Belt or direct drive lathe

[Frank RichesParticipant @frankriches20013]

Hi Everyone, I'm new to model engineering and currently setting up my workshop. My question relates to the pro and cons for a direct drive versus belt drive mini lathe.

I'm currently consideringt a Warco lathe.

Any thoughts and advise would be greatly appreciated.

[Frank RichesParticipant @frankriches20013]

[Thor 🇳🇴Participant @thor]

Hi Frank,

Welcome to the forum. If you with belt drive means a lathe where you change belt position on the pulley to change speeds this method will give you increased torque with low speeds compared to a lathe where speeds is varied electronically. I would prefer a lathe with brushless motor over a brushed one. On my Chinese lathe I can change the belt and in addition have VFD so I get variable speed in two ways.
Most hobby lathes will use a belt to transmit power from the motor to the spindle.

Thor

[JasonBModerator @jasonb]

The "belt drive" mini-lathes tend to drive via a two speed gearbox which can be noisy and also if overloaded the often plastic gears can be damaged. Some people replace these with metal gears but that increses noise quite a lot and should the lathe be stalled then there is more chance of the motor or control board being damaged. They can have a bit more power at slower speeds than direct drive depending on the true wattage* of the motor as the low range gearing gives the motor some mechanical advantage.

The "direct drive" mini-lathes still use a belt but that runs from motor direct to the spindle eliminating the need for a gearbox and its associated issues. As there is effectively only one drive ratio there can be some loss in low down grunt but often the direct drive ones have brushless motors which are more powerful at low revs than the usual DC motors used on the belt drive ones. I've a couple of direct drive Sieg mills and they are a lot quieter than my belt & 2 speed gearbox equipped mill and in most situations have enough power as well as an effective overload that cuts the power well before frying the motor or controls

* do check what wattage is being quoted in the spec, some suppliers state input others what you are actually going to get out of the motor

[Howard LewisParticipant @howardlewis46836]

Welcome!

Don't rush into a purchase. Find a local M E Club and join. You will learn a lot.

Study the many posts on the Forum which refer to mini lathes, and those powered by either brushed or brushless motor.

Both brushed and brushless motors, deliver their power to the lathe via a belt..

My mini lathe is relatively old so has a brushed motor driving by a belt,into a "High / Low" gear choice

Motor speed is selected electronically, give the spindle speeds shown on the digital read out..

The motor speed will most likely not be that of the spindle speed shown on the controls (Motor speed will be different by the gear (belt ) ratio between the motor and the spindle.

Power is fed ton the DC motor in a series of pulses, the frequency of which is determined by the control board speed setting.

As the motor speed is reduced, so will the power delivered (Which is why torque and motor speed is increased; in the same way as a gearbox in a car ) .

As I understand it, the more modern mini lathes are powered by brushless motors, (Where electronics take over the job of feeding current at the right time to the rotor of the motor, to provide the required spindle speed.speed.

Brushless motors deliver a more or less constant torqued over their speed range, meaning that, like most all electric motors, they draw more currents as their speed falls. One of the laws of physics!)

Continued running, at low speed and high current draw will cause the motor to heat up and possibly suffer damage

Control boards have become more reliable, but the best way to safeguard the control board is ALWAYS to turn the speed control to Zero before either staring or stopping (A motor starting up can draw much more than the normal running current, and shutting an electronically controlled motor from speed might produce voltage spikes that can damage the control board. Better safe that sorry.

As a newbie, you need to buy and study an study at least one of the books on lathework

Basic Lathework by Stan Bray, Lathework by Harold Hall, The Amateur's Lathe by L H Sparey (Old and heavily orientated towards the Myford ML7. The details differ, but the basic principles remain the same )

David Clark, Dave Fenner (Like Stan Bray, and Harold Hall previous editors of Model Engineers' Workshop) and Neil Wyatt has written a book featuring the min lathe.

Neil Wyatt has written a book on lathework, based on his recent experiences with the mini lathe's bigger sister, the SC4..

The essential thing is to grasp the basic principles of setting up and operating a mini lathe, and to learn by making simple tools. Not only will such things give experience of the machine, and machining, but confidence in using the machine.

Do NOT expect perfection out of the box. (this is where having knowledgeable friend close by to advise, help and demonstrate

Even a brand new machine may benefit from a little fine tuning..Sadly some machines arrive with built in faults (So so bad that machine has to be exchanged! )

You are at the very lower end of the budget hobby market

High precision COSTS! (A high precision Swiss, industrial bore gauge can set you back $5,000+ after a six month wait!l) An industrial machining line can easily cost MANY millions of £.

Do not expect, even a new, 3 jaw chuck to hold work absolutely concentric. (I have only once found such delightful chuck ) It is more like that a good one will hold work concentric to better than 120 microns (0.012 mm)

BUT correctly set up and used, incredible work can be produced (Witness the model seen at Exhibitions )

For maximum concentricity, or to hold square, octagonal or irregular work, you will soon find a need for a 4 jaw independent chuck (which then shoe the need for Dial Indicator m( ms ) and a magnetic base.

But you don't have to have everything at once.

As you learn and gain experience, you will, eventually become aware of greeter needs., so cross one bridge at a time.

Your budget does need to allow for measuring equipment, cutting tools and very possibly, a bench grinder.

