04-08-2015, 12:34 AM (This post was last modified: 04-08-2015, 12:36 AM by aRM.)
Hi Guys
Am about to order some cheapie Insert Imports for general turning of mild steels, salvaged scraps from truck spares ex work and the usual mix of odd-ball metals we tinker around with. Guess like everyone else, we also love to see a fine finish on our turned projects and often use our 4 Jaw to square-up blocks every now and again.
This may sound lie a real duh question, (and has to be asked), but what effect does INSERT PROFILE have on finishes ???
Suppliers generally ask for the last numbers we want, like will it be 08 or 04 etc. And we have used both without taking much notice of any remarkable difference. For example, we squared up this block of 2" x 4.5" BMS ( Bright Mild Steel) over the weekend and ended up with two different glazed finishes on the same side, one nice and glossy, whilst the other more matt and satinny, if I may be understood !!! We tried altering speeds and running at max we did get a nice smooth portion in certain parts of the block, but still achieved that satin look in parts as well.
Which also leads me to another question. All turning thus far we have done with that main LEVER in the LOW position. That's the second LEVER from the top, below the Speed Change lever, which says "KEEP IN LOW" in the pic.
The question ( another DUH one ) is, can we run any general turning, NOT THREADING, in the HIGH position ??? ( Heck man, got this off my chest, now for the barrage of reprimands !!! )
Guys, do overlook the ignorance. There's got to be some fools amongst the wise and rookies amongst the well-experienced, so do say it like it is !!! And then again, THE (honourable) PIXMAN should have been addressed directly here for INSERT clarification. However, we really would appreciate input from all U other Gurus as well.
The last numbers you refer to are the tip radius on the insert. I'm not sure that the actual shape has any effect on the finish, but the top geometry (chipbreaker) will, as will the grade.
Carbide inserts love to work, so yes, you can definitely run them in the high range. If you buy an insert from a large manufacturer, there is sometimes information in their catalogue that will give you the recommended speeds and feed rates etc. I know that Walter has this information in their catalogues, as a good friend of mine keeps pointing it out to me
Carbide Depot has a look up function for chipbreakers and grades that will give you some information as to what they are suited to. Sometimes they don't have what you are looking for and it is always useful to look at the actual manufactures catalogue. Fortunately, most have pdf version on their web sites. I have several downloaded and refer to them when I am searching eBay for a bargain.
Personally, I stick to brand name inserts over the cheap Chinese ones.
Cheap import inserts - I wouldn't and I don't. They chip, break and generally don't perform well. You have no idea what you are getting and little or no come back.
Buy a named brand that has an office here in South Africa, at least you will be able to 'phone them. If you choose an ISO standard insert, see what prices the different suppliers offer.
I think 'KEEP IN LOW' means just for threading. Running at a higher speed generally gives a better finish - but not always and not for all materials. The feed per rev will come into play as will the depth of cut. So use it 'high gear'
Cold rolled steel has an inherent problem - it is cold rolled and therefore has lot of stress especially near to the surface. This will affect the finish as you have noticed also at the start it is an intermittent cut which causes a whole lot of new problems - sometimes there little one can do about it.
What inserts are you looking for size,type ect. If you are looking for a general purpose one - there really isn't one, the insert manufacturers aren't daft. But the ones for stainless steel come close.
The 04, 08 is just the radius of the cutting 'edge' bigger the number bigger the radius. Bigger the number stronger the cutting edge is (well supposed to be).
Also generally bigger the radius bigger the depth of cut.
DaveH
PS Darren posted whilst I was writing - why some points are repeated.
A word about manufacturers data regarding speed, feed and depth of cut, for this data to be any use to you it's important to know what criteria the data is based on.
If you don't know ask them
Not all inserts have to be run at high speed to get the benefits - threading inserts - I don't run them at high speed - not good for my nerves
DaveH
(04-08-2015, 12:45 AM)Mayhem Wrote: The last numbers you refer to are the tip radius on the insert. I'm not sure that the actual shape has any effect on the finish, but the top geometry (chipbreaker) will, as will the grade.
