Help with lathe

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Sqwirl57

Sqwirl57

Member
Apr 13, 2020
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PA, United States
Im trying to teach myself to make my own guides but seem to have run into some issues. My cuts seem to start out well but as I get closer to the chuck I start to get "ribs" in the material. I'm a complete beginner so any advice is appreciated. Thank you!
20220921_051433.jpg
 
I don't know what's causing The Ridges but you should get a better cut closer to the Chuck than farther away. Also your material shouldn't stick out that far from the Chuck without support at the far end. Typically you drill a countersink hole in the middle of the stock and use the tail stock to hold it from moving at the far end.
 
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BlackICE said:
I don't know what's causing The Ridges but you should get a better cut closer to the Chuck than farther away. Also your material shouldn't stick out that far from the Chuck without support at the far end. Typically you drill a countersink hole in the middle of the stock and use the tail stock to hold it from moving at the far end.
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The center in the tail is typically in the rear end I just seperated it for a moment. This is how its setup while running

20220921_045459.jpg
 
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ChuckHunter said:
More RPM !
Cutting soft material like delrin you need to spin pretty fast! And take small cuts the closer you get to your final dimensions!
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With the current gearing I'm maxing out at about 1400rpm. Is that fast enough or should I change gears and go for the max which is closer to 2500rpm? Also, should I change gears so the tooling goes for a slower cut and just do the faster cuts manually?
 
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What's the Frequency kenneth? You will get a certain amount of vibration and movement from different materials, some of the softer ones like Delran will do that they will actually move enough to distort when feeding. I agree with the others, speed it up and hand feed it, see where the Distortion starts and pull your material back into the chuck if need be.
 
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ThomasT said:
It is hard to tell from your photos but your tool looks like it is sticking out a bit too far from the post. Also have you tried to feed from the Chuck toward the Center? If you have a Carbide tool try using it.

ThomasT
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Is this too far out? Hope the picture is better. I've also added a bit of angle to the tool since taking this picture last night.
20220920_201507.jpg
 
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Is the tailstock aligned, may be cutting taper? Tool bit for plastic should have more aggressive "top rake clearance" carbide is not the best for plastic, sharp highspeed steel is better check center height of tool bit, face of bit may be hitting work. More pictures and info would help close up of marks would also help, PM me if you like.
 
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Looks like the ribs are occuring at the unsupported center, so flex is part of the problem. Keep the unsupported length as short as possible. The rest of the problem is that required cutting forces are too high causing the deflection. Make sure the tool is on center and not heeling, that it is dead sharp, and that the geometry is correct for the material being cut.
 
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Here is a link that should be helpful.

www.curbellplastics.com

Plastic Turning Guidelines | Speeds & Feeds Chart | Curbell Plastics

Review machining guidelines for turning plastic on a lathe. Speeds and feeds chart for plastic materials provides angles, cutting speeds, and feeds.
www.curbellplastics.com www.curbellplastics.com

For tool bits:
www.grizzly.com

Search

Grizzly Industrial, Inc. is a national retail and internet company providing a wide variety of high-quality woodworking and metalworking machinery, power tools, hand tools and accessories. By selling directly to end users we provide the best quality products at the best price to professionals...
www.grizzly.com www.grizzly.com

ThomasT
 
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