Cutting holes with end mills

[drhender]

I am a mentor for a high school robotics team. Neither I nor any of the other mentors on the team have any experience in machining. We're acquiring a Velox VR-5050 this season and we need a little advice.

We will mostly be milling parts in 1/4" and 3/8" 60601 aluminum plate-- cutting profiles and drilling holes. I am wondering if we can get away with milling everything, including drilling holes with ends mills. Not having to change tools in the middle of a job would be a huge time-saver. Can we use a 5/32" and 3/16" end mills to drill thru-holes of the same size in 1/4 and 3/8" 6061 aluminum?

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[Jim Dawson]

Straight plunging with endmills does not work well and should be avoided when possible. The geometry of an endmill is not correct for drilling holes. If you can use an endmill that is smaller than the desired hole size and spiral plunge it works OK.

Normally I will drill all of the holes first, then change tools and do the milling operations.

[drhender]

I suspected as much. Can we get good precision with stubby drill bits without spot drilling first? That would reduce it to one tool change instead of two.

It has also occurred to me that we could drill the holes first and then during the tool change, we could drive screws through into the spoil board to hold down the parts. That would remove the need to use tabs to keep the pieces in place, saving the time that would be spent on clipping tabs and sanding/filing the tabs.

[dillonfitz]

Yes you absolutely can drill holes with endmills. I do it all the time and can hold 5 ten thousands with an endmill. You have to make sure the tool is rated for center cutting. I plunge pockets too to save time from helical ramping. I also plunge and drill in aluminum stainless and every other metal other that tool steels with endmills. If it’s tool steel then I drill first.


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[dillonfitz]

I suspected as much. Can we get good precision with stubby drill bits without spot drilling first? That would reduce it to one tool change instead of two.

It has also occurred to me that we could drill the holes first and then during the tool change, we could drive screws through into the spoil board to hold down the parts. That would remove the need to use tabs to keep the pieces in place, saving the time that would be spent on clipping tabs and sanding/filing the tabs.

I also only use carbide. No HSS period other than taps.


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[Jim Dawson]

I suspected as much. Can we get good precision with stubby drill bits without spot drilling first? That would reduce it to one tool change instead of two.

It has also occurred to me that we could drill the holes first and then during the tool change, we could drive screws through into the spoil board to hold down the parts. That would remove the need to use tabs to keep the pieces in place, saving the time that would be spent on clipping tabs and sanding/filing the tabs.

Yes, you can hold good tolerance without spot drilling. For small holes in the 3/16 range, we use 3 flute, solid carbide drills designed for high speed drilling in aluminum. M.A. Ford - Product Lines

You are proposing exactly what we do to hold most parts. We don't use a spoil board in the normal sense, but we do have an aluminum pallet, built for the particular run that is drilled and tapped for the hold down screws. Then the workpiece is positioned over the pallet, drilled, and screwed down to the pallet. Could be 30 to 50 parts on one run.

[mactec54]

I am a mentor for a high school robotics team. Neither I nor any of the other mentors on the team have any experience in machining. We're acquiring a Velox VR-5050 this season and we need a little advice.

We will mostly be milling parts in 1/4" and 3/8" 60601 aluminum plate-- cutting profiles and drilling holes. I am wondering if we can get away with milling everything, including drilling holes with ends mills. Not having to change tools in the middle of a job would be a huge time-saver. Can we use a 5/32" and 3/16" end mills to drill thru-holes of the same size in 1/4 and 3/8" 6061 aluminum?

You will have not problem doing that, center cutting end mills, you can even program it the same way, you can peck drill the hole and then use it to open up the hole to the size you need helical mill for holes works best

[LeeWay]

I do like to drill the holes undersized at first and then interpolate to the desired size. Especially for smaller tapped holes. I only have a couple drills on board my 10 tool carousel all the time, so rather than swapping in lots of precise tooling, I find this is easier and time efficient. I do precisely drill anything over 1/4" for tapping purposes.
Sometimes I will simply interpolate the entire hole. Especially when on the router table.
It would work fine in your case too i think, but might be quite a bit slower of an operation for you. It doesn't sound like you are doing production work though. If I had the time, I would drill first. Drill are far cheaper than end mills to replace and a good HSS drill bit can drill thousands of holes in aluminum.

