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Harrison M 300 (1978)

Problems with the gearbox

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David Clark visits a used tool shop in Colyton, Devon

Johannes06/09/2009 09:33:30
1 forum posts
Since a couple of years the 0 to 8 knob of my ( newly bought in 1978)
M 300 lathe, is "frozen". I left it for these years because I did not have enough space in my former attic workshop in the Netherlands, to dismantle this gearbox, and I did not have to cut screwthreads. Now that I have been moved to Burgundy, France, I have a workshop of around 100 m², and ,after ordering 3 phase electrics (no problem in France: for around € 900,00 EDF did give me the 2 other phases,50m 4 x 25 mm² , a new electronic kWh counter, day / night , 10 hours labour by 2 electriciens. I did the 230 / 400V house / workshop wiring myself,as I was an electr(on)ic engineer in my working days, I studied before the french NF C15-100, ). Now that my workshop gets ready ,I want to repair my beloved lathe. When trying to use the 3 pitch selector switches, there are yet only two (quick) feeds in working order, the rest is dead. I need to say that I never refreshed the Shell Vitrea 72 oil in the gearbox.
I have heard rumours that there is a (delrin) curved drum inside the gearbox, that selects the pitches, and that this drum sticks after years. Does anyone has (had) the same problems? Maybe Tony Griffiths has heard this problem before? Are there suggestions from collegues machinists? Johan Berserik
mgj06/09/2009 11:14:00
1017 forum posts
14 photos
I don't know about Harrison gearboxes, but I know a little about Delrin.
It has the advantage of being cheap. And easily machinable too I suppose.
The real problem with it is that it is immensely hydroscopic, and when it does absorb water it expands quite significantly.
Its notorious for jamming  gearbox and steering linkages where it has been used for plummer blocks and rod guides, and there was one other case where the absorption of water caused vast inaccuray in anti tank ammunition.  We have also had the problem where, in the dairy industry, people have tried to save money over PTFE, and the stuff has jammed shafts, or tried to jam them and then worn very quickly.
So that might be a pointer.
Have you given Harrison a ring. The website is
Buck and Hickman stock them so they are distributors, and they have a website with a phone number.
KWIL15/11/2009 18:17:33
3442 forum posts
66 photos
Harrison M300. The "curved drum" is in fact "Cam, Feed Selection" Part No CE-0050 which drives the 4 off "Block Cam Follower"  This part number from the 1999 Manual.
Cerainly clean out the gearbox, possibly with a light flushing oil before refilling with the correct Shell Vitre 220 oil.
Suggest you contact by email , he is the sales contact for spares and they will sell direct to you by Pro-Forma Invoice and subject to a minimum £20 order value
calder percival 121/02/2010 13:41:21
19 forum posts
1 photos
the selectors you talk about are held by split pins as sis the clutch plate on the right of the outside of the gearbox, if you are going to wash out the box use duck oil and be sure to free up the shafts as they come out of the box by applying oil around them. Harrisons are very helpfull and will do all they can to help you . nothing inside the box is scary and you will not harm it so go have a look !

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