To get the maximize life our of your Steep taper rotary toolholders in your CNC milling machines here are some of the best practices you can implement in your shop. Perhaps not all of them can be implemented every day or every time but it's well worth being aware of how to best protect your investment.
Collet Chuck Size
We often get asked to spec out tooling packages for new CNC mills and one of the questions we encounter most, or should, is how do you select the right toolholder collet size for your companies applications? The real choice is in the size of the collet chuck itself. So several considerations should be reviewed...
What size are your tools?
Your first consideration should be the size of end mills or drills you will be using most often. If you are doing smaller work you would require smaller diameter range collets. Generally you may prefer the ER16 and ER32 sizes. If the bulk of your tool requirements are in the mid range you can also use the ER20. The following is a list of tool diameters that can be used with each size collet chuck. Essentially, the most popular, and again, readily available from a number of sources, are the ER 16, ER20, and ER32... in no particular order.
How far do you need to reach?
A second consideration is the actual reach of the tool. Not projection reach, also know as “gage length” "l1" but projection diameter “D”. Obviously, stubbier is better for projection reach "L1". But, you also need to review the families of parts that you intend to run on the machine. If you intend to use the holder to "reach" into a tight fit then the OD of the projection "D" of the toolholder needs to be considered. Many shops don't always consider this and end up using much longer carbide shanked end mills to get into deep pockets when getting a smaller diameter ER collet and collet chuck would be much less expensive over the life of the job.
Sometimes there is just no getting around having a custom tool made. Give us a call at 916.765.4227 or email us if you just can't seem to reach into the part with your toolholder.
ER, IT’S IN THE DETAILS
The ER collet system has several advantages when using today's CNC computerized milling machines. The most significant advantage is flexibility to hold any type of round shank tool. An ER collet can be used in drilling, reaming, and tapping as well as milling applications just by exchanging the collet. Its accuracy also provides greater tool life than older style collet systems like TG or DA.
Another advantage is the flexibility of the collet for clamping a wide range of tool shanks with a small number of collets. ER 16 through ER 40 provide a collapse range of ~.039" flexibility for clamping cutting tools. This is a benefit for you because you will not have to carry as many collets in inventory for the different jobs you need to do each day.
The ER collet also provides more holding power by using two principles.
In addition to mechanical differences, the ER collet is also user friendly. It is a self-extracting collet, which eliminates the need for collet squeezers to extract the collet by any other means than screwing the nut off. This enables the operator to spend time running the machine, not extracting collets.
These basic principles allow the ER collet system to be the most widely accepted collet system in the world for holding round shank cutting tools.
ER style collet chucks should be used for the bulk of your needs. They are the most dependable, with the least runout, both in and out of the cut, are readily available (so the prices continue to drop) and will give you the best tool life out of the lot of them
We often run end mill "tests" to determine which one performs best. Obviously, our goal is to "win' the test and get more business for our manufacturer's. This is article is about one our "tricks" and it's also why represent both cutting tool manufacturers and rotary tool manufacturers. We want to insure that the products work together.
As a general rule most cutting tool & tolholder manufacturers prefer to use single angle (ER/DR style) collet chucks for general purpose cutting tool applications under 1/2" (12mm). The rules are a bit different in High Speed Machining, as there are many more things to consider, but the problems of TIR at high speeds, where you can hear and feel the chatter, are still there in general end mill cutting operations at lower RPM. It's all about runout and uneven chip load.
End Mill Holders are prone to runout problems for a couple of reasons:
Depending on the application, end mill holders can be used for holding larger insert style end mills, spade drills, etc. But somewhere between 1/2” and 3/4” there is a line that only you can determine when you need to move from a collet chuck to end mill holder. Generally we recommend using end mill holders only for very specific applications
Using small diameter end mills (1/4" and below) in end mill holders with set screws will have a adverse affect of both surface finish and tool life.
Determining if toolholder components need to be replaced is not a difficult task, but does require that the operator knows what to look for. Here's a few things you should be aware of when checking your rotary toolholders.
HSK is short for the German words "Hohl Shaft Kegel" or, in English, Hollow Shank Taper.
There are several major differences between "steep taper" toolholders, like NMTB, CAT & BT and HSK.
As machining spindle speeds have increased, BT and CAT tooling systems tend to lose accuracy due to centrifugal forces from running at high RPM. The mouth of the machining center spindle can grow, "bell mouthing". As it grows the BT and CAT tool is under constant drawbar pull, moves up the expanded taper. This causes the Z-axis offset to change. This can also cause the toolholder to stick in the spindle.
The HSK contacts the spindle taper and flange on the spindle face to make a solid union in both the axial and radial planes. In operation, HSK tool holders are resistant to axial movement because the face contact prevents the toolholder from being pulled up into the spindle at high speed.
Cutting tools generally takes higher radial forces because the flange contact and taper contact combine to resist deflection.
Technical Support Blog
At Next Generation Tool we often run into many of the same technical questions from different customers. This section should answer many of your most common questions.
We set up this special blog for the most commonly asked questions and machinist data tables for your easy reference.
If you've got a question that's not answered here, then just send us a quick note via email or reach one of us on our CONTACTS page here on the website
Our technical section is written by several different people. Sometimes, it's from our team here at Next Generation Tooling & at other times it's by one of the innovative manufacturer's we represent in California and Nevada.