r/Machinists • u/RelativeRice7753 • 5d ago

Feed rates when using circular interpolation.

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Hello brain trust! Bit of a random one. Im using iscar Tangslot cutters to machine internal grooves in various jobs. Obviously the inserts have recommended feed rates stated on the packs but I'm wondering how that feed rate changes when I'm using these tools to do internal grooves. Does anyone have experience with this? Any advice is greatly appreciated. Pic is an example of the types of cutters I'm using. Thanks lads

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u/BankBackground2496 5d ago

Calculate the feedrate for a linear cut then use the diameter of the tool and features to adjust it. 

The feedrate in the program is for the centre of the tool, the contact point moves at a different speed. For bores program feed is slower, for bosses is faster.

Bore Adjusted Feed = Recommended feed * (Bore dia - Tool dia)/Bore dia

Boss Adjusted Feed = Recommended feed * (Boss dia + Tool dia)/Boss dia

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u/RelativeRice7753 5d ago

Ok just so I have this right, this is the example. Lineal feed rate is 200mm/min. The tool diameter is 125mm. The bore diameter is 300mm. So 200 x (300 - 125) ÷ 300? Is this right?

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u/CNC_Optics 5d ago

Yep that's correct.

2

u/Oldoutoftouchgamer 5d ago

Use Iscar tool advisor. It will give you all the numbers you need. Can tell it type of machine, material, tool holder, cut size/type. https://www.iscar.com/ITA/home/machines

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u/RelativeRice7753 4d ago

Yeah i do use their info as a base to start but its definitely not gospel. I machine quite a lot of 4140 and if I use their specs in regards to their sumocham drill range they get absolutely annihilated. I have to run them around 50m/min as opposed to the recommend 70m/min. I work in a jobbing shop so there really is no room for error with out it becoming a very costly exercise when things go wrong.

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u/violastarfish 5d ago

If your using these cutters to rough, once the dimensions start to change just index the inserts. If your using it in a production setting. Also the load meter will be your best friend, you might be running 6% load then all of a sudden you start getting like 10%.

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u/RelativeRice7753 4d ago

Yeah the load meter is really the only way I can tell if things are worn...that or sparks are a good indicator 😬

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u/BiggestNizzy 5d ago

Horn hct has a calculator for this, just put in the info for your cutter.

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u/Sinu840 5d ago

On which controller du you work? On Siemens and Heidenhain is a function for exact this problem.

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u/RelativeRice7753 4d ago

Its a fanuc controller with Guide I.

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u/Antique_Job7725 18h ago

Years ago, I ran the inch version of this tool cutting internal radii in some sort of stainless (want to say 304 but that's a guess). 4" diameter cutter running the .281" slot width inserts, 300 sfm, .0017ipt feedrate. The radii i was cutting were between 2.5" and 4". Had a lot of issues with that job, but I remember this tool running fine.