Myford 254 metric screw cutting

[Old SchoolParticipant @oldschool]

i would like to cut some 0.5mm pitch metric threads on my imperial lathe the manual is a bit vague to me anyway. Help required please.

[Old SchoolParticipant @oldschool]

[alan-lloydParticipant @alan-lloyd]

You need an extra stud assy for the changewheels …plus 30,60,63,50,35 and 80 gears.From the head stock mandrel 30 into 60 inner 63 outer, mesh with 50 inner 35 outer, mesh with 80 on gear box, gearbox selector levers on b 1, do not disengauge the lead screw clamp nuts but use the reverse button, ignore the thread indicator, good luck.

[Old SchoolParticipant @oldschool]

Thanks Alan I have read that in my manual what I don't know is what the stud assembly looks like and where it fits on the lathe a picture of the stud and how it all goes together would be great help.

[John Stevenson 1Participant @johnstevenson1]

http://www.lathes.co.uk/myford/page10.html

**LINK**

6th picture down,

The stud assembly is the bolt and bush that holds the double gear into position.

You need another one of these [ might be in the tool kit ? ] and a 30 tooth gear on the top [ behind the pulley in the pic, driving a 60 T on the first stud. that also has a 63 tooth gear doubled up on it which drives a 50T

Again that is doubled up with a 35 that drives an 80 on the gearbox.

You then need to select B1 on the gearbox.

[JohnFParticipant @johnf59703]

Alan & Old school, you CAN use the dial indicator and you can release the half nuts when cutting metric but you must use this process which is particularly useful if you are working up to a shoulder or into an undercut.

After setting up your lathe to cut the required metric pitch and with your work piece in the chuck or collet follow this sequence.

1. apply the first cut depth on the cross slide and place the tool tip reasonably close to the work [distance depends on the pitch of the thread you are cutting, fine thread can be closer, coarse thread leave more room]

2. with the lathe running engage the half nuts on a particular number, number one is best, it can be any number but you must remember it.

3. At the end of the thread release the half nuts, stop the machine and wind out the cross slide to clear the thread

4. Start the machine in REVERSE and engage the half nuts on number 1 traverse back to the start point making sure the dial indicator passes 1 and then release the half nuts, stop machine, apply the second cut on the cross slide, start machine forward and engage half nuts on number 1

Repeat until you achieve full thread depth.

You MUST NOT manually move the carriage during the process

I appreciate that if there is no shoulder this may seem a faff but I have cut a great many metric threads this way and find it much better when there is a shoulder or undercut than trying to stop the machine before the tool runs into the shoulder or trying to whip the tool out before it does collide and damage both the tool and the work.

John

[John Stevenson 1Participant @johnstevenson1]

Posted by JohnF on 28/07/2016 00:49:24:

4. Start the machine in REVERSE and engage the half nuts on number 1 traverse back to the start point making sure the dial indicator passes 1 and then release the half nuts, stop machine, apply the second cut on the cross slide, start machine forward and engage half nuts on number 1

John

"Make sure the dial indicator passes 1 " ??

How can it pass 1 when it been engaged at 1 ? Once engaged it will always stay at one whilst being driven.?

[not done it yetParticipant @notdoneityet]

I think he means 'whatever number you chose', not necessarily number 1. Disengaging the half nuts while traversing forwards, before stopping the lathe and shifting the cross slide back, prevents running into an uncut area and breaking the tool. On reversal of the lathe, to return for a subsequent pass, the half nuts are engaged at that same number on the dial indicator (as lathe is now running in the reverse direction. Hence while disengaging half nuts they are always re-engaged at that same point every time. The important thing is the same number and always on the same turn of the dial indicator, as the thread would not necessarily be picked up on that same number without driving the lathe backwards

[Old SchoolParticipant @oldschool]

Thanks John I only have the gears that are fitted to the lathe I can make the stud, can I use standard Myford ML 7 gears as replacements for the missing one So?

[JasonBModerator @jasonb]

JohnF I don't see the point of your method as you are still using the feed screw to wind the carrage back to the start of the cut. The reason to disengage the nuts is so you can quickly return the carrage to teh start using teh apron handwheel.

