Learned something about drilling today

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tornitore45
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Joined: Tue Apr 18, 2006 12:24 am
Location: USA Texas, Austin

Learned something about drilling today

Post by tornitore45 »

The best tool to enlarge a hole in hardened steel is a carbide ball-nose end-mill.

I have 2 sets of those screwed up 1-2-3 block that have the untapped holes too small to clear the stud.
I admit to be a bit anal, some would say a lot, but that state of affair bugs me to the no end.

After ruining a $30 straight flutes carbide bit I decided that if I had to ruin a bit should be a cheap one; so I bought two 3/8" masonry bits for $8 total and went at it.

Surprising the 1st masonry bits went through 9 holes before being too dull to work but without chipped edges.
I saved the 2nd masonry bit to drill out the 3x2 long side holes. By refreshing the edge every hole it went really well.

To finish all the 1" and 2" long holes on both sets I decided to try a ball nose end-mill, one acquired at a flea market for $2.
It went through like butter.

You only need to drill out one block because only one block will have studs passing through, the other can be left screwed up by design as is.

This ball-end bit is odd looking. Instead of looking the grayish color of carbide it looks almost black.
Like to know if that is some clue to a type of carbide or treatment.

End-mills, like any other bit do not cut well near the center, but on the periphery the ball end has no delicate edge to chip and is the cat's miao for enlarging holes.

Another thing I learned before, is to use the knee to feed, instead of the quill lever. If there is any rough spot or unevenness (like crossing another hole) the bit is going to bounce, hammer and chip. By feeding with the knee, the advance is controlled and constrained, bouncing is much reduced.

I know, kind of a boring subject but thought I share.
Mauro Gaetano
in Austin TX
whateg0
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Re: Learned something about drilling today

Post by whateg0 »

Though none of mine are ground this way, I have been told by a friend that when I get my endmills ground, I should have a small radius put on them as it will reduce the chances of a chipped corner. I need to buy more endmills before I do that, though. I use the ball nose endmill for breaking edges sometimes on holes too big for my countersink. It works real nice. I've always wondered if a masonry bit could be used like that, though.

Thanks for sharing!
Mr Ron
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Re: Learned something about drilling today

Post by Mr Ron »

You made my day. It's a good day when I can learn something new. Thanks
Mr.Ron from South Mississippi
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tornitore45
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Re: Learned something about drilling today

Post by tornitore45 »

I wander why on the typical tool catalog that list over 4000 different end mills none are offered with a small radius. 90% of the end mills I have to discard are worn on the tip.
Mauro Gaetano
in Austin TX
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GlennW
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Re: Learned something about drilling today

Post by GlennW »

There are many of them out there.

I use them with various corner radii from .005" to .125".

A .005" radius on an end mill will give a greatly improved surface finish, just as it does on a lathe tool bit as opposed to a sharp corner.

Look for "corner radius" end mills.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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tornitore45
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Re: Learned something about drilling today

Post by tornitore45 »

Thanks, I can't believe with all the drooling on catalogs I missed it.
Mauro Gaetano
in Austin TX
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Harold_V
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Re: Learned something about drilling today

Post by Harold_V »

It's not difficult to hand stone a slight corner radius on an end mill. That was common practice when I was working in commercial shops. It drastically improves surface finish, assuming one pays attention to proper relief, and avoids rounding. Done poorly, the end results can leave a great deal to be desired.

That said, a radius may or may not be permitted if machining to a shoulder. All depends on the engineer. For home work, the choice is yours.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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ctwo
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Re: Learned something about drilling today

Post by ctwo »

I think I am going to try to round out some of my many chipped EMs. What do I have to loose? I was so disappointed in me last week for turning the knob the wrong way and driving a new, stationary EM into the work and chipping off the corner, just trying to find the edge... found it!
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
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neanderman
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Re: Learned something about drilling today

Post by neanderman »

I appreciate this thread for multiple reasons. I not only have some of those 1-2-3 blocks, it just good to read about tricks to avoid things like chipping.
Ed

LeBlond Dual Drive, 15x30
US-Burke Millrite MVI
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Files, snips and cold chisels

Proud denizen of the former "Machine Tool Capitol of the World"
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GlennW
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Re: Learned something about drilling today

Post by GlennW »

I prefer EZ Lap's to stones for dressing tool bits and cutters as they work very well on carbide too.

http://eze-lap.com/products/diamond-hone-stone/

Fine (red handle) has worked well.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
Rich_Carlstedt
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Re: Learned something about drilling today

Post by Rich_Carlstedt »

Congratulations Mauro !
You have discovered what I have been mentioning here and other Forums for years, use ball endmills !
They are superb for many things, and the most important is hole accuracy.
Somehow most machinists use center-drills for starting holes. Center-drills are for use of a dead or live center --period
When you want accurate starts for drilling holes through stock use a stub starting drill or better yet, a Ball Endmill
Having an assortment of carbide ball endmills is a step for great hole making especially deep hole drilling.
Check the flute pitch of the drill you wish to use ..say it is 1" for a flute to do 360 degrees. So the Ball drill needs to go 1/2 " deep.
This assures that the drill flutes (2) will be completely supported by the HOLE WALL !
If you have a hole started and it's location is slightly off, use a Ball endmill to help move the position over. ( less "grabbing too)
Because the Ball-endmill is stout, it helps to maintain the spindle's centerline.
We gun drilled tens of thousands holes upto 48" deep, and accuracy was paramount so we always used Ball endmills for starting holes for the least deflection .
Rich
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Harold_V
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Re: Learned something about drilling today

Post by Harold_V »

Rich_Carlstedt wrote:Somehow most machinists use center-drills for starting holes. Center-drills are for use of a dead or live center --period
I can address that issue, and it's a no-brainer.
Center drills were, and often are, used for starting a hole for the same reasons one might choose a ball end mill. It's very short and stout because of the oversized body. That mandates a hole will be quite nicely located, and, with the center drill stationary, as it is in a lathe, given the opportunity, it will find center without creating an oversized hole, very unlike the use of a ball end mill.

I'm not suggesting that using a ball end mill doesn't work, but I'm also not about to agree that center drills are not for starting holes. If they aren't, I live in wonder as to how we, at Sperry Utah, managed to develop and build the Sergeant Guided Missile. In my 7½ years of employment there (all in the shop), I never saw another method used, nor endorsed, for starting drilled holes (excluding drill jig use). It might help to note that we did NO deep hole drilling.

They work just fine for starting holes. If they didn't, they wouldn't have been used for so many years, by so many seasoned machinists.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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