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jaybird
06-18-2004, 09:30 PM
I own a 1340 gear head lathe with a 2hp motor. I have been using hss and carbide tooling.
In general terms, without getting into fpm and ipr etc, how deep of a cut should I expect to take for rough in work? Are the any indicators that would help me to determine the depth of cut I could be taking?

Also is it possible to be more aggressive with the depth of cut using and indexable cutter?

I am asking for generalities knowing that each project will dictate the set-up.

J

DR
06-18-2004, 09:41 PM
Pretty vague what you're asking....

With carbide insert tooling the manufacturers usually give recommended SFM, IPR and depth of cut. Use their recommendations as a starting point. Keep in mind mostly they're speaking about use in CNC machines with more power and rigidity than your machine.

nheng
06-18-2004, 10:22 PM
Depth of cut will be directly affected by speed and feed. You might be able to take a 0.25" to 0.375" DOC in mild steel or aluminum when crawling at 300 RPM and a light feed but maybe a third of this at higher speeds and feeds. HP is important but machine rigidity and "tuning" is as important to use the power available.

What DR says is a good direction to head. www.carbidedepot.com (http://www.carbidedepot.com) has inserts from a number of major makers and going into each maker will give links to speed and feed charts for A SPECIFIC INSERT. In addition to carbide types, you also have to deal with the intended use (finishing, light/med/heavy machining) and type of chipbreaker. For instance, go to Kennametal, DCMT, then click on the -UF, -MF, etc. chipbreaker type. This will open a page with informative charts.

I learned this stuff recently when I wasn't getting the finish I wanted in all cases. A finishing type chipbreaker may be designed for feed rate down to 0.002 IPR and DOC of 0.005" while one for roughing might be ten times these numbers and more. With the complexities and cost of carbide, it give more fuel to the argument for HSM use of HSS. I love inserts however and will not give them up so am homing in on several styles which cover most of my work.

I'm going to stick my amateur neck out and let someone with more experience swing the axe ... but when heat tolerance of the cutting tool is considered, the carbide will hold its hardness to a higher temp than HSS will.

As a result, you then need to look at metal removal rate (in^3 or mm^3 per minute). While a HSS bit might be able to peel off huge curls, the carbide will probably remove more metal per minute on the right machine.

Den

Forrest Addy
06-18-2004, 11:37 PM
Start out about what you've been using and work up.

A 2 HP lathe like yours and using HSS tooing I'd use 0.010" feed and .100 depth of cut at 80 feet per minute (FPM) in mild steel working for silvery chips that turn brown after a few seconds. That would be about 360 spindle RPM for 1" dia work.

Your lathe doesn't really have enough speed and power to take full advantage of the stock removal properties of carbide but I'd suggest 0.008 feed and 0.050 depth of cut at 400 FPM. That's about 1500 spindle RPM for 1" dia work. Work for chips that come off as little blue 6's and 9's.

Work up or down from there. Aluminum use 4 times the FSFM. Brass about double maybe a little less.