5/8” diameter, 3 flute end mill, cutting hole

[Toolmaker51]

I needed to drill a 5/8” diameter hole through 1-1/4” thick 6061 aluminum. I didn’t have a 5/8” drill, but had a 3 flute end mill. I had the mill speed at around 1300rpm. The three flutes at the end were fine initially, but the deeper I got they would load up in the flutes near the tip. When this happened the end mill didn’t really want to cut any more.

I would stop the mill and use a small screw driver to flick out the loaded up aluminum.

Is there something I can do to avoid the flutes loading up or is this just something that comes with the territory?

Loading up is when parent material practically welds self to cutter. Flicking off means you took short intervals. A slower speed with higher feed can help; carrying away heat via chips and compressed air. Another is creating boundary layer between material and cutter,ie WD-40 or legit cutting fluid. Aluminum tends to aggravate the situation, but nearly any material can be so induced, excess SFPM.

 

[Firstgear]

I was worried that I might be running too fast.....

 

[projectnut]

Here's a feed and speed calculator that might help:

Speeds & Feeds

The premier source of tooling, parts, and accessories for bench top machinists.

littlemachineshop.com

You are close to the optimum speed assuming you are feeding at 7 ipm or less

As an FYI I usually run the speeds and feeds 20% to 25% slower than the calculators recommend. Keep in mind the calculators are looking for a balance of optimum amount of time to complete the job against cutter wear. For most hobbyists the cost of cutter wear and breakage outweighs the amount of time to complete a job.

 

[Firstgear]

Yup....I was pretty close to the speed called for....

 

[MrWhoopee]

Maybe it's just me, but 1300rpm?!?! IMHO that way too fast and the bigger the bit, the slower the rpm. I'd be around 3-400rpm no matter a drill or end mill.

His cutting speed is fine for aluminum, 3-400 would be correct in steel. The LMS calculator is very conservative at 200 sfm for aluminum. Of course, I always take into account the ease of resharpening. If I can do it myself, no big deal.

 

[C-Bag]

His cutting speed is fine for aluminum, 3-400 would be correct in steel. The LMS calculator is very conservative at 200 sfm for aluminum. Of course, I always take into account the ease of resharpening. If I can do it myself, no big deal.

Yup, my bad, I saw 1300rpm and aluminum didn't register. D'oh!

 

[AGCB97]

I would recommend investing in some annulur cutters.... Anyways they do a very efficient job of cutting clean, accurate bigger diameter holes with little fuss. Plus you get the leftover core slug for another project instead of making a pile of swarf.

I agree. I've acquired/bought a set of annulars 1/2" to 2" by 16ths. I don't like fighting with twist drills anymore since annulars take so much less power.

And the best fluid for cutting aluminum IMHO is ALUMICUT. I've had the same pint can (which was given to me) since 1992

Alumicut Superior Cutting Lubricant - 1PT | eBay

Find many great new & used options and get the best deals for Alumicut Superior Cutting Lubricant - 1PT at the best online prices at eBay! Free shipping for many products!

www.ebay.com

even for hand hacksawing and filing.
Aaron