Plunging with an end mill?

[imagineer]

Are you starting with blanks that are at or near the finished outside diameter of the sprockets? If so, you won't be plunging the full diameter of the end mill. In fact, it's not bad practice to "nibble" rather than full depth side mill, leaving a small cut to side mill for a nice finish, particularly on not so rigid setups. It's often quicker too.

Yes, the diameter of the starting blanks will be very slightly larger than that created by the tips of the gear teeth. I'm hoping to pull this off by having my mill X & Y locations fixed and only moving the Z axis and rotary table.

After the gear teeth are machined, I'll adjust the X axis and make a final outside pass that created a uniform height of the teeth.

 

[imagineer]

Yes, the diameter of the starting blanks will be very slightly larger than that created by the tips of the gear teeth. I'm hoping to pull this off by having my mill X & Y locations fixed and only moving the Z axis and rotary table.

After the gear teeth are machined, I'll adjust the X axis and make a final outside pass that creates a uniform height of the teeth.

 

[Mill Lee farm]

It sounds like Z height is your concern? Could you just put the drill bit in a collet instead of using the chuck?

 

[imagineer]

It sounds like Z height is your concern? Could you just put the drill bit in a collet instead of using the chuck?

It sounds like Z height is your concern? Could you just put the drill bit in a collet instead of using the chuck?

I suppose, if I could find a 23/64" R8 collet.

 

[Eddyde]

I agree plunge cutting with a center cutting end-mill is best done with a predrilled hole, especially if you don't have a very rigid mill. If the drill is for pre-drilling, it should be at lease the next collet size smaller anyway. That being said, side milling would be the best way to go for that job, IMHO. Yes, I would stack and cut them both at the same time.

 

[sdelivery]

Incidentally, that 3/8 regrind cut within. 0005 of the mic'ed diameter. That was on an average bridgeport.
Plunge cutting can remove alot of stock in a short period of time.
Typically I rough the pocket by plunging then use the periphery to finish the sides of the pocket.

 

[MrWhoopee]

I suppose, if I could find a 23/64" R8 collet.

Turn the shank to 5/16.

 

[BGHansen]

I suppose, if I could find a 23/64" R8 collet.

Your 23/64" or 9 mm end mill will likely have a 3/8" or 1/2" shank. That's a typical practice (see photo below) so you don't need oddball collets.



Not adding anything that hasn't been said above, but it'd be best to predrill the holes. You could use a 1/4" collet with a 1/4" jobber or screw-machine drill bit to knock in a hole and not worry about having to reposition the mill's head.

Not that you need any more projects, but I started with a round column Grizzly mill. Yes, I cursed my poor planning many times having to jump from an end mill to a drill chuck and running out of Z. I finally came up with a bit of a solution that worked pretty well. I used an edge finder to find X, Y. If I had to move the head, I'd refind X, Y using an extended-shank edge finder; shop-made extensions like the drill extension shown below. I made 5" and 10" extensions with an edge finder mounted in each. They were made from 1/2" drill rod that was drilled/bored with a 3/8" hole; pressed in a couple of edge finders as they are pretty cheap.

Bruce

 

[Shotgun]

I can, but don't want to. The Z-axis travel and clearance needed to hold a drill chuck, versus using an end mill in a collet might warrant lowering the head on the mill. Being its on a round column mill (I know, I know...shut up), I'd like to avoid having to change the height mid-project.

I suppose I can look for the shortest possible drill bit, or cut one down such that I can switch from the drill chuck to a collet and still use the same head height.

Also, I don't mind it being a slow process. I've got plenty of time.

Collets can hold drill bits just as well as they hold endmills.