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Carbide inserts ~ lathe size

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JPower6210

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Newbie question- I am using HSS on my lathe and happy with it, but I would like to try out some inserts- In my reading I keep hearing that you need a big heavy lathe to effectively use carbide. So the question is: what is big/heavy? Is there a general guideline for how big for inserts? How big do you need before you can go to negative rake inserts and get the advantage of double sided inserts? More curiosity than anything. Thanks-

JP
 

SamI

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I'm running carbide on my 13 x 40" lathe and I'm pretty happy with it. Sure, carbide can be run at much higher speeds than I feel comfortable with most of the time but I get reasonable tool life out of my inserts, as long as the correct grade of inserts is used (some coatings cause rapid build up when cutting aluminium).

If you experience any chatter on your machine this can cause the carbide to chip, and on something like mini lathe where it's not uncommon to stall the motor then chipping inserts is fairly common in my experience. That being said I used carbide on my mini lathe with great success.

Many people prefer HSS on smaller machines such as the mini lathe because it can hold a sharper edge than carbide and therefore reduce the cutting force. Some people also claim a better surface finish however I have personally not found this to be the case. That being said, while I can grind special tools for a given purpose I am not the best at grinding HSS tools - I suspect if I experimented a little I could get a better finish.

As for the negative rake, that's what I tend to go for for roughing operations as it works out much more economical. I guess it's a bit of trial and error. My only advice would be to invest in good quality inserts. I have had mixed success with Chinese inserts. One batch were OK then the next barely usable. They're not that much more cheaper than the high end ones and the life of the insert seems much higher so it probably works out about even and at least you know that the inserts you buy today will perform the same as the ones you bought last time. Also you get more choice in coatings and chip breaker geometry of the insert which can make a big difference to the tools ability to cut and control the chip effectively.
 

JPower6210

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Thanks for the detailed response- I have a PM 1236, so not a mini lathe, but not as heavy/stiff as yours either- I don't get much chatter, but I also have not used a lot of carbide and the bigger DOC- sounds like it is worth experimenting with though-
 

Mitch Alsup

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Thanks for the detailed response- I have a PM 1236, so not a mini lathe, but not as heavy/stiff as yours either- I don't get much chatter, but I also have not used a lot of carbide and the bigger DOC- sounds like it is worth experimenting with though-
I have a Grizzly G4003G 12-36 and use carbide insert tooling almost exclusively. CNMG, CCGT, and some threading inserts. I can take cuts deep enough and fast enough that the steel turns purple as it unwinds off the nose of the tool.
 

Karl_T

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One trick to try is inserts made for aluminum. I use CNMG tool holders. even thought this is a negative rake two sided insert, the chip breaker is big enough that it actually cuts with positive rake. You still want to run faster and deeper than HSS. Also carbide will not do a skin cut - just rubs.
 

Bamban

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I use DCGT and CCGT turning inserts on my JET 1024, and the 16ER AG60 for threading, all carbide, ground sharp intended for aluminum. Threading I plunge straight in with the cross slide since I have the compound set sort of permanently for taper boring.
 

P. Waller

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The size and power of the machine is far less important then the size of the part.
A small machine may produce small parts using insert tooling with excellent results especially if it has sufficient spindle speed.

If producing parts at the middle to maximum size that a machine will hold this is when the problems begin.
 

mmcmdl

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I've run cemented carbide and inserts on 9" minis - 8' T lathes . The only time carbide or ceramic was not used in the last 30 years was when form tools were used . I'm not sure why I keep reading that carbide is only for bigger machines on the site . :confused 3:
 

shooter123456

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You can use carbide all you want on a small machine. I have a PM-1030v and use carbide almost exclusively. I have a HSS parting tool and needed to grind some tools to get to some hard to reach spots, but the rest is carbide. I have even gotten away with using a negative rake tool with excellent results.

As inexpensive as many carbide tools are, I don't think the whole "It isn't cost effective to use carbide insert tools on small machines." I have gotten a box of 10 inserts for $5 whos edges last a long while (hard to say specifically, maybe 2 weeks of semi regular use) and can be indexed easily. That means 20 edges runs for 40 weeks for $5. How much cheaper do people want?

I have used them on everything from plastic to 304 stainless, titanium, and hardened tool steel. They do the job just fine.

I also get the tool to form a chip usually, get nice finishes, and can remove material quickly (I have gotten over 5 in^3/min in aluminum).

Here is a video of my machine making some cuts in aluminum and steel. All of the tools are carbide, and I think the inserts are doing an excellent job, even on my small machine.

 

MarkM

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I think what is important is to use the right insert with the right tool holder with the right geometry for your machine. There are alot of smaller machines out there and a huge market out there for carbide tooling for the companies to invest in research and development knowing alot of newbies want it easy and like to just index there tools. There is a video on youtube from Pierres garage that tests some 1/2 inch carbide tools and he used a friends lathes that weighed no more than a couple hundred pounds. It cut remarkably well. Even to the point that he could remove tenths with the carbide tools. The right geometry is everything!
 

P. Waller

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How much cheaper do people want?
Free is what people want, welcome to the USA (-:
Hobbyists and small shops in the USA have made their wishes known, we do not want quality products we want inexpensive products.
The existing machine manufacturers listened and stopped making machines for this market, this small market was filled by Asian manufacturers willing to make a small profit per machine or tool, and here we are today.
 

shooter123456

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Free is what people want, welcome to the USA (-:
Hobbyists and small shops in the USA have made their wishes known, we do not want quality products we want inexpensive products.
The existing machine manufacturers listened and stopped making machines for this market, this small market was filled by Asian manufacturers willing to make a small profit per machine or tool, and here we are today.
Well I think that makes a lot of sense. For hobby work, most people won't be able to afford or justify the high quality tools. Sure it makes sense for an industrial user who will use a machine to make a living to pay a lot more and get something that will hold up to heavy use for a long time. But for someone who wants a small machine in the garage to use for 3 or 4 hours a week to tinker, it just doesn't make sense to pay a lot more for something much better. Likewise with tools, most hobbyists will never need the high quality inserts that will stand up to a ton of abuse and keep running day in and day out.

