b'different collets for every 1 mm (0.04") in-crement in tool shank diameter at a mini-mum, so it would take at least 17 collets to cover the 3.175 mm to 19.05 mm shank di-ameter range.But the base holder remains the same, he said, and you just change out the col-let to clamp on to different tool sizes.On the other hand, shrink-fit holders are sized based on tool shank diameter, said Dan Doiron, milling product manager at Emuge Corp., West Boylston, Massa-chusetts. This means that a shop would need a different shrink-fit holder for each tool diameter. In addition, he said, a shop using shrink-fit holders needs a heating unit to install tools in the holders, adding more cost to that option.While shrink-fit and Weldon flat tool-holders accommodate only one tool size, hydraulic and milling chucks allow the use of straight reduction collets to change tool sizes, Miller said. But he added that the presence of reduction collets in these chucks hurts their performance, result-ing in increased runout and/or decreased clamping force.Besides the versatility of the ER col-let system as a whole, users get the tool-holding flexibility of the individual collets in the system. This is due to the slotted ER collet design, which allows a good deal ofGuhringHeld by a collet, a thread mill cuts threads (above).compression and therefore can accom-modate different tool shank diameters,ERC collets (surrounding photo) are inspected twice explained Andy Moon, product man- to check runout accuracy.BIG KAISER Precision Toolingctemag.com/cteguide.com29Toolholders.indd 29 5/14/20 3:01 PM'