Drills & drill bits

Less typy, more drilly.


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Play around with it, you'll figure her out.

Well i gave it a good go, and once community quiet hours kicked in I did some reading and posted here. I tried again after work and still not have any great success. Trying to spend the least money possible to figure it out! I stopped at Home Depot and bought 2 Milwaukee Colbalt 1/8" bits. They drill fine at 3200 RPM, 500 RPM, or estimated 75-100 RPM in mild steel, but they stop drilling when they see the weld material. I'm talking estimated 75-150 RPM in a drill that is geared down to 500 RPM maximum. So something about this weld. The only thing I know I can use that's harder and reasonably usable in a hand drill is M42 Cobalt. I guess I'll order a few bits from out of town and see what happens.

md21722 said:

I discovered something else I need to figure out. Drilling through weld.

A good example is filling in some holes in plate that needed to be redrilled.


Any suggestions?

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What weld process, what filler material?

Newbie MIG weld with a Millermatic 211 ground down smooth with a 36 grit grinding disc on a 4.5" grinder then tried to drill the next day.

It may be that I need to do better welding. ;-) But the offshoot is what do you do when you get a jacked up weld?

It tells me to buy a bunch of cheap, decent, drill bits and one of them refuses to drill, bring out the big guns. I'm just trying to figure out what the big guns are.

Mike, I am accumulating hundreds of pounds of scrap for you.

As a side note, I have had great success drilling cast iron differential axle housings sitting on jack stands (for example, to add the air/electrical line for a locker) with nothing more than a standard 118 degree HSS drill bit, with slow speed, and solid feed. No problems with breakthrough whatsoever. A powerful drill blasts through without any problems. I have found that less feed, more blunt bits that are better for harder materails, and drills with weak motors cause more problems than they solve.

I find these bits last the longest for us when drilling plasma cut holes or other hardened edges. https://www.amazon.com/gp/product/B...8-a3b0-4f0d-b847-0ae9cb54558a&pf_rd_i=desktop

Also make sure to use plenty of lube!

Thats kind of interesting because in the informal reviews I've seen the Champions didn't do any better than the Norseman. Did you try the Norseman? If you think they're better than Norseman I may give them a try.

md21722 said:

Thats kind of interesting because in the informal reviews I've seen the Champions didn't do any better than the Norseman. Did you try the Norseman? If you think they're better than Norseman I may give them a try.

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Haven't tried norseman. maybe I will though its a smaller set.

The best price I've seen on Norseman SPM-29 is eBay for $74.99. Bowers Tool out of Fort Worth. They ship fast.

MSC is running a special this month $59.99 for bright finish Hertel 118 degree HSS. They aren't M7 steel or anything but they'll probably cut mild steel like there's no tomorrow.

What I've found is no matter what anyone says, or any drill speed charts say, when you're drilling by hand its a compromise. If you can drill vertically and put your body into it you can do OK. But if you try to drill horizontal you pretty much can't put enough pressure unless using aids like a dead man or switching up to a mag drill. Drill that would seem completely dull drilling horizontally can make great chips drilling vertically with pressure and cut a 1/2" hole in no time...

Call MSC. Get a YG1 gold point Cobalt. Drill slow with plenty of pressure. When it gets dull, sharpen it and go again.


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I looked at this some more. It turns out I explained the issue incorrectly. I can drill through a MIG weld with a regular HSS bit just fine. The problems comes up if I fill in a hole with weld, then grind it smooth and then try to drill it. It seems like if I grind I may blue the metal, which hardens it. Even M42 cobalt mostly just dimples it. I suspect carbide drills will be required.

After more research and having a buddy try, I determined that the abrasive grinding was causing the surface to marsenite. From Wikipedia, "Martensite, named after the German metallurgist Adolf Martens (1850–1914), most commonly refers to a very hard form of steel crystalline structure, but it can also refer to any crystal structure that is formed by diffusionless transformation.[1] It includes a class of hard minerals occurring as lath- or plate-shaped crystal grains. When viewed in cross section, the lenticular (lens-shaped) crystal grains are sometimes incorrectly described as acicular (needle-shaped)[citation needed]." Also from Wikipedia, Abrasive Grinding, "Effects on workpiece materials[edit]
Mechanical properties will change due to stresses put on the part during finishing. High grinding temperatures may cause a thin martensitic layer to form on the part, which will lead to reduced material strength from micro cracks. Physical property changes include the possible loss of magnetic properties on ferromagnetic materials. Chemical property changes include an increased susceptibility to corrosion because of high surface stress."

I was using too much pressure when grinding. I reground the surface and was able to drill it fine with regular HSS bits.

md21722 said:

I was using too much pressure when grinding. I reground the surface and was able to drill it fine with regular HSS bits.

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Was there any discoloration after the first go-round with the grinder?

When I was first grinding down I was putting pressure on the grinder and the steel was turning blue and glowing orange at the edges. I did make it smooth shiny steel before trying to drill. Once I figured this "marsenite" thing out, I went back and reworked it and everything drilled OK.

Reworked it how?

Drill then grind?

I hit it with a grinder & flap again using less pressure then drilled.

following this thread.
I ordered some Norsemen bits to try out.

I usually just buy the 15$ milwaukee sets for cheap bits since I use the small ones for pilot holes and just burn through the 3/8 and 1/2" bits in those kits for all the misc fab work.

(and single milwaukee for 9/16, 5/8.. 3/4) , i grab 3-4 sets at a time, and just run through them and buy another 3-4 sets. I have a 1.5HP drill press that I use for most stuff and a low speed high torque drill that will break your wrists if you dont respect it. for the rest, a milwaukee corded drill or my fuel cordless drill.

blondejoncherokee said:

following this thread.
I ordered some Norsemen bits to try out.

I usually just buy the 15$ milwaukee sets for cheap bits since I use the small ones for pilot holes and just burn through the 3/8 and 1/2" bits in those kits for all the misc fab work.

(and single milwaukee for 9/16, 5/8.. 3/4) , i grab 3-4 sets at a time, and just run through them and buy another 3-4 sets. I have a 1.5HP drill press that I use for most stuff and a low speed high torque drill that will break your wrists if you dont respect it. for the rest, a milwaukee corded drill or my fuel cordless drill.

Click to expand...

For what you are doing I suggest looking at the 6 and 12 packs or even 20 packs of drill bits you can buy in the common sizes. eBay, Amazon, McMaster, or MSC are some places you can get them.

I do a lot of 9/16, 5/8 , 3/4" holes through 1/4" for link brackets, track bar brackets, etc. those are the most common. I just use the 1/4, 3/8 and 1/2" bits from the cheap sets to start all of my holes off. lately I have been making a lot of my own 1/4" weld washers using hole saws and regular bits for the center. works great and way cheaper than ruffstuff. especially when you need a 12mm weld washer for a wj trackbar mount....

I do find myself using my old snap on set from time to time, but most bits are gone or missing from the years, similar in size to the 15/32 saved me for the 12mm the other day...