See Hand Scraping in Action (Video)

Have you ever heard of hand scraping? In my experience, even if you’ve heard of it, most people have never seen it in action. Having performed hand scraping for many years now, I can tell you – it draws a crowd! That may be because it looks rather odd. But the importance of this step in the CNC machine building process cannot be underestimated.

Simply stated, a machine tool that has not been hand scraped will never work properly. And Okuma is one of the few machine tool builders left who even do hand scraping.

Hand Scraping: Why Do We Do It?

Take a look at the video to watch hand scraping in action. As you can see, there’s a lot of craftsmanship involved, and we spend a lot of time in training to get this right. This may make you wonder, why do we do it?

• The purpose of scraping is to make the mating surfaces flat – flatter than a machining center or CNC lathe can achieve. So essentially, we’re scraping down the high and low spots that are a natural part of any machine’s component casting process.
• The goal is to establish 8 ¬ 10 bearing spots per square inch on the mating surfaces and create high and low spots so the part will not rock.
• At the same time, we’re also adding strategically placed high and low spots to create oil pockets so that when the machine starts up, it’s not starting with bare metal-to-metal ¬ we create a surface that holds lubrication.

We have specialists in Japan who hand scrape on a daily basis as a part of the machine building process. Here in the Americas we have several people who scrape components as well. This is done when we “configure to order” for customer’s specific requirements (adding options, etc.). We also hand scrape replacement components for customers’ machines that may have been damaged or worn out.

What Happens If a Machine is Not Hand Scraped?

Without scraping, a machine tool will never move properly. This is because if you have two mating surfaces that involve metal-to-metal contact and are not flat, they’ll stick, even if you have lubrication applied. Friction is your CNC machine’s enemy. Without hand scraping, you’re setting up the machine for a lifetime of wear and tear, every time you use it. This makes it more difficult to maintain accuracies and tolerances, and the machine simply won’t function as well as it could.

Scraping is the backbone of Okuma machines and is the critical foundation that makes it possible to enjoy many years of high-performance CNC machining. It sets the stage for accuracy, levelness, and allows users to achieve close tolerances consistently.

What do you think of the video? Comment below and share your thoughts, or contact us or your local distributor if you’d like to learn more.

Robbie Williams is Junior Applications Engineer, Okuma America Corporation.

[For a more detailed review of this process, check out our Hand Scraping white paper.]