I wondered if, instead of gear changes, you could alter the speed of the motor to achieve the same result.

 

I would say yes…but:

I recently did a pretty huge job using backgear on my lathe and was amazed by the amount of non-stop hard work a lathe can do, and I was VERY glad that I did not have to subject an expensive 1/2HP electric motor system to this level of effort.

 

In-my-opinion

Gearing and a decent single speed motor is the way to go if you’re going to get serious at this hobby and work your lathe hard at times.

 

Taps and dies are too restrictive for threadcutting, especially where concentricity is important.

I often partially cut a metric thread on the lathe, then finish with a tap or die so that concentricity is “guaranteed”.

Once you get some skills you will be in a position to put whatever thread you want onto or into whatever thickness of bar you want.

For very small threads taps and dies are very useful, I only have a basic metric set.

They are also very useful for cleaning up important threads, i have a few big imperial ones for cleaning out my mandrel/chucks etc.

 

 

Ady’s right – but with the best will in the world, a Hobbymat MD65 isn’t going to be a major workhorse. Well mine isn’t; it’s just not that chunky a lathe. And yes it has a reversible induction motor. It’s not impossible to control the speed of these – they are only a single-phase version of a three-phase induction motor after all, but if I was going to do this, I think I’d swap the motor out for a three-phase one anyway and save a lot of hassle.

 

The other major consideration with an MD65 though is that its lowest speed as standard is 200rpm – way too fast really. And even though you could achieve a much lower running speed with some sort of speed-controlled motor it would be running way outside its range of effective power production and be compromising the cooling somewhat. So if you were going to go for a lower running speed, I think that you’d be rather better off leaving the motor alone, and going for one of the low speed belt conversions. I’m pretty sure that these are still available, and it wouldn’t be beyond the realms of possibility to make one for yourself, either. I suppose that if you were going to be really flash, you could do the motor swap as well – but I’d keep asking myself whether on this lathe it would really be worth it, quite frankly. They are okay for what they are, but they have some distinct limitations. A big one is with the leadscrew, and it’s this, along with the 200 rpm min speed that make any form of thread turning very difficult to achieve.

 

All these things are fixable, I suppose – but you’d have to ask yourself very seriously whether it wasn’t worth saving the money you’d spend for a lathe where you’d have to make rather less compromises. I have no intention of keeping my Hobbymat in the long term; it’s quite useful at present for fixing bits of the Kerry I’m slowly rebuilding, but I’m certainly not going to throw any more money at it for improvements.

Hi, I agree with both what Ady and Steve say, and as you may have seen my photo album about the Hobbymat refurb that I am slowly doing, 7 years so far, but to be honest it sat in my garage taking a somewhat back seat for most of that time. It was bought second hand of ebay and had some modifications done to it by a previous owner. I like Steve don’t intend to throw very much money at it, about £20.00 so far for paint and a new piece of Ally and that will be about the limit. But on the question of £60/70 for adding a slow drive to the V belts I would think is quite a small amount compared to the cost of a three phase motor and converter.

Hi Steve, the ally was for the change wheel apron, see pic at top of this thread. The leadscrew support was originally Bakelite but I made a new one from part of a cast iron bearing housing, but I suppose ally would do for that, its just that the scrap bearing housing cost me zero cash.

Well there are speed controls, and then there are speed controls….The type of thing that works on a universal motor, eg the ones with brushes, don’t maintain torque very well at low speeds. They are OK for slowing down an electric drill, but not much more.

 

The type that work on a three phase motor are much better, and will give good torque at slow speed. However, at best you are only going to get the same maximum torque when going slow. So you can get it slow enough to keep control for screwcutting, but it will not replace a backgear for doing heavy cuts.

 

So the ideal is of course to have both, eg a back gear or the equivalent for gearing down to allow turning things like flywheels at low speed but with a good cut…I shouldn’t really say heavy cut because none of our smaller lathe really take what could be called a heavy cut, but I mean heavy enough that it is reasonable to attempt the job. Then if you also have a motor speed control, you can screwcut at low speed, and return to the start in reverse at high speed.

 

regards

John

 

Having done some experiments with this lately using a fractional horsepower motor and a controller where the torque compensation is very flexibly adjustable, I’d say that that it would appear that the torque holds up better with larger motors – anything over 1HP, it certainly works reasonably well. This may well be a limitation in the particular small motor I was testing, admittedly – but it does go to show that you’d really need a tried and tested solution before you were going to rely on it for low-speed running, I’d say. And you still have the cooling problem to cope with, and that would definitely be worse if you significantly loaded the motor while it was running slowly, especially if it was being significantly torque-compensated.

 

So as far as I’m concerned, it would definitely be the belts and pulleys solution first, and only then consider a 3-phase motor on the Hobbymat – if I was going to do it at all, of course!

Hi Steve, it is No: 107S Sunshine Yellow in the 100ml spray cans at about £2.49 each when I bought them. Not sure if they were on offer at the time, but it took almost four of these. They weren’t to bad to use, but they don’t like the cold too much, so I stood them on my oil filled radiater for a while before use, as it was just a little before Chrismas time when I did It, however I did prime the Ally with Hammerite Special Metal Primer first, which I allready had, and the saddle and tailstock had a coat of grey Plasti-Kote primer which I also already had. No real effort was made as it was only intended to be a tidy up job, I’m no painting expert.

Posted by Nicholas Farr on 02/05/2011 14:58:02:

Neither am I – and I certainly have quite a bit to do on various refurbishment projects, so I’m very interested in how people get on with the various painty substances they use, so thanks for the info.

 

As far as the Hobbymat is concerned, I have to repaint the tailstock from scratch. The top of it got somewhat ‘abused’ in its previous situation (heaven knows why), so I’ve cleaned it up and linished the abuse away, but I reckon that the chances of an exact match are minimal – hence having to do the whole thing.

 

Paul, no Hobbymat lathe I’ve ever seen or even dreamed of could take an 8″ chuck!

 

Regards, Steve