Milling Cutter insert radius

[VicParticipant @vic]

I can’t seem to find a definitive answer but is .8 really the smallest radius for carbide milling inserts? I’m guessing anything much smaller may not be very durable?

[Nigel Graham 2Participant @nigelgraham2]

There may be much finer ones for specialist work but milling does entail a very rapid percussive action on the tool tip, so you may be right about durability. Even so that does seem a large radius.

Carbide insert tooling is a very complex area. Might most of your sources be aimed at general-purpose machining where if a “sharp” internal corner is needed for the component’s function, such as a spline or keyway, a, HSS or solid-carbide slot-drill would be the usual finishing tool?

There is quite a bit of information on Sandvik’s web-site (sandvik[dot]cormorant[dot]com), some useful to us; though generally it is intended for industrial users of hefty great NC machine-tools and we need bear that in mind. For example,  we would not normally countenance “down” (in brackets- “climb” ) milling as preferable to “up” (conventional), at least not on the sort of fairly light  – or elderly second-hand – machines most of us use. Nor, probably, go into the mathematical extent given.

The text though does bear out your suggestion of durability: the tool edge is subjected to a hammering action as it meets the work edge.

Perhaps the best approach is to accommodate fairly large internal radii where that is permissible, or use a non-insert cutter for finish-milling – while remembering a dead-sharp internal corner can be a stress-raiser.

[JasonBModerator @jasonb]

Depends on the shape of the insert and it’s use.

If it is a facemill and takes say APMT or APKT type inserts then 0.8mm is common going upto 2.0mm but you can also find them down to 0.2mm particularly those for aluminium and non ferrous. Have a look through these for starters

If it is an older one that clamps a simpler shape insert then you can get down to 0.2mm

Having a few diffenten sets of inserts with different radii can be useful just like they are on the lathe or with solid milling cutters if you want to leave an internal fillet for strength or in my case mostly for looks when creating fabricated castings like the fillet on these parts that are half way through becoming “+” shaped

[John HaineParticipant @johnhaine32865]

One of the problems with miscellaneous inserts such as we buy from exhibitions etc is knowing just what the tip radius is!  A couple of years ago I posted here:

https://www.model-engineer.co.uk/forums/topic/measuring-insert-tip-radius/

…a method of measuring the radii using a simple jig (metal plate with threaded hole) and vernier caliper.

Might be of use.

[VicParticipant @vic]

Thanks for the replies and links folks.

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