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To Flat or Not to Flat?

Rex_Banner

Plastic
Joined
Jul 12, 2022
My co-worker doesn't put flats on endmills shanks, for solid holders. I don't agree with this, and I just wondered what other experienced people thought??
 

mhajicek

Titanium
Joined
May 11, 2017
Location
Minneapolis, MN, USA
Depends on how hard you run them. A sidelock holding a Weldon flat has about the best possible retention for hard roughing, and some say it performs better than shrink-fit, hydraulic, or milling chucks in those situations. It's probably cheaper to order cutters with Weldon flats than to add them yourself, if your time is worth anything.

If you're not pushing hard enough to pull the cutter out, and you have the desired process reliability, I wouldn't sweat it. The first time one of his cutters pulls out though, it's time to make a change.
 

50BMG DUDE

Aluminum
Joined
Jun 17, 2013
Location
Bonners Ferry
I always grind a small flat on round shank carbide mills used for roughing (don't want to take them out of balance for high speed) - A buddy showed me that he would grind it at a little back angle like a ball lock punch to keep it from pulling out at the same time. I've taken some obscene cuts with them in hard, nasty material and never had one pull out, break yes, pull no...
 

mike44

Aluminum
Joined
Mar 21, 2020
I bought ten 1/4" endmills for $15.00 at an auction. No flats . I was slotting 1018 CRS when the cutter pulled down. Work not ruined because this was a thru slot.
I then ground a flat on every one.
 

Rex_Banner

Plastic
Joined
Jul 12, 2022
I mean regular non-weldon flat cutters, in a Weldon flat solid holder, smooth cutter shank- to set screw,

And yeah there are a ton of fucked holders around the shop. I have only worked here for a few months. And when you see the "Top" guy doing this, it makes me question the company. You should see how he builds through spindle coolant tools.....non sealed holders, if coolant comes through the hole at all he says that's " through spindle"

Thank you guys, for all your insight
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
I always grind a small flat on round shank carbide mills used for roughing (don't want to take them out of balance for high speed) - A buddy showed me that he would grind it at a little back angle like a ball lock punch to keep it from pulling out at the same time. I've taken some obscene cuts with them in hard, nasty material and never had one pull out, break yes, pull no...

Same. You don't really need but a nick. Just enough to catch the setscrew. The flat preferably needs to be either ground dead flat or as you describe, deeper toward the cutting end. As you snug the setscrew rotate the tool to find alignment with the flat and let it either pull into the whistle notch (it will get caught in the front corner in this case) or bring it out against the rear of the notch if it's a dead flat notch. Then crank down good'en'tight.
 

Garwood

Diamond
Joined
Oct 10, 2009
Location
Oregon
I almost always grind a small flat. Last Sunday I was finishing up a huge job and just dead tired done. I threw together a 3/4" 5 flute in a side lock holder without grinding a flat and used it to drill 4340 3/4" deep with a 1/2" pilot hole. The endmill pushed up .025" after 12 holes so I had to comp and run it again. I'd have saved time if I ground the flat to begin with.
 

apoet

Plastic
Joined
Dec 10, 2021
Well it sure seems like there's a consensus. I've never taken the time to grind flats but that will change going forward - I must not be pushing my tools hard enough.

Are you guys just hitting the shank on a bench grinder by hand?
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
A Weldon flat is a flat with a shoulder at both ends.
A whistle notch is about 3* going the holding way.
A straight flat is Ok...but does not resist pulling out by the tool helix.
Need to go crazy tightening a no-flat cutter and carbide is so smooth it may still turn and ruin a holder.
With a flat...or none it is good the piggyback the set screw.
We used to have holders made with 2 screw holes .so when the holder was worn from one screw we would use the other one..so getting double the life of our holders.
*Pull-outs are great for making scrap..
Q: (Are you guys just hitting the shank on a bench grinder by hand?)
Bench or surface grinder OK..clamp it vise I on the SG to avoid a spin.
But no shop should be without a surface grinder IMHO.
 
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DanielG

Stainless
Joined
Oct 22, 2014
Location
Maine
I mean regular non-weldon flat cutters, in a Weldon flat solid holder, smooth cutter shank- to set screw,

And yeah there are a ton of fucked holders around the shop. I have only worked here for a few months. And when you see the "Top" guy doing this, it makes me question the company. You should see how he builds through spindle coolant tools.....non sealed holders, if coolant comes through the hole at all he says that's " through spindle"
"You are technically correct. The best kind of correct"
 

wesg

Titanium
Or a mill table, I saw it happen to a guy who I was working next to, some years ago.
I've seen more than one Bridgeport with a ramped slot in the table.

Another issue with set screw against a round shank is the screw gets buggered up. Looked to me like the ramp that gets swaged by the shank will limit the torque you can put on it and it eventually won't be holding as tight as you think it should. Maybe ... just a theory.

Bench grinder and hack a flat about 1/2 screw dia wide. Pull the tool out to bear on the screw while tightening.

Don't need any special wheels either, plain old AlO will do just fine for this on carbide.
 
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LexD

Hot Rolled
Joined
Sep 4, 2002
Location
Riddells Creek,Victoria,Australia

As Michiganbuck mentioned, a true Weldon shank flat is a precise groove with 45 degree chamfers on each side which matches up with a purpose made grub screw, also with 45 degree chamfers and an accurately controlled flat width to match the flat on the cutter shank. This arrangement not only prevents the cutter from spinning but also stops it moving up or down.​

 








 
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