Axminster BV20M?

Hello, new here so be gentle, I am just about to buy a SH Axminster BV20M lathe, but unfortunately it has no change gears for screw cutting and having tried Axminster and ARC euro trade I haven't been able to find or even cross-reference any other lathes that may use the same gear set, as I am lead to believe that it is Chinese in origin and may be the same as several other lathes, so as there are a lot of very knowledgeable people here I thought I would ask in the hope of finding something to fit.

Try Warco or Chester Macine Tools.

You should be able to measure an existing gear, even the fixed one on the spindle and then armed with the number of teeth and outside diameter work out what the gear spec is , probably MOD1.

A look at the chart in the manual or on the machine will show what tooth counts are needed and you can then decide which way to go from there either buying cheap metric gears from somewhere like Beltingonline or if you have a 3D printer you could print your own so long as you don't take too deep a cut.

Warco used to sell the BV20 as did several others. I have the manual as a pdf if you need it.

Being of oriental origin (Taiwan or China ) the gears are most likely to be Module., and as Jason says Mod 1, Mod 1.25 or Mod 1.5

On my larger Taiwanese lathe, (Think Warco BH600 or Chester Craftsman ) the changewheels are 1.25 Mod , and the pinion that engages with the rack on the bed is 1.5 Mod )

The chances are that the same lathe will have been imported by others, such as Warco, Chester, or Arc Euro etc, spare gears shoulkd be available.

Often changewheels increment in 5s, starting at 25 or 30 teeth, and going up to 80T.

The Sieg SC4 includes a 127T gear so that despite having a Metric Leadscew, it can cut Imperial threads.

Even id you don't want to cut Imperial threads, a set of changewheels will allow you to set up for a dine feed.

Most mini lathes have two 20T and two 80T wheels in their set, and allows a feed rate of 0.09375 mm per rev to be set, which should be sufficiently fine for most purp[oses.

If you have just one of the changewheels, certainly the driving pinion under the tumbler reverse, you can measure vthe OD in mm, and countbthe teeth.

The formula is : Diameter = (Tooth Count + 2 )/ Module.

Thus a 30 tooth Mod 1 gear would be 32 mm OD

Once you are certain of the Module, you should be able to find replacements. The chances are that the bore and thickness will be the same.

The 1 Mod gears for the mini lathe, (and probably it's smaller sisters ) are plastic, bur Arc Euro can supply metal ones, if you so require. I think that the S4 uses metal gears

HTH

Howard.

Does anyone recognise the BV20 in another clone, where perhaps spares are available?

Replacing missing gears can be a pain. Although the teeth and gears will be one of a few standards, the way they connect to shafts varies, and the set of gears needed to produce thread ratios varies with model. (My WM280 came with 11 change gears, so not just one or two.)

Ideally, the needed gears and fixtures are available off-the-shelf. (Either new or second-hand.) Luck is involved - the search can be anything between easy and impossible.

If model specific gears can't be found, the nearest commercial gears can be bought and modified to fit with home-made fixtures. Though within the capabilities of a reasonably equipped and skilled home workshop, it was beyond my reach as a raw beginner, especially as I wanted to use my equipment on day one rather than mend it.

Does the lathe have any gears in it? Like as not the gears needed to do fine feed are fitted and only the threading gears have been lost. If so, lathe threading isn't a common operation - small sizes are done with taps and dies - so you may have plenty of time to sort the gears out. Plain lathes don't do threading at all! Worst case, all the gears are missing, or the banjo is set to cut a rarely needed thread, and can't do the valuable fine feed.

Depends on what's wanted of the machine. Provided the motor turns the chuck, you can do and learn a lot on a lathe with missing gears. Maybe use it to learn, if it's suitably cheap, and then upgrade later? Or use it whilst looking for replacement gears or learning how to modify commercial variants.

Dave

Without changewheels, the machine is effectively a Training lathe. It is still capable of use, within its limitations.

