[lamed]

Hello.
I've been setting feed fates and spindle speed for a while by the ear. I'm looking for information about how to do it right. does anyone have a .pdf or knows the right link for me?

Let me know if this is the (wrong)
(I had to use that smily... so cute)

[paul gibson]

Lamed,

I would recommend investing in a Machinist Handbook. Bought the 23rd edition years back and it has been a great friend since. Another nice tool that will give you some help is a "Pro/Calc." Here's a link... http://www.ipnews.com/archives/swm_a...ng_patent.html with some information. Made by the same guy that makes the heads for Bridgeport type mills.

Regards
Paul

[Paulo E.]

Lamed,

As Paul Suggested The Machinist hand book is a great source to start. You can also get more information from the tool manufacturer. The manufacturer will usually give you SFM ( Surface Feet per Minute) and the inches per tooth. Most if not all tool manufacturers have a range of operation for their tools in relation to the materials they are meant to cut, unless your buying uncle Bob tools.

Here's both Formulas.

RPM = (SFM X 3.82) / Tool Diameter
FEED = Inches per Tooth X Number of Flutes X RPM

Please note this is just a starting point. As you will see even the tool manufacturers give you a range as a starting point. The rest depends on an incredible amount of factors, from tool stability, machine horse power to depth of cut and the list goes on.

Hope this points you in the right direction. :cheers:

[lamed]

Hi. Thanks for replying! Sorry for taking so long...

I found a book about cnc milling, and just like paulo said, the factor list is long and the formulas are pretty crazy. I still would be thankful if someone can give paulo's equations in metric system, and hopefully a bit more

Best regards,
Shachar

[Superman]

Here's both Formulas.

RPM = (SFM x 3.82) / Tool Dia (inch )
RPM = Surface Speed Per Metre / ( tool dia x Pi ) x 1000 ( metric )

FEED/MIN = Feed per Tooth x Number of Flutes x RPM ( for metric and inch )

[lamed]

Thanks superman!
I'm wondering about depth cut. Usually I use something around 25%-50% of tool diameter (the thinner the tool, the smaller the percentage.)
any sightful comments and calculations about that?

Thanks

[Paulo E.]

Ohhh Lamed....

Now I have to open a can of WhoopAss on you LOL then again Im not the one setting tools by ear so I guess all is forgiven :rainfro: As for learning formulas in Inch, Metric or want to teach me something about life, you or anyone is more than welcome to do so. We all have things to learn from each other even if you do set tools by ear (nuts)

Ps: GO AND BUY THE MACHINIST HANDBOOK OR CD NOW!!!

[bob1112]

I think buying a book is a friggin waste of time!! Why? Because there are many advanced geometries from different tool makers. Go by your cutter OEMs recommendations for a start point.

You need to understand surface speed, chip load, DOC, and step over. That is about it.

surface speed - speed of cutter in length/time. Smaller cutters require more rpm to meet the same surface speed.

Chip load - amount or size of chip (bite) per tooth. mills are also calculated at load/rev. You just divide by the number of flutes for chip load/flute.

DOC - axial depth of cut. usually a percent of cutter diameter. varies depending on material, feed, speed, etc.

step over - radial step over. usually expressed as a % of cutter dia as well.

Book might say 600sf, .001/tooth, DOC 50%, step over 100%. You do the mathe from there. Not exactly hard stuff.

[Paulo E.]

Viper, I totally agree with you on getting the info on the feeds and speed from the tool maker. As for the machinist hand book well... While not always the best source for information, specially in a field that improves by leaps and bounds on yearly basis, still is the core foundation and source of information for a lot of common machining practices. The book is a great resource someone who's just getting started & old timers alike. They don't call it "The Machinist Bible" for nothing.