An ounce of prevention

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by Tim Wilson

Cutting tool maintenance avoids problems before they become serious issues

Tool maintenance doesn’t get the attention it deserves. With shops focused on production, daily tool maintenance tasks–many of them straight-forward and economical–are often ignored. It’s a shame, because a proactive approach can save a lot of headaches.

“You can improve tool life by having a good tool holder,” says John Mitchell, general manager at Tungaloy Canada, Brantford, ON. “We see a lot that are three years old. The pockets start to get worn, and the insert can move, which shortens tool life. It’s not a lot of money– only about $100 for a lathe toolholder.”

It’s important to get this right, because you want maximum force when the tool is pulled into the spindle taper, and for that to happen the holder should be seated for full taper contact, free of contamination. The key is to create a culture with an eye to detail and cleanliness.

“I am in the field a lot, and tell people to keep the clamping board clean,” says Mike Roy, general manager at Schunk, Mississauga, ON. “This can be a rag wipe off a visual inspection, to make sure all the grease and residue is out of there. For many people, this is still a manual process to put the tools in and clamp them.”

Schunk has its Tribos precision toolholding system for clamping tool shanks, which automates the process via the company’s polygonal clamping technology. This can make tool maintenance easier by ensuring flexibility and quality, but it is by no means the norm.

“Most people will do a manual preset of the tool,” says Roy. “There is so much fine adjustment, and for them to automate would be redundant–they would have to go in and adjust it later anyway.”

Good habits are easy to come by. After every job, the spindle socket surface should be cleaned with a light oil to prevent rust. Remember that the tool crib or tool cart have to be kept clean, too. A paper towel or dust-free cloth should suffice. This is also the time to do an inspection.

“The main thing is to check the cutting edge for chips,” says Daljit Gahir, manager, technical support and sales, Modern Tool in Calgary, AB, a distributor with operations in BC, Alberta, Saskatchewan, Ontario and Nova Scotia. “After roughing, do an end zero code and a bracket tool inspection. I would advise operators to make this part of their routine. If you make a chip and it digs into a part, you might have to scrap it.”

Often, operator experience makes all the difference. Even well-trained younger workers need to be taught the importance of staying on top of things. Machines will have load meters for spikes–indicating an increased risk of an insert breaking–but having an experienced hand around can make all the difference, with problems addressed without a mandatory ‘M00’ program code stop.

“An older machinist will know if a chip is really good by the sound of the machine,” says Gahir. “He’ll know the right speeds, and will get the best cut and performance without burning an insert right away.”

Inevitably, there will be signs of wear on toolholder tapers, and here a power-brush wiping system can help. These are automated, with tapered brushes, and usually cleaned using ultrasonic systems. There are also devices for checking the pulling power on a machine, which is a good way to check for problems with the spindle system, which, left unchecked, could result in catastrophic failure. Sadly, many shops aren’t taking these steps in preventive tool maintenance.

“Inserts are such a small spend, a lot of shops run their machines without even thinking about them,” says Mitchell from Tungaloy. “But if they pay attention, then the carbide holder will last a lot longer. The same applies for milling cutters. If you over-run a milling cutter, it allows movement, and once you have movement, then your tool life will be dramatically shortened.”

The truth of the matter is that optimal power transfer and tolerance are reliant on the most accurate holder position. If you want the best surface finish, it is critical to reduce vibration and runout. Even the smallest chip left in coolant swarf can adhere to a toolholder taper. And that can lead to catastrophic failure. SMT

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