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JeffG
11-11-2004, 10:20 PM
I'm a newbie without local contacts - so thanks for your patience.

I have a manual bench knee mill similar to the Grizzly G3102. How do I tell if I'm feeding (X or Y axis) at the right rate? I can calculate a handwheel rotation rate, but wouldn't an experienced machinist do this by feel?

ben78
11-11-2004, 10:32 PM
I am by no means experienced or knowledgable in machining, but I hack away.. When I feed I do it by a combination of what sounds right, looks right and feels right. The combination will quickly tell you if you are feeding too fast, too slow and you just waste your time http://bbs.homeshopmachinist.net//biggrin.gif

If you break endmills you are going to fast OR your spindle speed isn't high enough, but faster spindle speeds doesn't mean you can feed faster as you still need to work out the sfpm of the tool for the material...

Elninio
11-11-2004, 10:43 PM
well you can feal by hand but it wont always be precision, if ya cant use one hand with ease then your pushin too hard. go slow on steel, bit faster on aluminum. I guess if you practiced alot you would get get a "feal" for it

J Tiers
11-12-2004, 12:04 AM
After a while, you do get a feel for what is working right.

Sound is important, is the machine laboring? Does the cutter have a "swish" of smooth cutting, or a judder, squeak, or other odd sound?

Does it feel like its working smoothly? Your hand can tell if the movement is even and related to cutting, or if it just got much harder to move it.

I have ball-cranks on my mill, and I have had to develop a two-hand rotation technique that keeps it going pretty evenly.

I think a "real machinist" would probably be at work, and would just engage the feed, or the boss would have a soft word in his (her) ear......mine has no feed except my cranking.

BillH
11-12-2004, 12:12 AM
With my micro mill, everything is done by feel. Its like a 6th sense you develope from expirience, a sub-concious skill that your brain learns. Like riding a bike, or flying R/C airplane, once you learn, you know.

Paul Alciatore
11-12-2004, 01:12 AM
Feel is perhaps the wrong term. It's more by ear. I started machining on a Unimat and there you had to go easy or it stalled or the tool broke or the belts slipped. You can not feel much through a feedscrew and handwheel. It's the sounds you hear and the nice or not so nice chips and surface finish you are making.

Start with aluminum or brass. Take some light cuts. Gradually work up to heavier cuts until the machine starts to protest or stalls or the tool breaks. That was too much. Now you know. And you should have observed the signs your machine gave you before that happened. Then try something harder like soft steel.

Finishing cuts are often much lighter than the roughing ones.

Paul A.

Forrest Addy
11-12-2004, 07:50 AM
It boils down to this. After a while you learn to trust your senses. Meantime you might bust a cutter or two but so what? That's why tehy call 'em "consumable tooling;" a few items of busted tooling is part of calibrating your touch.

SGW
11-12-2004, 10:38 AM
Start out buying "precision import" endmills. After you trash a few (or a lot...) of them developing your sense of what's right, it will be worth your money to buy really good ones.

I guess I go by sound and the way the chips are coming off. I'm not sure there is that much actual "feel" in the handwheel, although there is some of that too.

PSD KEN
11-12-2004, 10:19 PM
Yep, I started with the imports,Later I figured I knew what I was doing (HAH). Trashed a pricy 1/2 mill. ( With a mini-mill yet, how's that for determination?)
Back to the economy ones.

Rich Carlstedt
11-13-2004, 12:49 AM
If you hear a squeel..you are "Starving" the cutter. many new machinists have this problem.
Feed in faster till the squeel stops and notice the difference..besides the quietness.
This applies to drilling/milling and turning..
Now look at the chips..if they are darker ()than the base metal, your rotation speed is TOO fast...slow the R's or the cutter is gone..quickly.
Carbide allows high heat chips, so the comment on r's does not apply.
Most Home machines cannot overload a carbide cutter

J Tiers
11-13-2004, 01:38 AM
<font face="Verdana, Arial" size="2">Originally posted by Rich Carlstedt:
If you hear a squeel..you are "Starving" the cutter. many new machinists have this problem.

Most Home machines cannot overload a carbide cutter</font>

Nope, but with nasty materials, you can run into work-hardening that even carbide can't help.
That piece of 1095 or whatever it is DULLED a carbide tipped 4" cutter that was fed as fast as the machine could take. The material is such that a file will not cut the burr left on the edge of the part by the cutter....

Only by slowing the rotation and using a sharp carbide tipped cutter could I save the part....Sometimes the material apparently limits the speed more than the cutter.

BTW, it was easy to "feel" the cutter working right, and also the cutter dulling and starting to skid, even before the squeaking started.

SGW
11-13-2004, 08:53 AM
Oh, you can overload a carbide cutter, all right. I think I've still got the pieces of one I overloaded! Carbide doesn't bend worth a damn.