Drilling out steel

[gamble]

Cut out some 3/8" steel plate and wanted to true up the holes a little. Grabbed a bit and some wd40 to help keep things cool
This is the drill I have. and it was set to the lowest speed of 280
http://www.harborfreight.com/heavy-duty ... 38142.html


After about 10 minutes of drilling through one hole and not getting all the way through I give up.

Do I need a drill with more balls? Or can someone recommend me some really good metal bits?
I'm hoping to be able to chew through these holes in 10-20 seconds at a time.

[david47julie]

Trying to true up a plasma cut hole is very hard on drillbits when I want an acurate hole I just mark the spot with a short blast from the plasma cutter in the center of the desired hole or just pierce the plate in the center of the desired hole, I haves found it is better to have a small pilot hole than to cut bigger hole and try to true it up (it will take the sharp corners off your drillbit very fast) also good quality drill bits are a must and cutting fluid works better than wd40 in my opinion I hope that helps

[Shane Warnick]

What size hole?? Are you trying to drill from the top down or from the back or bottom of the hole the other way (in reference to the way the hole was plasma cut).

You have a $250 bench top drill press pushing a prob $0.50 drill bit with wd40 instead of cutting fluid or oil, trying to cut steel that has an edge that has been nitrided and is harder than your bit.

Let's just let that sink in for a minute.

I can understand your frustration. You can do anything with the right tools. Some things you can even do somewhat well with the wrong tools. Others you can't do at all. The only thing you get in that case, is experience.

There are a few posts on here already covering this topic in great depth, I don't remember if they are in tech tips or where, but a little search Kung fu should hook you up.

Shane

[little blue choo]

The drill is the deal,
The bits are the pits.

The drill you're using will do a good job but there is no substitute for good bits and even with good bits you will dull them quickly by drilling a plasma cut hole. As Shane said above "you're getting experience". I usually don't have any problems with my plasma cut holes but if I wanted to drill them I would just do a mark or pierce and then drill.

Rick

[Gamelord]

When you cut with your plasma, you actually harden the steel around the cut. This is why you are having a tough time. WD40 is probably one of the worst things you can put on your bit when you are wanting to cut. WD40 is a lube, not a cutting fluid or cooling fluid. Lube makes it harder to cut which runs the bit across the steel making it worthless. Get yourself some good quality cutting fluid like Rapid Tap (my favorite), set your drill press to slow and steady and let the bit cut through. Take your time and it should go throgh no problem. The better quality bit the better the cut and the longer it will last. Rapid Tap will smoke a bit while you cut, but as long as the metal is leaving the hole the heat is leaving with it. No metal leaving, heat builds up on the bit and the hole. Drilling a 12mm hole through 3/8" plate after plasma cut (about 1/16" undersized) I can usually get about 2 - 3 dozen holes before sharpening.

[Gamelord]

Rapid Tap - can be found at nearly any quality hardware store cuz it is that good.
http://www.ajaxtoolsupply.com/ratapcufl ... aQod4usG5w

[motoguy]

I can usually get about 2 - 3 dozen holes before sharpening.

Speaking of which...is the Drill Doctor a good option for bit sharpening?

[acourtjester]

I like the one i have
They had a very good sale some time back.
https://www.jbtoolsales.com/drill-docto ... aQoddHgGmw
I would get one from Zorro tools when they have a 25% off sale.

[_Ogre]

drill doctor is a great tool for sharpening bit, but not so good at sharpening bits under 1/4''
the only thing better than a drill doctor is having a neighbor with a drill doctor
like i do

[Black Forest]

If you have a way to grind carbide then you can regrind a masonry bit and then drill out your holes with that bit. Sometimes if drilling with a HSS bit and the speed is too fast and the feed rate to low or slow the work piece will work harden. The HSS bit is ruined and the only way I found to salvage the part is to use a masonry bit. A full carbide drill bit will also work but is very expensive comparatively speaking.

[4Dscreenart]

Good drill bits are well worth the money stay away from those "titanium coated bits". your drill bits need to be harder than the steel you are trying to drill through. I bought some good cobalt steel bits and they are well worth the money.

[robertspark]

+ 1 for cobalt 5 or 8%

use lubricant

+1 for drill doctor, very fast ... I normally do a batch at once and go through my drill box.

too much stuff from unknown lands about which seems like butter..... cobalt with a declared % seems to get away from this as the stuff from shores abroad don't provide anything but the usual hss / titanium coated.... which are file till you sharpen them....

one thing I have had success with is titanium coated drill taps.... they are cheap and good for aluminium + extrusion and for thin steel plate (control panel backplates).... especially if you build an openbuilds desktop router type CNC...

[cutnweld]

http://www.norsemandrill.com. All I use. All I will use

[mdwalker]

When I need a cleaner cut hole I use the method mentioned above where you just mark a point with the plasma and drill it. If you haven't read the articles yet, do a search for Jim Colt and read some of the articles he has posted on hole quality. With a properly adjusted machine you can get some pretty good holes. The one thing that seems to help more than anything is cutting holes at about 60% of the recommended cutting speed for the material you are processing.