[QuinnSjoblom]

Still kind of a beginner at turning. Laying out the boring/drilling attachment for the gang tooling on my mill turn setup and space is limited. i have 4 turning/facing tool slots on one side and im trying to decide between 3 and 4 boring/drilling tool slots on the other side. I can squeeze in 4, but clearance between gets tight. These are mostly small parts ill be working on and im curious how many tools i really need to get a hole bored. Most internal work will be under a half inch with biggest bore being maybe 3/4. Lets say for example i need an accurately bored hole that is 3/4 diameter and 2 inches deep, How many tools are really needed to get it done? I imagine its best to spot drill, then maybe 1/4 drill, then 11/16 or so, then finish with a boring bar, but can i get it done with less? 3, or even 2 tools? What happens if i try to just go straight in with a solid carbide 1/2" or so stub drill, and finish the rest with the boring bar? If thats too much, what about just skipping the spot drill and starting with a minimum length 1/4 solid carbide, then bigger drill, then bore? Or maybe start with a large insert drill? Best case would be if i had enough tools to get a hole bored plus one more for internal threading or grooving. The reason its important to avoid the tool changes is because this will be fully automated multiple parts with a pneumatic 5c closer and bar puller. Curious to hear strategies for getting tool count down on internal work.

[QuinnSjoblom]

hmm, maybe even only 1 tool, and get evn more done with it. Drill, bore, chamfer, profile.

https://www.youtube.com/watch?v=dhlztaJd5aE

[Jim Dawson]

It depends on your machine. I drill 7/8 deep with a 5/8 drill bit in 304 SS with no pilot or spot drill and 2.5 inches deep with the same bit in 6061. If you are going to bore then a spot drill is not needed, even if the drill walks off a a bit, boring will straighten out the hole. I normally use 135° split point screw machine drill bits, pretty stiff and requires less pressure to cut.

If your machine or workholding is not up to the task then drilling with a pilot bit might be needed.

That is a pretty cool bit in the video.

I would add as many tool holder holes as you can reasonably fit into the area. You don't have to use them all, but choices of where to put tools might make some setups easier.

[Superman]

hmm, maybe even only 1 tool, and get evn more done with it. Drill, bore, chamfer, profile.

A word of advice.... a Udrill does not create a flat base... some tips are square, some have a curved long edge... but the tip is rotated so the tip radius is what cuts the outer diameter. It can rough a counter bore base, but not able to make it flat

[QuinnSjoblom]

It depends on your machine. I drill 7/8 deep with a 5/8 drill bit in 304 SS with no pilot or spot drill and 2.5 inches deep with the same bit in 6061. If you are going to bore then a spot drill is not needed, even if the drill walks off a a bit, boring will straighten out the hole. I normally use 135° split point screw machine drill bits, pretty stiff and requires less pressure to cut.

If your machine or workholding is not up to the task then drilling with a pilot bit might be needed.

That is a pretty cool bit in the video.

I would add as many tool holder holes as you can reasonably fit into the area. You don't have to use them all, but choices of where to put tools might make some setups easier.

I wasn't sure how important it was to get a perfectly centered hole without walking before finish boring. Thought maybe the boring bar would deflect unevenly as it takes deeper/shallower cut. I suppose that's probably not really a concern if you leave more than just a light clean up pass for the boring bar after drilling. Probably best to leave a decent couple passes for the boring bar.

It's probably gonna mostly come down to the rigidity of my setup. I'll just have to go for it with a big drill and see what happens. As for horsepower, it's a 1:1 drive 1.8kw servo with over 20 ft/lb of torque so I don't think I'll have a problem there. Looking at the torque/rpm graph, it can actually push about 4hp for short periods, 2hp continuous. Btw, this will be mostly work in aluminum.

I'll grab a couple split point 135 deg to try out. Reduced pressure will be important in my case. I'm pretty confident in the rigidity of the workholding and gang tool configuration, but my machine is not as rigid as a heavy duty lathe, although it is still pretty rigid. So far I'm getting awesome results with od turning. Haven't turned any steel yet, but I was ripping through some brass at a pretty decent rate, higher mrr than I've ever reached with the milling spindle.