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Harrison L5 thread cutting

Thread cutting help

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Garry Scott 117/05/2019 23:17:22
1 forum posts

Hello everyone,

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.

  1. The information plate inside the gear cover is missing so if anyone could take a photo of there's that would be appreciated.
  2. I would like to cut metric threads and I have no idea what gears I should be looking for could someone please offer some advise.

Thank you all in advance.


Hopper18/05/2019 12:21:43
4768 forum posts
104 photos

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 218/05/2019 13:44:43
505 forum posts
87 photos

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 Foster18/05/2019 13:48:19
2317 forum posts
76 photos


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 212/06/2019 16:44:03
720 forum posts
16 photos

I own one of these, and bought the photocopied version of the Operator's Manual from

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 212/06/2019 16:49:35
720 forum posts
16 photos

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.

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