I really enjoy your videos because I come in expecting to know what you are going to say. And you always do, but then you always include that little bit extra that turns my understanding of an accepted practice into a logical and meaningful lesson that really solidifies and builds a foundation of understanding I can trust. Thank you for being such an excellent teacher.
Hi, Wow! That was the best lathe tool instruction I've ever seen. I've been using a lathe for decades for my personal needs, and that isn't very often. I learned to use a lathe, in a very basic and simplistic way, from my dad who used to work for AM&F in Brooklyn up until it closed in the late 1960s.. But he never got into tool geometry and application. Thanks for the great video. Tony
Marc, thank you for that one! It gave me new insight into what I am doing at the lathe and reinforced and clarified other practices that I had accepted from the beginning, but never fully understood.
Hi Marc, thank you again for a great video. This is the second time watching it and I picked up the more subtle aspects of the angle of attack. In regard to centre (oz) height tool positioning for internal and external machining a factor that I take into account besides the relevant point of rubbing as you pointed out is what happens with tool flexing. It is important to appreciate that as the tool is loaded while cutting it will flex in an arc determined by the tool and tool holder geometry. In this flexing if the tool swings away from the surface the forces on the tool tend to reduce and so consequently it springs back and moves to a stable position in the depth of the cut. A reasonably smooth and cleaner cut results. This is a negative feedback system and hence stable. If however the tool was to swing into the surface, it will dig deeper and the forces on the tool would increase forcing the tool even deeper into the surface. Erratic cutting oscillations may result causing high cutting loads on the tool edges and a poor finished surface.This is a positive feedback system and hence unstable. For normal outside turning if the tool is set on or below centre, the tool will swing away from the surface and if set above centre the tool will tend to swing into the surface. Hence for outside turning on or below centre is good. for inside turning the opposite is true, with "on centre" always being neutral. on any form of cutting and most things in life, a negative feedback system is always more stable and controllable. cheers and as always thank you for the great work.
Marc, thx for quick reply. It is a 3/8 radius. I’m making a wheel for model train. 1.5” diameter. It is for the “dish” on the front of the wheel. I’ll sharpen cutter, run it neutral, and use some good oil.Marty
Hi, I was reading a book on lathes, a classic book that I can't remember the name of just now, and it said to put the turning tool 5 degrees above center. First off it's hard to guess where the 5 degrees is for a given diameter that I'm turning. And lately when I found that my tool wasn't cutting well, I checked it I found that when I turned the chuck by hand, the tool was just slipping on the metal. It was set too high. So, I'm keeping it on center these days, just like you advised. Thanks again. Tony
@@LESPRODUCTIONSMAL I've shared your video with all my class mates and it's helped all of us so thanks for taking the time to make educational videos like this!
Marc, please give me your advice on this: i need to put a 3/8" concave radius, about 3/16" deep, on the end of a piece of 4140. The surface finish is poor. Am using HSS tool. I've tried different speeds. Have oriented tool so it is neutral or negative on the top (top rake). Have not tried positive rake; that will be next thing i try. Lathe is not very rigid, but all i have. Thx for any pointers you can send my way. Marty
Hi Marty! I do believe that you meant a 3/16" concave radius 3/16 deep because I am guessing that you are using a 3/8 tool blank. The problem here is the amount of tool contacting the part. A few things can be done to help minimize the chatter caused by a huge amount of contact and a tough metal. #1: support the end of the part with a tail stock center. #2: Slow down! Put the lathe in neutral and turn the part by hand, feeding the tool very slowly. #3: Set your razor sharp neutral cutting tool a little under zero (.003" per inch of part diameter up to .010" max for large parts) #4: Use a good tapping oil during cutting. #5: keep the groove a close as possible to the chuck and tighten everything up ( cross slide gib, compound rest gib, lock tailstock spindle), keep the tool as short as possible and don't let you compound rest overhang its base! In other words keep everything as rigid and tight as possible. You can reduce contact by moving the tool a few thousandths after each plunge. Plunge .010" and then using your compound rest (positioned parallel to the longitudinal axis that is locked) move .003" and plunge another .010" or less and then move you tailstock back to its original position. The deeper you get the less you will plunge for each cut but you will keep moving back and forth by .003" . Your groove will be very slightly over sized but probably withing the tolerance? Ultimately, if nothing else works (and if you own or have access to a mill) you could mill the groove by using the side of a 3/8" diameter end mill and by rotating the part held in a dividing head. I have a video where I cut a 3/8" groove on the lathe but I didn't have to be as careful since I was cutting free machining steel (C12L14). Here is a link if you want to watch it ua-cam.com/video/HGT35G31SoY/v-deo.html I hope this helps! Marc
Hi, Wow! That was the best lathe tool instruction I've ever seen. I've been using a lathe for decades for my personal needs, and that isn't very often. I learned to use a lathe, in a very basic and simplistic way, from my dad who used to work for AM&F in Brooklyn up until it closed in the late 1960s.. But he never got into tool geometry and application. Thanks for the great video. Tony
One of the best machining videos I've seen on UA-cam
I really enjoy your videos because I come in expecting to know what you are going to say. And you always do, but then you always include that little bit extra that turns my understanding of an accepted practice into a logical and meaningful lesson that really solidifies and builds a foundation of understanding I can trust. Thank you for being such an excellent teacher.
Hi,
Wow! That was the best lathe tool instruction I've ever seen. I've been using a lathe for decades for my personal needs, and that isn't very often. I learned to use a lathe, in a very basic and simplistic way, from my dad who used to work for AM&F in Brooklyn up until it closed in the late 1960s.. But he never got into tool geometry and application. Thanks for the great video.
