Speeds and Feeds - Aluminium

[Ben17484]

I’m using LMS calculator for speeds and feeds and feel I must be doing it wrong. The only data I entered is the work piece diameter at 20mm (the rest of the fields I left to their default) and it’s telling me I need a spindle speed of 4850rpm. With HSS it’ll be slower, but still 2670rpm. Am I missing some input I’m supposed to alter?

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[WobblyHand]

You can cut slower, especially if you use ground edge carbide inserts like TCGT, but yeah recommended spindle speeds are pretty high for aluminum. Basically machine maximum or high as you dare. I would try half speed on your spindle and see how it works. In the end, these feeds and speeds are just starting points. Try a speed and see how it works for you. Ideally you want manageable chips, rather than big huge spirals of doom. Long strands are dangerous. Do what your lathe wants to get decent chips. That'll require some experimentation, but it won't take long to figure out what works.

 

[markba633csi]

The charts are often for production shops where they want to spit out parts as fast as possible.
You, as a hobbyist, can take your time

 

[RJSakowski]

The charts also don't take into account available horsepower. What works for a machine with 10 hp. won't work on a machine with 1 or 2 hp.

 

[Illinoyance]

I Like FS Wizard. It outputs, among other things, the horsepower used for the speeds and feeds. You can edit the speeds and speeds to keep the horsepower within the capability of your machine. There are two versions. One is free. The other costs a little but handles a wider range of materials.

 

[Ben17484]

I Like FS Wizard. It outputs, among other things, the horsepower used for the speeds and feeds. You can edit the speeds and speeds to keep the horsepower within the capability of your machine. There are two versions. One is free. The other costs a little but handles a wider range of materials.

I the FS Wizard as well. I used the LMS version as it seemed simpler.

Thanks for the feedback all.

I wonder if there’s a quick reference for rough speeds and feeds per material per diameter for roughing and finishing? Something for common hobby materials on common hobby bench top lathes?


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[Jake M]

I wonder if there’s a quick reference for rough speeds and feeds per material per diameter for roughing and finishing? Something for common hobby materials on common hobby bench top lathes?

There really isn't, because there is so much variation in the machines, the tool selection, and the available horsepower. You'd need a hundred charts to even have a start at it, and you'd never cover them all.

The best way to approach that is to use the standard charts as what they are. A guideline. Not so much a "what is best" guideline, but a production calculation to produce parts as fast as you can without burning up tools faster than you get a return on additional tool wear. And even in that case, in the end, a production machinist on the latest and greatest CNC equipment is still going to have to look at the parts and make adjustments.

I find that a chart with diameter and what gear (belt setting) my lathe is in, which shows me the set speed in SFM, (make that any unit you like), is my best tool. I can look at that and say "that lump cut better in this area, and this mystery stuff burns up tools if I get faster than that. The aluminum will slip the belt if I push harder than this... That gives me a much better starting point than trying to use any standard universal number.

All in all, speeds and feeds are not so much a fixed and given thing as the charts would imply.

 

[Terry1956]

i have tried lots of speeds and feeds programs for aluminium, and most ended with broken mill ends or ones with so much welded on aluminium that they became useless. In the end I found that the on,y way that worked for me was using one flute cutters, lots of flood coolant and at a speed and feed around one third of what the program stated. As you will be aware of aluminium as a hard outer shell and a toffee like inner section. What works for the outer layer becomes a nightmare of too much heat when the cutter hits the Toffee section. I ended up doing lots of test runs and making notes of what worked and what killed the cutters. I found deep slots needed lots of compressed air or coolant to get the chips out. And you must clear the chips.

 

[PNW_Guy]

As a hobby machinist, I use 250 for the SFM of aluminum with a HSS cutter. The formula (the easy way) ends up being 1,000 / bit diameter (workpiece if using the lathe) in inches = RPM

For example, 1000 / .5 = 2,000 RPM for a half inch cutter. This always gets me in the ballpark, quickly. I don't use online calculators, nor do I trust the catalogs for SFM.

In your example, I'd run that part much closer to 1,500 RPM. It's conservative, but I'm not a production shop and I'm not trying to make more parts faster.

I also use HSS for aluminum on my lathe. Carbide likes to take big cuts, and HSS is much better when sneaking up on a dimension. Because I've purchased used machines and tool boxes a few times, I have several lifetimes of HSS blanks. Grining them isn't difficult once you get some experience.

 

[GeneT45]

I use whatever my lathe was last set at. Aluminum isn't picky. You can get an excellent finish from 200 - 2000 rpm. The 'official' speeds are only a guideline, and they are optimized toward production - i.e. "what's the fastest I can go?". Don't be afraid to slow down (unless you're selling your labor...).

GsT