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sjm
20th Feb 2011, 02:41 PM
Hi all,

Total beginner here, picked up my first lathe yesterday, and I have about 3 hours hands-on experience (after many hours of watching YouTube videos). I'm playing with branches off a local gum tree, and experimenting with different chisels. So far I've been able to rough out a few cylinders and make some basic tapers, beads and coves. However, parting is causing me grief. I'm getting horrible breakout, and would appreciate some advice on what's going wrong?

I've tried resting on the bevel and slowly lifting, and also "stabbing" straight in, neither method seems to work for me... Incidentally, in the image below, the straight section on the right was done with a skew, not a parting tool.

http://stevenmerrifield.com/hosting/parting.jpg

Thanks,
Steve

rsser
20th Feb 2011, 03:19 PM
Yeah, looks a mess.

Is it green?

Generally I'd present the parting tool so that the edge was aimed toward the centre line, slowly enter and then drop the tool handle end to raise the cutting edge and then progressively raise the handle end to arc the edge inwards.

The arc is in one plane. No side to side wiggling. The shaft behind the cutting edge should be no wider than the edge. The edge should be sharp it goes without saying.

sjm
20th Feb 2011, 07:22 PM
Thanks for the reply, I think I am doing exactly as you describe, which is the same as shown in this video: YouTube - Parting Tool Technique Although I'm going much slower. I'm using a 3mm tool with straight shaft, not a diamond shape. The branch was cut a few weeks ago from a tree that fell about 6 months ago, so it's not freshly green, but it's not totally dry either. It certainly doesn't ooze sap and the chips are not moist.

I guess what I want to know is if this is a common problem for beginners, and something that will improve with experience, or is there something fundamentally wrong, like motor speed or toolrest height?

Thanks,
Steve

RETIRED
20th Feb 2011, 08:41 PM
Thanks for the reply, I think I am doing exactly as you describe, which is the same as shown in this video:

Although I'm going much slower. I'm using a 3mm tool with straight shaft, not a diamond shape. That does not matter. I don't think I own a diamond shaped parting tool.

The branch was cut a few weeks ago from a tree that fell about 6 months ago, so it's not freshly green, but it's not totally dry either. It certainly doesn't ooze sap and the chips are not moist. Wet timber is sometimes harder to work than dry in as much that the timber is pliant and must be cut cleanly.

I guess what I want to know is if this is a common problem for beginners, yes and something that will improve with experience, one hopes or is there something fundamentally wrong, like motor speed or toolrest height?

Thanks,
SteveWhat speed are you going at?

The toolrest should be below centre and adjusted that when the tool is horizontal it is right on centre.

The other problem that most beginners have is hesitation: If you are going to cut, CUT, don't muck about.:D

rsser
20th Feb 2011, 09:59 PM
And have a play with some dry timber; grab a bit of pine or cypress.

Sawdust Maker
21st Feb 2011, 08:50 PM
Gees

don't know what your problem is :o

most of my between centres work looks like that :doh:

and some of my bowls as well :doh:

RETIRED
21st Feb 2011, 08:57 PM
Gees

don't know what your problem is :o

most of my between centres work looks like that :doh:

and some of my bowls as well :doh:SSSHHHH, I wasn't going to mention that.:wink:

powderpost
21st Feb 2011, 10:13 PM
Have a close look at the cutting edge to see if the corners are sharp, not slightly rounded. If they are rounded, sharpen the chisel until the corners are sharp. That is a common problem.
Jim

RETIRED
21st Feb 2011, 10:43 PM
Have a close look at the cutting edge to see if the corners are sharp, not slightly rounded. If they are rounded, sharpen the chisel until the corners are sharp. That is a common problem.
Jim:doh: Forgot that one. Thanks Jim.

RETIRED
21st Feb 2011, 10:45 PM
Just thought of something else.

On a diamond shaped parting tool the edge must be aligned with the widest part.

Probably why I don't like them much.

sjm
22nd Feb 2011, 08:46 PM
Well I thought the tool was sharp enough, but after the advice given here, I resharpened it, and now it's much better! There is still a little fraying around the edges, but nowhere near as bad. A valuable lesson learned, thanks all :)

oldiephred
23rd Feb 2011, 06:26 AM
From a safety perspective, I really don't think very highly about the one handed part of the demo. IMO should not be done. Take the extra time to cut and check.

rsser
23rd Feb 2011, 06:39 AM
It's safe enough once the bevel is rubbing. Worst outcome with poor alignment is burning the endgrain. And an essential technique when you part off and have to catch the piece.