[HopperParticipant @hopper]

Jason, I think he was talking about releasing the nuts so that one could cut the thread up close to a shoulder without fear of crashing the tool into it.

Still scratching my head about using #1 to re-engage the half nuts though. Will have to think about that one some more. It certainly is not apparent at first blush. I also am unsure about "go past 1" on a dial that is stationary while the nuts are engaged and the leadscrew turning and carriage moving.

Interesting.

[JasonBModerator @jasonb]

I just use an internal tool on the back side of the work and run the lathe in reverse. Cuts away from the shoulder at whatever speed you fancy.

As the OP has it on a VFD the braking could be set up to stop very quickly which would do much the same as releasing the nuts. So its just cut-stop- retract tool-rev-stop- wind in tool- repeat. Winding up the wick on the VFD for a fast return.

[Tim StevensParticipant @timstevens64731]

There is an alternative method to cut metric (or any other) threads on an imperial lathe. A recent MEW had articles covering this, and I have built my own on an ML7 using an absolute minimum of accurate machining.

If you can send me your contact details through a 'private message' on this board, I can send a photo or two.

And if you can tell me the teeth numbers of the gears you have fitted, I will show how to set up my system to cut the 0.5mm metric thread you need.

Regards, Tim Stevens

[BazyleParticipant @bazyle]

Agree the 'passes 1 ' is unclear,

The point about John's method is that the thread indicator keeps track of the rotation of the leadscrew for you but unlike imperial you can't let it (leadscrew) do a whole 8 rotations (for 8tpi leadscrew) after release and think it is realigned. You must backtrack to the exact point where you released the nuts to re-engage for the return journey. The thread indicator tells you this but best not to let it do a full rotation to keep track.

Might help to work it through using manual chuck rotation around the release point until you how and why it works.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Tim Stevens on 28/07/2016 12:01:43:

If you can send me your contact details through a 'private message' on this board, I can send a photo or two.

.

Sorry to intrude, Tim … I'm just being curious.

Do you have a particular objection to putting photos in an Album for everyone to see?

MichaelG.

[Tim StevensParticipant @timstevens64731]

Michael asks: Do you have a particular objection to putting photos in an Album for everyone to see?

No, not at all, but there are sometimes good reasons. In this case, I wanted to avoid the extra complication of learning the way to do as you suggest before our enquirer got any benefit. But there is also the point that someone called Neil might come along and say 'I'd like to cross your palm with silver, Tim, so can we publish this idea?' I live in hope, see …

Cheers, Tim

Edited By Tim Stevens on 28/07/2016 21:09:47

[Tim StevensParticipant @timstevens64731]

PS, I boobed – it was ME, not MEW. 13-26 May, No 4534, pages 724 to 728.

Tim

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Tim Stevens on 28/07/2016 21:09:14:

Michael asks: Do you have a particular objection to putting photos in an Album for everyone to see?

No, not at all, but there are sometimes good reasons. In this case, I wanted to avoid the extra complication of learning the way to do as you suggest before our enquirer got any benefit. But there is also the point that someone called Neil might come along and say 'I'd like to cross your palm with silver, Tim, so can we publish this idea?' I live in hope, see …

Cheers, Tim

.

Fair enough, Tim

MichaelG.

[JohnFParticipant @johnf59703]

John S, Not done it yet grasps the method perfectly, but to clarify I was referring to disengaging after traversing back to the start of the thread where if you want to disengage again you can but must let the indicator number 1 pass the datum mark. This will give you enough time to engage again on number 1 when running forward with your next cut. You can of course not disengage and just stop the machine then put on your next cut and traverse forwards.

Jason whilst I agree partly the point is that if you are screw cutting up to a shoulder unless you have an instant stop [magnetic brake] on your lathe you will probably run into the shoulder? Using the method described you can disengage the half nuts thus stopping the carriage as you would do with imperial threads but the difference is you must as you say re-engage the half nuts and traverse back to start your next cut. You can not return the carriage manually or you will loose the datum sequence.

If you are not stoping at a shoulder then you can just withdraw the tool, stop the lathe, reverse and and traverse back.

Belive me it works, been using it for many years.

John

[Neil WyattModerator @neilwyatt]

Bit confused Tim…

I think it's too soon to repeat Jacques device, even though it was in ME.

Neil

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