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Carbide inserts. 0.4 or 0.8

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petro1head21/02/2020 10:31:05
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732 forum posts
143 photos

Time for some new inserts. I am after ferrous and non ferrous.

I seem to have always gone for what I got origionally when I bought the tool holder, 0.4 however I notice Arc also sell 0.8 and just wondering what the advantage/dissadvantage of the two sizes

Edited By petro1head on 21/02/2020 10:31:20

Tony Pratt 121/02/2020 10:39:26
1029 forum posts
3 photos

I saw the following on their website 'We suggest the use of 0.8mm corner radius inserts for general cutting, and 0.4mm corner radius inserts for finishing.' From personal experience you can get chatter from using too large a tip radius

Tony

petro1head21/02/2020 10:55:15
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732 forum posts
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So prob best just to stick with what i Know, 0.4mm

Andrew Johnston21/02/2020 11:20:36
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5204 forum posts
599 photos

I use 0.2mm, 0.4mm and 0.8mm radius inserts. The 0.4mm inserts get used most for general turning and the radius is a good compromise when a really sharp internal corner is not needed. I use the 0.2mm inserts for smaller diameter work and where a sharp internal corner is needed. The 0.8mm inserts are used for heavy roughing, especially in steel and cast iron, and where I want a nice fillet.

To some extent the smaller the insert radius the smaller the final depth of cut can be and still maintain a decent finish, although many other factors also need to be considered. Similarly the larger the radius the higher the feedrate can be for a given finish, which may help with chatter problems. Speaking of which I've never had a chatter problem due to the 0.8mm radius inserts, but I do drive them fairly hard.

While I find it useful to have all three options available the 0.4mm insert is a good compromise.

Andrew

Douglas Johnston21/02/2020 11:35:24
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680 forum posts
32 photos

If you have a hobby size lathe I would stick to 0.4 radius as a good compromise. I must admit I like the 0.2 ones for a lot of what I do but the cutting point of the insert can be easily damaged if not careful.

Doug

Circlip21/02/2020 12:30:15
1045 forum posts

Bench grinder and a lick on the tip with a fine stone for us non NASA types.

Regards Ian

JasonB21/02/2020 13:01:51
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17323 forum posts
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Mostly 0.2mm for me with 0.4 kept for roughing steel and iron castings. The 0.8mm only come out if I want a decent corner fillet for things that I want to look cast. I find the smaller radius deflects long slender work less so good for valves and crankshafts, etc.

Emgee21/02/2020 14:12:19
1406 forum posts
212 photos

Like Jason I mainly use the .2mm rad inserts as they are more suitable for the type of parts I make but do use the .4 for some work as facing cuts with a .2 rad have to be less than tip rad to cut cleanly.

Emgee

Neil Wyatt21/02/2020 16:05:18
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17394 forum posts
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Ideal depth of cut for CCMT inserts is about 2/3 the tip radius.

Neil

Howard Lewis21/02/2020 16:19:13
2932 forum posts
2 photos

The larger radius should give a better surface finish, but at increased risk of chatter.

Also better if you have any concerns about sharp corners acting as stress raisers.

Personally. almost always use 0.4 mm , very rarely 0.8 mm, if not using the tangential tool.

Howard

Kiwi Bloke22/02/2020 02:35:25
355 forum posts
1 photos

Without knowing about your lathe, it's impossible to offer useful advice. My experience is that 0.8mm tip dia. inserts don't suit a Myford Super 7 - it's just not rigid enough to work the insert at depths of cut and feed rates that justify the larger tip radius. However, an Emco Maximat Super 11 takes them in its stride - even 'blunt' inserts, designed for hogging off metal, rather than fine finishing - and with a very good surface finish. Not bashing Myfords, it's just horses for courses...

petro1head22/02/2020 07:00:31
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732 forum posts
143 photos
Posted by Kiwi Bloke on 22/02/2020 02:35:25:

Without knowing about your lathe, it's impossible to offer useful advice. My experience is that 0.8mm tip dia. inserts don't suit a Myford Super 7 - it's just not rigid enough to work the insert at depths of cut and feed rates that justify the larger tip radius. However, an Emco Maximat Super 11 takes them in its stride - even 'blunt' inserts, designed for hogging off metal, rather than fine finishing - and with a very good surface finish. Not bashing Myfords, it's just horses for courses...

It’s a Warco wm290

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