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Rescuing a 920 lathe!

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John Rudd11/02/2018 16:43:07
1161 forum posts
55 photos
Posted by John Rudd on 11/02/2018 14:24:15:

Andrew,

I have genuine Gates 710 belts if you need one or two, but not at machine supplier prices. Contact me via private message if you need to.

Just been and checked....the belts are 730 not 710. Although some of the 9 x 20 lathes were fitted with the longer blt like mine.....Sorry for the mis-information.

Redsetter11/02/2018 16:48:19
72 forum posts

As a matter of interest, does anyone know the difference between the 920 lathe that uses the 710 belt and the one that uses the 730, as the belt length is fairly critical?

mick H11/02/2018 17:16:41
628 forum posts
18 photos

Just guessing really, but I suspect that it has something to do with the motor mounting.

Mick

mick H11/02/2018 17:24:42
628 forum posts
18 photos

Andrew, I have had no problems running mine at low speeds. I do not have any expertise in inverter / motor technology but I suspect that it will depend on your outfit. I am pretty sure that some knowledgeable person on this site could answer the question for you in more detail. Having said that, with the original setup you are going to get a speed of between 100 - 120 rpm anyway and that can be more than just annoying when you only want 50. I am probably talking rubbish but what about an additional 12v cooling fan eg from a computer? It seems to me that you have not got a lot to lose by trying it out.

Mick

Edited By mick H on 11/02/2018 17:26:04

John Rudd11/02/2018 17:39:55
1161 forum posts
55 photos

With the original motor running at 50 hz, 1400rpm or so, a 3 ph motor running at 25 hz would give the required 50 rpm spindle speed, with the motor running at some 700 rpm...There is of course a reduction in torque running slower motor speeds.....

I've not encountered any issue with my 9 x 20 other than a slippery belt caused by lubricant ingress.....( over zealous with the oil can...)

Andrew Tinsley11/02/2018 18:42:42
758 forum posts

Thanks John!,

I will sort out the belt size and stick the nail in the wall! As far as the 710 or 730 bet is concerned. I am told on good authority that it is indeed the choice of electric motor and its mounting plate (feet). My belt is 910 on the Chester 920, yet the manual says it is a 930! It just depends on what motors are to hand on assembly.

Regards,

Andrew.

Redsetter11/02/2018 19:11:31
72 forum posts

My Chester 920 has the 710 belt. I imagine the longer one is even more expensive. If it is a question of motor mount which seems reasonable, surely the toothed belt would have to be longer as well? I know I'm being picky but I'm getting interested, and there isn't much info on the 920 forums which relates to the UK versions of these lathes.

Considering how many must have been sold, they are quite rare secondhand and you never hear of one being broken for spares.

Andrew Tinsley12/02/2018 15:50:43
758 forum posts

Hello Redsetter,

You are quite correct in saying that a different length cogged belt is required if a 930 Gates belt is used. I am afraid off hand I can't remember the required size, but I have it noted somewhere if you really want to know the size!

Like you, I am amazed at the scarcity of second hand 920 lathes in the UK. I am not sure if I am correct, but I think they were only imported by Warco and Chester? Maybe they just didn't sell very well over here, unlike the USA! In their unfettled form they are a bit of a kit lathe and I am not sure how many people would have modified them to a high standard. It is a cheap lathe and I would think most were purchased by beginners, who would not have the experience to modify them. I would therefore expect that there would be quite a turnover of 920s, but apparently not!

I have never seen one being broken for spares. Although the one I have would be a good candidate, if I hadn't promised it to an impecunious friend, who is a novice engineer!

Regards,

Andrew

Redsetter12/02/2018 18:36:11
72 forum posts

I bought mine partly because I wanted a "reliable" belt drive rather than dubious foreign electronics, but in fact the belt drive is a weakness. I think they are good value if you know what you are doing, as the basic machine is quite sound. Some of the desirable modifications are not that simple for beginners and you would think that an improved version could be manufactured for very little extra cost.

Some of the non UK versions have interesting variations, such as tumbler reverse and some even have the hand wheel on the "English" side of the apron.

I have made a tumbler reverse and a long-travel tailstock for mine but so far have not felt the need for a four-bolt compound mounting, which is apparently essential. I suppose I am not taking deep enough cuts!

Andrew Tinsley12/02/2018 19:09:57
758 forum posts

Hello Redsetter,

Your thoughts are much the same as mine. The lathe isn't bad, but for only a bit more effort on the manufacturer's part and suitable price increase, It could have been an excellent lathe!

I find the belt system to be a pain and a friend's much modified lathe was spoilt by this weird system. I am still in two minds whether to reinstate this or do something about it!

