RE: [mill_drill] Undersized (5/8") drill bits...
Drills are not supposed to be the exact size of the hole that they will create, they are typically a hair under. Numbered drills are usually .0005-.0015 under. Gauge the hole that is being created, not the diameter of the bit, before you jump to any conclusions.
On Sat, Jun 22, 2013 at 5:09 PM, Vern <n7gtb@...> wrote:
I just measured the bit that I paid a higher price for, with the only 'precision' instrument that I have at the moment (i.e., Mitutoyo dial caliper # 505-626). Nearly as I could measure, it is 0.6235 across the cutting edges, and 0.6225 across the flutes midway up. Finally, at the opposite end of the cutters, it measured 0.6215".
The bit is stamped "USA", and bears the capital 'M' for Morse Cutting Tools. The plastic yellow box it came in, reads: "MORSE CUTTING TOOLS". On the next line is: "LIST:1424S 5/8 2-TONE S&D"
Sent from my iPhone
On Jun 22, 2013, at 3:04 PM, Rick Sparber <rgsparber@...> wrote:
I agree. Buy the best quality you can afford AND keep them sharp. I use a Drill Doctor which centers the point. An off center point will cause the drill to cut oversized.
On Jun 22, 2013, at 2:46 PM, Guenther Paul <paulguenter@...> wrote:
Well all i can say buy good bits. Nor form HF or china. There are American made bits and are on size. I had some china bits they don't even drill hard wood don't know how i git them but they are in the junk now
I would take to heart what RICK was telling you about the Drill bits.
I don't believe that you can buy a bit in a store that is "accurate". In
that I mean to say within .003... If you stop and think about it? All
of the drill bits and nuts and bolts that you buy now days in stores like
Home Depot, Lowe's, Harbor Freight, are mass produced by the Gazillions
and like the 5/8 bits are close.. That is the KEY Fraze here.. They are
CLOSE. But, as Mr. Sparber said. To get right on, you need to go to
a boring bar or a reamer..
Vern,Drills are for "knocking through holes". If you need precision, follow up with a boring bar. If you want smooth walls and precision, I follow the boring bar with a reamer. RickOn Jun 21, 2013, at 8:23 AM, Vern <mailto:n7gtb%40yahoo.com> wrote:> The other day, I had drilled a hole in an aluminum hub I had recently cast. When I attempted to fit it onto a 5/8" shaft, I discovered that the hole was undersized, so I measured the bit...I was surprised to find that it was 0.004" undersized. I later purchased a 'quality' HSS 5/8" bit from a local 'tool' supplier, thinking this would be better than the previous one from the big box hardware store. It too was undersized at 0.6225"...> > The second bit cost, was as much as the entire set that had the first, but doesn't appear to be any closer tolerance than the first. Is this a consequence of overseas production, or am I simply making false assumptions here?> > Thanks,> -Vern> > Sent from my iPhone> > ------------------------------------> > Yahoo! Groups Links> > >
- BS328 part 1 (Specification for twist drills), which is equivalent to a number of ISO standards, gives the cutting diameter of a drill as measured across the lands at the outer corners as h8. Back taper is between 0.0002mm and 0.0008mm per millimetre linear distance from the outer corner towards the shank. The total back taper not to exceed 0.25mm. Below 6.0mm back taper is not a requirement.
I imagine that all other drill standards will be the same as, or very similar, with regards to these dimensions. Just divide by 25.4 for inch equivalents and you should be close to USA standards.
--- In email@example.com, Goran Hosinsky <hosinsky@...> wrote:
> Searching Ebay (the German one) for a missing drill size (metric) I find
> that they offer two types of HSS drills: Rolled or ground, the second
> one being the more expensive. Might there be a difference in precision
> between the two types - and could that be the explanation of the start
> of this thread?