Metaling Affairs: Toolholding Today Get a Grip

March 19, 2012 No Comments
Print Friendly

by Andrew Skoog

toc_columns50pxTolerance requirements today are getting increasingly tighter with higher demands for consistency and quality. This means that more attention must be paid to selecting the toolholder to match these demands.

Generally speaking, many manufacturing facilities throughout North America have overlooked toolholding for milling machines. In recent years, many of these same manufacturers now consider toolholding as important in the conversation as the machine tool itself. Manufacturers supplying the medical, electronic, and die/mold markets generally have been a little ahead of the curve because their tolerances and surface finishes required them to adopt higher tolerance toolholders.

When looking for toolholding systems for any type of machining process, manufacturers first must turn their attention to rigidity, gripping force, balance, accuracy, and consistency.

Rigidity: Like your belief system, if well rooted, it won’t waver. Rigidity will depend on the taper contact and proper clamping in the machine tool spindle. Beyond that, the toolholder design, the material it is made from, and the projection length come into play.

Gripping force: Like your temper, it is good until the going gets too rough. All systems can be overcome, some quicker than others. What is “Farmer Tight”? No, it isn’t your belt or your pants. There are a few basic types of toolholders in the marketplace; the most common type requires a wrench to tighten the tool in the toolholder. To some, a torque wrench is a very useful tool. Others can’t be bothered: Farmer Tight is tight enough.

What is the preference in your shop? Many shops have been battling this issue for years—end mills sucking out of the holders, broken collet nuts, cracked toolholders, stripped wrenches and collet nuts, busted collets, cheater bars, mallets, Fridays versus Mondays, and the list goes on.

Balance: Like the tires on your car, imbalance leads to runout. Machine tool manufacturers that require balanced toolholders are referring to the assembly. A balanced assembly of a toolholder (including accessories such as pull studs) and cutting tool combination will create the proper balance. Most balance conversations come up for high rpm because we all assume that the faster you spin something the more likely unbalance is going to manifest itself. Most imbalances occur in applications where the rpm is less than 7000. Most of these applications are using larger tools while high rpm machines are running small toolholders with insignificant weight and likely are shrink-fit tooling that is symmetrical.

Accuracy: Like your taxes, when done right, you have no worries. Excessive runouts lead to poor tool life, poor surface finish, chatter and inconsistent results. Minimal run-out at the cutting edge of the cutting tool will ensure accuracy of any job. Right behind accuracy is reliability and confidence.

Consistency/repeatability: This single handedly separates all toolholding technologies. Consistency and repeatability is the mantra of anyone accountable for profitability and quality of manufacturing. Considering all the components listed above, the technology most repeatable and consistent is shrink-fit tooling. With shrink-fit holders, all setup operators set the toolholders the same way. The only variable is the cutting tool. Variables such as overtightening or undertightening a collet nut or not cleaning out a chuck sufficiently are eliminated.

When considering your tooling, there is always more to the equation than the initial price. The true cost is the labor involved after the purchase. Loading a toolholder in a spindle of a machine and tapping a tool to run true to center of rotation is expensive. If you need the technology and you don’t buy it, you will pay the price to not have it. pm_endmarkred-e1320337243152

Andrew Skoog is with Hexis in Minneapolis, Minn. He can be reached at

Copyright © 2012 Minnesota Precision Manufacturing Association. For permission to use or reprint this article please contact Amy Slettum, publications manager for Precision Manufacturing journal.


Sorry, the comment form is closed at this time.

E-clusive: Enhancing the Image of Manufacturing

By Nancy Huddleston Let’s face it – we’re humans and it’s in our nature to care about our looks...

E-clusive: It’s Time to Evangelize Manufacturing

By Nancy Huddleston It’s not every day that you hear someone say, “we need to evangelize manufacturing as a...