General | Collet Chuck Discussion: Double Angle vs Single ...

Some general information regarding the three types of tool holding you are asking about.
First off the DA has the least long term accuracy. Not to say that guys can't and don't get good results from a DA setup but the design has a flaw.
The DA (double angle) derives its accuracy by pulling up on two tapers facing each other. The angles are rather short and close together.
Only one taper is bearing against the fixed part of the system (tool holder body) The opposite taper is being pulled against the nut through threads etc....Wear in the threads through use will affect accuracy of the nut pull up and thus the top taper.
Also because the tapers are short a smaller contact area is available so and small defects or wear will have greater effect on the tool.

Advantage of the DA system is that it generally needs a smaller body (because of the small tapers) so for close or tight work a DA setup might be the best.
The DA setup is very nice for tools like a die grinder ....small and compact for size to body.

Largely replacing the DA's today is the ER system. Some of the advantage of the double angle collets is also present in the ER system...That is the ability to clamp over a wider range than other collet systems.
The nice thing about the ER collets is the much longer taper on the OD of the collet (as compared with the DA's) This longer taper seats in the rigid part of the holder , the body as as such will retain its accuracy better by not relying on the nut to provide its alignment.
ER's are now quite common and available in many different holder configurations.

Finally there is the TG family of collets....the TG's like the ER's haver a long base taper seating in the tool holder body. Their down side is that they will not close over a wide range of sizes per collet. So one would need a larger number of collets to cover the working range if all sizes are needed.
The plus side of the TG's is that they have greater holding power than the DA's or the ER's. So if you need hogging ability the TG's are just better.
My personal solution is to have Some ER's to cover everything in light or finishing service, and a selection of TG's for the rough/heavy work. This means that you do not need a full set of the TG's , just some of the larger sizes, say 1/4",5/16, 3/8, 1/2, 3/4 and 1"

Of course if you really need to hold the tools secure , nothing beats a "Weldon" style end mill holder....But then you give up some accuracy.
Cheers Ross

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Milling is a core operation in all kinds of manufacturing environments. There are five different kinds of milling holders, each with their own strengths and weaknesses. We’re here to help you choose with the breakdown and top recommendation for using each.
 

Milling chucks
Let’s start with the jack of all trades in the world of milling holders. Milling chucks’ high retention force combined with a simple twist-to-lock operation makes them ideal for general purpose operations. These chucks grip a tool shank by means of mechanical deformation of rows of needle bearings. These holders provide substantially more gripping force than a collet. Runout, however, is reduced compared to collet chucks, but is still better than double the performance of side lock systems. Their large bodies help dampen vibration and chatter. The option for high-pressure coolant delivery through the tool is also useful.

Top tip
The bigger the milling chuck, the more the clamping force. Larger size chucks have a higher starting potential clamping force. When paired with a reduction collet the final gripping force is higher than a direct clamping size chuck.

Hydraulic chuck
Hydraulic chucks are often more specialized because of their slim body shape, higher cost and moderate gripping strength—about half that of a milling chuck and about double that of collet chucks. The main differences between the holders, in terms of performance, are the superior vibration damping and simpler handling of hydraulic chucks. They are most often used for finish milling, reaming and drilling. They are extremely easy to handle. A simple clamping screw activates hydraulic chambers that allow the holder to clamp down on the tool.

Top tip
Never exceed a hydraulic chuck’s rated rpm; fluid is pulled away from the holder’s internal gripping gland, causing loss of clamping force.

Shrink-fit holders
Often compared to hydraulic chucks because they can also have very slim bodies, shrink-fit holders share similar gripping force as well. Handling is much more involved, but from an engineering perspective, shrink-fit holders are, fundamentally, the perfect tool holder. There are no moving parts, they are naturally symmetrically round and they use the properties of the holder itself—with the help of heat—to grip the tool. But as we know, a manufacturing floor is not a perfect environment. Variables must be considered when choosing equipment.

Best for moderate to heavy milling, shrink-fit holders are excellent at high speeds and are especially useful in low clearance, tight work envelopes because of their relatively slim design. Gripping power varies based on the tolerance of the cutting tool shank and outside body diameter: the heavier the wall, the higher the gripping force.

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Top tip
Shrink-fit holders have very tight-tolerance bores. They should be cleaned and dried between each tool change. If you’re considering shrink-fit holders or already own them, check out these tooling and spindle cleaners.

Side-lock end mill holders
These may be a bit simpler in terms of how they clamp than hydraulic and shrink fit, but these rugged holders definitely have their place. A flat in the tool engages with a Weldon screw on the holder that locks the assembly in place, all but eliminating the risk of pullout, even in the toughest metals. They are most effective when heavy roughing at low speeds. What side-lock end mill holders achieve in security, they often lack in precision. Avoid high speeds and cuts with higher risks of vibration unless you’re using high-performance tooling like the MEGA Perfect Grip.

Top tip
Never use tools with homemade, hand-ground flats in a side lock end mill holder.

Collet chucks
From a low-speed specialist to high, collet chucks work best at elevated rpm. This makes them excellent for delicate and precise work like drilling, reaming and finish milling. The collar-like gripping is tightened by way of wrenching a collet nut. This allows for more points of contact for the tool when compared to other chucks. Collets are most useful in repetitive work where the clamping requirement does not vary significantly.

They also are versatile because the number of segmentations on a collet can vary. More segments mean greater flexibility and a larger gripping range at the cost of some of the concentricity and stability of more rigid collets.

Top tip
High-performance bearing race nuts offer the highest gripping strength combined with stable runout accuracy. The bearing keeps the race from sliding against the surface of the collet. The friction of a solid nut sliding across the collet face twists the collet and increases runout as well as increases the clamping torque required.    

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