How to eliminate machining saddle burrs

Just as holemaking is common in metalworking, so is deburring the tops and bottoms of produced holes. Chamfering tools are effective, as are the familiar Rotoburr-style scraper blades. These tools also deburr machined edges fairly well and, given the right extension or blade geometry, can access hard-to-reach areas deep inside parts. Add a few Scotch-Brite pads, a drill press and a bench grinder to the mix, and there’s little that any skilled machine operator can’t deburr.

However, these traditional deburring methods are slow. Features that can’t be reached while in a machine — which is often much of a part — must be manually scraped, buffed and chamfered. If an operator isn’t paying attention, a machine tool might sit idly while he or she is busy deburring parts. And a bit too much pressure with a grinding wheel or blade could mean the inadvertent scrapping of a completed, possibly very expensive machined component.

Worker health and safety are also a consideration. As machinists would attest, cuts, scrapes and repetitive stress injuries are common during manual deburring, never mind the potential inhalation of abrasive grit. Surely safer, more productive methods are available?

The ability to deburr both sides of a hole (above) in a single operation is a huge timesaver. Image courtesy of Whitney Tool

Two for One

“You don’t want to pay CNC machinists to deburr holes,” said Samuel Dean, director of sales and marketing at Whitney Tool Co. Inc., Bedford, Indiana. “You want to pay them to program and set up and maintain machinery, which means that the deburring — or as much of it as possible — is done inside the machining center where consistency is assured and there’s no chance of missing a hole. This is why it’s so important to convert manual deburring operations into automated ones so that shops can more efficiently utilize their production floor staff.”

One step in this conversion process is the use of Burr-Zit and Handi-Burr deburring systems from Whitney Tool, he said. Often referred to as clothespin tools, Burr-Zit deburrs the front and back of hole diameters from 1.98 mm to 25.4 mm (0.078″ to 1″) in a single in-and-out pass. The Handi-Burr line of spring-loaded deburring tools extends that diameter range to 50.8 mm (2″). Multiple lengths, geometries and coatings are available, and the Burr-Zit series can be purchased in kit form to cover a range of hole sizes.

Dean said Handi-Burr typically is reserved for manual deburring operations in a drill press or power tool while Burr-Zit is suitable for CNC and manual equipment. He also said both tool types are only for deburring, in that they produce a rounded edge. If a qualified, dimensionally accurate chamfer is needed, it should be machined using an actual milling cutter.

Deburring in a Snap

Matt Baumet, technical sales engineer at Heule Tool Corp., Loveland, Ohio, suggested several similar alternatives. The company’s Snap front and back chamfering tools, for example, feature a replaceable, spring-loaded blade and are intended for use with CNC machine tools while providing more accurate chamfering than tools for only
deburring.

“It depends on the hole size and material,” he said, “but you could expect to hold plus or minus a couple thousandths on a chamfer.”

Also available are the Cofa “universal deburring tool” for elliptical or contoured surfaces, the Defa adjustable chamfering tool and the X versions of Snap and Cofa for deburring cross-holes and intersecting bores.

“The Cofa and Cofa-X are specifically designed for irregular surfaces,” Baumet said. “Let’s say you’re deburring a hole drilled on an angled surface or a cross-hole in a piece of tubing. Here, the blade actually pivots in and out of the holder for continuous engagement. You get a nice, even chamfer all around the hole instead of the football shape you’d see using a standard chamfer tool.”

Here again, multiple grades, geometries, diameters and lengths are offered, and both companies provide application and programming advice to those getting started. While Dean and Baumet might not agree on which brand of deburring tools a shop should buy, they do agree that deburring is a machining process that bears lots of low-hanging fruit.

“There are still an awful lot of people out there doing it by hand,” Baumet said. “Sometimes it’s because that’s all they know, other times because they don’t want to spend the money on a dedicated deburring tool. Either way, there’s plenty of room for improvement.”

Using an automated deburring tool like the Cofa, tedious deburring of small parts by hand can be eliminated for maximum efficiency and burr-free parts. Image courtesy of Heule Tool

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