Tony
Marc, thank you for that one! It gave me new insight into what I am doing at the lathe and reinforced and clarified other practices that I had accepted from the beginning, but never fully understood.
Hi Marc, thank you again for a great video. This is the second time watching it and I picked up the more subtle aspects of the angle of attack.
In regard to centre (oz) height tool positioning for internal and external machining a factor that I take into account besides the relevant point of rubbing as you pointed out is what happens with tool flexing.
It is important to appreciate that as the tool is loaded while cutting it will flex in an arc determined by the tool and tool holder geometry. In this flexing if the tool swings away from the surface the forces on the tool tend to reduce and so consequently it springs back and moves to a stable position in the depth of the cut. A reasonably smooth and cleaner cut results. This is a negative feedback system and hence stable.
If however the tool was to swing into the surface, it will dig deeper and the forces on the tool would increase forcing the tool even deeper into the surface. Erratic cutting oscillations may result causing high cutting loads on the tool edges and a poor finished surface.This is a positive feedback system and hence unstable.
For normal outside turning if the tool is set on or below centre, the tool will swing away from the surface and if set above centre the tool will tend to swing into the surface. Hence for outside turning on or below centre is good.
for inside turning the opposite is true, with "on centre" always being neutral.
on any form of cutting and most things in life, a negative feedback system is always more stable and controllable.
cheers and as always thank you for the great work.
U are great sir
I m a gate 2020 aspirant nd you are helping alot ❤️
Thank you Marc for making these informative videos!
thank you Marc I love the short qick ones, packed with a lot of information!
Good stuff. Learned lots. I like your teaching style.
Great video and thank you for your time.
Marc, thx for quick reply.
It is a 3/8 radius. I’m making a wheel for model train. 1.5” diameter. It is for the “dish” on the front of the wheel.
I’ll
sharpen cutter, run it neutral, and use some good oil.Marty
Will take your advice from now on without question. Applaudissements.
Just enough additional information in a nice short format.
Thank You Marc for this excellent explanation.
Thank you again, Marc. The theory helps me apply the practical...
Hi,
I was reading a book on lathes, a classic book that I can't remember the name of just now, and it said to put the turning tool 5 degrees above center. First off it's hard to guess where the 5 degrees is for a given diameter that I'm turning. And lately when I found that my tool wasn't cutting well, I checked it I found that when I turned the chuck by hand, the tool was just slipping on the metal. It was set too high.
So, I'm keeping it on center these days, just like you advised.
Thanks again.
Tony
Excellent video. This is very informative.
This was incredibly insightful, thank you!
@@LESPRODUCTIONSMAL I've shared your video with all my class mates and it's helped all of us so thanks for taking the time to make educational videos like this!
Very informative video. Thank you.
Very well explained.
Another great video.
good video.
Wonderful Marc! Thank you...
great video . Saved to bookmarks .
Marc, please give me your advice on this: i need to put a 3/8" concave radius, about 3/16" deep, on the end of a piece of 4140. The surface finish is poor. Am using HSS tool. I've tried different speeds. Have oriented tool so it is neutral or negative on the top (top rake). Have not tried positive rake; that will be next thing i try. Lathe is not very rigid, but all i have.
Thx for any pointers you can send my way.
Marty
Hi Marty! I do believe that you meant a 3/16" concave radius 3/16 deep because I am guessing that you are using a 3/8 tool blank. The problem here is the amount of tool contacting the part. A few things can be done to help minimize the chatter caused by a huge amount of contact and a tough metal. #1: support the end of the part with a tail stock center. #2: Slow down! Put the lathe in neutral and turn the part by hand, feeding the tool very slowly. #3: Set your razor sharp neutral cutting tool a little under zero (.003" per inch of part diameter up to .010" max for large parts) #4: Use a good tapping oil during cutting. #5: keep the groove a close as possible to the chuck and tighten everything up ( cross slide gib, compound rest gib, lock tailstock spindle), keep the tool as short as possible and don't let you compound rest overhang its base! In other words keep everything as rigid and tight as possible.
You can reduce contact by moving the tool a few thousandths after each plunge. Plunge .010" and then using your compound rest (positioned parallel to the longitudinal axis that is locked) move .003" and plunge another .010" or less and then move you tailstock back to its original position. The deeper you get the less you will plunge for each cut but you will keep moving back and forth by .003" . Your groove will be very slightly over sized but probably withing the tolerance?
Ultimately, if nothing else works (and if you own or have access to a mill) you could mill the groove by using the side of a 3/8" diameter end mill and by rotating the part held in a dividing head.
I have a video where I cut a 3/8" groove on the lathe but I didn't have to be as careful since I was cutting free machining steel (C12L14). Here is a link if you want to watch it ua-cam.com/video/HGT35G31SoY/v-deo.html I hope this helps! Marc
very helpful thank you
Thank you very marc.
Thanks Marc
i have problems getting a good finish on 12l steel with an atlas 10 lathe- lantern toolpost- any ideas
i am in Thailand .Thankyou for your vdo . I i i .
Merci encore.
funny is 99& tool is that figure 3 even wits less angled, but if you say its bad lol. why manufacturers do that
Hi,
Wow! That was the best lathe tool instruction I've ever seen. I've been using a lathe for decades for my personal needs, and that isn't very often. I learned to use a lathe, in a very basic and simplistic way, from my dad who used to work for AM&F in Brooklyn up until it closed in the late 1960s.. But he never got into tool geometry and application. Thanks for the great video.
Tony