Again, the books will advise on what to but, and how to use for a given job.

Complicated models from expensive kits and material can come later when you know nor about hot to operate the machine.. Spoiling a bit of mild steel bar is far less of a problem that if the workpiece is an expensive casting!

Hope that all this rambling will be of some help.

Howarfd

[Chris MateParticipant @chrismate31303]

My 330 Lathe has a gearbox, but tentioned belt driven from motor to input shaft. My mill is direct drive into gearbox by motor.

The lathe=Belt drive to gearbox(No plastic gears anywhere), but the 160mm chuck has weight.
I made a mod to my lathe to give it in the forward direction a "soft start" by adding a longer belt and then tentioning it with an extra jockey pully spring loaded. When the motor spins up I felt if puts an abrupt load on the gearbox with a tentioned belt  & 160mm chuck, so the mod work like this…. With motor off, the belt is slack. As soon as the motor starts, there's say 1 second (1001 count) where the belt automatically tention due to the direction it runs & jockey pully spring tention, this "delay" gives it a noticible soft start. Once running it pulls strong enough to break a tool tip like an cut off tool if feed in too fast, so there no lack of grip. This mod is not necessary on a well made lathe with larger gears inside wich can take the jolt.

The mill=Direct drive
On the mill direct drive there no large weighted chuck, so no problem.

Edited By Chris Mate on 23/01/2023 22:04:03

[HuubParticipant @huub]

Lathes are not direct driven because they have a spindle bore to turn long bars.

Some lathes have a Norton gearbox for easy gear (speed) change. They always run at max RPM and are loud and have a lot of torque in low gear. Others have a single pulley and a variable speed control. These are really "quit" but have very low torque at low RPM. Some lathes have a pulley and a 2 position gearbox. They ar not so quit and have a bit (2 times) more torque in low gear.

Some lathes have brushed motors and are loud but I also have a 1.5 kW brushed DC motor that makes less noise than my 600W brushless DC motor (BLDC). A timing belt pulley (teeth) makes more noise than a V-pulley. Metal gears make more noise than plastic gears. I made metal gears for my mini lathe but replaced them after a short period of use becasue the where to noisy.

Most of the time I have plenty of torque on both my lathes. Sometimes when turning 70 mm stainless steel or 180mm aluminium, i would like to have more torque. Also threading larger diameters 20+ mm requires a lot of torque. Then my lathes are not optimal but the job can be done. It just takes more time and hassle.

What you really needs depends on what you want to make. What ever lathe you have, it has its limits and some times you wish you had a smaller or larger lathe.

I don't expect your first lathe will be your last lathe. Once you have learned to use it, you probably will change your demands.

[Perko7Participant @perko7]

Both my lathes (one about 95 years old and the other about 5 years old) have belt drive. The old lathe has flat leather belts, the newer lathe v-belts. I would not consider anything else. The belts, if tensioned sensibly, provide an in-built torque limiter so that if you accidentally dig in when turning (it happens to all of us at some time) or worse still drive the toolpost into the chuck (I've not done that one yet) the belt will slip preventing any major damage before you are able to cut the power.

Both my lathes are powered by a 1440RPM 240V AC motor. Speed changes for me are therefore reliant on changing the belt position, which is clumsy and inefficient but I'm happy to do that for the quantity and nature of the work that I do on them. If I had more $$$ I would trade one in on a new machine with a quick-change gearbox but still retaining belt drive.

Anyway, that's just my opinion. Best to talk to a few others in your local ME club who have experience on a wider range of machines.

[Dave HalfordParticipant @davehalford22513]

Bear in mind that the distance between centres quoted by all suppliers does not include the three jaw chuck so you will loose around 75mm that end and for drilling from the tailstock you loose drill length and chuck at that end as well.

[JasonBModerator @jasonb]

For the sake of not confusing Frank too much please bear in mind he is asking about MINI-LATHES so changing speeds by belts and pullies although liked by some does not apply to minilathes.

As I said above typical 7x# Mini-lathes have two options

1.Belt Drive. Actually belt to lay shaft with two gear ratios between shaft and spindle

2. Direct Drive direct from motor to spindle.

The Warco Mini & Supermini fall into the first catagory being belt to 2 gear rations to spindle

Sieg C2/C3 are direct from motor to spindle via belt and have more powerful motors which compensates for any mechanical advantage the geared option may have offered.

[Brian GParticipant @briang]

Warco and Amadeal both offer more powerful brushless motored mini lathes with back-gears, which (if the drive is properly implemented) sound a lot more appealing than the older 350W brushed DC motored type I am used to.

Brian G

[JasonBModerator @jasonb]

Just be aware that those two are probably quoting input wattage not the output that Sieg suppliers quote.

[Ron LadenParticipant @ronladen17547]

My first lathe was a belt drive mini lathe where the belt drives a layshaft with plastic gears which Jason describes above. I stalled my lathe twice and the second time broke the plastic gears, I then replaced the gears for a metal set but they are noisy plus I modified the belt drive to one which would slip in a stall situation. It worked well but I doubt you would want to get into having to do that.

If your budget will run to a direct drive mini lathe like the Sieg SC2 and SC3 which have 500 watt output brushless motors then I would consider those, your choice of course but based on my experience with the belt drive its the way I would go if getting another mini lathe.

Ron

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