No room for error: General Industry Coverage

END USER: D&N Machining Co., (479) 996-2738, www.dnmachining.com.
CHALLENGE: Tap 100 2″-8 blind-holes without breaking the tap or scrapping a part.
SOLUTION: A tap engineered to effectively produce threads in holes more than ½” in diameter.
SOLUTION PROVIDER: OSG Tap & Die Inc., (800) 837-2223, www.osgtool.com.

A single mistake when tapping large, complex, expensive parts for the energy industry can make a job shop go dark. Finding a tap that can execute the job accurately, efficiently and affordably when threading a difficult-to-tap workpiece only adds to the challenge.

D&N Machining Co., Greenwood, Ark., faced this situation when machining two outer piston ring housings for a customer in the oil field industry. The housings are 4140 steel forgings that weigh up to 5,000 lbs. each, have a hardness of 32 HRC and feature a 30″ bolt circle and 32″ major OD. They required D&N to tap 50 2″-8 blind-holes 3½ ” deep in each housing—100 holes total.

To ensure it had a tap for the job, D&N purchased the one tap the shop could find in stock from a toolmaker. “Purchasing the tap was basically done out of necessity,” said Matt Hankins, owner of D&N.

Courtesy of OSG Tap & Die

The HY-PRO HXL tap from OSG is for threading difficult-to-cut alloy steels, such as 4140 and 4130. Below: An HY-PRO HXL tap shows little wear after tapping 100 holes in 4140 at D&N Machining.

However, the toolmaker recommended tapping at 10 sfm, which seemed too slow and could possibly cause the tap to break during the cutting-force-intensive threading operation, according to Hankins. Because of the part size, he thought it would be problematic to locate an EDM large enough to remove a broken tap. Also, with multiple machining hours already invested in each expensive workpiece, scrap wasn’t an option. There was no room for error.