Why aren't 118⁰ split point drills a thing?

[Jake M]

A little off subject but I have a question. I am a mechanic by trade and I work on a ton of diesels and therefor see my fair share of broken off stainless bolts in various sizes too. Question is what would be you guys go to drill bit for this kind of work? Material, degree and anything else you could add. Also do muy fair share of exhaust manifold bolts where drilling dead center is an absolute must

I keep (the shop keeps) double ended sheet metal shorties in stock for that sort of thing. 1/8, 3/16, and 1/4. We get them from Kimball, but you can get them anywhere really. Usually in the auto body stuff. Essentially they're disposable drills for "crap" jobs. Far cheaper to the customer than averaging in me maintaining my drill bits. Bog standard HSS drills, split point, not a lot of depth to the flutes, Gotta be CAREFUL not to fill the flutes if you're going deeper, but they're stout. Or pilot some, drill some, pilot some more, drill some more. That's often good medicine anyhow, as burying a tiny drill deep in anything in "freehand mode" is best avoided. Once you get the pilot in, any reasonably sharp drill will be fine. I just use straight up high speed steel. We don't (can't....) keep a decent grinder wheel at the shop, so I sharpen with a drill doctor there. Not the greatest edges possible, but plenty good enough. The magic to that is not so much the drill, as stainless actually cuts fine. The magic is feed pressure. You've got to lean on the drill, HARD. if ANY drill stops cutting and rubs, it's game over with the hand drilling thing. That's where the nightmares come from. If you let off the pressure, it'll work harden, and then it's nothing but tears. In a workshop environment, no fixtured machine tools- That means fighting work hardened metal ALL THE WAY THROUGH. Part of the art is knowing when to not even bother fighting for it, and make access so that you don't have to fight, and can keep that required pressure, and never let it harden. .

If your shop by chance does business with Kimball, it's just their black oxide version. Your sales critter will know just what they are.
McMaster has them as well, these are pretty close kin to the ones I use.
Or you can get them ten thousand other places too.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

 

[westerner]

As to broken exhaust bolts in a head- this happened so often in the fleet I maintained, I took the time to build a jig to ensure I could hit dead center on the broken one using the unbroken for location.

 

[RaisedByWolves]

Also do muy fair share of exhaust manifold bolts where drilling dead center is an absolute must

It’s not though, you’re falling into “only tool is a hammer” thinking.

With an air grinder and proper carbide burrs you can get the bolt out whether you start off centered or not.

Sure you want to be able to just drill it out, but having another tool in the toolbox, ie, another way of solving the problem is golden.

I work on outboard motors and can make good money at this as the marinas don’t want to deal with anything older than 15-20yrs old due to corroded bolts.

Having more defined skills than the average mechanic where a corroded bolt will be a showstopper, I just fudge my prices a bit to reflect 1-2 out of 10 motors will have a broken bolt and go from there.

Some might think this is not fair to the guy who doesn’t have broken bolts, but it’s also isn’t fair when I give someone a bill and they ghost me for it being higher than they anticipated.

This way it works for both of us as they get a set price for something no one else will work on, and every now and then I get a bonus when things go by the book.

Which is rare.

 

[RaisedByWolves]

As to broken exhaust bolts in a head- this happened so often in the fleet I maintained, I took the time to build a jig to ensure I could hit dead center on the broken one using the unbroken for location.

Common with dodges.

They even sell the fixture.

 

[GeneT45]

That’s one trick I have learned over the years is tilting to bit to center up on the bolt. I personally have found a good cobalt bit to work the best. I just wasn’t sure if there was anything out there better. I have just purchased some new 3 flute drill bits but have not tried those

You can 'move' a punch mark in the same manner (tip the punch).

GsT

 

[RickKr]

Sharpen them yourself. I used a drill jig I made for this one, mostly,though I sharpen by hand, using a combination of conical and facet grinding.. I use facet points because conical grinding gives a chisel point, no walking with facet grinds..

Nice job. Be nice to see the jig you made. I'm able to do similar 4-facet sharpening using a Tormek sharpening machine, using the Tormek drill sharpening jig (DBS-22). A most useful article on drill point geometry is by Joseph Mazoff. Discovering it and the 4-facet point geometry was a the major motivator for me to buy the Tormek. I had tried a Drill Doctor twice before and hated it.

Below is my first attempt, not perfectly balanced, but acceptable and I was thrilled. Now, as drills need sharpening, I put this type of point on them. However, I cannot think of a time when I haven't first piloted a hole in metal with a center drill and almost always do so in wood as well.

Rick

 

[GeneT45]

Nice job. Be nice to see the jig you made. I'm able to do similar 4-facet sharpening using a Tormek sharpening machine, using the Tormek drill sharpening jig (DBS-22). A most useful article on drill point geometry is by Joseph Mazoff. Discovering it and the 4-facet point geometry was a the major motivator for me to buy the Tormek. I had tried a Drill Doctor twice before and hated it.

Below is my first attempt, not perfectly balanced, but acceptable and I was thrilled. Now, as drill need sharpening, I put this type of point on them. However, I cannot think of a time when I haven't first piloted a hole metal with a centerdrill and almost always do so in wood as well.

Rick

I have only achieved acceptable results with the DBS-22 about 40% of the time. OTOH I can get a 4-facet grind 100% of the time with my single-lip cutter grinder - albeit without the benefits of water-cooled slow grinding. I've thought about making a simple fixture to mimic the setup on my SLCG for use on the Tormek.

GsT

 

[th62]

Nice job. Be nice to see the jig you made. I'm able to do similar 4-facet sharpening using a Tormek sharpening machine, using the Tormek drill sharpening jig (DBS-22). A most useful article on drill point geometry is by Joseph Mazoff. Discovering it and the 4-facet point geometry was a the major motivator for me to buy the Tormek. I had tried a Drill Doctor twice before and hated it.

Below is my first attempt, not perfectly balanced, but acceptable and I was thrilled. Now, as drills need sharpening, I put this type of point on them. However, I cannot think of a time when I haven't first piloted a hole in metal with a center drill and almost always do so in wood as well.

Rick

I posted the jig nere some time ago, here it is again: https://www.hobby-machinist.com/threads/drill-sharpening-jig.107818/

Nice job. Be nice to see the jig you made. I'm able to do similar 4-facet sharpening using a Tormek sharpening machine, using the Tormek drill sharpening jig (DBS-22). A most useful article on drill point geometry is by Joseph Mazoff. Discovering it and the 4-facet point geometry was a the major motivator for me to buy the Tormek. I had tried a Drill Doctor twice before and hated it.

Below is my first attempt, not perfectly balanced, but acceptable and I was thrilled. Now, as drills need sharpening, I put this type of point on them. However, I cannot think of a time when I haven't first piloted a hole in metal with a center drill and almost always do so in wood as well.

Rick

I posted thejig some time ago, here it is again.. https://www.hobby-machinist.com/threads/drill-sharpening-jig.107818/