Thread: Problems with off the tool finish

What diameter is your work piece? Chances are you are putting pressure on the cut, deflecting the work piece or have poorly aligned centres on the lathe. There are other causes of course.

I'd suggest that you are moving the tool too fast down the piece thus cutting a spiral groove. Either slow down the left/right chisel movement or speed up the rpms of the piece.

Thanks for the replies. The piece is on a taper from 43mm to 32mm, I'm traversing downhill.

I tried slowing down the lateral movement, but it didn't seem to make much difference. Speed is about 1400 or so, can't remember without going and looking. One step from flatout on the Woodfast anyway.

I never thought to check the centre alignment, I'll do that tomorrow.

This is one of those occasions when a bit more speed would be helpfull.

+1 more speed.
Regards Rod

Spindle alignment has little to do with this as the tool is hand held.

The speed of the lathe on that size should be t least 2500 RPM.

I also agree that your traverse speed may be too quick.

When you are using the skew is your cutting edge at 45 degrees to the timber? The closer you get to 90 degrees the less material you are in contact with.

I would also suggest that your tailstock centre may be coming loose by working its way into the timber (the reason I don't use cone centres) or you may have movement in the quill, make sure you apply the lock.

While not a skew man, one tip from a friend long ago: When turning spindles, there is a ratio of 10 to 1 for stability. A 1 inch diameter spindle that is 10 inches long will remain pretty stable when cutting. Going beyond that ratio, the wood can start to 'whip', which means vibrate. Things that make the vibration worse are too much tool pressure, and too much pressure from the tailstock. Finding the balance can be tricky. This is where steady rests come in handy, or if you have a light touch, and can reach under or around the tool rest, your other hand can do the same thing. If your steady rest hand is getting hot, you are using too much pressure, and hand pressure should equal tool pressure, so in other words, very light. To get rid of the spirals, you have to go back to where there are none, and start the cut again, or very gently start where there are bumps, and try to nibble them off till you are down to round.

robo hippy

Originally Posted by

Spindle alignment has little to do with this as the tool is hand held.

I would also suggest that your tailstock centre may be coming loose by working its way into the timber (the reason I don't use cone centres) or you may have movement in the quill, make sure you apply the lock.

say it better than I did, this is what what I meant about spindle alignment (poorly aligned centres on the lathe).

As others have said you are not running the lathe fast enough, at least 2500 rpm is good for this diameter.

You are also pushing too hard and not allowing the tool to cut properly. The wood spirals and the tool is following the pushed wood.

Is the small diameter at the head stock as it is easier to push down hill towards the head stock, the spurs keep you driving. Also a good cup or pin & ring centre for the tailstock is better than a cone centre as the cone wants to push further into the wood.

To stop some of the vibration in the wood on this small diameter use your hand as a steady and fulcrum.

By looping your thumb over the tool rest and your fingers cup the wood you can then rest the skew against your hand and run along the peice, if it gets hot in your hand you are either pushing the tool too hard or holding the wood too hard, back off till comfortable

Thank you very much for all the replies. It got the better of me last night and I went back to the shed.

Centres line up

Cranked the speed up to 2000rpm, as fast it the Woodfast will go in it's current configuration.

Made sure the tool was sharp

Made a conscious effort not to push too hard

Made an effort not to traverse too fast or push too hard

Much better result straight away.

I use a cup and pin (I think anyway, standard issue woodfast) in the headstock, but until now I've had a cone in the tailstock. I think I have a Woodfast cup and pin live centre, I'll give that a squirt tonight.

Jim, I try to use the finger position method you prescribe as much as possible (although a bit scary when a catch occurs).

Going downhill from tailstock to headstock is what I was doing.

I have the skew at about that 45. I'm making some tool handle and I'm trying to use the skew as much as I can to try and get a handle on the damned thing.

Can't get anymore revs out of the old girl in it's current form, although I have access to enough bits to put a 3 phase motor on her and use a VFD, should be able to get a bit more pace that way. I'll probably leave that until we get into our new digs sometime next year - cause then I'll have real 3 phase to play with.

I'm going to play some more tonight. I'll report back and again thanks for the replies.

I had to turn a 6mm elm shaft, about 13" long a short while back. I used a 1" oval skew and a little 3/8" round skew to finish. I supported it with my hand and although there was a little vibration at times it was quite straight forward.

Other times when I have had a spiral it has always been due to vibration of the wood. No real problems and if you arepushed for time and it keeps happening then the spiral sands out very easily

Spent some more time at the lathe tonight. Using all the tips, I have managed to get probably 98% of the turning free of the spiral straight off the tool.

I think, after tonights effort that vibration is the cause of most of the problem. The piece is 405mm long overall. Too long probably, but by using the finger steady and faster rpm's it's manageable.

I'm going to turn a piece the same finished size except shorter next time I get a chance and see what effect that has.

I did notice that roughing the square down to a cylinder at about 50 mm diameter, the finish was easier to get smooth. Directly related to the aforementioned ratio me thinks.

Thank you for the help.

One question about rpm's, if turning say a bowl that is about 9 inches across, does the same thing apply, faster is better? Or is it just a "feel" thing, experience telling when to slow down or speed up?

One question about rpm's, if turning say a bowl that is about 9 inches across, does the same thing apply, faster is better? Generally, but only when it is round. Or is it just a "feel" thing, experience telling when to slow down or speed up?

That too, in spades.

Bowls work similar but different.

Always start the lathe on slow then build up the speed to where you are comfortable and the wood is also comfortable.

There is 2 things that control the speed , your ability and the wood.

No good going too fast if it frightens the bejesus out of you.

As you get the bowl blank more into round then you can creep up the speed and get a better cut of the tool.

Again sharp tools help