drill a bolt

Grade 8 bolts drill nicely. In fact I will do the same today.

i

Its a steel bolt.

I hope you're right. This is a metric button head fine thread. Won't be easy to find another. Murphy is my partner. I wouldn't even ask if i had a practice bolt or two.

Karl

Unlike US alloy socket heads, metric socket heads come in different grades. The most common (class 12.9) is similar to US alloy socket heads, and perhaps 5 points harder than a grade 8 cap screw on the Rc scale.

It depends on the material Karl not the rating as a bolt. Carbon steel and Stainless are both avaliable in grade 8.

Got a trick to keep from breaking bits on the back side?

Then you'll be good with a HSS Split point drill at 40 SFM and oil for a lubricant. Keep a good bite on your drill but it won't work harden and peck often as you refresh the cutting oil. The real difficulty is breaking through the far side. Snug up the Z axis clamp a little and pay attention. LOL

So what's the size? Maybe one of us has a spare for you laying in the junk drawer :-).

----- Regards, Carl Ijames

Squeezing my butt cheeks together didn't seem to help, not the drill anyway. Snugging the Z at the end will keep the drill from grabbing and that's the problem. On a manual machine, the spindle will release any slop or backlash as you break through and drills turn into wood screws in a hurry.

I saw a guy rapid a drill an inch or more into an aluminum part once and when the spindle came up, the drill stayed - unbroken - in the job.Ruined the collet. The part was a mold cavity so somebody had to figure out how to get the thing out. I'm glad that guy wasn't me. The thing I've wondered about since is where the aluminum went? The drill and the stock couldn't have occupied the same space but it sure looked that way. LMAO

And technically, there is no such thing as a metric grade 8. There is 4.8 steel , 5.8 steel, and 8.8 steel as well as 10.9 and

12.9 steel There is A2 and A4 stainless (304 (or 305) and 316.

Drill and thread a block of sacraficical material (I'd use aluminium). Thread the bolt in, drill through both.

I have to drill safety wire holes in a dozen bolts every month or so. I have a jig to line it up and use an air drill.

I bust an HSS bit nearly every time, not bad for 36 holes. Since it always breaks finishing the hole I can usually drive it back out with an automatic centerpunch followed by a pin punch.

Also I don't think the button head mentioned are made in 12.9, I think they are only made upto 10.9, maybe due to the smaller socket limiting the tightening torque possible. The supplier should know.

EDR

make that "EDM".....

Slow, messy, but does not care how hard it is...

David Lesher fired this volley in news:h4n5jo$hnm$3 @reader1.panix.com:

I guess most folks are lucky enough to have sinker style EDM shop nearby. The only two in my area are wire machines.

But... I can buy a Rockwell drill bit via overnight web-order, and do the job faster and cheaper than taking it out somewhere.

Or, I can anneal the bolt, drill it, then take it to any one of eight or ten heat-treating shops around here.

LLoyd

Back up the workpiece with a bit of scrap steel or even aluminum. The workpiece (and the backing beneath it) should be in a vise.

Yep, that's my experience as well. (Butt cheeks squeezed tight or flappin' inthe breeze)

They should have a hole popper. Those are very fast so you shouldn't have to spend much.