ID Gripping Dilemma
Manth-Brownell (Kirkville, New York) needed an affordable solution for an internal grip on their pickoff spindle of their EuroTurn 6/32 six-spindle screw machine (32mm thru capacity). The job called for a brass turned part with thread milling. They needed to backwork the part but couldn’t grab the outside of the part with the OD pickoff attachment because it would distort the threads.
One solution to this dilemma would be to buy the ID pickoff attachment from the machine tool builder. It would cost $36,000.00 – and they would have to the purchase a $7,650.00 kit to downsize from a 42mm to their existing 32mm size. The setup time involved would be about eight hours. Wes Skinner, President of Manth Brownell, had no idea how long this particular job would last, or how soon he would have another job with ID chucking to substantiate the purchase. Mr. Skinner states that he could have moved the part over to another machine for the second operation, but knew that there had to be a more productive solution. Coincidentally, he was attending a regional PMPA meeting the same day that he was contemplating the issue and ran into Cal Macomber (Director of Sales & Marketing, Hardinge Inc.) and Neal Des Ruisseaux (Manger of Workholding Engineering, Hardinge Inc.) who he’d been doing business with for forty years. They put their heads together and jotted notes and drawings on napkins.
Hardinge Engineers the Solution
Hardinge Inc. engineered an exclusive expanding collet (patent pending) to fit the machine’s existing OD pickoff attachment. Changeover from a standard OD gripping setup to an ID setup would be a matter of changing just the collet, rather than changing the entire attachment. The Hardinge expanding collet would cost much less than purchasing the ID attachment and offered additional savings in setup reduction. Installing the Hardinge collet would take less than 15 minutes to insert the collet, set it up and get the position for proper ejection and clearance. The built-in spring ejector provides automated parts removal for faster throughput. This newly developed collet fits Euroturn OD pickoff spindles as well as Gildemeister and Tornos Deco machines and can be made to hold workpieces of specific size and/or shape.
Manth Brownell (Kirkville, New York) is one of the largest manufacturers of turned parts in North America. They have been devoted to the screw machine industry for over forty-six years, with over 146 machines inhouse, and are an ISO 9002 and QS 9000 registered company.
Length Control of Finished Part
This shop was able to make a comparison between the Hardinge collet assembly and an ID pickoff attachment that was on loan to them. Aside from the setup time and cost savings, they report that with the Hardinge expanding collet there is little problem holding tolerances on machined features as the machine goes from a cold start to normal operating temperature. As a matter of fact they found improved length control - the part easily maintained a .0002 to .0003” tolerance, as compared to .004 to .006” with the ID pickoff attachment. Mr. Skinner attributes the collet’s indifference to temperature to its design and the fact that there is less friction than would be present in a larger assembly.
A Million seven hundred fifty thousand Parts Run
Manth-Brownell is currently running this part 10 shifts per week. The shop produced one million parts using the first expanding collet prototype furnished by Hardinge and another 750,000 parts have been made with a second collet, without any problems. James Wilsey, Manth Brownell’s machine operator and setup person, anticipated some chip-buildup problems, but Hardinge designed openings around the assembly that facilitate flushing of the chips. James uses shop air to blow out the collet once in a while, but the shop has never had to take the collet assembly apart to clear any chips.
Hardinge Inc. (Elmira, New York) has a dedicated manufacturing department with design and applications engineers, along with phone correspondents for special workholding applications such as this ID expanding collet. For additional information contact Hardinge Inc. at 800-843-8801.