Tool Geometries For Lathe & Mill Explained - Great Video Tutorial

Hi Ted

Thanks for your comments. When I got my first lathe, a smallish one (38mm spindle) - I did little homework, I just thought I could turn up some spacers and bushes and aligning tools for working on my old bikes.
The lathe had 12mm tooling, so not too expensive and I just drifted into insert tooling. So I made stuff and had a lot of fun with the machine - it did so much work I had to replace several bearings which had worn out (all be it, they were probably cheap Chinese bearings) - but eventually I got frustrated with a machine that had no threading dial, had manual change gears - so power feeding largely got ignored - and other things.

So now I am starting again with a new lathe (arriving soon I am told - we will see) -
I ducked over to my local supplier and picked up some HSS (8% cobalt) blanks and I have a small engineers protractor for the angles.

Now for some rough grinding while I wait for my replacement white stone grinding wheel. This time around I will put my nose to the metaphorical grindstone and be a lot more particular about, ground angles on the tooling, feed rates and of course the final arbitrator - chip formation, surface finish and accuracy.

Cheers


Mal
29913326744_5bf34478f6_b.jpg
 
One thing to keep in mind, Mal, is that most reference works that show and tell about how to grind HSS are pretty dated. That simply means that the machinery they used when those were written was old, heavy, and slow. And steels were a pretty narrow chemistry and heat treatment. Which boils down to this: What they do show and tell may or may not give you the optimum results. It's a combination of equipment and material that will dictate how the tool really must be ground. Just use those guides for what they are, guides. With the materials you may run across in a scrapyard, for instance, you may or may not know exactly what it is, nor how it will cut on your particular machine. Especially since you are also breaking in a new machine, you will have to learn it as well. No doubt you will have adjustments to make on the machine; expect to adjust your grinding techniques as you go along. Don't be afraid to try something a little different. Might be wrong, might be right....but you will have learned something if you are paying attention.
 
Thanks Tony

What a great position to be in at the bottom of the mountain - any thing I learn will be up. I will certainly experiment - however I acknowledge that millions of hours of practical machining have helped to develop the guides, so I guess I will start there and then tweak based on the results I get. My wife has taunted me saying, "you won't be game to use the new lathe" - that first cut will be an interesting moment.
Luckily the lathe will be installed by a tech from the supplier, so I won't be going solo straight up.

The machine is one where the engine runs 100% of the time and uses a clutch to engage the drive and a clutch/brake to stop the spindle - like driving I guess. Where as what I had before was just a switch - turn spindle on / turn spindle off.

It also has chuck guards, coolant and a 1,001 gears and knobs - I expect it to keep me busy for quite awhile learning how to use it.

Mal
 
A trigon insert (WNMG) holder is an excellent roughing tool, it will turn and face. Also used in boring bars therefore 2 tools using a single insert. http://www.mscdirect.com/browse/tnp...wid=F8XL49ij&gclid=CISz2-vA9M8CFYFehgodY-4DKw

CNMG 80° inserts are good finishing tools that also face and turn and are available for boring bars, also 1 insert for 2 tools. http://www.mscdirect.com/browse/tnp...wid=F8XL49ij&gclid=CPOm-c7A9M8CFY5ahgodSkwO4Q

For work that requires very low cutting forces such as thin walled parts or deep bores 3 or more X the diameter in steel a positive rake triangular insert with the smallest available nose radius works well.

When turning close to a center a DCMT 55° is the only choice for the most part, these will turn very close to the center.

Choose wisely
 
"V" series (35°) diamond will get you closer yet, so between the two, C series and V series, you generally won't need the "D" series, although the smaller the angle, the more delicate the insert.
 
Tony


These are the difficulties I also face - one choice or two spread choices like you suggest (which has merit I must add).

