What Speed Do You Spin At?

[Turners cabin]

I believe most turn at a speed that is too high and rely on the speed to provide a good finish rather than good technique.I know this is somewhat controversial but it is my opinion.
 if you have ever seen me turn I rarely run the lathe at any speed but use sharp tools technique and control to achieve the end result.
When teaching more experienced students they often  have trouble with spiral chatter on bowl work, this is caused simply by high speed and differential grain density the answer is simple, drop your speed and sharpen the tool problem solved,for Bowl turning any speed over about 1000 rpm is simply not needed in my opinion.( these comments relate to Bowl work and not other areas of turning)
Nick Arnull.

true words there nick a sharp tool will always win over brute force

[The Bowler Hatted Turner]

David let me try to explain what I meant by "amateur". Both professional and hobby turners will turn out(no pun intended) work of a high standard, if not straight away then eventually. They will all serve, whether they like it or not a period akin to an apprenticeship during which they will learn "the rules" for instance "don't cut uphill"etc. These rules have been unchanged for 100's of years and only changed or adjusted by innovative new tools or devices that are developed over a period of time and have been proven to work. I am well aware that pole turners turn at a lower speed than those using an electric powered machine (and their work is no less of a quality for it) but we have over the years developed tools and steels for those tools to cut at higher speeds and it is my opinion that the call for turning at slower speeds was made by an amateur turner, an amateur being a non professional and non specialist turner as opposed to a professional or hobby turner that can specialise due to experience.

[woodndesign]

David let me try to explain what I meant by "amateur". Both professional and hobby turners will turn out(no pun intended) work of a high standard, if not straight away then eventually. They will all serve, whether they like it or not a period akin to an apprenticeship during which they will learn "the rules" for instance "don't cut uphill"etc. These rules have been unchanged for 100's of years and only changed or adjusted by innovative new tools or devices that are developed over a period of time and have been proven to work. I am well aware that pole turners turn at a lower speed than those using an electric powered machine (and their work is no less of a quality for it) but we have over the years developed tools and steels for those tools to cut at higher speeds and it is my opinion that the call for turning at slower speeds was made by an amateur turner, an amateur being a non professional and non specialist turner as opposed to a professional or hobby turner that can specialise due to experience.

What's to explain ... if one's not time served ... make a living from turning ... then you're an "amateur" .... how will we ever encourage anybody into turning.

[edbanger]

Here Here David

I guess that my comment about turning at slower speeds for safety gave me the title of "amateur" allow I've only been turning for 5 months I'm a pretty good turner and I would like other people to find what I have found in woodturning.

I'm a member at my local club and chatting to other members find that many don't turn, one old boy had one go and in his words "it didn't go well" so he never returned to his lathe. If he had a lathe with a starting speed of 500rpm I guess it might not have gone well dependent on what he was trying to do.

If you have a lathe that can spin at 3000rpm and you know what your doing all well and good but if your new to woodturning and your told the faster you spin the lathe the better the finish you might think you know what your doing and wick-it-up BANG a piece leaving the lathe spinning at 3000rpm hitting you will be a bit different from a piece hitting you on a lathe spinning at 300rpm but you you still get a very good finish spinning at 300rpm.

Ed

[Bryan Milham]

A short story about my first turning experience.

I’d gotten into woodworking from buying our first home and doing a lot of DIY. The tool collection grew and the DIY became maintenance level. Free time meant I could and did, pick up where I’d left off at school and make things out of wood.

Then one day the wife saw an advert for a ‘Woodwork machine’, as it happens a Coronet Major. Complete with Table Saw, Planer Thicknesser, Morticer, oh and a lathe. Well we looked, I liked it and so bought it.

Getting it home in pieces (the only way to lift and carry it) I built it back up and decided to play with my new toy. There were some saw blades with it but also some turning tools. So I put a bit of wood on the lathe (thankfully just a small bit between centres) and turned it on!

0 to 5000 rpm in nothing flat – I hit the stop button and walked away terrified while muttering rude expletives under my breath!

Thankfully my Ever-Loving bought me a course at the local adult education centre, night school, in Great Malvern, the first thing the nice man (I do wish I could remember his name) showed me was the pulley system and how to ‘lower the speed’, I’d put it together and set the pulleys for the table saw, not the lathe.

That lathe and my next were both pulley driven so the speed ranges were preset, I learnt to turn at the lower of the available (pulley) speeds for the wood size as it ‘felt’ safer.

Variable speed now means I (and I think most of us) have better control of the speed but I still prefer to work on the slower side. And from reading this thread, I think it is safe to say that the majority of us turn slower than we thought we did, having now had cause to stop and look at the speed indicator.

[Graham]

I am very new to turning and try to remember to turn the speed down before stopping the lathe ( my speed dial does not go all the way to stop ) On the odd occasion I have forgotten I find it quite disturbing to see the wood go from zero to 1000. I would not want to be learning on an older lathe.

