Drill bit thoughts

[dr sportster]

Some guys when drilling like to start with a smaller bit then slowly step up in size. Seemed normal to me .Then a guy on here criticized saying something like I can look at a guys drill bits and tell he is doing that method and it is very bad to do this to your bits . Holes should be made with the final size drill only according to them. What are your thoughts and experience ?

 

[shaun wallace]

I drill 3/16-1/4 pilot hole when drilling 3/4 up. Seems to help making hole where you want it even tho used starter punch.

 

[Welding man]

I was taught many years ago to step drill when I went to machinist school. I drill a lot of holes. I drilled over 400 yesterday with one 1/4 in bit. I always step drill when using my lathe, starting with a center drill and working my way up. I think it depends a lot on the material being drilled and the size of the hole, I challenge anyone to drill a 1 1/2 hole without a pilot hole. I was told by a drill bit salesman a while back that I shouldn't step drill. I have 4 drill presses and a big milling machine and probably close to 3000 drill bits, so I do what it takes to get the job done.

 

[TJ in KY]

I was taught that the pilot hole should be at least as large as the chisel point on the drill. I always use a pilot hole on and up. With no power feed on my drill press it is helpful especially on thicker steel

 

[Eric in IL]

If you are going to drill a pilot hole, it only needs to be the size of the web on the final drill.

But there are many variations of us living in a perfect world. If you have all the tools of a machine shop at your disposal, you would only drill one pilot when the final hole is going to be larger than one inch. Smaller than one inch, you would probably just drill the final hole.

 

[PJH]

I'm 73 years old and I've drilled thousands of holes. Once in a while I'll accidentally get one drilled precisely where I want it, but it's a rare occurrence and sometimes even a cause for celebration, depending upon the importance of the hole. Having said all that, I always start with a pilot hole. Maybe that's what I'm doing wrong. This discussion will be interesting to me.

 

[MJMJ]

It's worth remembering that there are several members whose primary reason for being here is to tell everyone they're doing things wrong. I wouldn't worry too much about it.

 

[Determined]

When all you have is an electric hand drill an you need a 1 inch hole in heavy plate you do what need to do to get the job done.

Hard on the bits, maybe but they are a consumable item and they can be re-sharpened.

My larger bits have been chipped up and re-sharpened on the grinder wheel more times than I can count yet I still have the same set I purchased 30 years ago.

 

[DIM]

I worked 27 years in a tool room. My job was drilling holes in dies. I drilled all types of steel and from tin up to 15 inches thick.I used different methods for ever jobs.Everyone here may be right. I know if I wanted a slightly over size hole I did not use a pilot hole. Most of time on large hole I used a pilot.
.

 

[cwtech]

I was taught that a pilot drill/hole should not exceed half the diameter of the finished hole.

Example: Pilot drill for a 1/2 hole should not exceed 1/4.

 

[gtractorfan]

Speaking of drill bits I bought these Dewalt bits (pretty expensive) without looking at them before buying. Anyone else have any like this? I don't know how I'd resharpen them the same way without a cutter grinder.

 

[Janicholson]

Correct is a pilot hole just the size of the Web (or core) size of the final size. The Web is the very center of the bit that has the flat, non drilling, point. This allows the larger drill to cut freely and not force its web point into the metal. Stepping sizes close together wears the margins and makes it easy to jamb in the hole. Jim

 

[Eric in IL]

Welding man, I agree about the 1 1/2 hole if you are using a HSS drill.

I used Cor-Bor drills at the shop where I worked. No pilot holes needed. Just program the position coordinates and push the start button. It was so fun and satisfying to watch the smoking chips come flying out of the holes.

 

[rustred]

i was taught the same way Jim. too big of pilot and you screw up the bit. say you drill a 7/8 hole then want a 1 inch hole then use a 1inch bit to to drill it and you will see the bit edges are rounded off. talking like 1/2 to 1 material. even when buying bits the counterman will say not for enlarging holes.

 

[timcasbolt]

(quoted from post at 13:50:22 07/15/22) Speaking of drill bits I bought these Dewalt bits (pretty expensive) without looking at them before buying. Anyone else have any like this? I don't know how I'd resharpen them the same way without a cutter grinder.
<img src=https://www.yesterdaystractors.com/cvphotos/cvphoto130583.jpg>

have a bunch of those type drills. They work very well for drilling thin material. Can't resharpen them without a special machine made for that purpose.

 

[Geo-TH,In]

Depending on how shape the bit is, the metal and if I using a hand drill.
I may need a pilot hole and other bits to get to the final size.
Sometimes soft metal and I can do everything with one bit using the drill press. Always nice to see if I shaped the bit properly when I see two curlies produced by the bit..

 

[retired farmer]

I bought a set several years ago. Used for special occasions.

 

[caterpillar guy]

I suppose it is harder on drill bits and if I'm drilling holes freehand and need a 1/2 or more then I do what I have to which is to drill in steps sure is easier on me. In the drill press I may or may not drill a pilot hole depends on the material and drill as well as size of hole. A 3/4 will go pretty good with no pilot in a drill press with no auto feed.

 

[guido]

drsportster,
Janicholson is correct.
I can tell by the drill bit, if it was used on a too big pilot hole.

One of the ways to ruin a drill bit is having too big of a pilot hole!


Guido.

 

[Mike(NEOhio)]

I was a tool and die maker, 30 years in machine shops. No hard and fast rule here. Do what you need to do to get it done. How rigid is the machine? How much power? Power feed or hand? Material being drilled? I agree with too big a pilot hole but that's because it's easy to push the feed rate which wears the diameter back from the flutes. With a power feed machine it's acceptable.

 

[Welding man]

Proper speed, feed and coolant all will increase bit life also.

 

[Gene Davis (Ga.)]

The Drill Doctor Co. makes a sharpner that will do split point bits like those are.

 

[dr sportster]

So far I have learned pilot hole size matters . Nver knew that good info !

 

[guido]

dr sportster,

Even these tapered reamer drill bits need a pilot hole,

Guido.

 

[mikeb789]

I once did what gtractorfan did- accidentally bought those piloted bits without looking at them. Then I used them to drill a hole in a refrigerator door (that had a glass window) and when it broke through, it slammed and broke the glass. New door costed $500. I will never use that kind of bit again because you can't feel when it's about to go through.

 

[rustred]

exactly! i have the same reply.

 

[rustred]

i can tell also as i said.

 

[mrslesq]

Close to 30 years ago I had my 20 x90 Harvestore converted to use a Big Jim silo unloader. I had to have doors installed every 10 feet up the side to have access to the unloader. The metal door frames needed to have many holes drilled. The guy used self tapping screws to drill the pilot holes. Each screw did several holes. He then used a bigger drill and then a bigger drill (the final hole size). The self tapping screws were fast for drilling the pilot hole. I picked up the old ones and used them for final destination uses.

 

[Brad Buchanan]

Hey Doc. For smaller holes I like to center puch and go at it with hss bit. for larger I sometimes drill a 1/8 pilot hole or even better center punch and then mag drill, cutter and lotes of coolant.

Brad

 

[buickanddeere]

My little brother is a tool and die maker . He claims that as long as the bits are properly sharpened , operated at the ideal rpm , without a wobble ,with the proper pressure and enough coolant . The hole will be a success .

 

[timcasbolt]

(quoted from post at 01:08:06 08/03/22)
My little brother is a tool and die maker . He claims that as long as the bits are properly sharpened , operated at the ideal rpm , without a wobble ,with the proper pressure and enough coolant . The hole will be a success .

hat's all it takes.