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Portass Model S

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Stepan Ptacek21/09/2010 07:43:53
4 forum posts
Hello there,
I am new to this hobby and forum.
I am trying to set up Portass Model S lathe into working order and start using it. I find difficult to put together gear cogs that I would get at the end the thread I want. Does anybody have this lathe manual or more information and they do not mind to share it? Thank you
Terryd21/09/2010 10:08:23
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1946 forum posts
179 photos
Hi Stepan,
When you say 'thread' do you mean the leadscrew (along the front of the lathe which drives the saddle with the cutting tool?)
 
If so there should be a slotted bar on the end of the lathe where the gear train is.  This can be loosened and rotated with an idler gear attached which links the drive gears.  See the picture below, it's not very good but you can make out the slotted bar (often called a 'Banjo') with a large idler gear and the whole assembly has been adjusted so that the gears all mesh.   Note that the banjo on this lathe has two arms, some only have one.
 
Also try this web site  the guy who runs it is very helpful and is called Tony.  Also there are many books on the market which explain in detail all aspects of the small lathe.  Most use very similar mechanisms.  A good example is "The Amateurs Lathe' by L H Sparey.  This book is like a bible for lathe users.  Enjoy and ask any other questions.
 
Best regards
 
Terry
 
Picture of Boxford lathe leadscrew gear train:
 

 

Edited By Terryd on 21/09/2010 10:21:59

John Olsen21/09/2010 10:27:24
1294 forum posts
108 photos
1 articles
The information we need is the pitch of the leadscrew and the gears in the changewheel set that you hopefully have. Some sets of changewheels go by steps of five, some by steps of four. Once we know what you have we can sort out a table, or if you are lucky someone might have one for that lathe.
 
Probably the first thing to get worked out would be a fine feed, since that is more likely to be of immediate use. This is the same sort of setup as for a very fine pitch screw, but is used a lot when turning cylindrical shapes to save winding the handle.
 
regards
John
Terryd21/09/2010 15:57:05
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1946 forum posts
179 photos
Hi again Stepan,
 
Try here for information about your lathe.
 
Regards
 
Terry
Stepan Ptacek21/09/2010 18:53:37
4 forum posts
It looks that I have not explained myself properly. Before I bought the lathe I saw the part on Lathes web. However it does not say which wheels were usually included with the lathe either metric or imperial. I have some gears which came with the lathe however I do not know if that is all set. What I know is that part of them is not from this lathe as they have different bore as well as two key-ways opposite each other. Perhaps from Atlas lathe.
I wanted to put together either whole set or to find how I can improvise those missing gears, how to use them for power feed and then learn how to make with them metric and imperial threads. I know that there are books for learning how to make threads and I will be purchasing them or if I find some local course open in the evenings that could be the way to do it. Hopefully this is better explanation.
Nicholas Farr21/09/2010 21:23:48
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3988 forum posts
1799 photos
Hi, I believe the Portass lathe had as standard change wheels from 20 up to 65 in 5 teeth stages i.e 20, 25, 30 ect. and I think the bores are 5/8 inch. The Portass S, Randa, Zyto, Bonds Maximus, were all much the same lathe. I'm not sure if they are able to cut metric theads without having a special change wheel or two. Hope this helps.
Regards Nick.
Stepan Ptacek21/09/2010 22:11:58
4 forum posts
Thank you Nick and others. Just found from another source (Tony Griffiths) that there should be 2x20, 1x25,1x30,1x35, 1x40, 1x45,1x50,1x55,1x60. For metric conversion (usualy paid extra) there should be 1x 63 or 1x65. As I have checked I have most of them apart from metric conversions but those Atlas ones have one 63 slightly damaged (I will have to replace 2 teeth) with reduction inside I should be able to use it and rest hopefully will somewhere appear.
John Stevenson21/09/2010 22:41:32
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5068 forum posts
3 photos
Stepan,
measure on of the gears across the teeth and post that size here and how many teeth, also the bore and width.
From that information we can work out if something popular like the Myford will fit to make you a full set.
 
John S
Stepan Ptacek30/09/2010 23:59:12
4 forum posts
Thank you for your advice guys. After hopelessly trying to measure the tread on the lead screw and all questions which are running through my head I have decided to learn it properly. I was lucky enough to find that one of the model engineering clubs organises drop in sessions in one of the colleges. Went first time today and it looks like sold to me. I will keep you posted once I learn enough to be more specific with my questions.

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