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post #1 of (permalink) Old 08-25-2000, 12:11 AM
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Drilling technique?

This maybe a dumb question, but I was just making a set of heavy duty shackles, and it came to me.........

Everything I do on my 4x4s is mostly a matter of trail and error. I didn't pay much attention in shop class when I was a kid (and kicking myself for it), and I have never really had anyone to show me how to do things properly or "the tricks of the trade" etc. I just buy tools and then try to figure it out on my own.

Right now I am making a set of shackles for a girl who is having some tire rubbing problems. I have come up with a decent technique with the limited tools I have, and have created a template for making these shackles for profit.

So far this is what I have learned from the last 5yrs or so of working on my Jeep and now a Samurai:

High-speed drill bits dull quickly.
Titanium drill bits break easily.
Cobalt drill bits rock, especially using a drill press.

Most of my drilling is mild steel, up to 3/8" thick. I'm currently using a small bench drill press with a 1/2" Cobalt bit on 3/8" mild steel, at 1100 rpm (recomended by the drill press manufacturer).

I set up my template, secure the piece on the deck, and pour some oil in the hole of the template. I drill a few seconds, pour oil, drill a few seconds and keep repeating this until the hole is finished.

Tonite I had to use Air Tool oil, but I usually use 3in1 Oil.

Is that speed right (manufacturer recomendations aren't always the right ones)?

Is my technique right?

Is there a better oil I should use?

Are there other drill bits I should be aware of?

I only just started using Cobalt a few months ago. I didn't know about them before that. They are expensive ($25 CND for a 1/2" bit), but I feel they work better, and last longer than any other bit I've used.

Thanks for the help!

jo-jo
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post #2 of (permalink) Old 08-25-2000, 12:25 AM
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Re: Drilling technique?

[img]/wwwthreads_images/icons/smile.gif[/img] Since getting a brand new THOR 1/4" drill for Christmas in 1955; and more or less continuously drilling holes ever since; here is what I have learned: HIGH SPEED bits are just fine for any mild steel work. Bits from the factory never seem to have enough "rake" on them so I usually have to reshape them myself. I never use any kind of fixture, but freehand the bits on the SIDE of the grinder wheel. I set the angle of the cut and the rake by eyeballing it in. Run the drill press slow enough that the continuous curled shaving can be formed. When the bit is right, that shaving will just stream out in one long piece. When drilling deep holes, pull the bit out frequently to allow the shavings to escape. Always use genuine thread-cutting oil as it has friction-enhancing properties to help cut, but will prevent galding when used to tap threads. Make a pilot hole before drilling bigger diameters, but avoid a pilot that is too small. Half the finished diameter is about as big as you want to go with the pilot. Good quality high speed steel bits will last a long time with any kind of care. VERMONT AMERICAN is a good brand, and there are many others. [img]/wwwthreads_images/icons/smile.gif[/img]

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post #3 of (permalink) Old 08-25-2000, 12:33 AM
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Re: Drilling technique?

Hmm......thanks Dave........this brings up another question I forgot to mention:

How do you sharpen a drill bit? You mention using the grinding wheel to reshape the bit. Sounds like something I would have to be shown, rather than learn on my own. Do you use the wheel to sharpen as well or do you use a file?

I've got an aweful lot of dull drill bits kicking around the shop, and at $10 a pop for those ones I would hate to toss them. I've been holding onto some of them for years hoping that someday I would find out how to sharpen them.[img]/wwwthreads_images/icons/smile.gif[/img]

The proper cutting oil sounds like a very good idea I will look into tomorrow.

jo-jo
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post #4 of (permalink) Old 08-25-2000, 12:50 AM
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Re: Drilling technique?

[img]/wwwthreads_images/icons/tongue.gif[/img] I could show you in just a few minutes, but maybe the description will suffice.....Stand in front of the grinder with the cut end of the bit bit held by your left hand and the blank end with the right hand. Bring the bit up to the side of the wheel at the angle that is already on the bit. Position the bit so it has uphill angle with the cut end high. So now you have angle to the wheel equal to the regular grind that is on the bit, and the uphill angle is the rake angle. As you grind the bit, you swing it in an upward arc beginning as the cut edge touches the wheel, and then on up to grind the heel of the bit. If you are too flat, the cut edge will be suspended by the metal of the heel and will not bite in. Try the bit and if it doesn't cut, repeat the process, trying to remove material from behind the cut edge so it will not float. Sometimes I miss the mark and have to go back, but when they're right, they cut like you will not believe. Grind bits sparingly, and have a water dip right there to dip after each pass. You should be OK after you try this a few dozen times. Forget that file.[img]/wwwthreads_images/icons/crazy.gif[/img]

CJDave
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post #5 of (permalink) Old 08-25-2000, 01:13 AM
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Re: Drilling technique?

Ok, at least I have a dozen or so bits to practice with![img]/wwwthreads_images/icons/tongue.gif[/img]

THANKS![img]/wwwthreads_images/icons/smile.gif[/img]

jo-jo
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post #6 of (permalink) Old 08-25-2000, 01:19 AM
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Re: Drilling technique?

[img]/wwwthreads_images/icons/tongue.gif[/img] Remember to grind each flight alternately so you bring each cut edge back the same amount so the bit won't want to shudder as it cuts. Grind...turn 180 degrees...grind....dip in water...grind...turn 180 degrees...grind...dip in water. And so forth.[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #7 of (permalink) Old 08-25-2000, 06:39 AM
 
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Re: Drilling technique?

this is a stab in the dark joJo, But I would also think 1100RPM

is a little fast for drilling in metal.

I use the bridgeport mills at work as my personal drill presses, and to bore a half inch hole in 1/4 in mild steel Ive slowed them down to about 180-300 and soaked them with cutting oil ( NO SUBSTITUTES ON TEH OIL!)

thanks for the sharpening lesson Dave, ive got a PILE of bits to try that on also, ive tried many times before with a littel diamond hone to no avail.

Ill keep trying!



OzarkJeep

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post #8 of (permalink) Old 08-25-2000, 07:16 AM
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Re: Drilling technique?

Snap On tools make a excellent drill bit set. The "Thunderbit"
I believe the drill bits range from 1/16" to 1/2". They are
titanium coated or something, they cut fast. They aren't cheap
either, but they are worth it.

Wayne

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post #9 of (permalink) Old 08-25-2000, 07:56 AM
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Re: Drilling technique?

[img]/wwwthreads_images/icons/tongue.gif[/img] One thing I did forget to mention......as you make your upward sweep against the grinder wheel, you have to put some ROTATION on the drill in the same direction as it normally rotates. So you go up and roll to hold the edge of the bit against the stone, duplicating the original shape, just adding a little more "rake". What I have found with multi-speed presses is that if I take off the 1800 RPM motor and go with a 1200, it gets the speeds down to where they are just about useable. [img]/wwwthreads_images/icons/crazy.gif[/img]

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post #10 of (permalink) Old 08-25-2000, 03:20 PM
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Re: Drilling technique?

<blockquote><font size=1>In reply to:</font><hr>

this is a stab in the dark joJo, But I would also think 1100RPM is a little fast for drilling in metal.

<hr></blockquote>

Well for the drill size and metal thickness, that was the manufacturers recomendation. I don't believe everything I read though, that's why I posted here to find out what you guys thought.[img]/wwwthreads_images/icons/smile.gif[/img]

The slowest my press will turn at is 620rpm so I will experiment with that. Thanks for the help.[img]/wwwthreads_images/icons/smile.gif[/img]

jo-jo
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