Collet Chuck - How does it work?

[ConductorX]

I purchased a Grizzly G0759. I also purchased a set of HSS Coated end mills and a Collet Chuck that I thought would hold all of the end mills.

I learned via YouTube that an end mill with a flat spot for a set screw is suppose to go into an endmill holder not a Collet Chuck.

Is this correct? Do I need to buy a set of end mill holders at $20+ each or a set of collet end mills?

I am not finding any end mills without the flat spot.

Thanks and sorry for the very basic newbie question.

"G"

[lynnl]

Well, the flat spot is there to facilitate use in an end mill holder, but they can still be used in collets of the appropriate size...not the collet chuck.
The collets in turn are held in the collet chuck.

[ConductorX]

Good, so I can put a 3/4 end mill into a 3/4 collet and the collet chuck should hold it with no problem.

How tight should I tighten the nut on the collet?

"G"

[J Tiers]

Good, so I can put a 3/4 end mill into a 3/4 collet and the collet chuck should hold it with no problem.

How tight should I tighten the nut on the collet?

"G"

Since both the collet and end mill are hardened, you need the collet closed "tight". Not 4 foot cheater bar tight, but past "snug". Try it on some scrap steel, and you will soon figure out how tight is correct. Collets WILL let the cutter creep outward and ruin the work, not every time they are used, but for sure it will happen, usually on a part you have spent a lot of time on already.

End mill holders are not expensive (try Victor Machinery), and DO work better. You get the setscrew into the flat, then tug outward on the cutter as you tighten, to make sure the cutter cannot creep farther.

[dalee100]

Hi,


Do not let J Tiers scare you about collets slipping. They are no more prone to slipping than holders are. If your tooling slips, YOU screwed up - not the collet. In 30 years of machining and 20 years of running the floors, I have found tool slippage for either collets or endmill holders to only be a problem when you are pushing a tool right up to and perhaps a bit past it's capability for depth of cut and feed rates. Something that so seldom happens in a home shop as to be non-existent.

Endmill holders rob daylight from your Z-axis and the excess length also allows for more tool flex. But they do have their place, as they allow you to use larger shank tooling than collets can often accept. And tapered endmill holders will allow you to reach down inside a deep pocket to work.

If you already have the collet set, there is no reason to buy any endmill holders unless you need one for a real reason.

Dalee

[Magicniner]

Collets WILL let the cutter creep outward and ruin the work.

If you don't keep them clean and don't tighten them adequately, check the recommended torque for your collet system, you'll realise why so many people guess low, have a SNAFU and blame the collet system ;-)

[MattiJ]

Hi,

If your tooling slips, YOU screwed up - not the collet. In 30 years of machining and 20 years of running the floors, I have found tool slippage for either collets or endmill holders to only be a problem when you are pushing a tool right up to and perhaps a bit past it's capability for depth of cut and feed rates. Something that so seldom happens in a home shop as to be non-existent.

Dalee

Agreed.
Common problem with collets is not tightening them properly. Recommended ER32 tightening torque is 100...135Nm for tool shanks over 3mm.
With the typical tiny collet nut wrench that is pretty much "white knuckles and key shape imbedded to your aching fingers"-torque. I'd guess that most people would instinctively tighten ER32 to something like 20Nm, only 15% of the maximum allowed tightening torque.

http://us.rego-fix.com/er-system/pdf...rque-chart.pdf

[Toolguy]

All end mills work fine in a collet. You need the ones with the flat for the setscrew holder. Many carbide tools don't have the flat. Each kind has it's place. You don't say what kind of collet chuck you have. Be advised, ER collets must be put into the nut before inserting the endmill, drill or other tool. This is because they have an eccentric ring in the nut that goes in the groove of the collet in order to pull the collet out of the taper when changing tools. If you don't put the collet in the nut first, noting works right.

[Magicniner]

I have Collets and EM holders, I hand grind a flat on tooling I want to use in holders and use tooling with flats in collets, I even use small straight shank collet chucks in EM holders, it's all good ;-)

- Nick

[J Tiers]

Yes, they DO work fine..... USUALLY.

Like I said, they will screw up only when it is important that they do not. I may use the collet 100 times and have no issue. When # 101 comes along, then there is a problem.

WHO CARES WHO OR WHAT GETS THE BLAME?

You ARE gonna screw up, it's a fact of life. So make it less likely. When you have the setscrew version, it just is not an issue. It's harder to screw up.

And, there is another factor. The end mill does three things. It applies torque, it applies a side load, AND it applies an impact load as the cutter teeth hit the material several time per rev. That is very much the case as the cut starts, less so, but still present, during the cut. Just the sort of thing to loosen up and move the cutter.

Then there is the issue that the flat often ends up right where you want to grip with the collet. Don;t do that with a US collet like 3AT etc, it will cause trouble with holding force, and raise the risk of movement. The grip length of a typical collet of that sort is not long, and the grip is often not parallel. It can't grip well when part of the shank is missing, even if it is lined up to cover and extend past the flat.

In fact, the same guys "who never make a mistake", and say collets are great, will razz your azz if they see a picture you post of an end mill in a drill chuck. THAT they will say will OBVIOUSLY slide around and cause trouble. Yet they say a collet, which often contacts on a similar area in reality, they say is perfect, no problem, etc. Truth is the two can be very similar unless the collet is new and totally unworn, being used in a new, perfect, and un-worn collet closer.

