Adding new tool settings

Hello again,

I hope you are all well.
I have some new tools to add for my project but am unsure of the correct way to add them, could someone please shed a little light on the subject for me please if you can?

The tools I have to add are as follows.
4 x tapered ball nose end mills the packaging reads.

R0.25-D3.175-5.05(followed by the little degree symbol)
I take this to be R=radius .25mm and D= shank diameter 3.175mm or 1/16" and then 5.05 degrees.
like wise they increase in radius by.25mm up to 1mm each with a decrease in degree or angle.

I also wish to try and use a 20 degree V-bit but am not sure how to add this either and also a 90 degree diamond tip drag bit which is going to prove a bit tricky I feel.
Any help in this matter would be greatly received…

Many thanks.


Hi Brian,

I agree taper bits are harder to add. With the exception of 45 an 90 degree tapers, it does require some math if don’t know the length of the tapered tip. To help with this, I will add an angle field in taper tool setup. Then whichever field (tip length or angle) is edited last will automatically calculate the other field.


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Thank you Stewart.
Is there any thing I should know about the tool path setting used for a taper ball end?
I see videos of a roughing pass first and then the use of a tapered ball end to achieve a very fine 2.5d carving.
my current project requires some very fine detail in wood so I have opted for some small ball ends on a .25mm what kind of finishing passes would i use, what kind of stepovers etc?

many many thanks,


For tapered milling, the step over fraction is calculated based on the widest part of the taper. I can’t answer for the specifics of your project, through. Also, KM does not currently model tapered ball mills accurately. This is on the todo list. So you’ll have to set it up as a smaller shaft diameter ball mill. This may lead to slight over-cutting on steep faces.

Thank you, should I buy some straight shanked ball ends instead to finish my project?

For accuracy, that’s probably best. I’ll see if I can get ball taper support into 3.9 in the next week.

Thank you so much. Have a great weekend.

Sorry to be a pain, how would I add the 20 degree v-bit?
Many thanks

Let me push an update this evening that fixes this for you.

In short, the flute length is (radius / Math.tan(angle)) where radius is half the flute diameter and angle is in radians (180 / Pi)

KM derives the taper angle from ((flute base diameter - tip diameter) / 2) and flute length as two sides of a right triangle.


I literally don’t know what to say…thank you so very much you are a legend.

updated tool dialog allows you to enter an angle and have the flute length calculated

Good morning Stewart.
That is fantastic news, thank you so much.
Can I use these new settings in conjunction with the others to add a tapered ball end ?

Many many thanks again


Not yet. Taper ball is a little more complicated.

Thank you again for all your help, I am having trouble with a contour path using a 20 degree bit, the move animation shows the tool passing though the work piece! am I missing something?

Right-click export your workspace and send to me (DM on Discord is easiest) or email [ sa at grid dot space ] I can take a look. I’ve been working on that code, so it’s possible I broke something. You might check if the routing is proper in 3.8

unfortunately i get the same tool path in 3.8 and it just runs through some areas, there do not seem to be any obvious reason to it regarding the geometry of the model although there are some nonmanifold edges!

I verified this is a bug I introduced in 3.9 – I am able to get proper routing in 3.8 – if you can’t, try enabling true shadow under the expert menu. Easy fix. Will push it out later today.

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Thank you once again. it works a charm with true shadow enabled.

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thank you so much for this software Stewart. I have managed my first real piece of work from concept through blender to cnc.

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