Replacing ball nose

[Aussie]

What are the signs that a 1/16 tapered ball nose bit needs replacing ? more than usual fuzzies ?

Thanks
Ron

[Rcnewcomb]

more than usual fuzzies ?

That is one of the signs I look for.

Other indicators:
If you start to see burning on the material rather than slicing through it
If it used to leave a smooth finish but now it is rough

Some people verify by dragging a thumb or fingernail along the flutes to see if it will scratch the nail.

[chemstock]

Dull bits start to vibrate. you will be able to hear the whine as they age.
usually a 1/16" bit just breaks. I have to buy them in a 10 pack to keep ahead.
I mill hardwoods like maple or oak and only get about 10 hours on a bit before it retires.

[Aussie]

Dull bits start to vibrate. you will be able to hear the whine as they age.
usually a 1/16" bit just breaks. I have to buy them in a 10 pack to keep ahead.
I mill hardwoods like maple or oak and only get about 10 hours on a bit before it retires.

Wow 10 hours!!!! I only carve hardwoods and some of these carves are over 20 hours.... I had better stock up on bits.

[Xxray]

10 hrs, your chipload must be way out of specs and/or you are using ultra cheap bits, might do better with a few quality bits than dozens
https://www.precisebits.com/ https://www.cutter-shop.com/information ... chart.html [And of course, ball nose bits are not the optimal tool to do mill work]

I don't track averages but I must be around 100 hrs before I discard, and thats all types of materials and wood including plexiglas and corian. Signs I look and listen for is creating dust instead of chips, and burning of course whether by smell or sight, and a change in pitch while cutting which indicates the bit may be struggling.
Fuzzies not a real good indication, some woods [mdf too] are prone to minor tearout no matter what you do. They key to optimum performance with any bit lies in finding your sweet spot between RPM & feed speed, which varies by material, species and job type, there is no 1 setting that will do it all, and it greatly affects the quality of the project and the bits life span. When you spend $50 on a bit you do tend to want to milk out as many cuts as possible.

[chemstock]

I use Amana Tool or CMT orange. the 10 hrs is for seasoned white oak or hard maple.

[Kevin Holden]

Hi everybody this is my first post.

Coming from mass production experience we solved this problem very easily. Due to the fact that many CNC operators unfortunately had little woodworking experience, our technicians worked out that when a tool is sharp and machined a given material, the spindle 'pulled' a given amount of amps, but when it was blunt it 'pulled' more amps.
Therefor they installed an amp meter on every CNC in our factory and supplied a chart that stated the tool type, material, spindle speed, amps when sharp and amps when blunt.
Years later they took this a step further and the CNC would flash a warning light when the tool was reaching its predefined 'blunt' point. The operator would then change the said tool and reset the program as required. Therefor this solved the issue of when a tool is 'blunt' for the not so well informed on the factory floor.

Having said this though experience (those of us who have it) can easily tell just by the sound if a tool is struggling.

My electrician told me it would be very easy to install an amp meter to my CNC spindle, but to be honest I don't need it, I just listen.

Kevin

[Rcnewcomb]

Hi everybody this is my first post.

Welcome aboard, and thanks for the suggestions. I likewise learned to hear what a good cut sounds like. However, as my ears age the meter to measure current draw may be in my future.

[GEdward]

I agree with X Ray that there are just too many variables to make any reasonable prediction for how long you can use a bit unless perhaps if you only machine MDF, plexiglass, Corian or some other material with consistent structural characteristics. Which is why Kevin Holden's load monitoring approach works in a manufacturing setting I suspect. Most, if not all, VFD inverters have a load monitoring option on the display but I don't think that will get you there by its self. The original post is inquiring about a 1/16 tapered ball nose bit which, given its size, I suspect he is using for 3D or fine detail moulding or texturing work. The variation of the loads on a tool that small swing wildly within the job depending on the constant changes in depth of cut, the direction of cut relative to the grain and inconsistencies of the wood its self: like knots or resin pockets. Between the fan on the spindle coolant radiator and the dust collector, listening for the tell tale sounds associated with a dull tool is problematic for me personally. So what I do if I don;t like the appearance of the finish my small tapered ball nose end mill is giving me, I change it out for a new one. If the finish does not improve then I change back to the used one and just deal with the fuzzies. If the new tool shows marked improvement in the finish, the old one gets canned. If I really wanted to concern myself with knowing how sharp my small tbn bits are I'd probably just get a good jeweler loupe and visually compare them to a new bit BEFORE I started a long or demanding job.

I recently did a 3D job for a local church. It consisted of three hard maple door panels each with a recessed Sacred Heart of Jesus statue that took 18 hours total. I used a well used 0.25mm tapered ball nose end mill for all three panels and the client, who is doing the finish work, was quite pleased. I have no idea how many hours are on that tool but it will get used again on my next fine detail 3D job I am sure.

Ed

[mtylerfl]

OT

Hi Ed,

Have you posted pictures of the doors you did for the church? I would love to see them!

[GEdward]

Hi Mike,
I did not take any pics yet since the customer wanted to do the finish work. He said he will get me some pictures when he has them done. I'm hoping he does a good job.

Ed