End Mill for Bearing Pockets in Ti

[JRB Blades]

I have been using the AKS 3/16" bearing that are .373" in diameter. Up until now I have been using a 13/32 carbide tipped counter-bore with a 3/16" pilot running at around 300-350 RPM. It works OK, although it does leave a nasty burr right around the pivot hole. To avoid this, I am considering getting a solid carbide end mill and centering the chuck with a 3/16" rod into my pivot hole, locking everything down and switching to the carbide end mill to avoid this dreaded burr.

My question is do I go with a 2 or 4 flute for this job? I am using 6-4 Ti from AKS also. Also, do you guys run these wide open (2500 RPM on my mill) or not?

Thanks!

 

[Stang Bladeworks]

Definitely dont run wide open. Stick to 300 ish rpm. Be sure to use coolant. If you are using an endmill use a smaller one with a rotary table. Endmills dont have a perfectly flat bottom by design so a plunge cut wont leave a flat floor on the pocket. Sounds like you just need a better counterbore. You need to use a fair bit of force to avoid rubbing in titanium. This will cook any endmill quickly.

 

[JRB Blades]

Definitely dont run wide open. Stick to 300 ish rpm. Be sure to use coolant. If you are using an endmill use a smaller one with a rotary table. Endmills dont have a perfectly flat bottom by design so a plunge cut wont leave a flat floor on the pocket. Sounds like you just need a better counterbore. You need to use a fair bit of force to avoid rubbing in titanium. This will cook any endmill quickly.

I do have a rotary table, maybe I'll try that method and keep my RPMs around 300ish. I have notice that the Ti likes pressure. Unfortunately that was the only end mill around that size with a 3/16" pilot that I could find. It's only carbide tipped, so don't know if that makes a difference. It has been working, just slower that I would like and keep having to go back and take more out of the pocket to get the .062".

Thanks

 

[Stang Bladeworks]

I do have a rotary table, maybe I'll try that method and keep my RPMs around 300ish. I have notice that the Ti likes pressure. Unfortunately that was the only end mill around that size with a 3/16" pilot that I could find. It's only carbide tipped, so don't know if that makes a difference. It has been working, just slower that I would like and keep having to go back and take more out of the pocket to get the .062".

Thanks

If you don't have one, I highly recommend a quill DRO. It will get the pockets dialed in one try. If you end up going the cb route ticonnector and usa knifemaker sell great ones.

 

[JRB Blades]

If you don't have one, I highly recommend a quill DRO. It will get the pockets dialed in one try. If you end up going the cb route ticonnector and usa knifemaker sell great ones.

Yea, I have the 3 axis DRO. It just seems that when I use the fine adjustment knob to get down to .062", it compresses or squeezes the Ti and when the DRO reads .062" it isn't really that deep, I have to keep pecking at it to get it to that depth. Maybe I should abandon the fine feed knob and just use the big handles to do it.

 

[BossDog]

I have done it 4 ways: plunge an end mill after locating it (using a rod to locate it), a rotary table, an annular cutter (spot weld cutter) and a counterbore. For a liner lock, I use a counterbore and hand drill it mostly now. I do have a Z axis on my mini mill to get the depth. I usually shoot for .020-.023" proud for the roller balls in the bearing. You can go to tighter tolerance but things start to tricky then. For auto knives I use the annular cutter which leaves a "post" in the center to act as a support pillar to hold the pivot barrel.

An end mill gets you a flatter channel bottom so the bearings ride smoother.

Generally, with the counterbore, I use a fair amount of pressure- quite a bit more than say drilling the same size - and slow rpm, in the 300-400 range. I use the "down knob" on my Precision Mathews mini mill to get to depth and let the counterbore dwell for several seconds at the bottom. This helps reduce the "ripples" it will leave other wise. The counterbores I use I have custom made in carbide to fit the bearings we sell. I don't have any idea what size Alpha supply's are.

 

[JRB Blades]

I have done it 4 ways: plunge an end mill after locating it (using a rod to locate it), a rotary table, an annular cutter (spot weld cutter) and a counterbore. For a liner lock, I use a counterbore and hand drill it mostly now. I do have a Z axis on my mini mill to get the depth. I usually shoot for .020-.023" proud for the roller balls in the bearing. You can go to tighter tolerance but things start to tricky then. For auto knives I use the annular cutter which leaves a "post" in the center to act as a support pillar to hold the pivot barrel.

An end mill gets you a flatter channel bottom so the bearings ride smoother.

Generally, with the counterbore, I use a fair amount of pressure- quite a bit more than say drilling the same size - and slow rpm, in the 300-400 range. I use the "down knob" on my Precision Mathews mini mill to get to depth and let the counterbore dwell for several seconds at the bottom. This helps reduce the "ripples" it will leave other wise. The counterbores I use I have custom made in carbide to fit the bearings we sell. I don't have any idea what size Alpha supply's are.

AKS bearings are .373" in diameter and they are .062" thick. I also use their hardened washer that is .389 diameter and .020" thick, so I normally shoot for .062" deep for my bearing packet, so that I have .020" on either side of the blade. I've heard that the hardened balls in the bearing can gall the titanium and mess up my fitment over time. I have looked at the USA Knifemaker carbide counterbore, but they are too small for the hardened washers that I use, otherwise that would be a no brainer to use that one. I love all of my other carbide counterbores from USA Knifemaker!

 

[JRB Blades]

Definitely dont run wide open. Stick to 300 ish rpm. Be sure to use coolant. If you are using an endmill use a smaller one with a rotary table. Endmills dont have a perfectly flat bottom by design so a plunge cut wont leave a flat floor on the pocket. Sounds like you just need a better counterbore. You need to use a fair bit of force to avoid rubbing in titanium. This will cook any endmill quickly.

I know this thread is old, but I am going to start using the rotary table method with a 5/16" carbide end mill. How deep of a cut to you take at a time? Say you cut .010" at a time. So you start your plunge cut in the middle of the pivot hole and go down .010". From there do you lift the end mill and move the table and plunge again to the same depth (using the quill DRO) or do you keep the end mill and the depth (.010") and move the table out from there and start the rotation of the table.

 

[Stang Bladeworks]

I know this thread is old, but I am going to start using the rotary table method with a 5/16" carbide end mill. How deep of a cut to you take at a time? Say you cut .010" at a time. So you start your plunge cut in the middle of the pivot hole and go down .010". From there do you lift the end mill and move the table and plunge again to the same depth (using the quill DRO) or do you keep the end mill and the depth (.010") and move the table out from there and start the rotation of the table.

I would go 20 or 30 thou. Doesn’t matter where you start but do the final cleanup pass at full depth. Make sure to test fit along the way. It’s easy to overshoot. If you do the math you can correlate degrees of rotation to travel at the tip. This can speed up the fitment process.