Metal Burrs...
Joe AutoDrill
We were discussing why there is a larger burr on the back side of a manually
drilled hole in materials like steel or stainless VS aluminum or brass.
My theory is that the material is harder and requires more thrust and thus
"breaks" or "shears" earlier and leaves a heavier burr because of it.
Agreements, differing opinions, misc. ramblings?
Regards,
Joe Agro, Jr.
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V8013-R
Mark Rand
wrote:
>Opinion gathering...
>
>We were discussing why there is a larger burr on the back side of a manually
>drilled hole in materials like steel or stainless VS aluminum or brass.
>
>My theory is that the material is harder and requires more thrust and thus
>"breaks" or "shears" earlier and leaves a heavier burr because of it.
>
>Agreements, differing opinions, misc. ramblings?
>
Sounds fair. A possible test would be to drill a hole with a normal drill,
then with a split point or four fact ground drill. If the reduced thrust
required for the latter drills resulted in less burr, that would support the
assumption.
Mark Rand
RTFM
Joe AutoDrill
news:sf7tp591vum64ta1g...@4ax.com...
I was basing my opinion on the fact that when a feed control is used to stop
the burst at break through, the burr can be minimized greatly. Still there
in all cases, but much less so than when the thrust is enough to just break
through that little remainign "cone" that develops on most materials.
--
Tim Wescott
> Opinion gathering...
>
> We were discussing why there is a larger burr on the back side of a manually
> drilled hole in materials like steel or stainless VS aluminum or brass.
>
> My theory is that the material is harder and requires more thrust and thus
> "breaks" or "shears" earlier and leaves a heavier burr because of it.
>
> Agreements, differing opinions, misc. ramblings?
<ramble>
I think it's more likely something like the elongation of the material.
If all the forces needed to cut, shear, and stretch the material were
scaled equally, then I would expect that you'd get the same burr on a
block of Jello as you would on steel.
To test, try the experiment with some 6061-T6, and some 1100. If I'm
right you'll get a much bigger burr on the 1100. Call back with your
results when you get all the 1100 scraped off of your drill bit.
</ramble>
--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
Ed Huntress
"Tim Wescott" <t...@seemywebsite.now> wrote in message
news:xKednR0EBqnPPgPW...@web-ster.com...
> Joe AutoDrill wrote:
>> Opinion gathering...
>>
>> We were discussing why there is a larger burr on the back side of a
>> manually drilled hole in materials like steel or stainless VS aluminum or
>> brass.
>>
>> My theory is that the material is harder and requires more thrust and
>> thus "breaks" or "shears" earlier and leaves a heavier burr because of
>> it.
>>
>> Agreements, differing opinions, misc. ramblings?
>
> <ramble>
> I think it's more likely something like the elongation of the material. If
> all the forces needed to cut, shear, and stretch the material were scaled
> equally, then I would expect that you'd get the same burr on a block of
> Jello as you would on steel.
I agree, but another issue is that the force required to cut aluminum and
brass is a lot less, so, when the metal is partially extruded and the drill
is breaking through, the outer parts of the lips cut the aluminum or brass
more cleanly. At least, that's the case with fairly hard aluminum or brass.
Really soft aluminum, in my experience, leaves a horrible burr (I've had to
drill quite a bit of 1100 in the deep dark past, unfortunately). It has a
lot of elongation and it's hard to get a clean cut. It just keeps extruding
ahead of the drill bit.
>
> To test, try the experiment with some 6061-T6, and some 1100. If I'm
> right you'll get a much bigger burr on the 1100. Call back with your
> results when you get all the 1100 scraped off of your drill bit.
> </ramble>
(Why don't I ever read ahead? <g>)
--
Ed Huntress
Denis G.
Shaw’s book (“Principles of Metal Cutting”) has several pages
discussing the formation of burrs, but he also cites a reference
devoted entirely to this subject: “Deburring and Metal Finishing
Handbook” by Gillespie. Limited excerpts from Google books:
http://books.google.com/books?id=gdq6qajigqoC&printsec=frontcover&dq=%22Deburring+and+edge+finishing+handbook%22&lr=&cd=1#v=onepage&q=&f=false
or http://tinyurl.com/yjcn83h Page 1 has an overview of the subject.
Andrew VK3BFA
Cosmic Forces?
Andrew VK3BFA.
Buerste
"Joe AutoDrill" <auto...@yunx.com> wrote in message
news:0Nwnn.73254$1n5....@newsfe04.iad...
Nearing the far side of the material, the force on the bit overcomes the
threshold of plastic deformation and the material deforms rather than cuts.
When you think about it, drilling is a violent operation. You're driving a
wedge into the material and ripping it apart...hopefully in a controlled
way. It's the same with wood. From the few holes I've drilled in wood,
I've learned how to modify my cutting configuration and control the material
and prevent the break-out or burr with a back-up to the material.