Randy McEachernClick image to enlargeBy Randy McEachern

Chip control is critical in drilling operations

 

To better manage your chips in drilling operations, first, review the chip formation. You should drill one or two holes, stop the process, review the chips, check the hole size and finish, then make any required changes to the drilling process. Understanding different characteristics of indexable insert drills, solid carbide drills, and exchangeable tip drills is important to ensure good chip control and a reliable drilling process.

Managing chips with Indexable insert drills

  • Most indexable drills have only one insert working at the nominal diameter, therefore is considered by some to be and unbalanced cutting action. Each flute will produce a different shape chip, usually a cone shape from the central insert, and C's or 6's from peripheral
  • Improved chip evacuation is initially achieved by improving chip formation. When examining chips on indexable insert drills it's important to identify there will be differing chips produced from the peripheral and central inserts.
  • Long chips may cause chip jamming in the drill flutes. Also, the surface finish may be affected and the insert or tool may be at risk. The goal is to have short chips in a C or 6 shape.
  • You can shorten chips by selecting the right insert geometry for the specific material being drilled, and adjusting cutting data accordingly.
  • Geometries designed for long chipping materials with gummy characteristics, such as low carbon steels and stainless steels, are usually designed with a deep chip breaker, sharper cutting edge, and intended to run at low to medium feed rates (0.002 – 0.006 in. depending on diameter of drill). Use caution not to over feed this type of geometry which will produce a long straight chip and can wrap around the tool.
  • Other geometries suitable for a range of materials may have a medium depth chip breaker, very strong reinforced cutting edge and will function in a broader feed range from low to high feed rates (0.002 – 0.013 in.) depending on drill diameter). These will offer good chip control in most materials, and are the first choice for unstable conditions and interrupted cuts.
  • Feed rate is the most significant factor in achieving good chip formation, and speed can be used to optimize smaller changes to the chip. Speed is a also an important factor to determine tool life.
  • It can be difficult to eliminate the continuous pigtail style chip from the centre insert. The best case is when the drill achieves a cone on the centre insert and 6 or 9 shape on the periphery insert.

Solid carbide & exchangeable tip drills;

  • With solid carbide or exchangeable tip drills a symmetrical tool provides a balanced cutting action and produces similar chips from both flutes. You will have slightly different chip shapes than indexable drills.
  • Many solid carbide drills and exchangeable tip drills may have dedicated geometries for specific materials, and others will have an optimized geometry designed to work well in a range of materials. It's important to use correct cutting data for the drill selected in your operation.
  • The goal is to achieve a chip with a 6 or C shape for good evacuation and hole quality. There will always be some pig tails at the start. If the chip is unacceptable, increase the feed remaining within the recommended range for the drill.
  • Oncee you have the correct size and shape, take a closer look at chip condition.
  • Scartch marks on the chips influence the hole quality negatively. Check the feed rate; the probable cause is too high a feed. When possible, change to a more suitable geometry.
  • The starting chip for solid carbide and exchangeable tip drills can give insight to problems with the operation. If the chip has needles on the periphery, there may be an issue with unbalance in the drilling process. Causes: runout, incline entrance, high feed, or unstable or weak conditions, which will lead to corner breakage or wear.
  • Hydraulic chucks are the first choice for reducing runout, eliminating vibration, and providing balanced cutting action.

Summary:

  • Use the shortest drill possible for good stability.
  • Select the correct geometry for your material and application.
  • Review the chips and optimze feed rate for good chip control.
  • Reduce runout and vibrations by using proper drill holders (ISO 9766) or
  • hydraulic chucks.

Randy McEachern is product and applications specialist for holemaking and tooling systems, Sandvik Coromant Canada Inc., Mississauga, ON

 

Canada's Gold

by Andrew Brooks

Canada’s mining industry has its ups and downs, but a positive value proposition will always bring work

Tapping into an Untapped Market

By Mary Scianna

Paul Ellery, owner of Ellery Manufacturing, a 34-year-old Surrey, BC, machine shop has had so much trouble finding good skilled machinists for his CNC shop that he’s hired head hunting companies in Toronto, the UK and the Philippines.

CBN inserts for sintered metal machining

Tungaloy Corp. has extended its TurnLine range of Mini T-CBN inserts to incorporate a BX470 insert grade. The line is capable of boring diameters as small as 4.5 mm with indexable inserts. The BX470 grade designation has been added to the Mini T-CBN line for the effective machining of sintered metals.

The future for manufacturing?

New "Smart Helmet" for industrial work enviroments

Inside the factory of the BMW 7 series

The BMW 7 Series is an automobile model developed by the German manufacturer BMW. This series is the high end brand, representing what BMW does the best in comfort, technology and mechanics. There are six successive generations. The first named E23 was released in 1977 and the E32 released in 1986, the E38 in 1994, the E65 in 2001, the F01 in 2008 and the current G11 in 2015.

Skilled Labour to the Rescue

By Michael Ouellette, editor

Threading, Three Ways

by Kip Hanson

Time-saving alternatives to traditional threading techniques

Clearing Chips

by Kip Hanson

Still struggling with bird nests? It might be time for a different toolholder and a different pump.

High Speed Milling: Furiously Feeding

by Kip Hanson

Three cutting tool providers offer advice on high feed milling

WATCH: Engineering projects you don't want credit for

WATCH: World's funniest engineering fails. Who approved these blue prints?

Stringer Success

Article by Kip Hanson | Photos by Deny Cardinal

Quebec aerospace manufacturer expands aluminum machining capabilities with extrusion mill

Welding Titanium

by Shaun Relyea

Know where the difficulties lie and prepare for them

Balancing the Value Chain

by Michael Ouellette

Powerful Machines on Another Level

A roundup of seven systems that put in some impressive work.

5 Ways to extend cutting tool life

by Mary Scianna

Save costs and improve machining performance

Stay In Touch

twitter facebook linkedIn