Boxford and Raglan produced Training Lathes devoid of Leadscrews and changewheels, on which Apprentices could learn their craft and skills.

(Last Sunday, I used the Louhgborough at The WaterWorks Museum! A very nice little lathe )

So, as S O D says, use the lathe to learn, while you search for the gears. To avoid problems when compounding, if possible try to source all from the same manufacturer. On mini lathes, some manufacturers use 3 mm keys, while others use 4 mm, so there could be problems trying to compound gears from different manufacturers, with differing standards.

Howard

I’ve had a BV20 for over ten years and only done single point threading on it a couple of times not long after I got it. For my use it’s much quicker and easier to use taps and dies. I do of course though use the gears for auto feed though, at the lowest rate. I haven’t touched the change wheels for at least ten years. Obviously though others use their machines for different projects that may require regular use of change wheels.

Thanks for the info guys, I am making a little headway in that it seems the Warco BV20-1 looks to be nearly identical so that is somewhere to start, I mainly bought it to be a replacement for my ancient round bed Drummond which, although I have used it off and on for the last nearly 50 years it got a duff chuck which requires a few taps to centre.

As the Axminster carriage movement seems quite course is one of the reasons for wanting some change wheels, but I am still not sure if it has a disengage feature which could be a pain, can't see a carriage lock either, but still in the process of pulling apart, looks OK for wear but need a little fetteling, while I'm asking what would be the best oil for the box as it lost some during the move....looks like two people could move it easy, but it took three at a struggle!

Also, I wanted to ask for recommendations on fitting an electronic speed control? I believe these lathes use an induction motor so require an inverter to control speed, is there a budget option for this? It should in theory be OK as it has a reduction box, so torque shouldn't be an issue, the Drummond was just used for basic turning and had a washing machine motor so fitting a speed control was easy and cheap.

Mind you I haven't done any screw cutting since my school days, and probably won't do much now, but having the change gears would be useful if only for a power feed.

Very recently I sold my lathe - a BL200/Axminster BV20 lookalike. I had fitted it with an electronic lead-screw but retained all the change gears which were included in the sale. They would fit your lathe. If you like, I can email him to see if he could be persuaded to part with them?. He is a forum member, so he may contact you directly.

John

The lowest speed on my BV20 was far too fast for thread cutting so the very first job I did on it was to make a smaller motor pulley to slow it down. It’s been on the machine ever since.

So, all that you need now, if no handbook to list them, is for some kind sould to tell you about the changewheels,

Tooth counts, Module, and dimensions.

If you are lucky you might well find a source of supply of suitable gears!

Howard

I've already given Dick a possible source for a complete set of gears, above. I still have digital copies of the lathe manual supplied with my lathe and another for an identical lathe from a manual site on the web.

The gears are listed in the chart below and are described elsewhere in the manual as being MOD 1.5. Pressure angle of choice, if you are going to the trouble of making them, likewise the width. Just have to match the one on the gearbox output shaft.

Vic - one manual I have suggests it's possible to introduce an 18 tooth gear in the train as a tumbler reversing gear so that the leadscrew turns "the other way", Then you can turn right hand threads away from a face at any speed you like.

Dick, you ask about the ELS. I did a series of videos on YouTube about fitting one to my lathe. Introductory video here. It's not difficult but neither is it cheap! Probably more expensive than buying/making the gears and banjo, but far, far more convenient.

Here's the relevant page for the gear tooth counts:

John

You'll need to change the motor to a 3-phase one matched to an inverter. People like Newton Tesla do suitable packages (like the one I fitted to my BV20) although some mechanical modification was needed to the motor mounting. It works really well. Don't know how 'economical' it is these days though.

I've done plenty of screw cutting on mine, with fair results overall. There's no auto knock off on the feed or screw cutting indicator, so you just leave the lead screw permanently engaged, stop and reverse on each pass (having taken the cut off of course), You just get used to it.

regards Mike

Edited By Mike Hurley on 13/07/2023 17:37:36