Inliners International Forums General Discussion Engines Tapping Cast Iron

I am going to drill and tap the thermostat housing on my chevy 250. I have heard various advice on whether or not to use oil or other cutting fluid when drilling and tapping cast iron. Can anyone provide me with the definitive answer?
Thank you.
Ken

cutting Or tapping fluid will give you a better tread finish over straight oil. But anything is better then trying to tap/cut them dry.

What he said (Larry).

What they said. Try to find a three flute tap if you can...much less likely to break. If you have a bottom to your hole, a standard tap will push the chips DOWN into the hole. Sooner or later they build up and stop the tap. If your hole goes through into a void, the chips will fall into the void (block, head, water passage, etc)

A spiral tap will pull the chips out and let you tap to the bottom of the hole. If you have a thru hole you may still get some stuff coming out into the back side.

Pipe threads are tapered so the part jams in the tapered threads.

Not sure what you're wanting to do with the hole your tapping but this pretty well covers what I know about the subject

When I was taking metallurgy classes in college, the reason given for being able to tap cast iron dry is that it has a very high percentage of carbon mixed in with the iron molecules, which acts as a lubricant when it is cut, filed, or tapped. It's also the reason that when you cut cast iron, you get all that black gunk as residue. It's mostly carbon particles (graphite).

That said, there's no real good reason not to use cutting or tapping fluid when you're tapping cast iron. It will give a smoother cut and have less chance of binding the tap or breaking it. I've been using a product called RapidTap for cutting, drilling, and tapping various kinds of metal since the late 70's, and I can personally swear by it. It works really well. You can find it at any good hardware store, Home Depot, Lowe's, or industrial hardware supply store. Just remember when you're tapping threads in a hole to back the tap off counterclockwise every revolution or two to clear the chips from the hole and to keep the tap from binding or seizing in the hole.

When drilling & tapping cast iron.
You never use any cutting oils,wax etc,nothing!!!! period.

I worked @ a machine shop,that machined Turbonetics turbine housings & other products of theres,no cutting fluid on CNC mill,tapping etc. Do not use any cutting fluid.


Another friend of mine owns a cylinder head shop,same thing,never use cutting fluids or oils on any cast iron etc.

OOHH B.T.W.,,,,
Did I say do not use cutting fluids???

Quote" less chance of binding the tap or breaking "
Wrong!!! using cutting fluids on cast iron will make it grab your tap & break it,do not use fluid for cutting cast iron.
http://books.google.com/books?id=7eaCQoB...num=4&ct=result

There might be some hybrid/special cutting fluids,paste or other stuff,available now,,,but I have not heard about it,anyone?


MBHD

Thanks, Hank. That's a pretty definitive answer, and a good one. I stand corrected. I knew that you normally cut cast iron dry, but I wasn't aware that you COULDN'T use cutting fluid on it.

Don't get me wrong,,I have used cutting oils in the past before I was informed this was incorrect,it worked,but I have broken taps before using cutting fluids & I could tell when using cutting oils for cast iron, it always seemed to grab more.


MBHD

I agree. Another reason not to use it in a CNC machine, is the coolant will make the cast iron dust in the machine rust. Once it mixes with the coolant, it will cause rust spots on parts you run long after you are through with the cast iron job. Plus cast iron dust is very abrasive and harsh on the coolant pumps, and way and lead screws, etc. People that dont work with it very often don't see that aspect of it. I would much rather prefer aluminum or stainless or even Ti over cast iron any day....

I have used the same Tap(4 flute)when tapping heads for the last FOUR years with either tap magic or tap-o tap oil from goodson Gold Formula And I never have had any break or get stuck.Yes i have done it dry on cast iron but the taps do no seem to last as long.
But i do have to agree with CnC dude It will mess up a pump on a fluid system an cause other metals to rust.But I tap buy hand so
no problems there for me.When milling the Boss's out I do with
what is known as a dry cutter end mill/s Another words are ment or can be used For Dry cutting.

But just my 2cents and the way of doing things.

Gentlemen,
Thank you all.
Ken