checking end mills for runout

[wmpy]

I am having problems with end mill runout. I previously suspected the tool holder collet to be the problem. You can read all about that here if you like.

Premium ER collets

Who makes a good ER collet with low runout? REGO-FIX? Techniks? Or do you guys have good success with the Maritool collets? I had a job running great- incredible tool life, good chip formation, good cycle time. I was happy. Then, the 5/16" solid carbide 3-flute end mill that I'm slotting with...

www.practicalmachinist.com

The collet was a problem. I have that sorted now, but I am still getting bad runout. I am now on to suspecting the end mills themselves.
The end mills are 5/16" 3 flute, .060" R carbide mills that I use to rough out a slot.
Please see the picture below for how I am measuring the runout. Does this look like an accurate way to check them? The test indicator in the photo was zeroed on the lowest flute. It's now reading on the highest flute. Repeatedly checking the flutes gives consistent results, so I'm inclined to think that there's nothing wrong with my method, but maybe one of you can tell me otherwise.
I brought this up to the manufacturer and told them how much runout I was getting. They told me that was outside of their tolerance and that they would send me some new end mills. They assured me that they would check these new end mills before sending them, but I am getting the same measurements and poor tool life with these new tools. I can see that they are from the same batch as the originals. So, did the end mill manufacturer fail to check these, or is there something wrong with the way I'm checking them? I am currently looking at other manufacturers since my experience hasn't been great with this one.

 

[rklopp]

Your method looks legit in principle as long as your V-block is decent. Your repeatability is a good sign that the method is working. Do you have a known good or any other endmill you can check?

 

[michiganbuck]

The best collets run out .0002 and if your spindle runs out .0002 you have nearly half thow...and the EM may run out another tenth..
Checking an end mill in the spindle one can sometimes give a 180* twist and get nearer zero.

Back when I was running high precision grinding out of collets I had my common sizes marked for the run-out high side.

At one time I preferred balas collets but even they had to be inspected for burrs before trusting them.
I liked to check EMs out of a close bushing held in a V block.

​

 

[wmpy]

Your method looks legit in principle as long as your V-block is decent. Your repeatability is a good sign that the method is working. Do you have a known good or any other endmill you can check?

I did check some other end mills I had, and they were all within a tenth.

 

[mhajicek]

I did check some other end mills I had, and they were all within a tenth.

Well thars yer problem then. Need better endmills. I would have expected better from Garr.

 

[wmpy]

Well thars yer problem then. Need better endmills. I would have expected better from Garr.

Me too. It's a bit of an oddball, too, so I'm having problems finding others that make the same thing.

 

[dandrummerman21]

Did they simply send back your original endmills? lol.

 

[wmpy]

Did they simply send back your original endmills? lol.

Nope. I still have the OGs.

 

[wmpy]

The best collets run out .0002 and if your spindle runs out .0002 you have nearly half thow...and the EM may run out another tenth..
Checking an end mill in the spindle one can sometimes give a 180* twist and get nearer zero.

Back when I was running high precision grinding out of collets I had my common sizes marked for the run-out high side.

At one time I preferred balas collets but even they had to be inspected for burrs before trusting them.
I liked to check EMs out of a close bushing held in a V block.

​

I started out checking the end mills in the spindle. I was chasing my tail, though, so I started digging deeper. I'll see if I can find a precision bushing to check them in.

 

[crossthread82]

Does it need to be a 3 flute? Swiftcarb makes a 4.

 

[wmpy]

Does it need to be a 3 flute? Swiftcarb makes a 4.
View attachment 378288

SwiftCarb actually makes a 3 flute like I'm using. I'm waiting on a quote, but I'm afraid it's not stocked.
This is for slotting .530" deep in 4140. I take it in three depths. I started with a 2 flute. It would deflect a bit. Then I went up to a 3 flute for the increased core stiffness. I don't know if I could get away with 4 flutes for slotting. Maybe worth a try?

