Thread cutting help
|Garry Scott 1||17/05/2019 23:17:22|
|1 forum posts|
To start I am a complete novice and never turned in the past but I've always wanted to so I bought a Harrison L5 lathe.
Because I'm new to all this I need abit of help with the screw cutting element of the lathe.
Thank you all in advance.
4768 forum posts
I can't offer any advice on the Harrison but if all else fails you could get yourself a copy of Martin Cleeve's book "Screwcutting in the Lathe" and calculate what gears you need from first principals. He does have charts included to cut metric threads on an imperial lathe that could be adapted to suit the Harrison.
|Alan Waddington 2||18/05/2019 13:44:43|
|505 forum posts|
Assuming it has a norton gearbox fitted (some L5’s don’t) You need a 127 tooth wheel to cut metric threads
Edited By Alan Waddington 2 on 18/05/2019 13:45:54
|Clive Foster||18/05/2019 13:48:19|
|2317 forum posts|
I assume you have the standard L5 with three speed feed box rather than the full screwcutting version. If so the charts shown here :- **LINK**
are probably correct. Not sure what computer software and printing capabilities you have but it should be possible to work up your own without unreasonable effort. I find laminating ordinary printouts in the usual plastic pouches gives an adequately durable data panel. Replicating if it does get damaged is simple so long as you remeber to save the original. I have a cheap laminator from LiDL which does such jobs just fine.
Cant find a nice download picture of the metric conversion data but I do have a copy of the table from the manual. PM me if you'd like a basic copy.
|Nigel Graham 2||12/06/2019 16:44:03|
|720 forum posts|
I own one of these, and bought the photocopied version of the Operator's Manual from lathes.co
Apart from anything else it will mean you are less likely to be caught out by that small gearbox on the headstock. (Yes, I have been...)
Norton Gearbox or not, and mine doesn't have one, you will still need a 127T wheel for cutting metric threads, but you may also have to reverse the lathe to wind the saddle back still in gear for each pass. I am not sure if you can use the lead-screw reverse gear to avoid running the spindle backwards - I think that would lose the correct meshing.
BEWARE though if you do run the lathe backwards under power and it has the same screwed spindle as on my lathe, you do risk the chuck unscrewing itself from the nose.
You might get away with a 63T wheel instead of 127, but it introduces a small pitch error and is best used only over short threads.
|Nigel Graham 2||12/06/2019 16:49:35|
|720 forum posts|
Just re-read the OP, suggesting this lathe has come without change-wheels.
If so try G & M Tools, or Home & Workshop Machinery, for a start, for replacements as well as that 127T wheel.
Also for a thread dial-indicator if that's missing.
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.