I am going to grind some tools and get a feeling for the new lathe and make some decisions when I understand what metal the beast will carve off - therefore this will influence the tooling choices I make. The old lathe was never happy pulling much over 600rpm, the new lathe should be good for three times that speed - so I think I need to wait and experiment before splashing the cash on expensive insert tool holders.

The machinery supplier phoned this morning to say our new lathe is pre delivered and ready for transportation to our workshop next week. So let the games begin.

Mal
 
What lathe are you getting. I'm sorry if you posted on it and I can't remember. I try to read all the posts made, so some of then tend to fall through the cracks developing quickly in the gray matter.

If you're game to try triangular insert tooling, I might be able to round up enough stuff to get you started at least. I dislike it myself. I don't know what all I might have, exactly, because it's not front and center in my tooling. If you'd like, I can look and see what I have. Surely a couple of turning tools and perhaps a boring bar or two as well. Can't promise any inserts, but wouldn't be surprised at all if I have some. And then whether they fit the holders I can't say for sure. It's just that I have acquired some over the years in lots I have come across and just set aside. I have preferences, and they ain't it. I know some people love them, but I have never really been satisfied with them. About the only thing I might have used them on in any great amount would be some heavy duty roughing of some driveshaft forgings the oilfield uses in their mud motors. And that only because I only worked there and had to use what I was given. No say in it.

That's another thing I wanted to mention. earlier it was recommended that you talk with some seasoned job shop guys. You can learn a lot from some of them, if they let you, but insert choice is rarely totally theirs. They may get to pick from whatever the shop has on hand, but they don't usually get to do the tool purchasing. That's not how they make the company money. They make chips. Sometimes the supervisors do the buying, in NC/CNC shops sometimes the programmers do it....it varies, but my point is that the actual machinists and operators usually have no idea what's really available on the market and may not be the best source of information on what to buy, being that you are starting from scratch. Like the job I mentioned where I used the triangle inserts....if you had asked me at the time, I probably would have said "Here, this is working". But it wasn't my favorite. But then, until I started buying tooling, I really had no idea what was out there (and it's always changing) and never got to work with the factory reps when they came, and never was consulted about how well what I was using actually performed.
 
Hi Mal
I'm glad the video helped, I found it informative as well.
Picking the "correct" insert/tool holder is daunting for us amateurs. After some searching I decided to go with an inexpensive 'starter set' to get some first hand experience and see what works for me. I purchased this set from Amazon
https://www.amazon.com/Indexable-Ca...urning+Lathe+Tool+Set+SCLCL+SDJCR+SWGCR+SDNCN
41uzJVu2D8L._SX425_.jpg
It has a nice selection of the 'popular' tool styles and the holders are of surprisingly good quality. The inserts that come with the holders are OK but I suggest you get some brand name replacements after you decide what tool type you like.

At some point you need to jump in and test the water, this set was a good one for me and I'm happy with these styles. I purchased a bunch of quality inserts and will be using these as my main cutting tools.
Best of luck and enjoy the hobby.
Rich
 
Tony Wells said:
What lathe are you getting. I'm sorry if you posted on it and I can't remember. I try to read all the posts made, so some of then tend to fall through the cracks developing quickly in the gray matter.

If you're game to try triangular insert tooling, I might be able to round up enough stuff to get you started at least. I dislike it myself. I don't know what all I might have, exactly, because it's not front and center in my tooling. If you'd like, I can look and see what I have. Surely a couple of turning tools and perhaps a boring bar or two as well. Can't promise any inserts, but wouldn't be surprised at all if I have some. And then whether they fit the holders I can't say for sure. It's just that I have acquired some over the years in lots I have come across and just set aside. I have preferences, and they ain't it. I know some people love them, but I have never really been satisfied with them. About the only thing I might have used them on in any great amount would be some heavy duty roughing of some driveshaft forgings the oilfield uses in their mud motors. And that only because I only worked there and had to use what I was given. No say in it.

