Lintel Steel, Blu-Mol Cobalt bits

3930dave · Mar 2, 2008

Picked up my first tractor in Nov, so am now trying to get used to working with much heavier steel....

I needed a heavier piece of angle iron (pretzeled the first one) for a home built rear blade, so picked up a 42" piece of Lintel steel (brick support for openings) from Home Depot. I have only one drill bit that worked well on this, a 3/32 Blu-Mol cobalt bit I picked up about 10 years ago. Other brand new "cobalt" bits just mostly made noise.

1) Is Lintel steel typically much harder than run of the mill steel (pun intended) ? It is convenient for me to pick this up at a building supply place, but if I'm just killing drill bits for no reason, then I'll source from a metal shop.

2) Anybody bought Blu-Mol cobalt bits lately, or can recommend an equivalent ?

One nice thing with this old Blu-Mol bit is that it is has higher twists/inch. I don't know if that makes sense, but essentially it is a denser bit (more metal), which I view as critical, esp. in a 3/32 or smaller.

I've fired off an email to Disstontools, who now seems to have the Blu-Mol line. The pkg for the old bit I have lists made in the USA (S. Deerfield Park, MA), but I suspect they are off-shored by now. I've got my fingers crossed, hoping their current bits still perform as well.

Rgds, Dave.

Shmudda · Mar 2, 2008

Dave,

That angle you purchased is just A-36 steel, which is just a very common 36,000 psi yield strength material, nothing fancy.

As for your drill bit, any regular drill bit should cruise thru that angle without a problem, as long as it's sharp, and the relief angle of the bit is correct.

You really don't need cobalt bits until you get into the higher strength carbon steels (100,000 psi or above) or the alloy stainless steels.

Craig

3930dave · Mar 2, 2008

Thnx Craig,

I wasn't expecting trouble... some of my bits could be sharper, but I bought 2 new ones, a regular black oxide, and a house brand cobalt - no joy on each...

Might have been something funny with this batch of steel, the old Blu Mol bit was the only thing that would drill, and I had to spend a fair amount of time with some diamond bits in my poor man's Dremel to cleanout the in-between portions (drilled around a larger hole).

I had this old bit kicking around from from a past project.... gonna see if I can find a few more of this type.... I don't often see this type of problem, but when I do, these Aggressor Blu Mol bits make a big difference.

Rgds, Dave.

BayouMan · Mar 3, 2008

Hey Dave,
The steel you are using is just run of the miil steel as mentioned earlier. I have found that pilot point bits work excellent in this application. I have Dewalt bits up to 1/2" and have no problem drilling a 1/2" hole free hand and they work great in a drill press as well. I'm sure there are other manufacturers out there.

Mike

3930dave · Mar 4, 2008

Hi Mike,

Good point

I have one or 2 bits that are pilot point.... I'll try them the next time I bend/break something on the tractor.... We have 25cm of snow coming tonight, maybe I'll need to fix my blade again soon.... Have been eliminating the weak links... you know how goes it....

I was at an industrial supply place yesterday... I may try their Cobalt bits next too, are supposed to be a better quality. Spent some time looking thru their catalogs, the hard thing to duplicate is the higher # of twists/inch that I have on this old 3/32... I'm beginning to think they stopped making this class of bit because it lasted too long....

Who knows... maybe somebody dumped a bunch of Nickel into the batch of steel I got, sure seems much harder than I was expecting.

Rgds, Dave.

chickenman · Mar 5, 2008

rpm, feed and coolent all may be factors

running to high a rpm and/or not feeding with enough pressure will burn up a drill

no coolent or cutting fluid will burn up a drill

3930dave · Mar 5, 2008

Thnx chickenman, good reminders... I only had motor oil around, so next on my list should be some cutting oil.... been quite a while since I've been around heavy metal... I seem to recall the old-time stuff had a fair amount of Sulphur, maybe there is something better now....

Good news... cleared snow today.... Lintel didn't bend (I'd be in really big trouble if it did) and the authentic Gray eyebolts stayed put, rather than bending like the regular consumer versions I'd used previously....

One step at a time....on a good day, maybe 2.....

Rgds, Dave.

sandman2234 · Mar 6, 2008

Chickenman probably hit it with the speeds/feeds. I don't know what type of drill motor your using, or how slow it will go, but typically the average person goes about two or three times as fast as they are supposed to. Controling the feed is also a problem in a hand held drill motor. I have drill motors that won't go slow enough to run a half inch drill thru steel.
Consider a drill press. Typically they can be slowed down to a point that drill bits don't suffer. Good used ones have come down in prices at auctions, but a good metal working drill press isn't going to be something that you will ever regret buying. A gear reduction drill motor might be a little cheaper than a box full of drill bits.
David from jax

skipmarcy · Mar 6, 2008

Dave, The last cobalt bit set I bought was from Snap-On and they performed very well. These were purchased somewhere around 1999/2000, don't know if Snap-On still has the exact same bits but they are worth it if they do. They are the split-point and don't walk badly for those times you just can't get a center punch in there or have an uneven surface to start on.