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Making lathe tools

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Wolfie24/10/2010 22:00:51
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502 forum posts
Hi all. I'm Chris from Ryedale and although I have been a plastic model maker for many many years I am just turning my hand to a steam engine.
 
Dictated by the fact that I'm skint and dependant on someone elses garage that I can't really fill up, I have a very small lathe (Axminster Micro) and I'm struggling to cut lathe tools that work. I have joined my local SME (PEEMS, Pickering) and a chap there told me for a nice finish to grind a tool with a fair radiused point on it.
 
This hasn't worked, it binds and chatters and generally cuts like a dog and the more I radius it the worse it gets. It was lovely too all honed and graceful

And as for parting off tool don't go there, I'm finding it easier to hacksaw the piece off and clean it up after I've looked at loads of web sites and books but its not working for me.

I have 2 sets of Stuart plans, the S50 and a beam engine. Its the beam engine I really want to make but I thought the S50 would be a good place to start and get all the mistakes out the way. I'm making them from scratch too as I can't afford the castings.
Andrew Johnston24/10/2010 22:27:26
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7061 forum posts
719 photos
Hi Chris,
 
Welcome to the forum.
 
I'm not familiar with the Axminster Micro but I assume it's a small (micro!) lathe. Your fellow club member is correct in that a round nose tool will often give a better finish. However, what he might not have mentioned is that a round nose to the tool increases the radial cutting forces on the tool and also increases the power required. Unless you have a large, rigid lathe this may well cause exactly the problems you have been seeing. Try a tool with a nice sharp point at the end; It should cut with less chatter and less power required. By all means put a small radius on the tool end, say 0.1 or 0.2mm. This will give a slightly better finish, but not give the problems caused by a larger radius.
 
Regards,
 
Andrew
ady24/10/2010 22:27:35
612 forum posts
50 photos
From my own newbie experiences, stiffness is miles more important than power, miles.
 
There aint much you can do with a wee c1 but a decent sized billet of steel on the cross slide cut as a toolpost to replace that pansy original could improve matters.
 
A sharp tool is better for a small lathe IMO, because you have less stiffness, and a small cutting point needs less stiffness/power.
Your cross slide and saddle need to be nice and snug.
 
A bit of rake for the tip usually helps.
 
Practice on easy metals to start with, like aluminum.
 
Just start cutting, and keep at it. You pick stuff up as you go along.
Use the muscle between the ears all the time, listen to the cut, watch the cut, learn from the cut. Use a roughing out job to experiment with different tooltip grinds.
It all comes together eventually.
 
It's a trade which takes years to learn and is truly fascinating.
John Olsen25/10/2010 01:52:24
1294 forum posts
108 photos
1 articles
With small machines, you do need to keep the radius fairly small. The kind of thing that you can stone on with a hand held stone, rather than putting it on with a bench grinder.
 
The other thing is keep the tool really sharp. The test for this is to see if the edge will take a scraping off your thumbnail. If it just skids, the tool is blunt. I should emphasise that this is done with the tool held in your hand!
 
Watch the speed, it is easy to be going too fast on smaller machines, and this will take the edge off your tools quite quickly.
 
regards
John
Ian S C25/10/2010 02:08:23
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7468 forum posts
230 photos
My small lathe is a Super Adept, A design about 80 years old, its 6" between centers and a center hight of 1 5/8", mine has an electric motor that once ran a cash register, 180 watts, but the original was foot powered. I find that a tool with a minute radius on the tip works well, keep the speed up the feed down and it will take a cut about .020" deep. Parting off ?? wots that, no it wont do that but who cares. Just keep the tool SHARP, proberbly the best way to find out why is to use a lathe with a foot motor.
Ian S C
KWIL25/10/2010 09:13:02
3681 forum posts
70 photos
Nobody has mentioned tool height to our new friend, apart from stiffness as mentioned this has an effect as well! Top rake is essential except for brass.
DMB25/10/2010 09:59:12
1585 forum posts
1 photos
Hi Chris from Rydale and Ady,
 
I recommend trying to turn and face a piece of brass bar, since it has a fairly high cutting speed, no need for any cutting oil or other lube like you would if turning steel and you will not run into difficulties with chips sticking to the tool, like you probably will with Ali.
Pay attention to rake needed and WEAR EYE PROTECTION against the flying beass chips. The eye hospital does not have a magnet that will extract brass chips. If you havent got the proper gear, use ordinary reading glass or have a see-though plastic/perspex deflector set close to the tool.
Hope above helps and good luck.
John.  
mick25/10/2010 11:37:08
421 forum posts
49 photos
There's currently a really good beginers guide to the lathe being published in the MEW, which in your situation is proberly worth the cover price just for that series.

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