Thread: Cast Iron and cutting fluid

Had a big fight with one of the bosses today over me not using cutting fluid to drill cast iron

Every book ive ever read says dry, but what is the reason for NOT using it?

I have my own, but im interested in your answers

CatHead;
You're correct, machine cast iron dry.
Reason is cast iron contains Graphite in it's
structure.
Jamie

I always cut cast iron dry as I was told. It was THE way.

A couple of jobs later I work in a brake caliper mfg. plant and all of the cast iron is cut with flood coolant. Now there are different types of cast, much of ours is ASTM A536 Grade 65-45-12. Stuff cuts like butter and tool life is incredible. We only have bad results when the coolant misses the tools. -Mike

I expect that no matter how much lubricity C.I. has, once you get past a certain volume of material removal (chip load/speeds/feeds), coolant becomes necessary to deal with heat.

Every machine tool made from Cast Iron is cut dry, wether it's milled with a 100 HP planermill or a 100 HP planer using flat tools to create the table top. Every drilled and bored hole is cut dry, sometimes a grease type material was used on big taps, the one's over 2 inches dia, little taps, always used dry.

The only time any coolant was ever used on cast iron is when surface grinding such as a table top and done on a Mattison type machine with a 6 inch wide wheel.

The CNC Way Type Surface Grinding Machines also use coolant, but they are typically only removing a very few thousanths to clean up a milled or planed surface.

The iron Holescreek refers to (ASTM A536) is ductile iron (nodular iron). Its chips don't break as finely as those for gray iron, so coolant is less likely to make the horrible, abrasive, gritty, sludgy mess it does with gray iron chips.

Some parts in machine tools are nodular iron, and still they are cut DRY.

I agree, Gary, dry is the way to go even for nodular. It still leaves lots of dust, just not as bad as gray iron.

If I had high-pressure, coolant-through-the-spindle machinery, I might cut nodular wet, depending on what I was doing.

There's good reason for coolant on cast iron specifically when cooling is needed at the cutting edge and to control part temperature.

When sawing and drilling there is the danger of chips piling up and packing in the clearance space. While this is much reduced in cast iron thanks to its crumbly chips and graphite content the tendancy is not entirely absent. Water based coolant helps separate the chips and cools the cut zone.

When a large proportion of the workpiece has to be machined away in a few rapid operations the may be a rapid heat gain in the workpiece. A water based flood coolant will keep the temperature increase within small limits and the part can be machined without concern for finished dimensions being affected.

Mosly I machine cast iron dry picking up the chips as I make them with a shop vac. When I need to drill deep holes (4X drill dia or deeper) I use a laundry squirt bottle and soluable oil. For rapid stock reduction with HSS cutters I mist the cut zone with soluable oil.

Hard and fast rules soon break down when actual practicality enters the picture. In the case of Turning or machining centers I'd use coolant regardless for temperature coltrol and tool life. Manual machines, only as indicated.

Actually to many people baby the machines and the cutter rubs off the material, but then again I was tought by the people that built the machines, if you have 20 HP or 50 HP at the spindle, use it, the heat come off in the chip.

Precision boring for spindle bearings and gear shaft bearings in headstocks and spindle carriers were done dry, and those were done on Precision Machines like SIP, DIXI and other boring mills.

Cincinnati even furnished as standard equipment on every knee and column milling machine and every Vercipower Milling machine and every CNC machining center a cover for the area that drained the table of coolant so Cast Iron Chips would not clog up the return path to the sump.

I've been machining cast iron heads and blocks dry for 30 years,I've been doing it wrong all this time.The only time I see the sizes change from heat is when I'm honing the bores,and it gets about 10 gallons a minute.

In the shop I work in, we use air to blow the chips & dust away. From what I understand, the dust produced from machining cast iron combined with coolant will produce a fine lapping compound that can sneak past way seals & cause premature wear & other problems. Any thoughts on this? Tom

If you use anything with oil in it to machine CI, you've got a mess. All of ours is machined with fully synthetic coolant. The machines stay clean and there's no dust. We do both gray and ductile.
JR

Where you get the lapping compound effect is really from machining sand cast iron. There tends to be a little to a lot of sand in the outer layer and sometime even pockets of the stuff.

Always clean your machine well when cutting CI. I have always cut dry, but when I went to thread the holes in the base of my mill 3/4-10 I had to use cutting fluid. It helped a lot. Maybe something to do with the Meehanite?

We do a lot of ductile on Makino horizontals. We run all the facemills and slabmills dry. When drilling we use Thru spindle coolant on as much as possible. Alot of the holes can get to 4 and 5 times diameter so it is nice to be able to use an indexible with TSC. We use a full synthetic and don't have any problems.

ive machined lots of cast iron fixtures and had lots of problems using tapered reamers on them dry UNTIL i read my Dads old Machinerys Handbook, printed somewhere in the 1930's.
had lots of information about steam locomotive's and speeds and feed for shapers and planers.
and in the section concerning cast iron it stated to use lard for cutting cast iron.
so i did.
it cut easier and gave a great finish even made the tools last longer.
ther only problem was i had a craving for eggs and fried potatoes, but that lard smelled just like bacon frying...jim

I cut cast iron gears from DuraBar every day. Mineral oil flood is used to flush chips and remove heat from the work area. The biggest benefit is dust suppression. Without flood coolant, the graphite dust clings to the way lube surfaces. Really gums up the machine. I much prefer a clean shop and wouldn't be possible dry cutting iron in the volume we do.

Originally Posted by Holescreek

I always cut cast iron dry as I was told. It was THE way.

A couple of jobs later I work in a brake caliper mfg. plant and all of the cast iron is cut with flood coolant. Now there are different types of cast, much of ours is ASTM A536 Grade 65-45-12. Stuff cuts like butter and tool life is incredible. We only have bad results when the coolant misses the tools. -Mike

What type of coolant are you using? and what concentration?

Originally Posted by Forrest Addy

There's good reason for coolant on cast iron specifically when cooling is needed at the cutting edge and to control part temperature.

Hard and fast rules soon break down when actual practicality enters the picture. In the case of Turning or machining centers I'd use coolant regardless for temperature coltrol and tool life. Manual machines, only as indicated.

This is a good explanation. The main considerations to machine wet or dry would be size control, tool life, how fast you need to get the parts done and what kind of mess you want to clean up. Both types of mess (wet or dry) both suck.

Originally Posted by CatHead

Had a big fight with one of the bosses today over me not using cutting fluid to drill cast iron

Every book ive ever read says dry, but what is the reason for NOT using it?

I have my own, but im interested in your answers

.
..maybe it is just me, if my boss says use cutting fluid I would say, yes sir, no problem sir, how much should I use Sir, Flood coolant ok Sir, and do it, of course I have been unemployed for 5 weeks and won't start my new job for another week. Still being without a job does give you more reason or concern with keeping a boss happy.