Cast Iron Woes

Inner10

I can't shoot it, I ruin my bits drilling it, and I loose my head with Teks...what do you guys do?

I did a job a while ago in an old church with cast iron poles (about 25" circumferance). I piped my conduit down em by drilling a small pilot hole and enlarging it until I could pound in a lead sheild. Every time I tried a HexTek I kept snapping the tops off, I didn't even try to shoot it since I figured it would shatter. I was thinking of using an adhesive, but that doesn't allow a nice tight fastening...any ideas?

Now they want their 30+ pound speakers mounted to the pole. I was going to anchor steel strut to the pole then bolt the speaker bracket onto that. The issue is I need either an innovative way to anchor to the iron or a strap of some sort to fasten the strut to the pole.

Any ideas?

Teetorbilt

Cast iron is relatively soft although it can contain clinkers which can be very hard on drill bits.

Try and find some Black & Decker Bullet bits. They're TiN coated and will cut great for a while.

Keep the speed down to around 250 RPM, turning the bit faster actually slows down the job. Cut cast iron dry.

To mount speakers I'd drill and tap for bolts. Don't over-torque and use LocTite against the vibration caused by the speaker.

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Bob Kovacs

Use the band clamps that they use on metal traffic signal poles- they'll hold far more than 30 lbs, and install far easier than drilling and tapping. Just don't ask me where to find them....lol

Railman

Use cobalt bits. They are excellent for cast iron. They can be found pretty much anywhere these days. Don't confuse the Low's "Cobalt" brand of bits. You can also drill at much higher rpm with cobalt bits. They are harder, but more importantly, they can take extreme heat.
Joe

Inner10

I've been using Hilti Cobalt bits (best ones they have). I've been drilling em dry yet at high speed, they dull the bits pretty fast.

Tapping is out of the question I can't even put two turns on a tek screw this stuff is beyond hard. When you drill it, it chips off into powder...and it drills slow.

The straps are a fantastic Idea, I was looking for a clamp like the sprinkler systems yet the traffic light style is even better...just have to find em!

Railman

If cobalt don't cut it, I'd try solid carbide. 1/4" is a common size, & then use an expandable anchor.
Joe

Inner10

Who makes a good carbide bit? Any suggestion on the anchors? The lead sheilds have been working best so far, its a seriously thick pole.

I'm still leaning towards the strap solution, this is a structural component of the 100++ year old building so I don't want to pepper it with holes or god forbid have the aged iron crack.

naptown CR

cracking would ruin your whole day maybe even year

rustyjames

I also think a stainless band clamp would be the best way to go. You can probably get them through Grainger or McMaster-Car.

Double-A

Don't do that! Drills work great at high speed into wood, but read the manufacturer's specs on drill speed and you're gonna find they recommend a lower speed to prevent heat build up, work hardening and dulling as a result.

Yes the bit seems to go in faster, but they quit working properly just as fast.

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"My clients’ wishes are the center of my attention." -- David Guido, a contractor in Woodstock, N.Y.
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