Today’s Machining World Archive: January 2006, Vol.2, Issue 01
Dear Shop Doc.,
We are a multi-spindle screw machine shop with Wickmans and Davenports. We have a job running 3/4” diameter, 1.5” long, drilled, tapped and formed parts on aluminum 6061. It’s a one-time job running one million pieces at an hourly rate of $75.00 per hour. My problem is we keep getting long stringy balled chips, which bind the machine up, producing bad parts. Right now we are running the job on the Wickmans using oil coolant. Would using water-soluble coolant get rid of this problem? Are there drawbacks to using water-soluble coolant on a multi? What should I do?
Dear Oil Bind,
If you’re having a ball problem with your chips, you may want to run water-soluble coolant because it will run better and faster to break the chips up, and the quality of your parts will improve. Also, your tooling will last longer with water-soluble because when you use regular oil, the chips ball up around your tooling, so the coolant isn’t able to cool your tools down. Water-soluble coolant will flush the chips away. Also, water-soluble coolant is good for when you want to recycle your chips. You will not have to spin them to get the oil off before you sell them.
However, when you decide to use watersoluble coolant with a multi-spindle like a Wickman or a Davenport, you’re making a great sacrifi ce. Water-soluble coolant is going to damage your spindle bearings, slides, holders, bushings, shafts, indexing head, or stem (on a Wickman). You will eventually have to pay to replace these things, and it’s even possible to destroy the casting of a machine, leaving it irreparable. There is some lube oil that will not mix with the water-soluble that will protect your machine some, but not enough.
Before you switch to water-soluble coolant, which you know will damage your machine, you owe it to yourself to try a few alternatives to break up your chips. Sometimes increasing the feed-rate on insert type drills, such as those made by Allied, will aid in breaking up chips for a drilled hole. Boyar Schultz makes an oscillating drilling attachment, which could aid in thinning the drilled chips. Strategies such as gashing cams (on Davenports, not Wickmans) will thin the chip where form tools are used.
If alternative methods such as these already suggested still do not produce your desired quality, your decision simply comes down to economics. This job sounds like it could be awfully lucrative, so it could be a good business decision to sacrifice a machine and run watersoluble. If you decide to do so, you probably will want to use a Davenport rather than a Wickman because the machines are a fraction of the price.
Sometimes you have to spend money to make money. Try some alternatives, then do what you have to do to make money.
Shop Foreman, Graff-Pinkert & Co., Oak Forest IL