With regard to the 4 bolt compound mounting. my friend found that it wasn't strictly necessary as long as you put in some decent gib strips and located them (end on, a la GHT method). He did however finally do a much improved 4 bolt mod, which I think was purely a machining exercise to show off his skill. Whoever bought that lathe got a real bargain!

Redsetter12/02/2018 19:22:34
72 forum posts

Thinking about it, I did make new gib strips with better locating screws. I think the point about the compound mounting is that when the lathe was designed as an Emco in 1970? it was never intended for industrial rates of production using carbide tooling. Tell that to the kids today.....

mick H13/02/2018 10:32:23
628 forum posts
18 photos

My Chester 920 is my second. The first was a Warco which I bought secondhand and despite all the advice freely given about taking someone who knows lathes, I did not know any such person and ended up with a lathe with a badly worn bed down at the business end. In all other respects I found it to be a fine machine and after a fashion learnt to compensate for the worn bed enough to do some reasonable work. I did extend the cross slide travel, which probably wasn't really necessary but it did give me the opportunity to fit the Arc Euro anti backlash bearing set which was. I also made a 4 bolt compound mounting which reduced the top slide flexing on heavier cuts. As I have already mentioned the best mod of all was the inverter drive which transformed the machine and did away with the hassle of belt changing and belt breakages. That clutch knob can easily slip out of an oily hand and bang goes another fragile and expensive belt. This one had a 730 belt which was always a bit loose and could slip off the pulley with the clutch out. It would also run with a 710 but that was a bit tight until well run in. I also made a Steve Bedair type tumbler reverse but never actually used it in anger. I also upgraded the gib strip adjusting screws with the addition of bearings and this smoothed the cross slide action considerably.

Eventually the worn bed got the better of me as I became more critical of my own work and I sought to give it away to a youngster or other impecunious soul who maybe wished to get started but I found giving it away a lot more difficult than may be imagined. I heard a few "hard luck" stories which I just did not believe but eventually it found another home. I did take the inverter drive off and reverted it to original condition.

The features that I liked best about the 920 were its compact size and the threaded mandrel nose but these things were not easily found on other lathes. A Myford for instance was just a bit too big for my workshop. The ability to just screw on / screw off different chucks was a great time saver as well as an encouragement to use the right chuck for the job, & I was not prepared to give it up so I went for another 920 but found that Chester were then the only importers. I have of course refitted the inverter drive and apart from just the odd squirt of oil, the belt drive door is now rarely opened. Cosmetically, the Warco had the edge on the Chester which does have a few rough bits on the castings. It doesn't affect the running of the machine but I am sure that smartening up these areas wouldn't have put a great deal on the price.

Sorry to ramble on but the old hip is twingeing badly and keeping me out of the workshop so I had to find something to do.

Mick

Redsetter13/02/2018 11:19:25
72 forum posts

They were also imported by Axminster for a while, with the option of a slow-speed pulley attachment which bolted to the bracket plate somehow. It would be interesting to know what this was like, as I have never seen one.

Andrew Tinsley13/02/2018 11:33:18
758 forum posts

Hello Redsetter,

I have the series of ME articles that someone on the forum kindly sent to me. They detail a low speed conversion with I think a kit that was available from Axminster. PM me if you want a copy!

So yes I should have remembered about Axminster importing the 920. Memory is getting bad!

Andrew

Martin Hamilton 113/02/2018 18:42:05
25 forum posts

Their was also the Excel Pinnacle 918 lathe.

Andrew Tinsley13/02/2018 18:49:42
758 forum posts

Thanks Martin!

That was a 920 importer that I didn't know of.

Andrew.

Niels Abildgaard14/02/2018 06:52:35
116 forum posts
11 photos

An one hand mobile- video of an old lathe/man with VFD.

VFD drive is by far the best part of the shown man -machine combination.

I cut threads in direct drive and I have not spoiled electric motor yet.

**LINK**

John Haine14/02/2018 07:58:49
1987 forum posts
112 photos

Can you fit link belts? Then you can adjust to fit.

As for using a vfd, if you get one with flux vector control the motor can develop full torque down to almost stopped. It may need a cooling fan though.

Martin Hamilton 114/02/2018 13:59:41
25 forum posts

Just remembered their is also the Amadeal CJ 23B - 9x20 & CJ 23B x 750mm between centres, these 2 lathes come with 1200w motors + variable speed 100rpm - 1800rpm. Still sold today by Amadeal in London, these versions are made by Red Bull, don't know if this is the same maker that also makes the Chester 920.

Martin Hamilton 114/02/2018 16:10:48
25 forum posts

The manufacturer should have read Real Bull.

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