That's another thing I wanted to mention. earlier it was recommended that you talk with some seasoned job shop guys. You can learn a lot from some of them, if they let you, but insert choice is rarely totally theirs. They may get to pick from whatever the shop has on hand, but they don't usually get to do the tool purchasing. That's not how they make the company money. They make chips. Sometimes the supervisors do the buying, in NC/CNC shops sometimes the programmers do it....it varies, but my point is that the actual machinists and operators usually have no idea what's really available on the market and may not be the best source of information on what to buy, being that you are starting from scratch. Like the job I mentioned where I used the triangle inserts....if you had asked me at the time, I probably would have said "Here, this is working". But it wasn't my favorite. But then, until I started buying tooling, I really had no idea what was out there (and it's always changing) and never got to work with the factory reps when they came, and never was consulted about how well what I was using actually performed.
Click to expand...

Hi Tony from Down Under

Bit of a way from Texas - though funnily we have a town called Texas about 100 miles South of where we live. So a very generous offer but I am happy to have the conversation -

The machine I am buying is a Colchester 2000 in the short bed version 625mm between centres. It is a manual engine lathe though I could have bought a variable speed lathe - to be honest all I could see in years to come some problem with electrics - this way all it should need is a new electric motor - and hopefully not for a long time.

Reason for picking this lathe - was I wanted a nice quality lathe with a 50+mm spindle bore, a footprint that would fit in our home workshop (over here we tend to just call it a shed) - good threading capability and a nice slow low speed (this one has 25 rpm minimum speed / 2000 rpm max), also this one has a 7.5hp 3 phase motor (so reasonable grunt), also fitted with DRO and a bunch of other specs.

While I am a newbe in one sense, I see that as a relative term - I have fiddled with my previous lathe on and off over the last 7 years - but I made stuff which was not accurate really and I just muddled through - now I want to go back to basics and improve my metal work.

16556648072_f5855e5a89_h.jpg

Here is an example of a special bearing puller I manufactured using my old lathe and my milling machine. As you can see it looks like it was made using a stone axe - it works real good but it is rough and ugly.

The funny thing is I used triangular insert tooling to do most of my turning on the old lathe and was not aware there might have been better options. Because the old toolpost height was 12mm and the new lathe has a 25mm toolpost - I am retooling -

We can afford to buy some nice tooling, but I don't want to have a whole cupboard full of stuff that doesn't get any use because I have moved on to something that is way better.

So I am going to run the new lathe (next Tuesday he arrives) and then see how it works - but experience tells me - that experience comes from using stuff, so I will have to make a decision and get somethings to try - and then dig in deeper to get my tooling requirements sorted out more permanently.

Sorry to rabbit on so long.

Thanks to one and all their advice and opinions - keep them coming, as my wife says, "you have big ears."


Mal
Australia
 
Rich V said:
Hi Mal
I'm glad the video helped, I found it informative as well.
Picking the "correct" insert/tool holder is daunting for us amateurs. After some searching I decided to go with an inexpensive 'starter set' to get some first hand experience and see what works for me. I purchased this set from Amazon
https://www.amazon.com/Indexable-Carbide-Turning-Lathe-SCLCL/dp/B00OI8GAP4/ref=sr_1_1?s=hi&ie=UTF8&qid=1477401764&sr=1-1&keywords=7+Pc+5/8''+Indexable+Carbide+Turning+Lathe+Tool+Set+SCLCL+SDJCR+SWGCR+SDNCN
41uzJVu2D8L._SX425_.jpg
It has a nice selection of the 'popular' tool styles and the holders are of surprisingly good quality. The inserts that come with the holders are OK but I suggest you get some brand name replacements after you decide what tool type you like.

At some point you need to jump in and test the water, this set was a good one for me and I'm happy with these styles. I purchased a bunch of quality inserts and will be using these as my main cutting tools.
Best of luck and enjoy the hobby.
Rich
Click to expand...

Hey Rich

Thanks for the tip - certainly something to think about.

Regards Mal
 
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