Cutter speeds - where is an authoritative table or formula?

This person has charts for wall mounting depending on lathe size.
www.ebay.com

WALL CHART for 10in 12in ATLAS METAL LATHE - CRAFTSMAN - 16 Speed | eBay

Each is FULL-SEAL HOT LAMINATED with heavy duty (5-mil) FILM. The chart is totally sealed for years of use and wipes clean with a soft cloth. Using one chart, you can easily find the correct tool cutting angles and the proper cutting speeds for any of 22 different materials.
www.ebay.com
 
Formulas and charts are good to have and you should know how to calculate speeds but ... they are just starting points, not written in stone. For every speed, there is a feed; finding that combination is what you're looking for. If you calculate a speed and it is too fast or too slow for your lathe, you can still produce an accurate cut by adapting the feed to accommodate that speed, at least on a manual machine. What you're doing here is really learning how to cut metal on a lathe. If you watch, listen and feel the lathe as it cuts, it will tell you what it wants from you.

For example, say you calculated the speed for mild steel but then dialed in a big depth of cut. This will likely chatter so your response is to reduce depth of cut and reduce your speed or increase feed and the chatter will resolve. The lathe will tell you what it wants.
 
Google "Tom's Techniques" and watch his video on speeds. I didn't write down the recommendations for non-ferrous materials, but the simple formula for mild steel is (as mentioned above), 400 divided by the diameter.

If using a 1/2" end mill, 400 divided by 1/2 or 800 rpm. Same for drills on the mill or lathe.

If turning a 2" round on the lathe, 400 divided by two or 200 rpm.

The numbers for brass and aluminum are something like 1000 instead of 400, but take a look at Tom Griffin's videos for the actual numbers.

Bruce
 
WobblyHand said:
That's a pretty good idea.
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Here's an example I made up for the lathe.

I based the per-material feed and speed ranges on a few textbooks, erring on the slow side because I don't run a production shop. That is something to keep in mind: most speed and feed recommendations are calculated to minimize labor hours, with little regard for tool life. For a home shop, you can stick to the low end for roughing and maybe the middle for a finish. You 'll probably want to make some test cuts on different materials to get a feel for which part of the range works for you, given your machine and tooling.

I would advise making your own chart against downloading one, as you are very likely going to have a limited set of tools and a limited range of materials or diameters, so you can reduce the information overload like in that colored chart posted above.
 

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A lot of the published charts and tables are to indicate maximums for the production minded.
Hobbyist can use any speed and feed that works for them, often much below the maximum speed shown on charts.
What is important is chip formation and heat control. As a hobbyist I found it more useful to learn to read chips and as mikey wrote find what works best with my own set of tools and equipment. A log book can help you record what works and what doesn't for future reference.
If you have a QCGB then it is easy to try different speeds at the start of a job to find what works best.
 
Tozguy said:
This fella offers many good videos. A couple of videos in particular on chips feeds and speeds were very helpful when I was starting out.
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Great share. I needed that. When it comes to speeds/feeds/DoC I'm a complete new guy. I'll need to watch it a couple times I think to sink in.

Observing chips makes total sense. At the risk of thread hijacking I'm curious about how his approach applies with carbide inserts and chip breakers. When it comes to the 416 I'm usually cutting I've been going for nice golden brown "C" chips rather than the long continuous shiny curly chip. Is this wrong? In fact I hate the long spiral stringy things that often turn into a birds nest when I have to do a shallow cut.

For example to get that I turn a 1.250 diameter rifle barrel tenon cut down to 1.0625 at 850rpm using .020 DoC with the gear box set to D3. The chart on my lathe (PM1340GT) says .001"-.00055"/rev for the D range. I'm not exactly how to read that to know exactly what my feed rate is. I assume it's something between 1 and .5 thou/rev. By trial and error I discovered that gave me a decent finish and that golden brown "C" shape chip (or also like a "6" shape). I do cut dry and my part does get a little warm. This is with a DCMT 32.51 55 degree diamond insert.

I'd love to know if I'm doing that right or if I could improve on it. Burned up some inserts getting to this point and it's ok but if I could do better I'd like to know.
 
Marc, the author of that video will also answer questions for you. I think that you can get his addy from the website. Not that the fellas here can't help but Marc is available too (at least he was the last time I emailed him).
 
benmychree said:
Some of the tool companies make a slide rule type of speed/feed calculator out of hard cardboard, so no need for calculations.
In school we used a formula; RPM= cutting speed X 4, divided by the diameter of the moving part, the cutting speed for soft steel being 100 FPM.
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This ^^^^

RPM=Cutting Speed x 4/diameter.

Commit it to memory, your wife should hear you mumbling it in your sleep.

Rough cutting speeds:
Mild steel = 80-100 sf/m
Aluminum = 2x to 10x mild steel (160-1000 sf/m)
Stainless = 40 sf/m
Tool steel = 40 sf/m

These numbers are rough approximations for HSS and subject to change based on the actual alloy. They WILL get you making chips very quickly without trashing your tool. Feed rates are a matter of finding out how much the machine will take. Start low and keep turning it up until you hit the limit of rigidity or power. CNC programming for production requires calculating maximum metal removal rates, manual machining not so much.

It's been at least four decades since I've needed more than a calculator, and usually not even that.
 
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