What they SHOULD HAVE SAID, BUT DID NOT is that collets are not all the same. A typical US collet, morse taper, 3AT, 3C, 5C, or even R-8, is a piece of crap mechanically. It works, but is best for soft materials of perfect size. An ER collet is much better for tool holding because it has a longer and parallel grip

Not all end mill holders are made the same. I have some for MT2 that stick out a whopping 3/8 of an inch beyond the spindle. Not a big issue for taking up space.

[BCRider]

A good practice until you get a feel for how tight the collets need to be is to put a witness mark like across from the collet face to the end mill. Then inspect it after the first cut to see if the line indicates any creeping.

I found on my new R8 mill that a snug but no where near white knuckle tightening was enough to hold even mills that were larger than the shank for cuts as heavy as I'd want to make on a belt drive head.

But on the 5C collet blocks I found the opposite. Namely to hold work against moving I needed to really torque down on the nut for larger size collets and anything other than a light cut.

[danlb]

Hi,


In 30 years of machining and 20 years of running the floors, I have found tool slippage for either collets or endmill holders to only be a problem when you are pushing a tool right up to and perhaps a bit past it's capability for depth of cut and feed rates. Something that so seldom happens in a home shop as to be non-existent.

It's important to note that beginners are the ones most likely to push a tool beyond it's capabilities, and thus are likely to run into endmills that slip in a collet. They are the ones most likely to try "innovative" work holding techniques and climb milling.

So advice to the beginners:

Whether you use an R8 collet or an ER style collet, make sure the collet is exactly the same size as the tool shaft. R8 collets do not work well when you force a 1/2 inch shaft into a 15/32" or 12 mm collet. They work badly when the collet is too big too. Note: All my endmills have shafts that are in increments of 1/8 inch. There is something wrong if I find I need a collet measured in 32th.

Make sure there is no swarf inside the collet nor on the shaft of the tool.

Make sure the tool is dry. Oil will diminish the holding power of the collet.

Watch the cut as you go. A slipping endmill will slowly dig deeper and deeper as it pulls out of the holder. I once milled a 3 inch x 1/2 wide inch pocket into aluminum. It started at 1/4 inch deep, but was closer to 1/2 inch by the end of the first pass.

I use end mill holders for larger mills, and R8 or ER collets for the smaller ones.

Dan

[Rich Carlstedt]

There are collets made especially for holding endmills.
Here is a sample, it is a Universal Engineering collet ( now Devlieg) . Note the button on the side.
when you insert the endmill, and tighten the collet, the button locks into the flat space, preventing the endmill from coming out.
http://www.tools-n-gizmos.com/store/...xm=on&ppinc=1a
Click on more and larger pictures

Jerry Tiers is absolutely right , somewhere along the path, you will "pull" an endmill ( been there, done that)
And it will always be on that "Rush" and important job !
A good way to protect yourself is to get some Red Nail Polish ( NOT paint, and not any other color )
and place a dab right at the junction of the endmill and the collet.
"IF" the endmill pulls , instead of seeing a pink blurr at the junction point , you will easily see a sharp bright clear line.
Nail polish is quick drying, so it works well in moments, and the lacquer is hard, allowing it to crack and not smear. It also has an easy applicator for the function - perfect--! and its cheap.....

Rich

[BCRider]

I like the idea of the nail polish and I can see how if the end mill pulls that it would form a visible line. But the spot of color would be up underneath in a spot we don't casually see during operations. I still like the idea of nail polish or a sharpie spot but it DOES mean needing to bend over and look up at the spot. And likely with a flashlight since it would be shaded from most work lights. So it's not the sort of thing you'd be looking at during most cuts. It is more a thing to check at the ends of passes until you figure out if the torque used can be trusted on that size of end mill.

[danlb]

What they SHOULD HAVE SAID, BUT DID NOT is that collets are not all the same. A typical US collet, morse taper, 3AT, 3C, 5C, or even R-8, is a piece of crap mechanically. It works, but is best for soft materials of perfect size. An ER collet is much better for tool holding because it has a longer and parallel grip

Thanks for bringing that up. It motivated me to do a little more learning about the subject. I found the R-8 specification calls for 1 inch of grip. My 2MT Morse taper collets provide a grip area that appears to be 5 to 10 times the bore diameter. The ER styles seem to vary a lot.

I'd noted long ago that ER collets had multiple styles. Some appeared solid from end to end, some have a pocket on the end furthest from the nut. As a result, one style has a shorter gripping area than the other due to the counter bore. I found charts (1) that specified the gripping area for various ER collets. It confirmed the observation that the smaller ER collets (er 11, 16, etc) have less gripping area than the R-8. In addition, the larger ER collets (er20 and above) have that pocket for gripping shafts smaller than 8mm (1/3 inch) and thus have less than 1 inch of grip. Once they are above 8mm they are the full length of the collet.

The reality is that a closely matched shaft in a quality collet will do fine when the gripping length is significantly longer than the diameter of the shaft that is being gripped. I have never seen a 1/2 inch shaft wobble in an undamaged 1/2 inch collet of any design.

Dan
1. http://www.takayama-shoji.co.jp/rego...nformation.pdf