[bodrighywood]

I am very new to turning and try to remember to turn the speed down before stopping the lathe ( my speed dial does not go all the way to stop ) On the odd occasion I have forgotten I find it quite disturbing to see the wood go from zero to 1000. I would not want to be learning on an older lathe.

Far more important to make sure the lathe is at a lower speed when starting up. I suspect many of us have thoughtlessly not done this and put a heavy piece on with the speed up after a smaller job. Especially likely if we have lathes that don't have variable speed.

Pete

[Graham]

That was my point 

[seventhdevil]

that's very important when turning large diameter like i have recently been doing up to 28". i had to remember to turn the lathe down to 250 max before i turned it off or a kill switch cut the power and the blank just runs down.

there is too much inertia in a blank that weighs 50kg plus for the jet 3520b to handle but as long as i remembered then i was ok or i have to turn the whole thing off and on again.

[Graham]

there is too much inertia in a blank that weighs 50kg plus for the jet 3520b to handle but as long as i remembered then i was ok or i have to turn the whole thing off and on again.

Sorry, could you explain that ?

[seventhdevil]

there must be some sort of kill switch on my lathe, a jet 3520b. if i hit the nvr switch on the lathe whilst i have a large bit of wood spinning it appears to be too much for the lathe to stop with all that inertia so it cuts the power and to reset i must turn the lathe off at the plug, listen till the thermal switches have clicked and then i can turn the lathe on again. if i don't do this i am unable to start the lathe to continue turning.

i don't know if it is a safety device for the user or the lathe but it just means i must slow the speed down to about 200rpm and then i can hit the stop button.

the 28" i recently turned was going round at about 50 rpm and this would have cut the power turning it of at that speed so i've had to get in to the habit of slowing work down before i turn the lathe off.

[Graham]

Ahh. Not sure I would like that.

[seventhdevil]

it only seems to happen when working on bits over 24" (not sure what weight) but most of what i turn is under that sort of size and weight band that affects it.

the jet 3520b handles most stuff very well and is a good machine. i've another 6 blanks from this walnut left to turn ranging from 10"-18" all 6-7" thick and would not expect to have that problem with any of them.

[Paul Hannaby]

The inverter drive acceleration / deceleration rates are generally set for an "average" sized piece of wood. If you are turning something much larger / heavier you need to change the parameters so the acceleration / deceleration time is much longer. Otherwise the inverter drive detects an overload condition and trips out.

Check your user manuals for how to do this.

[Derwent Woodturning club]

there must be some sort of kill switch on my lathe, a jet 3520b. if i hit the nvr switch on the lathe whilst i have a large bit of wood spinning it appears to be too much for the lathe to stop with all that inertia so it cuts the power and to reset i must turn the lathe off at the plug, listen till the thermal switches have clicked and then i can turn the lathe on again. if i don't do this i am unable to start the lathe to continue turning.

i don't know if it is a safety device for the user or the lathe but it just means i must slow the speed down to about 200rpm and then i can hit the stop button.

the 28" i recently turned was going round at about 50 rpm and this would have cut the power turning it of at that speed so i've had to get in to the habit of slowing work down before i turn the lathe off.

Hi Steve,
I may have an answer to your 'problem' but I may be wrong as I don't know the Jet 3520 spec in detail.

Most big, variable speed lathes use a 3phase motor driven by an inverter. This means you still have good power at low speeds, as the speed is controlled by modification of the frequency, not the voltage/current.

All these inverters have a host of settings, as they are used in all sorts of applications, but the one that could be relevant to yourself is usually specified as 'Coast to stop or Ramp to Stop'. If it is set at Ramp to stop, the inverter will use DC braking to try and stop the motor in a set time. For many that is 10sec but it can be set at any value. The shorter the time, obviously the more braking is required. However, the braking puts a load on the inverter. If the load is too high, which I guess is what is happening in your case with large lumps of wood, the inverter will overload and cut out. You then have to power off and on to reset it. The inverter can cope with smaller (lighter) bits of wood, as it won't require so much braking.

The alternative of 'Coast to stop' means that when you stop the lathe, the inverter just removes any drive to the motor. There isn't any braking applied and it will just slow down of its own accord. Obviously a large lump of wood, with a lot of momentum, will take longer than a small piece.

It is easy to find out what setting you've got, but be very careful with what I am about to suggest. Put a piece of wood on the lathe. Turn it to a nice, smooth cylinder that you are happy to put your hands round. Now remove the toolrest and switch off the lathe. If you can slow the lathe by holding the wood, it is set to Coast to stop, but if you can feel the lathe trying to keep going, it is set to Ramped or Braked to stop.

Unfortunately if it is the latter, you would need to find and change the settings of the inverter. You may prefer to contact Jet for help doing that.

All my lathes are set to Coast to stop, for another good reason. Some of my chucks cannot be locked onto the headstock. If the inverter was set to Brake to stop, and I am turning very large, heavy pieces, the inverter can stop the motor but the momentum of the piece keeps it spinning, thereby unscrewing the chuck off the lathe 

Sorry for the rather extended reply but hope that helps.