drilling cast iron - need some advice

[david c.]

Hi guys -

I have a sweet old pair of cast iron chairs that I picked up at a garage sale for $5 apiece. I am going through the wire brush/wire wheel routine. PITA but it will be worth it. Anyway, I want to put these on my front porch, which is covered in tile. I already know the chairs will rip up the tile, so the plan is to drill the bottoms and bolt in some nylon slides. I got some black carbide drill bits but the chairs are holding fast. I have dulled two bits without drilling one (of the eight) holes. Any advice? What kind of pressure should I be putting on the bit? Should I use any oil? I'd love your collective wisdom. Thanks is advance.

David

[masraum]

Actually, disregard. Apparently you don't want oil for cutting cast iron.

http://www.practicalmachinist.com/vb/general/drilling-cast-iron-232319/#post1650685

There is enough graphite in cast iron to act as a 'lube'.
Do not use oil as the chips will stick in the hole and the tap will break when backing out.

Compressed air sent via a 1/8 or 1/4 inch brass tube attached to an air gun will remove chips. Wrap a rag around the tube or at least wear gloves. The chips will come out so fast they will penetrate skin. Wear safety glasses or goggles.

If drilling by hand, say a #7 for a 1/4-20 tap you better predrill with a smaller size. Drilling by hand will not be rigid enough and the hole will be oversize. Usually the case if it is Mehanite type cast iron for a machine tool. Cheep import iron is easier to drill.

Drill it using 60 to 80 Ft/min cutting speed with HSS Drill

[look 171]

Use regular High speed steel. Pick em' up from a good hardware store for a couple of bucks is all you need, much better then most fancy drill bit products out there. Cast iron is a little harder then Maple so go slow and use a center punch to get started to prevent walk. How big are these holes?

[look 171]

WD 40 will do, no need for special oil because cast iron is pretty soft.

[masraum]

Drilling holes in cast iron with portable drill

Drilling Into Cast Iron

Apparently, it should be pretty easy. I can only imagine that you did what I've done when drilling metal in the past and had the drill going way to fast.

[Evans, Marv]

If they will be setting on tile (ceramic/vinyl), I don't understand why you need to go to the trouble of drilling & bolting sliders on them. I would think the simple felt adhesive pads you can get in stores or Costco (a set of different sizes & shapes) would be just as good. I've used them on lots of different things, & they always seem to work very well. Simple & effective.

[david c.]

Thanks for all the tips guys. After ruining about four drill bits and getting nowhere, I decided to go to Home Depot and start looking at what sorts of glue on sliders I could find. I haven't found what I need yet because this is for outdoor use (so the felt ones won't work), but sort of a plasma cutter or some sort of laser I'm not getting eight holes through these old chairs.

[Esel Mann]

Double check the drill direction! Especially if someone else could have used it since you last did.
Also for whatever the reason i too have gotten mixed results with the cheaper bits from hd or lowes when drilling cast iron, steel, etc

[rusnak]

Tile on a front porch? Wouldn't it be easier to place an area rug where the chairs are going?

[Evans, Marv]

How about using epoxy with those Teflon sliders?

[cstreit]

Ive never had a glue on or stick on slider last for long, always comes off. I'd want to bolt them on too Fwiw

[sc_rufctr]

Are you sure it's cast iron?

It's soft compared to just about any other metal. You should be able to drill it with ease.

[Aragorn]

Rather than drill cast iron, couldn't you just use something like plasti dip to coat the bottom of the legs? Would offer some form of grip to the tile and should be non-marring. Works pretty well on tool handles.

Coatings and Adhesives, Rubber and Plastic Coatings | Plasti Dip Interntional

[gtc]

JB weld the sliders to the feet.

[red-beard]

First: I expect you have Wrought Iron, not cast iron, unless it is super super cheap stuff. Impurities in cast iron make it brittle. Wrought iron is nearly pure and doesn't rust as easily.

Second, you always use lube when drilling to cool the cutting tool. Overheating a cutting tool will dull it quick.

[david c.]

Wrought iron indeed! I'll send some photos. The JB weld idea is a good one - I'll give it a shot.

[356racing]

To drill wrought iron I use a tig torch to get the area near molten, let it cool enough to handle and drill away with low speed and cutting oil.