Advice on running very thin bits feed and speed on alum

Good day.
I bought some 1/32 and 1/16 bit for aluminium and was wondering if anyone is running the same size bits. looking for some advice for the feeds and speeds.
these are from Spetools

It seems using these on the touch plate would break them???
I had a brand new Amana 1/8" used probably about 10 min fall of a table and break.

Thank you.

I mostly do aluminum and have used as small as 1/16" bits. (These are the ones I’ve used). I’ve used it on the touch plate with no issues, but I can understand your hesitation given those small sizes! I’ve only used them for drilling operations so unfortunately, I don’t have any recommendations on feeds and speeds.

I machine quite a bit of aluminum. Generally, across the board, I’d keep you surface Speed at 800-1,000 SFM. For feed, I personally shoot for .0007” IPT (inch per TOOTH) per Rev. on the 1/16” tool. I don’t run anything in aluminum smaller than that, but if I did, I would simply halve the feed.

You didn’t mention you axial and radial DOC. My answer is based on an axial of 1 x Diameter and a Radial of .75 x Diameter.

Mileage will vary and others may chime in with slightly different formulas that work for them. This is what works for me.

Your mileage will vary by several factors: your spindle TIR (runout), tool geometry and your decision on the topic of coolant being the most important…especially TIR. If your runout is .001” and your chip load is .0007”, you have a problem.


I recently purchased a Kionix KX134 and decided to throw it on the old AvidCNC PRO60120. You know, get a “real” sense of the vibration in the machine.

Real world your 0.0007" is actually more like +/- 0.0018" from the vibration in the machine. Which is interesting because that is the “about” the natural frequency of aluminum rectangular plate.

Not sure why the link text for the research paper came out as it did but the link has more info;

ShieldSquare Captcha.

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Exactly my point. Calculating .0007" IPT for a tool geometry that is suited for that chipload presents a real problem when your spindle runout is greater than the chip load. You end up putting all the stress on only one or two flutes and the other(s) aren’t doing any work.

But dynamic runout is very hard to quantify as it changes based on several variables, mostly being spindle RPM. Your article reference is very interesting. I reminds of the early 2000’s when we conducted harmonic frequency response tests on over 50 machines in a large manufacturing company on the west coast to determine stability lobes for each machine using a system called Blue Swarf. Two things impressed me from those studies; two identical machines, (same age, very similar spindle hours, same make and model, same manufature dates, Same spindle carried, same end mill EDP# and same material) yielded significantly different frequency response. Second, after we fine tuned everything to maximize production and reduce cycle times the operators (mostly) all knew exactly where two or three of the stability lobes existed on the speed/feed curve. That last one wasn’t so much a surprise as an affirmation that nothing replaces experience.

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There are times in my life where I feel I am making educational progress. But when I read the replies that people who are certainly way, And I mean way more educated than I. I am humbled by my lack of chromosomes. The reply above could have been cooking instructions for unicorn haunch and I would have believed it.

I love these forums for this difference in experience and knowledge. Thank you all for contributing.

I will continue to work towards improving my skills and helping when I can but again these replies remind me how much I don’t know.

This is a long winded way of saying I am awed by how much I don’t necessarily need to know to enjoy my cnc but damn I have a long road to go.

Oh, but you have a roadmap for the way forwards. Has nothing to do with chromosomes or brain power. It is numbers of years and old cranky dudes snarking at each other that will show you the path to travel.

Glad you are along for the ride. The mountain always looks taller from the base than it does from the peak.

PS. Not all old dudes are right, btw. Take everything I say with a grain of salt! :rofl:

Well I am a bit of an old guy myself (52) the roadmap makes learning more fun for sure.