New Precision Matthews Lathe Set-Up: Part 2 

Regarding parting, at 11:55 the part is running true. At 12:13 the part is wobbling. I believe the lateral pressure from parting caused the part to move in the chuck meaning the chuck wasn't tight enough. I am not an expert though.

Regarding your tailstock, when it's set up correctly, you use the lever at the rear to lock it in place. No need to use a wrench on the nut. That's what the lever is for.

As a rule of thumb, unsupported stickout shouldn’t be more than 2x stock diameter - so 1” round bar shouldn’t stick out more than 2” - otherwise you’re asking for a ride into chatter town, always work as closely to check chuck as you can for maximum rigidity - but like you, I learned by trying! Blondihacks lathe series is fantastic for learning!

Hi, nice lathe. Very quiet too! Regarding parting, some food for thought: - How thin is your blade? It flexed a lot when you started the cut, almost like if you were parting off on a threaded section (with a thin blade). I'm not seeing the holder moving, only the blade flexing, so maybe that blade was too thin (and the RPM was too low). - You didn't seem to have excess stickout for the cut, but maybe it was too much for the thickness of the blade. - Also it doesn't seem to me that you had the tool off center, it was cutting nice curly chips. - When starting, with HSS, slow will get the job done - but I think you're going too slow. 1018 with 20mm O.D. I think I'd start with 150-180 RPM with a 3/32nds blade. "Same" lathe. - Looks like the entire compound lifted when the blade broke. I'd check the compound play in all joints from the cross slide upwards. Also wouldn't hurt to check the carriage play. But at the least the compound should be locked during the operation and in a position where the parting tool is overhanging the cross-slide. Sorry for my poor english, I'm trying to help with little things that might make a difference. - There was some wobbling on the part before the blade broke, which wasn't happening at the beginning of the cut. Did the blade dig into the work and stalled the motor at some point (not shown on camera)? Sorry to ask but the times it happened to me, the part always ended up like yours (wobbling). And then yes, it runs crooked and the part grabs the blade. - Confidence and feel play a big role on the parting operation. Don't give up, you'll get there! (I had never seen a blade breaking before, yikes!) Stay safe!

I'm not a pro by any means. But watching the video back a few times, it looks like there was a lot of runout on the part a couple of seconds before it broke. Maybe too much infeed creating tool pressure to be high. I ordered this same machine, I'm just waiting on delivery. I can't wait to make some chips.

Your RPM is too low as you’ve been told already, but the depth of cut is too shallow as well. Your depth of cut should be around half of the radius of the tool for turning. So if you’re using an insert that has a.03 radius your depth should be .015. As for the parting tool, it was probably chip build up due to the low RPM and an inconsistent feed rate. Don’t get discouraged. Get a copy of Machinery’s Handbook and practice with something more forgiving like nylon. When we were taught how to use a lathe in school we all started with nylon before moving on to brass, then aluminum and finally steel.

Check out the edge technologies height setting tool. Its absolutely a game changer and is faster and more accurate than eyeballing the tool height. They arnt really that expensive either.

More RPM. Cs×4÷Dia is what works for me. So if you have 5/8" steel, which is 100 for the Cs, you'd do 100×4÷.625=640 RPM. It appears you were going too slow at the start.

Why is it always the part being worked on is wobbly? I usually use square to make sure it's straight, but it's always wobbly!

Your speeds are way to low. Turn your compound 180deg. Always try to cut on a forward direction. Maybe your parting tool was lower than the centre point. When you cut the face and drilling a centre drill, work piece as close to the chuck as possible.

What model is your lathe??

Thats a lot of stick out without a center.

My advice would be to get some actual live help and learn the difference between a RH and LH tool. Making videos may not be the best way to start off.

I've found its alot safer and cheaper to eat chips on the couch than it is to make chips in the shop ....... 🩸 🤕