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X2 Mill Belt Drive MEW Issues 199/201

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John Shepherd28/03/2013 10:47:31
222 forum posts
7 photos

Hello

I am interested in carrying out the belt drive conversion to my X2 mill described by Neil Wyatt in MEW issues 199 & 201.

I have some questions about the pulleys and Poly V belts, if Neil or anyone else can answer these perhaps it may help others also.

1. I have had trouble finding a one off stockist for the belt. If any one knows a supplier that will sell small numbers of the right belt I would be grateful for their details.

2. In the photograph the belt is shown as 325 PJ but in the scrip says it is a 312 -PJ. I assume the photograph is correct unless something changed during 'production'.

3. There are no vertical dimensions for the either the large or small diameter pulley. I am assuming the large one is 10mm, but it would be useful to have the small pulley height if possible.

I like the general idea of this modification and it looks much more practical and easier to do than others I have seen.

Regards

John Shepherd

Ian P28/03/2013 12:03:38
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2524 forum posts
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I have never had problems getting polyvee belts in the UK. I have not actually purchased belts from 'simplybearings.co.uk' but I have bought bearings and other parts and they gave an excellent service. (no connection etc)

In my opinion the article had too many similar photographs but a bit vague on some details.

I did notice, is that the method of installing bearings shown does risk potential damage to the new ballraces. Apart from the the fact that the peice of angle iron the writer used could bend, picture 41 just made me cringe as the inner race is unsupported so all the force neede to seat the shaft is being transmitted through the ballrace itself.

When installing bearings in shafts and housing its is important to apply pressure ONLY to the inner or outer race (whichever is the relevant press fit) so that at no time is any axial force applied to the balls or track surfaces.

A plate (washer) of substantial thickness that bears on the inner and outer race is also acceptable as its unlikely to dish more than the axial movement in the bearing.

 

Ian

Edited By Ian Phillips on 28/03/2013 12:05:11

Stub Mandrel28/03/2013 12:38:52
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4311 forum posts
291 photos
1 articles

Hi John,

You're in luck - I broke work for Easter yesterday and I'm taking a break after helping my daughter out with Pythgoras!

The number for the belt is the length in mm. They are produced at all sorts of sizes, and I think that some suppliers will substitute for the nearest size.

Either a 312 or a 325 will do as there is only some 6mm of adjustment needed between the two sizes. A 305 (nominally 12" belt should fit OK and may be easier to source. I got my belt from Arrow Rugby but they seem to only have 330 or 280 at the moment. 280 will probably be too short, but I'm sure you could adapt to a 330 belt if you move the motor mount back a little.

I also tried a belt from Bearings R Us but ordered a '300j' by mistake - which is 30" not 300mm! I will be using this one as a new lathe drive belt.They don't list shorter sizes, but if I recall correctly they said they could source the size I needed, but opnly after I'd ordered from Arrow.

So it seems availability fo exact sizes is hit and miss - I suggest ringing up Arrow Rugby or Bearing R Us to find out what is the closest size they have. I also suggest ordering eight ribs - its easy to split the belt in two and then you have a spare on the shelf of exactly the right size.

My pulleys are nominally 12mm thick at the flange, but as long as they are thick enough for the grooves, and the big pulley is thick enough to be stable on the spindle you will be OK. You could go down to 3 grooves without trouble, I suspect.

For the record I haven't had to make any adjustments since initial setting up of the drive. I did some milling just a few days ago, and the machine is much nicer to use with the three modifications.

I shall probably follow Johan Crous and add a cooling fan on top of the motor, as now it is more rigid and quieter I think I am working it harder.

Neil

Stub Mandrel28/03/2013 13:02:42
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4311 forum posts
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1 articles

Hi Ian,

It's unusual to get constructive criticism on articles from readers so I appreciate your post. Praise is nice; questions are thought provoking; rude comments are what they are! - honest opinions like yours are helpful!

The reason for using angle iron was I thought it would be less likely to flex.

I have to apologise for making you cringe. The forces involved in drawing the spindle into the bearing lke that were actually quite modest, not much more than a push fit, ceratinly not enough to be called a press fit - don't forget the inner race has to be able to move slightly on the top end of the spindle to allow you to adjust the preload, and the bearing seat at the bottom end of the spindle was no tighter. I did describe the 'gentlest persuasion' needed to remove the old race. In contrast, the outer bearings are an interference fit in the housing. Perhaps I should have highlighted the difference in fit in the text.

It''s hard to judge what pictures are needed; I felt there may be too many, but they could be edited out if it was felt they were excessive. On the other hand, a step missed out might put a beginner off from attempting a task well within their capabilities, so it's not an easy judgement to make.

It's much harder to decide what level of complexity to aim for in the text. As you have done the operation yourself, it can be easy to skip over something without realising.

I enjoy writing about model engineering as much as actually making things (and it's warmer!) but just like making things, writing is a learning curve too!

Neil

Neil

John Shepherd28/03/2013 13:22:20
222 forum posts
7 photos

Neil

Thanks for the reply. The only excuse I now have for not doing the mod is the cold workshop!

Regards

John Shepherd

Ian P28/03/2013 20:23:25
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2524 forum posts
102 photos

Neil

I am not sure I would have described my post as constructive! but it certainly was not meant to offend. I am not in a position to criticise your skill an an author either as I have never written any articles (I am full of good intentions to write some but after realising how hard it is, keep putting it off). I do realise, more than I ever used to) that without people such as yourself our engineering magazines would just not be around.

As regards the bearing installation, angle iron is stiffer than a flat strip but only at the stiiffened edge. A large washer, even if it deformed under load would still apply the force concentrically. In general though, ballraces seem to be much more robust than we are led to believe and do tolerate loads that they are not supposed to.

Ian

Stub Mandrel28/03/2013 20:44:00
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4311 forum posts
291 photos
1 articles

Ian

In general though, ballraces seem to be much more robust than we are led to believe and do tolerate loads that they are not supposed to.

I was worrying about the weight of some of the things I was putting in my mini lathe - then it ocurred to me that the roller bearing I had fitted was bigger than those fitted to cars...

Neil

oldvelo29/03/2013 20:21:20
276 forum posts
54 photos

Hi

I am looking forward to Issue 199 with regard to belt drive conversion to an X2 Mill Drill

As always I am interested in how others do things .

However we have to wait for the MEW in New Zealand for around six weeks delay before it is on sale

here.

Eric

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