Harrison 140 Leadscrew clutch Question

[Keith 66]

I have a job to do that involves cutting a thread in a cast iron lathe backplate.
I am not experienced in thread cutting on the lathe but fortunately have a skilled toolmaker mate who will show me the ropes. Now i have owned this 140 since it came out of the college where i worked & when got the machine i gave it a good clean up but that was about it. Never done screw cutting with it.
On the left hand end of the leadscrew is a sliding collar / clutch to engage the leadscrew into the gearbox. Trying the machine with leadscrew engaged to the gearbox for the first time it was apparent that the clutch was slipping & not driving the saddle at all as soon as the half nuts were engaged
So maintenance time! pulled the leadscrew & slid the clutch off the end of the leadscrew
The clutch contains two ball bearings in recesses & a pressure plate to drive the leadscrew, It is tensioned by a stack of belleville spring washers or rather should be.
Upon opening it up it was easy to see why it wasnt driving, someone has been in there before, all the spring washers were arranged the same way nested into each other so they didnt work.
I look at the manual & it shows just 5 washers, & the parts list just says number required 1 !
I clean them all & there are 8 pairs 16 in total.

Anyone know how many should be in there? Be nice to get it right so i can use it!

 

[Keith 66]

Having cleaned it up i found the threaded plug that holds the washers in had two tiny witness marks from the two locking grubscrews so it was clear the plug hadnt been screwed in far enough to tension the washers even if they had been in the right way.
So i got them all in & screwed it to where it should hopefully be & its now back together. Just had it powered up & everything seems to work.

All i got to do now is learn how to drive that bit properly!

 

[Tigman]

Have you got the gearbox with yours ?

 

[Keith 66]

Yes, Its a late metric machine with the three thumb levers on the gearbox.

 

[Tigman]

Mine doesn't have the gearbox, I 've only cut a few threads so I'm no expert

 

[addjunkie]

Yes, Its a late metric machine with the three thumb levers on the gearbox.

If your machine is metric, is your back plate an imperial thread, in which case you may need to keep the lead screw engaged and reverse the machine.

Id do a but practice screw cutting to get a feel for it before you do the job, its easy enough, but easy enoughto Cock up too!

 

[Keith 66]

Its for the never ending saga of my Boley 4LE, that has its own thread. Suffice to say i have got the poxy thing back together but the 3 jaw chuck is ******** & there was no 4 jaw.
But i have a nice 4 jaw chuck of the right size came off a Boley & Leinen that had been out in the rain for ten years (write off), But that chucks backplate hole is smaller. Plan is to bore it out & cut new thread to fit the 4LE.
Not sure what the Boley Nose thread is yet, The spindle is 41mm dia, Sods law is that i have no less than three Whitworth thread gauges & have lost my metric one!
Some say that the Boley has an Imperial nose & indeed the closest i can see is 7 tpi but I cant believe a German manufacturer would use an imp nose thread. Will wait until we can measure it right.
New metric thread gauge ordered. I will find the old one the day after the new one arrives.

 

[addjunkie]

Its for the never ending saga of my Boley 4LE, that has its own thread. Suffice to say i have got the poxy thing back together but the 3 jaw chuck is ******** & there was no 4 jaw.
But i have a nice 4 jaw chuck of the right size came off a Boley & Leinen that had been out in the rain for ten years (write off), But that chucks backplate hole is smaller. Plan is to bore it out & cut new thread to fit the 4LE.
Not sure what the Boley Nose thread is yet, The spindle is 41mm dia, Sods law is that i have no less than three Whitworth thread gauges & have lost my metric one!
Some say that the Boley has an Imperial nose & indeed the closest i can see is 7 tpi but I cant believe a German manufacturer would use an imp nose thread. Will wait until we can measure it right.
New metric thread gauge ordered. I will find the old one the day after the new one arrives.

You will need the thread angle too, some are 55 degrees other 60. Is there no details on line lathes.co.uk etc

 

[doubleboost]

Yes, Its a late metric machine with the three thumb levers on the gearbox.

Same lathe as mine very nice bit of kit

 

[Keith 66]

You will need the thread angle too, some are 55 degrees other 60. Is there no details on line lathes.co.uk etc

Nothing on Lathes.co.uk site, i have some thread angle gauges also boring bars with correct angles ground on their tips.

 

[Seadog]

My few seconds browsing comes back with M40 x 3.5

BOLEY 4 LE lathe Used machines - Exapro

For sale used BOLEY 4 LE available in Germany (DE), find used Lathes - 0 - 3000 mm on our marketplace

www.exapro.com

 

[Brad93]

3.5mm pitch you potentially need to keep the half nuts engaged.

1.75mm you have to keep them engaged so it's stands that 3.5mm will be the same.

I think these are a 4mm pitch leadscrew

 

[Keith 66]

I reckon you are probably right, But that is a fine lathe with a fine price tag to match!

 

[Keith 66]

Got my thread gauges today measured the Boley spindle nose & yes it is 40mm x 3.5mm pitch.
The Harrison's leadscrew is 6mm pitch according to the manual. On looking at the changewheels already set up on it they are 25t 100t & 80t which happens to be right according to the manual, dialed the gearbox to the right pitch & the lathe is now set up good to go.
The Harrisons did have numerous gearbox & leadscrew options over the years that sometimes overlap & looking at the manual there are at least three options, im pretty sure im on the right chart, we shall see!
Will nip up the gibb in the compound slide a little tommorow as its slightly loose.

I even found two new boring bars the right size & 60 degree angle.
Im thinking that i will have a practice on some sacrificial stuff before i bore the boley & leinen backplate out, cant afford to knacker it!
As far as sacrificial stuff goes i have some high density modeling foam & will saw out a couple of blanks to ruin before i hit the real thing!

 

[addjunkie]

Metal would be better to practice on. Screw cutting involves an element of feel!

 

[Tigman]

Post a few days pictures please ? Or a nice video !

 

[Keith 66]

I have had a practice cutting an external thread today with some small stuff 12mm x 1.75 as I had some spare tools.
Getting used to stopping & starting the machine with half nuts engaged, was all going quite well with a nice thread nearly finished, then i forgot to back the tool out before i put the lathe in reverse. Snap went the tool. Ooh its broken! Lesson learnt, remember to back the tool out between cuts & dial in appropriate amount each cut. Now got to grind some tools. I have angle gauges & a drawer full of HSS to practice with!

 

[addjunkie]

I have had a practice cutting an external thread today with some small stuff 12mm x 1.75 as I had some spare tools.
Getting used to stopping & starting the machine with half nuts engaged, was all going quite well with a nice thread nearly finished, then i forgot to back the tool out before i put the lathe in reverse. Snap went the tool. Ooh its broken! Lesson learnt, remember to back the tool out between cuts & dial in appropriate amount each cut. Now got to grind some tools. I have angle gauges & a drawer full of HSS to practice with!

And then your going to need to practice going in blind internally, far more interesting, and winding it in rather than out!

I don't really use the dial numbers, just mark the dials with a dry wipe pen, wind out, then back into the marks, plus the next bit. Wipe pen off and start again. I have DRO for final depth.

 

[Keith 66]

A lot more practice required before i start on anything big & internal, Good tip about the dry wipe.