End Mills for Bearing Pockets in Ti

JRB Blades

JRB Blades

Knifemaker / Craftsman / Service Provider
Joined
Jul 22, 2013
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266
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 counterbore 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!
 
I've done that procedure on G10 and it worked out. On titanium? I don't know how that will go. If I were to take a stab at it I would do 4 flute and run it fast, figuring that I'd be better off rubbing than grabbing a big chip and torqueing the setup, which on my minimill would throw off the alignment, unless you have a large solid mill. Just kicking around some numbers in FSWizard slotting with a 3/8 carbide TIN coated end mill with a .005 depth is 634 rpm with a feed of 2.64in/min. I think you'd plunge at a lower feed.

You could do your counterbore and then follow up with a countersink or chamfer mill to clean up the burr. You could do that on the machine or by hand. I'm guessing you'd get a burr with the end mill too.
 
TILLER said:
I've done that procedure on G10 and it worked out. On titanium? I don't know how that will go. If I were to take a stab at it I would do 4 flute and run it fast, figuring that I'd be better off rubbing than grabbing a big chip and torqueing the setup, which on my minimill would throw off the alignment, unless you have a large solid mill. Just kicking around some numbers in FSWizard slotting with a 3/8 carbide TIN coated end mill with a .005 depth is 634 rpm with a feed of 2.64in/min. I think you'd plunge at a lower feed.

You could do your counterbore and then follow up with a countersink or chamfer mill to clean up the burr. You could do that on the machine or by hand. I'm guessing you'd get a burr with the end mill too.
Click to expand...

Yea, good idea with the follow up just to clean up the burr. I lock the handle on the mini mill and use the fine feed adjustment to get down to my .062" depth for the bearing. Although the bur seems to be exactly where the teeth of the drill part meets the pilot, so I figured a 4 flute end mill would eliminate that.
 
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I use counterbores but I don’t have a problem with burrs. I’ve also used end mills and even rotary table for one off custom sized stuff. My counterbores are solid carbide and I use 1/2”, 3/8”, .357” or 5/16” depending on which bearings I use
 
You won't get very good precision locating your hole with a rod like that. I don't know if it matters but if it does you should use an indicator to sweep in your hole.

Also, an endmill doesn't leave a flat bottom hole, it leaves a shallow cone.
 
Drill the pivot hole undersized and ream to 3/16. Use the carbide counterbore then re-ream.
 
I do drill my pivot hole with a #15 and then use a carbide reamer to get it to 3/16". I'll try to re-ream it after milling the bearing pocket and see if that will eliminate the burr.

I think I'll also try a smaller end mill and use my rotary table to get the bearing pocket cut out. Maybe that'll help.

My bearings are .373" diameter, so 13/32" was the closest I could find with a 3/16" pilot unfortunately.

I do have an indicator so I can find center of the pivot hole I suppose.
 
barlowchiro said:
13/32" was the closest I could find with a 3/16" pilot
Click to expand...
That is what I use. I buy them from that amazing place. For me setting up on the rotary table is too much effort. I mill enough extra with the counterbore to use a hardened washer on both sides of the bearing.
 
there are 3 different ways to do this
#1 use a piloted counterbore.. with the same dimensions as the hole and bearing .. Pilot is the same as the pivot hole ,outside diameter same as the bearing race (Outside) (Most popular way )
#2 (more precise) use a rotary table to machine in the circle for the bearing (with or without Race) can also put race groove into blade with carbide. (Most Don't do this )
#3 have a custom made carbide hole saw made to cut only a race (like a doughnut) for the bearing balls to go into.. and do not use a race to hold the loose balls.. (NO One does this)
i guess you just have to ask yourself how precise do you really want it , and how much you willing to spend to do it that way ?? most go the cheapest/easiest route!!!
 
Jesse Latham said:
That is what I use. I buy them from that amazing place. For me setting up on the rotary table is too much effort. I mill enough extra with the counterbore to use a hardened washer on both sides of the bearing.
Click to expand...
Where do you get your counterbore?
 
Pinoy Knife said:
there are 3 different ways to do this
#1 use a piloted counterbore.. with the same dimensions as the hole and bearing .. Pilot is the same as the pivot hole ,outside diameter same as the bearing race (Outside) (Most popular way )
#2 (more precise) use a rotary table to machine in the circle for the bearing (with or without Race) can also put race groove into blade with carbide. (Most Don't do this )
#3 have a custom made carbide hole saw made to cut only a race (like a doughnut) for the bearing balls to go into.. and do not use a race to hold the loose balls.. (NO One does this)
i guess you just have to ask yourself how precise do you really want it , and how much you willing to spend to do it that way ?? most go the cheapest/easiest route!!!
Click to expand...
Where did you buy your counterbore?
 
i made mine using a solid carbide reamer.. re ground the tip to the pilot size ,then re sharpened the bottom of it to cut.
after making sure everything was accurate on the grind down being 90 degrees to the side..
using a reamer you can have any size and 4 flutes are standard..
sorry for the delay i was in the shop all day..
 
Pinoy Knife said:
Jesse like this one ??

3/8" Counterbore, Carbide Tipped, 3 Flutes, 5/16" Shank Diameter, Straight Shank, 4 1/16" OAL, USA Made, (.375" Diameter), 56403: Amazon.com: Industrial & Scientific

3/8" Counterbore, Carbide Tipped, 3 Flutes, 5/16" Shank Diameter, Straight Shank, 4 1/16" OAL, USA Made, (.375" Diameter), 56403: Amazon.com: Industrial & Scientific
www.amazon.com

he still needs the pilots... but yea it would do it...
hope i aint breaking the rules posting this ........
Click to expand...
I have a counter bore from McMaster Carr just like that except it's 13/32. Just getting that bur around the edge of the pilot hole when I use it.
 
 
Yes carbide inserts. I sand the pilot a little. I find them too tight in the reamed hole. Oil helps the pilot.
 
You would have to be the Mike Jordan of workholding to plunge cut that pocket. But anyway, if I were gonna try it I'd use a 4 flute end mill. Rotary table is what I finally settled on, as long as that's an option for you. I finally bought a used one one on eBay for a few hundred dollars...i thought it was way too cheap to end up with a good tool, but it does really well. Plus now I use it for all kinds of things. I had already spent a lot of money on piloted hss counterbores that didn't work as well. Could have done without that...
 
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