I am pretty sure all of my carbide tools and inserts (Probably over 200 inserts and 10ish holders) cost less than a single high quality holder and pack of 10 inserts. And they do the job I need from them.
 

Mitch Alsup

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Hobbyists and small shops in the USA have made their wishes known, we do not want quality products we want inexpensive products.
Almost:: we want inexpensive tools, and if American tooling costs 10x what foreign tooling costs, foreign tooling will be purchased.

Last year I was looking a a boring bar with CNMG inserts. Kennametal wanted $60 for the tool holder and $5 each for the inserts. The chinese were willing to sell a kit of 5 different sized boring bars and 10 inserts all for less than the American boring bar.

This is straight microeconomics--the consumer optimizes his utility function--and has nothing to do with the USA--it simply what happens when thinking people make purchases from a well supplied market.
 

P. Waller

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Excellent justification.
Try again
 

MrWhoopee

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Here's a video of my SB Heavy 10L boring out a 6 in. pipe coupling using a 3/4 dia. boring bar with a CNMG432 insert.


This is pushing the limits of the machine, but it did a fine job without chatter.
 

macardoso

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I use carbide for just about everything on my lathe (Enco 12x36). I use the CCMT or CCGX in the 32.xx size for just about everything. Those are probably the biggest you can take full advantage of. You can certainly use bigger inserts, but you're paying for more carbide than you'll use.
 

SamI

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Almost:: we want inexpensive tools, and if American tooling costs 10x what foreign tooling costs, foreign tooling will be purchased.

Last year I was looking a a boring bar with CNMG inserts. Kennametal wanted $60 for the tool holder and $5 each for the inserts. The chinese were willing to sell a kit of 5 different sized boring bars and 10 inserts all for less than the American boring bar.

This is straight microeconomics--the consumer optimizes his utility function--and has nothing to do with the USA--it simply what happens when thinking people make purchases from a well supplied market.
Like yourself I bought an eBay special bunch of boring bars in various sizes as a lot for very little money. I would still say that a premium tool offers better value and I will invest and replace them as and when I need / can afford them.

My reasoning behind that is the Chinese boring bars look the same as a premium but they are made from lesser materials to slacker tolerances. On the other hand I have an £85 carbide boring bar with a 12 mm shank. This gives a better surface finish and can bore to a significantly greater depth at higher speed and a greater depth of cut than my 16mm chinese boring bar shaped piece of mystery metal. As such instead of having two or three boring bars for increasingly larger holes I have one that I use for almost all of the boring I do. Because chatter is almost non existent in most bores I don't chip inserts often. Last night I was using a 6mm chinese special boring bar and with the chatter I was chipping inserts left right and centre and that was taking it as easy as I could.

OK in the example above I am comparing carbide with steel boring bars but the point I am trying to make is that just because something is cheaper it doesn't necessarily mean it is better value. I knew this when I bought the cheap ones and if I could go back in time I would probably buy them again just so that I had a range of sizes available to me. I wouldn't however compare them with a premium brand of tooling that costs 10 x the price and expect them to perform the same.
 

Nick Hacking

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I'm a novice and I really haven't got my head round all of the different relief angles yet. I've tried grinding HSS tools from blanks and they really didn't work well at all.

I've read on here that one can buy pre-shaped HSS inserts to use in tooling designed to hold carbide. From my research, no-one seems to be selling them in the UK.

I've been watching Steve Jordan on Youtube. He's a retired professional with a tiny Chinese mini-lathe and a small Myford. He uses a lot of carbide tooling to great effect and I've been trying to copy him. So far my results are not bad on my Myford and very pleasing indeed on my Sheldon. These are both old machines that are down at the small end of the scale.

My (very limited) experience suggests that it's a matter of playing around with tools and techniques until you find a combination that works for you. All absolute statements are false (sic).

Kind wishes,

Nick
 

jdedmon91

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My two cents, I here a lot of talk about geometry of inserts in this thread and other threads in home machining boards. Also a lot of praise for HSS tooling. From the first day years ago I stepped on a shop until today I’ve used some sort of carbide tooling, from braised on to indexable inserts.

One thing stick out in my mind, back in the late 70’s we attended a presentation at Eaton from a Valentine insert engineer, the 3 things he preached were speeds,feeds,and depth of cut.

Manny times I shown, explained and been told that inserts and tools that are positive rake like industry uses will not work at home shops on our little lathes. I’ve called BS more times than I could count. I’ve used CNMG 432 inserts in holders on my last two lathes. The one I did this with was a 9 x 20 Lathemaster, that I used a standard MCLNR 164 holder with a dovetail machined into the tool holder. My present lathe is a Grizzly G0750g 12 x 32. 90% of the tooling are dovetailed direct fit tooling that I modified to fit the QCTP.

My biggest limitation is HP not rigidly, that controls my depth of cut. I’ve had great results with the tooling package I use and would not hesitate to recommend it to anyone

In fact I have a gentleman locally I’m mentioning who I picked up a MCLNL 164 on EBay for under $10 plus shipping, we just finished dovetailing it and installed the adjuster so he could use it on his Smitty.

Below is my go to turning tool

Here is a few more while I was working on them



Sent from my iPad using Tapatalk
 

macardoso

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Never seen anyone do that before! Very creative
 
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