Tips/Techniques Using ER Collets

Tips/Techniques
This is a set of tips on how to use ER collets as gleaned from an article published in "Modern Machine Shop" after an interview with Jonathan Harvey at Rego Tool. Rego is the initial developer of the ER Collet system.

Here is my summary:

1.Ensure adequate clamping length - always engage the tool at least 2/3 of the way into the clamping portion of the Collet.

2. Always use a torque wrench to tighten the collet nut to specifications. But..... the article doesn't say what that torque should be. So I did a google search and pulled together the following chart as a guideline. I'd recommend finding torques for your own collet set if you can find it. To-date, I've never used torque to tighten my collets. So this is a new beginning for me. My claw wrenches don't even have a provision for measuring torque so I may need to drill a hole to take a fish scale.

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3. Ensure proper alignment of the collet, collet nut, and tool. Assemble the collet into the nut correctly first, then insert the tool to the correct depth, then torque the nut to specs. Note - correct installation of the collet and collet nut is very often done incorrectly. The correct method is to identify the eccentric lip/ring inside the nut, insert the collet into the nut on an angle to engage the lip, and then rock the collet to snap it into full engagement. Reverse this process to remove it. Here is a link to an image that illustrates the process. I used a link instead of a direct image in order to avoid copyright infringement for the image.


4. Remove the backup screw if your collet holder has one. Most ER Collet suppliers have already removed this stop screw because its too easy to use incorrectly. If your collet holder has one, Rego recommends removing it. (To be honest, I've never even seen one.)

5. Keep your holder and collets clean. A precise fit of the collet, tool, collet holder, and spindle tapers requires a tight clean fit. Always keep these surfaces clean and free of chips and dirt and brush or blow any dirt out of the expansion slots.

6. A small tip of my own - always use collets within their design range. Never use a tool that has to be forced into the collet, and never use a tool that is too small for the design range of the collet. Many collets are marked with their design range. Sometimes even the design range is too big. In this case, it helps to have a set of metric collets that will have a collet that will almost always fit when the imperial collet is just a tad too big.

Here is a link to the original full article for those who would prefer to read that:

 

Susquatch

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According to the European Standards DIN6535, the double flats are required on shanks of 25mm and 32mm, and a single flat on 20mm and smaller shanks.

I have a 1" and 1 1/4" endmills and holders that have the double Weldon flats.

I guess I don't think that the DIN Standard is really Weldon. It is its own thing. In the Weldon design, the flats are not in line with each other. They are at 90° to each other and press the shaft into its "saddle". There never was a single Flat Weldon that I know of, but there are lots of single flat arbours and endmills.

Unless I missed something, the Weldon system predates the DIN standard by decades. It is a very old proprietary design that has since been adopted by many other manufacturers in modified form ever since the patents expired. Machinists and tooling companies have simply adopted the name "Weldon" to mean anything with grub screw flats. DIN may mention it, but I really don't think that the DIN standard and the Weldon Standard are the same let alone identical.

In many ways it's sort of like Coke-a-Cola. Every beverage company in the world makes a Coke-a-Cola soft drink. People call them Cokes, Cola, and Coke-a-Cola. If you order a coke at a restaurant, half the time you will get a Pepsi not a coke. But there is really only one real Coke-a-Cola.

Of course, there is very low chance the world will ever change this Weldon naming practice. So it seems I have two choices - accept the world's version of what a Weldon shank/arbour is, or die sticking to a meaning that has already died long before I will. The jury is still out on which it will be for me.
 

thestelster

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The Weldon imperial shank dimensions are governed by ANSI B94.19-1985. The metric counterpart is the DIN6535.


In the Weldon design, the flats are not in line with each other.
Actually, yes they are. As per my endmills and holders.

But, yes, they'll always be called Weldon.
 

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Susquatch

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The Weldon imperial shank dimensions are governed by ANSI B94.19-1985. The metric counterpart is the DIN6535.
We are gunna have to agree to disagree Stel. In my mind, ANSI and DIN don't get to decide what Weldon patented in the 1940s. The best they can do is swipe the name and redefine it. On the other hand, if the word Weldon was preceded by ANSI as in ANSI Weldon Standard xxx.xxx, I would accept that.
 

thestelster

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In the winter of 1918, Carl A. Bergstrom opened the Weldon Tool Co. in Cleveland. Working from his shop atop the Blackstone Building, he developed a new kind of endmill, one with a 30° helical flute. The thing cut like crazy. Yet Bergstrom quickly realized that his toolholder lacked the gripping power to hang onto his cutting-edge endmill, as the darned thing kept spinning right out of the holder. In a fury, he grabbed that newfangled tool and ground a flat spot on its side, giving the toolholder’s clamping screw a place to bite into. Bergstrom had invented the Weldon shank.
 
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