Carbide inserts love to work, so yes, you can definitely run them in the high range. If you buy an insert from a large manufacturer, there is sometimes information in their catalogue that will give you the recommended speeds and feed rates etc. I know that Walter has this information in their catalogues, as a good friend of mine keeps pointing it out to me
Carbide Depot has a look up function for chipbreakers and grades that will give you some information as to what they are suited to. Sometimes they don't have what you are looking for and it is always useful to look at the actual manufactures catalogue. Fortunately, most have pdf version on their web sites. I have several downloaded and refer to them when I am searching eBay for a bargain.
Personally, I stick to brand name inserts over the cheap Chinese ones.
We have both the KENNAMETAL and WALTER catalogues and are these small !!! Seems like there' no other way but to sit and study these and make some sense out of all that technicality.
Will remember that the geometry is more important than the profile when looking at some of these.
Yup, the Brand named ones do and will make matters a lot easier.
Thanks again
aRM
(04-08-2015, 01:18 AM)DaveH Wrote: Cheap import inserts - I wouldn't and I don't. They chip, break and generally don't perform well. You have no idea what you are getting and little or no come back.
Buy a named brand that has an office here in South Africa, at least you will be able to 'phone them. If you choose an ISO standard insert, see what prices the different suppliers offer.
I think 'KEEP IN LOW' means just for threading. Running at a higher speed generally gives a better finish - but not always and not for all materials. The feed per rev will come into play as will the depth of cut. So use it 'high gear'
Cold rolled steel has an inherent problem - it is cold rolled and therefore has lot of stress especially near to the surface. This will affect the finish as you have noticed also at the start it is an intermittent cut which causes a whole lot of new problems - sometimes there little one can do about it.
What inserts are you looking for size,type ect. If you are looking for a general purpose one - there really isn't one, the insert manufacturers aren't daft. But the ones for stainless steel come close.
The 04, 08 is just the radius of the cutting 'edge' bigger the number bigger the radius. Bigger the number stronger the cutting edge is (well supposed to be).
Also generally bigger the radius bigger the depth of cut.
DaveH
PS Darren posted whilst I was writing - why some points are repeated.
Hello DAVE
Good to hear from U.
Will look again and see what Walter offers in the standard CNMG / WNMG Inserts and for Threading as well, although we have some of the Iscar TIP inserts.
Generally, we found the higher speeds do help in getting a finer,nicer finish. We will try our machine in the HIGH GEAR and see what gives.
The tool nose radius as it relates to feed rate has a profound effect upon the surface finish you get. Also, it's often critical to use at least the size of the tool nose radius as your minimum depth of cut. That's primarily true with carbide inserts because they need heat in the process to get a shiny finish in most materials, soft steels in particular.
Those inserts which have a molded-in chipbreaker (top form geometry) will have a range for depth of cut and feed rate and feed rate in the materials which a particular grade and coating were aimed at. In general terms a larger tool nose radius will get a smoother finish than a smaller radius if both are run at the same feed rate per rev. The profile shape of an insert (90º, 80º, 55º, 35º) and the approach angle of its holder have an effect too, just much less pronounced.
If you are using CNMG and WNMG negative rake inserts, tell me what materials you are turning, and the amount of stock removal you wish to get per pass. Also, the spindle power of the machine will matter with negative rake inserts. I would hope you have at least 3HP on the lathe to use negative rake inserts effectively. I can help with chipbreaker selection and grades when I learn more about what you are trying to use and what materials you are cutting.
Your machine certainly appears to be right for these inserts, I simply don't understand the bit about "keep in low"! If that's what they want, why is the lever option there at all? Perhaps they want it in low only for threading? You definitely want higher speeds and feed rates. I can't quite see the top information plate in your photo, but it appears you have a specific gear arrangement for turning feed rates. See if you can find in your machine's documentation why the notation about "Keep In Low."
(04-08-2015, 01:27 AM)DaveH Wrote: These are the ones I'm currently using - for everything steel, stainless (303) brass, bronze aluminium even plastic.
DaveH
DAVE
That looks familiar - ISCAR, right ???
Only thing is I know we have mostly WNMG and CNMG type toolholders which we need to check on and see if we can get similar to what U suggest.
Will check with the local Guys here in Durbs
Thanks again for the good pointers
aRM
