Lathe depth of cut vs feed amount, how to balance.

[pontiac428]

The way I see it, the material's properties dictate the feed, the lathe's power/rigidity determines the depth of cut. It might not matter much with aluminum, but stainless will clue you in on how that works rather quickly.

 

[Aukai]

As beginner I have not done well with feel, but I can hear real quick if things are not happy.

 

[RaisedByWolves]

You should only be using the half nuts when threading, so that really shouldn't be a consideration. When threading you'll usually run into issues on the tool end long before the half nuts are seeing much of a load.

Most of the small machines use the half nuts for both feed and threading.

As beginner I have not done well with feel, but I can hear real quick if things are not happy.

The term “feel” encompasses all your senses working in unison.

Well, except taste.

Don’t taste your tool is advise that has gotten me far in life.

 

[SouthernChap]

I think when the more experienced members here say "feel", they mostly mean not just the sense of touch but all the senses.

The input from the sense of touch is something that requires practice to calibrate and even experienced machinists will sometimes have to recalibrate when using a lathe they've not used before, albeit probably with a fair bit less time spent practicing.

However, the senses of sight and hearing (not taste or smell, unless you're This old Tony) are useful even from the get go for beginners (like me).

When @WobblyHand says "your lathe will tell you" he's not being that metaphorical.

If you start to get close to the edge of the envelope of your lathe's capabilities with a given combination of material, feed, speed, and tool nose radius (the latter is often under appreciated by beginners but tool pressure is a driving factor here and nothing increases tool pressure like a large radius on the tool cutting point) it will start to 'talk'.

It'll start off as a fairly quiet moan and then (sometimes, pretty rapidly) can rise to a dreadful howl. My little 7x previously sounded like I was torturing a cow if I tried to take too deep a cut or push the feed in the wrong direction on steel (on non ferrous materials it was quieter; maybe like I'd gagged the cow in question...and now I'm getting uncomfortable with my own analogy ).

You can also see the effects of picking the wrong feed/speed/DOC/tool nose radius. The surface finish will be unsatisfactory. If you get the "howl" mentioned above, you'll likely see signs of chatter.

In her "Lathe Skills" playlist on YouTube BlondiHacks has a couple of videos on speeds and feeds and also on chatter. They're worth a watch; as is the rest of the "Lathe Skills" playlist (and that's true if any of her videos; she's a good teacher).

The suggestion given by others to experiment with different materials and speeds and feeds and DOC is the best one really.

I'd add to that a suggestion to experiment with different nose radii on your tooling.

Either by honing the radius yourself with a stone (if you're any age at all, you'll need some magnifying eyewear for this!) if using HSS, or buying different spec inserts if using carbide).

Oh and practice on known materials. Don't use that bit of 'mystery metal' you found by the road. Buy stock specifically to practice on. Start with 6061 aluminium as it's reasonably priced and machines reasonably well.

Brass is generally fairly expensive, but if you pick what is known as a 'free machining' brass (it's called C360 in the States I think, we call it CZ124 in the UK), you get some instant gratification as brass is one of the easier metals to get a nice surface finish on.

For steel, the beginner's alloy of choice is 12L14 (mostly called EN1APB or 230M07PB in the UK). It's relatively cheap, so good to practice with.

As beginners working in our shops on our own, we generally don't have the benefit of a more experienced machinist looking over our shoulder and imparting their wisdom in real time. So, be kind to yourself about your learning and being prepared to go through some stock in that learning journey.

 

[RaisedByWolves]

I think when the more experienced members here say "feel", they mostly mean not just the sense of touch but all the senses.

The input from the sense of touch is something that requires practice to calibrate and even experienced machinists will sometimes have to recalibrate when using a lathe they've not used before, albeit probably with a fair bit less time spent practicing.

However, the senses of sight and hearing (not taste or smell, unless you're This old Tony) are useful even from the get go for beginners (like me).

When @WobblyHand says "your lathe will tell you" he's not being that metaphorical.

If you start to get close to the edge of the envelope of your lathe's capabilities with a given combination of material, feed, speed, and tool nose radius (the latter is often under appreciated by beginners but tool pressure is a driving factor here and nothing increases tool pressure like a large radius on the tool cutting point) it will start to 'talk'.

It'll start off as a fairly quiet moan and then (sometimes, pretty rapidly) can rise to a dreadful howl. My little 7x previously sounded like I was torturing a cow if I tried to take too deep a cut or push the feed in the wrong direction on steel (on non ferrous materials it was quieter; maybe like I'd gagged the cow in question...and now I'm getting uncomfortable with my own analogy ).

You can also see the effects of picking the wrong feed/speed/DOC/tool nose radius. The surface finish will be unsatisfactory. If you get the "howl" mentioned above, you'll likely see signs of chatter.

In her "Lathe Skills" playlist on YouTube BlondiHacks has a couple of videos on speeds and feeds and also on chatter. They're worth a watch; as is the rest of the "Lathe Skills" playlist (and that's true if any of her videos; she's a good teacher).

The suggestion given by others to experiment with different materials and speeds and feeds and DOC is the best one really.

I'd add to that a suggestion to experiment with different nose radii on your tooling.

Either by honing the radius yourself with a stone (if you're any age at all, you'll need some magnifying eyewear for this!) if using HSS, or buying different spec inserts if using carbide).

