How do I know a cutter is still sharp?

[Smithdoor]

If a employ wait for cutter glows red. Then they ask is cutter dill.

My self I check like would I a knife
If I am working with tool steel or ss steel I use new cutters and taps This type of steel will work hardened .
Brass will cut better with slitey dill.

Dave

 

[markba633csi]

A magnifying glass is helpful to check the sharpness- especially if your eyes are poor (like mine)
m

 

[f350ca]

I would say your end mill is dull, I've never used any particular one long enough in one go to get a feeling but 8-10 hours seams like maybe an order of magnitude longer then you can expect them to last.

Greg

 

[ttabbal]

I've only done aluminum on my mill with a flycutter, but a left hand square tool eats it for breakfast. And I can hone it to keep it nice and sharp. I might try a nice carbide one later, but I figure I have a lot of HSS bits I can grind as I break them while learning.

I didn't bother to mill it, just set up the fly cutter, engage the power feed, and watch the chips fly.

 

[Hidyn]

As a bit of an aside, in a machining class I took, we would test the sharpness of our tooling by scraping across the tops of our fingernails. That gives a pretty good indication of sharpness.

 

[Bob Korves]

The worst thing you can do with an end mill is to let it rub with a slow feed on a light cut. It wears the cutting edges very quickly, When you are in contact with the work, you should be making real chips, not dust or squealing noises. Also, end mills cut on the ends, but are at their best when cutting on the sides. Try to use them that way whenever you possibly can, you will get much more metal cut than using the end of the cutter, before going dull. For instance, if you want to cut a 1/2" wide by 1/2" deep rebate on the corner of some stock, do not take .030" deep passes using the end of the mill. Instead, if possible, use the side of the end mill almost to the full depth and cut the notch with the side of the end mill. After you get the width you want, then make a light cleanup cut to finish the bottom of the cut. Review: cut with the side and make real cuts. If the cutter is bogging down on a small mill, decrease the rpm and get real chips.

 

[chris.trotter]

Big cutters on mini mills exacerbate the problem.
I think your weak link is the economy cutter.
I recommend you buy yourself one or more top quality end mills and see what that experience teaches you.
You need to keep the cutting forces low so your low power/not rigid machine can handle the work. Use correct speeds and feeds. Don't let the cutter overheat.

The thing is that it was cutting beautifully just the other day. 99% sure the cutter was not overheating - chips never got beyond straw colour. Point taken about cheap cutters not lasting a long time.

Motor oil is not a good substitute for proper cutting oil, in fact, I'd call it a very poor substitute; I use TapMagic

I have several bottles of that stuff I inherited - will switch, thanks!

If a employ wait for cutter glows red. Then they ask is cutter dill.

As above, chips were straw coloured, cutter looks fine - zero discolouration.

I would say your end mill is dull, I've never used any particular one long enough in one go to get a feeling but 8-10 hours seams like maybe an order of magnitude longer then you can expect them to last.

Whaaaat. Dats crazy.

The worst thing you can do with an end mill is to let it rub with a slow feed on a light cut. It wears the cutting edges very quickly, When you are in contact with the work, you should be making real chips, not dust or squealing noises. Also, end mills cut on the ends, but are at their best when cutting on the sides. Try to use them that way whenever you possibly can, you will get much more metal cut than using the end of the cutter, before going dull. For instance, if you want to cut a 1/2" wide by 1/2" deep rebate on the corner of some stock, do not take .030" deep passes using the end of the mill. Instead, if possible, use the side of the end mill almost to the full depth and cut the notch with the side of the end mill. After you get the width you want, then make a light cleanup cut to finish the bottom of the cut. Review: cut with the side and make real cuts. If the cutter is bogging down on a small mill, decrease the rpm and get real chips.

Yeah, ok this is definitely what I was doing a lot of, my mistake.

So is fly cutting the standard way to remove a lot of material for operations like squaring stock? From what I've read/seen, flycutting is meant for at most 5 thou at a time. Wrong?

What is the accepted way of mass material removal (that also works on a mini-mill)?

 

[Smithdoor]

They to me and after the cutter/drill bit red and chips are blue black
At this point the cutter is wasted
The drill you cut end off and sharpen drill

Look at color of chip does as would like a straw to blue color this can from lack coolant and or higher speeds

Dave

The thing is that it was cutting beautifully just the other day. 99% sure the cutter was not overheating - chips never got beyond straw colour. Point taken about cheap cutters not lasting a long time.


I have several bottles of that stuff I inherited - will switch, thanks!


As above, chips were straw coloured, cutter looks fine - zero discolouration.


Whaaaat. Dats crazy.


Yeah, ok this is definitely what I was doing a lot of, my mistake.

So is fly cutting the standard way to remove a lot of material for operations like squaring stock? From what I've read/seen, flycutting is meant for at most 5 thou at a time. Wrong?

What is the accepted way of mass material removal (that also works on a mini-mill)?

Sent from my SAMSUNG-SM-J320A using Tapatalk

 

[Bob Korves]

What is the accepted way of mass material removal (that also works on a mini-mill)?

Mini mills do not have the power and rigidity to hog large volumes of metal off the part quickly, nature of the beast. You must live with it and work around it. Try to use stock that does not need much removal, plan the design to not need much removal, or bulk large amounts of material with a band saw, hack saw, or other means.

 

[extropic]

snip

What is the accepted way of mass material removal (that also works on a mini-mill)?

I think you know that mass material removal and mini-mill are contradictory terms. You're limited to smallish cutters and/or light cuts.