[mattbesquare]

My drill set is crap, import stuff. I know, I know, save the flaming.

Anyway, as to be expected every single it is off from its spec'ed size, sometimes as much as the next gauge up. I just measure before using them and still have the full range, but measuring is a pita.

Should I not be measure at the shank? Is the shank supposed to be a little smaller than the cutting side? Just making sure it isn't me. Need to find some money to get an accurate set. It is a great starter kit though, I use them a hellalot.

[Bubba]

If the points are ground off center and or the angles on the lips are not the same, you will get the kind of variation your talking about! You need a drill point gage to really see the difference

[Arich0908]

If I understand what your saying exactly the drill bits you are using are not the size they claim to be.
I measure every bit I use and if the hole needs to be an exact size ill use a bit that is smaller then move up one size slightly with a reamer. My bits are the same size no mater if its the shank or cutting edge . Unless its tapered off.
I also have some cheaper over sea tools and I use a pair of digital calipers to measure every one prior b4 use.
I haven't been machining long but ive come to find out prep and precision is 70% of the machining process . Just take a few more mins and make sure you dont want to ruin your work piece.

[mactec54]

mattbesquare

The question you asked, yes the shank is normally smaller than the drill point/ cutting end, so your drills are correct if the size is different on the shank to the cutting edge

[mattbesquare]

mattbesquare

The question you asked, yes the shank is normally smaller than the drill point/ cutting end, so your drills are correct if the size is different on the shank to the cutting edge

alright, a little confused now. I thought drill bits were made with presized rod then spiral cut and 30 degree cutting face?

why would the cutting side be larger and how would i get a good reading on a spiral with no opposite edge? Maybe two plates of predetermined size, zero caliper, load bit and measure? I have a huge collection of reamers I got locally, some new old stock, but not even close to the size of my drill bit box. And after using a center drill bit, then drill, then ream...it is exactly what I do for alignment pins, or pneumatic valves, etc etc, but bolt holes? its a little extreme, mostly I just go to the size it calls for, measure (The shank) then go up or down depending on the reading. Its just a real PITA..

[mattbesquare]

If the points are ground off center and or the angles on the lips are not the same, you will get the kind of variation your talking about! You need a drill point gage to really see the difference

ok, so off center point grind, I could see how that would make the hole off. but I am measuring the bits at the shank, and they are all off. That is moreof the problem.

[japroach]

The cutting portion is larger because you don't want the shaft to rub.

If its an odd number of flutes, you could use something like this: http://www.okokchina.com/Files/uppic...alipers495.gif

[mactec54]

mattbesquare

Its just as easy to measure the cutting end as it is the shank, that is the normal way to measure any tool that you are going to use, with a odd number of flutes it is a little harder to measure, but in your case it's just a standard 2 flute drill so should not be a problem

[Dano523]

A drill bit is always going to drill a larger hole than what the drill bit is.

Even if the bit drill dead center boring, the shavings coming up the bit are going to enlarge the hole/channel.


If you are looking for perfect sized holes/channel, then drill first with a slightly smaller bit, then use a reamer or boring bar to unify the hole/channel to the desired dimension.

[fatal-exception]

Drills aren't precision tools. Just work around their shortcomings if the hole size is that critical.

[mattbesquare]

Alright gotcha, I will continue to undercut and ream as needed.

I knew the hole size issue, which is why I have so many fricken reamers. But was just wondering if the shank matched the cutting threads.

[Dano523]

Not always, since the shank is just the stock bar round to start with, then the drill bit it channel ground, and sharpened, so the cutting edges/flutes can be a tad smaller when it's all said and done then the starting tool rod.

[fatal-exception]

I measured some drills last night, and the shanks equal the exact diameter of the drill, the theoretical drill diameter. Now, they probably don't cut that exact size, but the starting wire is the exact size. These are bright ground bits from Shars.

Paul