Oh and practice on known materials. Don't use that bit of 'mystery metal' you found by the road. Buy stock specifically to practice on. Start with 6061 aluminium as it's reasonably priced and machines reasonably well.

Brass is generally fairly expensive, but if you pick what is known as a 'free machining' brass (it's called C360 in the States I think, we call it CZ124 in the UK), you get some instant gratification as brass is one of the easier metals to get a nice surface finish on.

For steel, the beginner's alloy of choice is 12L14 (mostly called EN1APB or 230M07PB in the UK). It's relatively cheap, so good to practice with.

As beginners working in our shops on our own, we generally don't have the benefit of a more experienced machinist looking over our shoulder and imparting their wisdom in real time. So, be kind to yourself about your learning and being prepared to go through some stock in that learning journey.

Well said.

One thing, when cutting brass cover your ways and try not to make dust. Brass is abrasive and brass dust will get in your ways and make lapping compound when combined with the oil.


As to smell, a joke I learned from an old timer is to sniff something and tell the person what it is, making them think you can identify it by smell.

The key is knowing the material by sight or knowing it before hand to make this convincing.

A2 has a slightly different look than O-1, which looks different than SS, hot rolled and cold rolled are obviously different looking.


I borrowed a press operators mic once and noticed it was off by .001. A couple days later we were setting up a die and he was miking a piece of lead and I told him something was not right , sniffed his mic and told him it was off.

He got out his standard and was amazed it was actually off and needed adjustment.

 

[Jimsehr]

I think when the more experienced members here say "feel", they mostly mean not just the sense of touch but all the senses.

The input from the sense of touch is something that requires practice to calibrate and even experienced machinists will sometimes have to recalibrate when using a lathe they've not used before, albeit probably with a fair bit less time spent practicing.

However, the senses of sight and hearing (not taste or smell, unless you're This old Tony) are useful even from the get go for beginners (like me).

When @WobblyHand says "your lathe will tell you" he's not being that metaphorical.

If you start to get close to the edge of the envelope of your lathe's capabilities with a given combination of material, feed, speed, and tool nose radius (the latter is often under appreciated by beginners but tool pressure is a driving factor here and nothing increases tool pressure like a large radius on the tool cutting point) it will start to 'talk'.

It'll start off as a fairly quiet moan and then (sometimes, pretty rapidly) can rise to a dreadful howl. My little 7x previously sounded like I was torturing a cow if I tried to take too deep a cut or push the feed in the wrong direction on steel (on non ferrous materials it was quieter; maybe like I'd gagged the cow in question...and now I'm getting uncomfortable with my own analogy ).

You can also see the effects of picking the wrong feed/speed/DOC/tool nose radius. The surface finish will be unsatisfactory. If you get the "howl" mentioned above, you'll likely see signs of chatter.

In her "Lathe Skills" playlist on YouTube BlondiHacks has a couple of videos on speeds and feeds and also on chatter. They're worth a watch; as is the rest of the "Lathe Skills" playlist (and that's true if any of her videos; she's a good teacher).

The suggestion given by others to experiment with different materials and speeds and feeds and DOC is the best one really.

I'd add to that a suggestion to experiment with different nose radii on your tooling.

Either by honing the radius yourself with a stone (if you're any age at all, you'll need some magnifying eyewear for this!) if using HSS, or buying different spec inserts if using carbide).

Oh and practice on known materials. Don't use that bit of 'mystery metal' you found by the road. Buy stock specifically to practice on. Start with 6061 aluminium as it's reasonably priced and machines reasonably well.

Brass is generally fairly expensive, but if you pick what is known as a 'free machining' brass (it's called C360 in the States I think, we call it CZ124 in the UK), you get some instant gratification as brass is one of the easier metals to get a nice surface finish on.

For steel, the beginner's alloy of choice is 12L14 (mostly called EN1APB or 230M07PB in the UK). It's relatively cheap, so good to practice with.

As beginners working in our shops on our own, we generally don't have the benefit of a more experienced machinist looking over our shoulder and imparting their wisdom in real time. So, be kind to yourself about your learning and being prepared to go through some stock in that learning journey.

In my 70 plus years of machining I think top back rake allows the biggest depth of cut on light duty lathes. Very high positive Back top rake.

 

[WobblyHand]

My recommendation was to start making chips, first with easier to machine stuff that's cheap, to build up initial experience. Not said was to then branch out using other materials that are harder to machine or more expensive materials.

Won't take long to run into materials that prove more difficult to deal with. Was a revelation for me to burn up a HSS parting tool on 304 when I first started out. Each material has its quirks that need to be learned. Part of the fun and the learning experience.

 

[RaisedByWolves]

My recommendation was to start making chips, first with easier to machine stuff that's cheap, to build up initial experience. Not said was to then branch out using other materials that are harder to machine or more expensive materials.

Won't take long to run into materials that prove more difficult to deal with. Was a revelation for me to burn up a HSS parting tool on 304 when I first started out. Each material has its quirks that need to be learned. Part of the fun and the learning experience.

304 can go jump in the lake.

I recently made some grill parts out of unknown 1/8” stainless, but did not have enough material so I put in a order with sendcutsend .

I got 304 because it was easy 30% cheaper than anything else.

I was able to drill it fine using cobalt drills, but it stopped my counter sink cold about half way in on every hole.️

No wonder it’s so cheap.