 

[crossthread82]

SwiftCarb actually makes a 3 flute like I'm using. I'm waiting on a quote, but I'm afraid it's not stocked.
This is for slotting .530" deep in 4140. I take it in three depths. I started with a 2 flute. It would deflect a bit. Then I went up to a 3 flute for the increased core stiffness. I don't know if I could get away with 4 flutes for slotting. Maybe worth a try?

You're probably looking at these then. In my experience custom tools from swiftcarb only take a couple days. You should be fine slotting with a 4 flute, you're only going 0.5xD.

 

[wmpy]

You're probably looking at these then. In my experience custom tools from swiftcarb only take a couple days. You should be fine slotting with a 4 flute, you're only going 0.5xD.

View attachment 378289

Those are the ones I saw.

 

[mhajicek]

Me too. It's a bit of an oddball, too, so I'm having problems finding others that make the same thing.

5/16", .060" rad, 115 results:

Square/Radius/Chamfer Endmills

ecomm.productivity.com

 

[guythatbrews]

Your check is fine and repeatable just a bit tedious finding the high side. Not terribly surprised you found a bad batch, and they sent replacements from that same batch. I've seen some crazy stuff wrong with cutters. At least you can deal direct with mfg instead of having to go through the distributor middleman, and at least they acknowledged a problem.

I always stick with a 2 or 3 flute cutter for slotting, unless I'm in a jam for cutters. A 4 flute will always deflect. May not be much but it will deflect.

 

[michiganbuck]

QT: GUY; (Your check is fine and repeatable just a bit tedious finding the high side.)
I agree it is an ok/fine check.. no point in getting a bushing for checking only a few EMs.
You say this EM is used for roughing..what process is used for finishing?

 

[DavidScott]

A 4 flute corncob will slot just fine, and much better than anything else I have tried, in a straight path.

 

[wmpy]

QT: GUY; (Your check is fine and repeatable just a bit tedious finding the high side.)
I agree it is an ok/fine check.. no point in getting a bushing for checking only a few EMs.
You say this EM is used for roughing..what process is used for finishing?

I use a 5/16" 4 flute EM to finish the sides and get the final slot width (.323"/.320") I need.

 

[wmpy]

A 4 flute corncob will slot just fine, and much better than anything else I have tried, in a straight path.

I will look for a corncob rougher. I ended up ordering some 4 flute corner radius end mills from MSC to try out because the 3 flute EMs seem to be hard to come by. I will see how well 4 flutes can slot.

 

[CarlBoyd]

I am having problems with end mill runout. I previously suspected the tool holder collet to be the problem. You can read all about that here if you like.

Premium ER collets

Who makes a good ER collet with low runout? REGO-FIX? Techniks? Or do you guys have good success with the Maritool collets? I had a job running great- incredible tool life, good chip formation, good cycle time. I was happy. Then, the 5/16" solid carbide 3-flute end mill that I'm slotting with...

www.practicalmachinist.com

The collet was a problem. I have that sorted now, but I am still getting bad runout. I am now on to suspecting the end mills themselves.
The end mills are 5/16" 3 flute, .060" R carbide mills that I use to rough out a slot.
Please see the picture below for how I am measuring the runout. Does this look like an accurate way to check them? The test indicator in the photo was zeroed on the lowest flute. It's now reading on the highest flute. Repeatedly checking the flutes gives consistent results, so I'm inclined to think that there's nothing wrong with my method, but maybe one of you can tell me otherwise.
I brought this up to the manufacturer and told them how much runout I was getting. They told me that was outside of their tolerance and that they would send me some new end mills. They assured me that they would check these new end mills before sending them, but I am getting the same measurements and poor tool life with these new tools. I can see that they are from the same batch as the originals. So, did the end mill manufacturer fail to check these, or is there something wrong with the way I'm checking them? I am currently looking at other manufacturers since my experience hasn't been great with this one.

Wmpy

2 questions on your measuring method.
1) The picture looks like you are measuring on the relief and not at the cutting edge. Where on the end mill are you measuring. A close up photo would help.
2) The picture shows you are measuring pretty close to the tip, are you on the tip radius?

CarlBoyd