[drhender]

We don't have the luxury of a tool changer-- that would be nice. All of our tool changes will be done by hand and will likely require resetting the Z height. Any suggestions about how to at least avoid having to reset the z height after tool changes would be appreciated.

Our jobs will mostly be one-off pieces, so we'll want to avoid specialized work-holding as much as possible.

Here's the workflow that I think we're looking at:
* Place the aluminum plate and clamp around perimeter with hold-downs for drilling.
* Run the first operation to drill all of the holes.
* Drill pilot holes in ALL internal through cuts with a bit equal to the size of the smallest hole (typically 3/16 or larger)
* Drive screws through smallest holes that don't need to be enlarged - at least 2 (preferably 3) per final part
* Remove hold-down clamps around perimeter
* Run second operation to cut perimeter of the part(s), any internal through cuts, and a final interpolation to resize larger holes to final diameter.

I've been watching some of John Saunder's YouTube videos (NYCCNC) and they sometimes use double-sided tape or painters tape and super glue to hold down plate for milling. That is also an option for work holding.

[dillonfitz]

We don't have the luxury of a tool changer-- that would be nice. All of our tool changes will be done by hand and will likely require resetting the Z height. Any suggestions about how to at least avoid having to reset the z height after tool changes would be appreciated.

Our jobs will mostly be one-off pieces, so we'll want to avoid specialized work-holding as much as possible.

Here's the workflow that I think we're looking at:
* Place the aluminum plate and clamp around perimeter with hold-downs for drilling.
* Run the first operation to drill all of the holes.
* Drill pilot holes in ALL internal through cuts with a bit equal to the size of the smallest hole (typically 3/16 or larger)
* Drive screws through smallest holes that don't need to be enlarged - at least 2 (preferably 3) per final part
* Remove hold-down clamps around perimeter
* Run second operation to cut perimeter of the part(s), any internal through cuts, and a final interpolation to resize larger holes to final diameter.

I've been watching some of John Saunder's YouTube videos (NYCCNC) and they sometimes use double-sided tape or painters tape and super glue to hold down plate for milling. That is also an option for work holding.

Check out mitee bite toe clamps. I use them all the time. My favorite are the t slot ones with a brass hex toe clamp. It has a cam screw that locks the part to the table.


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[Jim Dawson]

We don't have the luxury of a tool changer-- that would be nice. All of our tool changes will be done by hand and will likely require resetting the Z height. Any suggestions about how to at least avoid having to reset the z height after tool changes would be appreciated.

Our jobs will mostly be one-off pieces, so we'll want to avoid specialized work-holding as much as possible.

Here's the workflow that I think we're looking at:
* Place the aluminum plate and clamp around perimeter with hold-downs for drilling.
* Run the first operation to drill all of the holes.
* Drill pilot holes in ALL internal through cuts with a bit equal to the size of the smallest hole (typically 3/16 or larger)
* Drive screws through smallest holes that don't need to be enlarged - at least 2 (preferably 3) per final part
* Remove hold-down clamps around perimeter
* Run second operation to cut perimeter of the part(s), any internal through cuts, and a final interpolation to resize larger holes to final diameter.

I've been watching some of John Saunder's YouTube videos (NYCCNC) and they sometimes use double-sided tape or painters tape and super glue to hold down plate for milling. That is also an option for work holding.

Sounds like a reasonable workflow.

Setting the Z height after a tool change should only take a minute or less. Faster yet with one of these https://www.ajaxtoolsupply.com/zsein...RoCOVkQAvD_BwE

Always set z zero to either the top of the work surface or the top of the spoil board or fixture plate.