Author Topic: Lathe Speed for Roughing Gouge  (Read 3969 times)

Offline Les Symonds

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Re: Lathe Speed for Roughing Gouge
« Reply #15 on: April 29, 2019, 04:14:02 PM »
... terms such as "slow", "fast", "safe", "comfortable"  etc. mean different things to different people and often rely on a degree of experience that a novice can't be expected to have. I'm confident that the method I use can be used by a turner at any level and is ultimately safer than using wooly terms to avoid the question....
Am I missing something Paul...I don't recall having used any such terms at all in my post? I certainly do not use woolly terms, either.

Les
Education is important, but wood turning is importanter.

Offline michaelb

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Re: Lathe Speed for Roughing Gouge
« Reply #16 on: April 29, 2019, 04:40:32 PM »
As you can see from the various replies lots of advice and all can be correct for different turners but without doubt in my opinion is that of Pete  start slow and increase speed as comes into balance , but Les is right as no piece of timer is uniform and as turners we want nice  grains , burrs etc so treat each piece with care and look at the wood and let the wood be your guide.   I very rarely use a rouging gouge a 3/4 bowl gouge just moves as much timber and gives better control.

Do make sure with bark on full face guard on £14.00 .

happy turning   
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Offline seventhdevil

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Re: Lathe Speed for Roughing Gouge
« Reply #17 on: April 29, 2019, 08:20:28 PM »
surely a formula could only work to simply state the speed of the wood going past your tool at a particular rpm. it can't tell you if that bit of wood is safe at that speed.

as i said before it will all be down to the weight of the lathe being used and it's center of gravity which will be different for every single set up.

you could work out some sort of formula for your own set up if ose so wished but by the time a new turner has worked one out said turner will have quickly gained some experience and probably some common sense and realised that their own intuition will be the best option.

Offline Paul Hannaby

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Re: Lathe Speed for Roughing Gouge
« Reply #18 on: April 30, 2019, 11:40:17 AM »
Les, it wasn't a direct reply to your last post, just a general one to some of the others and to other advice I have heard which doesn't really pin down what can be considered a safe approach to speed selection on the lathe.

Steve,
Yes the formula simply gives the rpm to achieve a given peripheral speed of the wood past the tool for a given diameter and as I said at the beginning of that explanation, the overriding factor is balance and safety and it is just a rough guide for a generic piece of wood but one that gives a safe upper limit in normal circumstances.
The formula is the same for every lathe. The bit that differs is how a particular lathe can cope with vibration and imbalance.

What I don't think is good advice is to suggest to increase the speed until there is vibration because for a well balanced piece of wood, there is a good chance you can considerably exceed a safe working speed before there are any noticeable vibrations so in my opinion, a method of determining a safe upper limit is needed which isn't reliant on someone's limited experience or perception.

Digressing slightly - balance is a complex subject in its own right. I'm not an expert on that but from what I have learnt, you can't always treat something as a simple mass. The actual balance at different points along any object might vary, that's why when they balance car tyres they sometimes end up with one weight on the outside of the wheel and one on the inside. It is possible to balance a piece of wood with counterweights, I have done it in the past with eccentric turning but for most occasions, we just have to remember to limit speed to below the point where the vibrations caused are more than the machine and mounting points for the wood can safely cope with and a decent cut can be achieved.

Offline The Bowler Hatted Turner

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Re: Lathe Speed for Roughing Gouge
« Reply #19 on: April 30, 2019, 11:54:51 AM »
Although I tentatively agree with Paul's comments I have to point out that there are those that will be unable to do the maths, some are scared of numbers and always get it wrong. There are many factors that should be taken into consideration, on spindle work (with the grain running inline with the bedways) length and diameter play a part. If the wood is too thin or too flexible reducing speed can help take any "whip" out of the workpiece which may account for vibration over an off balance piece of wood. You must also take into consideration the straightness of the piece as that will also affect vibration as will the position of any spring wood or summer wood present. Another thing to consider is which way up has a wet piece been stacked as the moisture will sink to the ground and that too can cause an unwanted vibration.
Advice has been given here about starting the lathe on a slow speed and then speeding it up  but more importantly you should start your turning journey slowly and learn the correct methods of doing things before you start to put larger off balance pieces of wood on the lathe, this is the biggest failing of all wood turners, they try to run before they can walk. As an apprentice I was not allowed to touch the lathe for the first six months I just stood and watched, then as I progressed I was only allowed to turn small bits to begin with eventually being allowed to turn six inch diameter porch supports. May I suggest that you start by turning nothing bigger than two or three inches diameter, learn your tooling presentation and sharpening and master it before moving on to more complex stuff, you will be a better turner for it and the quality of your work will improve immensley.