be sympathetic about when seen elsewhere.

Clive.

[John Stevenson 1Participant @johnstevenson1]

With the addition of two extra gears on the input drive train, a 33 and a 34 you can cut most of the metric threads without any adaptation and save the cost of the very expensive Myford metric attachment.

[Adrian 2Participant @adrian2]

Good to know John. Thank you.

[RobboParticipant @robbo]

What JS modestly omits to say is that he used to sell these gears online, but stopped when his dear wife died.

So he probably has a few left. I bought a pair years ago, and sold my Myford metric conversion set.

[Author]

Posts