Low cost vs. real cost

Courtesy of Dapra What is the real cost of a cutting tool when it is applied? Carefully controlled tests provide the answer.

One of the perennial issues in metalworking is the cost of cutting tools. Many tool manufacturers promote low-cost tools or “free” cutters with the purchase of inserts with the idea that their use can save shops money. However, what shops should be asking is: “What is this free cutter actually costing me?” or, “Is this cheap insert really saving me money?”

Initial savings gained by using a free cutter body or a low-cost insert can frequently affect performance by sacrificing tool life or cycle time. Upgrading to a high-performance tool will likely cost more per edge initially—sometimes significantly more. How do you determine if a specific cutting tool is a good value for the shop?

Determining the answer is not easy, unless you have the support and knowledge of a qualified cutting tool manufacturer and representative and an accurate in-house calculator designed to weigh the pros and cons of each cutting tool option. In either case, the inputs must be carefully measured, with the ultimate goal of using the results to lower cost per part.

Most cutting tool cost calculators are spreadsheets that measure all pertinent variables in a cutting application. For example, Dapra uses a spreadsheet that includes the metrics outlined in Figure 1. These metrics are often interrelated. The goal of a test report is to measure the variables involved to make an accurate determination of any cost savings.

Figure 1. Variables included in Dapra’s cutting tool cost calculator.

Workpiece material and hardness

Shop labor rate

Operation (application type)

Machining time cost

Coolant use

Cost per insert

Machine type, hp

Cost of edges in the cut per load

Spindle taper and maximum rpm

Number of indexes needed to complete

Cutter styles being compared

Time required to index all inserts

Insert styles

Tool change time cost

Gage lengths

Tooling cost total

Coating types

Job cost (tooling + indexing + machine time)

Number of flutes (actual and effective)

Dollar savings on the job

Cutter diameters

Productivity improvement