[AT] Drill bits for drilling our old tractor steel and iron.

Fri Oct 25 14:22:52 PDT 2019

I get my drills form places like Harbor Freight, or Lowe’s. I don’t break very many drills, but if I do, I don’t worry about it. I always get the Cobalt drills, they do last longer. You’ll find that the ones that break are usually the smaller sizes, which makes sense since they can’t take as much pressure when you start pushing a little. 

I worked in a tool and die shop during college and mainly ran one of the huge drill presses. I was really good at it and most of the tool makers brought their jobs to me. The shop owner actually went out a bought a brand new drill press for my use. Nobody could figure out how I was able to drill pocket holes from the back side of a multi-angled piece and make it come out perfectly perpendicular to the front face. It took some time to set everything up, but other than that it was really pretty easy to figure out. I never understood why they didn’t know how to do it themselves, and I never told them how I did it.

Some of the drills I used were large, expensive, and made for special applications. It cost a lot to get them sharpened, especially the pocket drills and specialty drills, they all were sent to a special shop for sharpening. It was important to keep them sharp and the only way to do that was to control the drill press speed and adjust the automatic feed properly. The bigger the drill, the slower the speed and feed.  The drill press also had an automatic lubricator that recirculated lubricant from a sump to the table and back again. Never had any sign of smoke while drilling, so I wasn’t abusing the drills. But it did get messy at times and if the lubricant wasn’t changed out regularly, mold would start to grow and it would start to really smell.

The key thing when using drills is to avoid excessive pressure, whether you use oil or not. Smaller drills will bend slightly under pressure and give you a slightly oversized hole, or one that is not truly round. The drill may also get a permanent bend. When I use my drill press I don’t pull on the handles a lot and just let the drill do it’s thing. Sometimes I will let up on the pressure for a second or two and then reapply slight pressure. It takes a little longer to drill a hole this way, but the holes are cleaner and the drill doesn’t get too hot. The harder the material, the slower the speed and the less the pressure. It also helps to drill smaller starting holes when drilling harder metals, then increase the drill size a little at a time until you get to the desired size.

Sharpening a drill is not a big deal if you understand how to get the right angles and make sure both cutting edges are the same length. When I was in ninth grade shop one of the tools we made was a gauge for checking the angle of a drill edge. I still use it today. One key thing when sharpening a drill is to use slight pressure on the grinding wheel so as not to generate to much heat. Just a slight touch at a time will get you good results. Make sure to get the right angle on the back side of the cutting edge. If you don’t, it won’t matter how sharp the cutting edge is, it won’t bite into whatever you’re drilling.

Not all resharpened drills will keep an edge like a new drill. The manufacturers sometimes temper the cutting edge a little and the rest of the drill will be slightly softer. I’ve seen drills that snap when they get stuck in a piece of work, and then seen others that twist the flutes almost straight when they get stuck.

----- Original Message -----
From: rbrooks at hvc.rr.com
To: 'Antique Tractor Email Discussion Group' <at at lists.antique-tractor.com>
Sent: Fri, 25 Oct 2019 16:01:59 -0400 (EDT)
Subject: Re: [AT] Drill bits for drilling our old tractor steel and iron.

Steve

Did you figure out why the resharpened bits did not fair as well?

Bob

From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of Stephen Offiler
Sent: Friday, October 25, 2019 8:08 AM
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Subject: Re: [AT] Drill bits for drilling our old tractor steel and iron.

I've done some work in this area, Dean.  Here's the long version:   my company (Central Tools Inc) makes a variety of dial indicator sets.  We have some dial indicator mounts based on Vice-Grips.  Here's a link:

https://www.centraltools.com/6450-brake-rotor-ball-joint-gage.html  

Note in the image a black block pinned to the Vice-Grip.  That is where the dial indicator support (our "Flex-Arm" is shown) attaches to the Vice-Grip.  We have to drill holes in the Vice-Grip to pin the blocks on.  And we have drilled a LOT of holes in a LOT of Vice-Grips.  We've offered this set for many years.  It was an old established product when I joined the company 23 years ago.

Getting to the drill bits:  we use cobalt.  They don't last terribly long; we get somewhere around 50 holes per bit.  Purchased in quantity, the bits are only about $1.75 each so about 3.5 cents per hole.  We have a guy who likes to resharpen them in his spare time, but it's actually more economical for us to toss them.  Resharpened bits only go 15-30 holes and his labor costs as much or more than a brand new bit anyway.

Not long ago we conducted a big experiment to see if we could find better drill bits.  Understand that we use a fixture on a drill press; this is not a rigid CNC setup; therefore we cannot use carbide.  The best modern non-carbide drill bits use powder metallurgy to create alloys with properties you can't get with traditional metallurgy.  Vanadium is one of the critical factors.  If you Google "powder metal drill bit" you'll find them readily available.  The cost is definitely at the "Snap-on" level.  The ones I experimented with were ballpark 10X the cost of my cobalt drills, so I'd need to make 10X the holes to break even.  Results of that experiment:  the powder metal drills lasted, at best, only modestly longer than the cobalt.

Steve O. 

On Fri, Oct 25, 2019 at 3:12 AM <deanvp at att.net <mailto:deanvp at att.net> > wrote:

The closest drill bits I have that I would call decent are a set of reverse direction drill bits made by Irwin that are Cobalt.  I’ve used them for removing broken off bolts, etc. but even those are not worth writing home about.  On grade 5 bolts they are ok but on really hard stuff they don’t cut the mustard. Cobalt drill bits do have a negative and that is they are very brittle. But…  what brand and version of drill bits have you guys found that are better than the average bear and work good on our old iron which seems harder than the current stuff. I’m fed up with my multiple indexes of drill bits that might work in wood if I was patient. On steel a nail might work better. :-) I know its going to cost and I’m prepared for that. What is the “Snap-On” of drill bits?  What have you had a long and successful relationship with.  However, I am convinced that no matter how good they are I will break anything less than 1/8”  So a set from 1/8 to ½” in 1/64th “  increments is about my style. Or as an alternative. What drill bit sharpener do you recommend? I do have a lot of drill bits that could be sharpened. Not sure some of them are worth it though.

Dean VP

Snohomish, WA 98290

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