Turning a Diameter to Size on the Lathe

Another in the basic lathe operation video series, this one covers turning to a diameter. I talk about tool set-up, roughing and finishing cuts and how to zero the dial for an accurate diameter.

[@fentzke]

Wow, these videos are amazing. A rare combination of expertise on the subject, great teaching, and quality camera work. I usually find videos to help me accomplish a specific task, but I am watching these for fun like a football game. Other good resources I have used to learn machining and fabrication skills are Machine Shop Essentials, Questions and Answers by Frank Marlow, and my favorite book on the subject, Metalworking, Sink or Swim by Tom Lipton. He has some very funny stories in addition to sharing his tips and tricks he learned over a career as a metal worker. I never got the chance to take metal working classes in high school, but it feels like I have the best shop teacher in the world now. Thanks, Tom!

[@ednichols2748]

Great video Tom! Here's a trick I learned from an old German toolmaker: rather than sneak up on a size, when I want to turn to a +/- 0.0002 tolerance, I snug up lightly on the the ways for cross slide and carriage, and lock down the compound. If I'm turning common-as-dirt 1018 cold roll, I normally use carbide inserts, but to keep with your example, using a HSS tool I would crank the rpms up so the SFM is 135 ft per min., or ~435 to 450 rpm for 1-1/8 stock and a target of 1.0000". I'd use a sharp tool with a nose radius of 0.016 to 0.018, and feed at 0.002" to 0.004" per rev depending on the desired surface finish.. As you show, its very important to get the tool on center. Then take a "skim cut", as you did, but turn across the full width of the part. Let the part cool if needed ( or run coolant), and mic it. Let's say it mic'd 1.1083". Set a dial indicator to pickup the cross slide movement & zero the indicator. Next subtract target dimension from the skim cut diameter ( 1.1083 - 1.0000 = 0.1083) Divide this amount by any whole number that will give a result that is equal to or slightly larger than the tool's nose radius. For example, 0.1083 / 6 = ~0.018" and a close enough match for our tool nose R.. This gives us the depth of cut ( radius to dial in for the first of 6/2 or 3 passes. This cut should mic at 1.1083 - 0.036" = 1.0723. Let the work cool if needed and mic it. Lets say it mics 1.0731. Subtract our target (1.0731-1.0000 = 0.0731. Divide by the number of remaining passes (2) = ~ 0.0366", Divide by this amount by 2 and dial in this DOC, This pass should mic 1.0731 - 0.0366 = 1.0365. Let the part cool, mic it. Let's say is mikes 1.0368. Repeat the process, in this case 1.0368 - 1.0000 = 0.0368. Divide by 2 and dial in the DOC for this last pass. Let the part cool in needed, and mic it. You'll be within 1 to 2 tenths, if not dead on size. The math may seem complex here, but it can readily be done in ones head once you understand the process. This works because it reduces tool nose pressure ( by taking a cut that is equal to or greater than the nose radius) and by compensating and adjusting for any residual pressure or part flex over nearly consistent tool pass pararmeters. Give it a try - it really works - and especially when boring an ID. Google "Sanvik 3 Pass Method" for better how-to info on boring a close tolerance hole using this method. (By the way, the method I described here works on my newest CNC lathe, as well as my 43 year old 15" Clausing, my old pre-WW11 Southbend, and my little Chinese wonder from Enco :-) Accuracy is 99% machinist technique, and 1% machine :-)

[@alsatian9130]

Tom, I just want to personally tell you thank you. All that you did, to help us beginners out, I can speak for myself here; gratitude! I hope you can hear it personally. Your time/kindness will never be forgotten. Thank you Brother. --Joe

[@bradsmith1046]

Thanks Tom For us beginners your detailed discussion and excellent filming is really very helpful I look forward to seeing your other vids in the future.

[@shed.projects5150]

anyone who dislikes this , should not be watching teaching videos. Great vid Tom.

[@danmoreton1788]

It is the basics that are the foundation to good machining techniques. I always enjoy watching your videos!

[@mikehart6708]

Thanks Tom. I always learn something when I watch one of your videos.

[@lockbuilder]

Tom, Glad I found your channel. You have a great way of describing and showing operations in a simple easy to understand way. Please keep 'em coming!

[@brentnicol6391]

I'm a qualified fitter and turner and I love doing anything on the lathe and milling machine. I love to see videos like this out there to teach the younger generation. To the 23 that disliked the video, I think they must be some sort of dress makers. LOL. Thank you sir for the teaching.

[@paulgreenlee190]

That was great advice Tom, I have been struggling with getting accuracy from my dials. I discovered one thing of importance, I had movement in the dial after I took the back lash out. I pulled the rod and shoe and couldn't see anything wrong. I have a 1960 13" South Bend Lathe. The screw head is slotted so I took a screw driver and tightened it. This did what it should be doing, no extra movement other than back lash. Thanks so much for the lesson and advice.

[@Nik-ok9nu]

Such fantastic videos! I've been watching for hours and see no end in sight! I have learned more today watching your series of videos than I have in all of my other "Youtubing" and reading! your teaching style speaks well to how I learn! I am getting very excited to apply all of my new found knowledge on the lathe! Very excited!!! Thank you!

[@SPIRITOFTHOMAS]

Great videos. Thank you for sharing your knowledge. Took your advice from the 'parting video' and ordered a quick change tool post. 1955 9 inch Southbend...worn out, but we get by.

[@aryesegal1988]

Thanks, Tom. I really love your videos and the way you explain things. Wish I had your experience! :) Looking forward for your next videos.

[@burtlade1705]

Hi Tom,

[@petera1033]

Thanks for your videos Tom - as a 'noobie' I am enjoying watching all of them. My Hardinge HLV arrives in early January and most of the people I have spoken to regarding tooling have pretty much insisted that carbide inserts are the way to go - however I am buying a bunch of HSS blanks and a decent grinder and will also try and teach myself how to grind my own - your videos have been helpful

[@ahmedmuawiyah8985]

Thank you Mr. Tom. Your videos are excellent, cheers.

[@thadstuart8544]

great demonstration and helpful tips. thank you

[@fellovercliff4525]

Nice man, just what I need. Cant wait to go through the rest of your videos.

[@cliffjones1511]

Thanks Tom, every little bit helps.Allways good to see how a Pro does it.

[@paulmeynell8866]

Just found your videos , just what I needed thank you