Drill bits for metal and using them properly

[Nutball]

I was just drilling some holes in Stihl bars to fit on Echo saws, and my 1/4" bit had trouble advancing after the tip easily drilled its way in. I remembered I may have damaged it in the past when drilling 2 holes close together, so I got out a new bit and started a new hole. It worked great for about 2/3 through the bar, then started having similar difficulties with squeaking and not cutting well. Occasionally it would start cutting better in other holes, but got to the point where I'd basically ram it several times just to finish the holes.





I was using WD40 and short durations of drilling less than a second long to keep the bit cool. Maybe the RPM was too high? Maybe the steel had uneven hardening? I'm pretty sure I avoided any rivets and blued parts of the bar. I was drilling at 870rpm.


I also had a regular washer I was trying to drill out with a 1/2" drill bit. I think I got 1 washer drilled, but the next would rather cut the drill bit down to size than let the drill widen the hole.


Am I using the wrong kind of drill bit? Wrong rpm? Poor quality bits?

Any tips on how to sharpen drill bits?

 

[Bryan Newton]

It could be caused by both to fast and poor quality bites
I know When drilling stainless and other hard steels a slower speed is best and I have found out using cutting oil for drilling holes works best I have tried different products for drilling holes but alway go back to cutting oil also once the bit gets hot or makes a screeching sound they need resharpened

 

[huskihl]

You don’t “need” carbide, but they sure make life easy. The bits from @Wilhelm will drill a 6mm adjuster hole through a Cannon belly bar in 40 seconds.

 

[srcarr52]

Stainless and alloys like chainsaw bars are made of work harden. So if you let the bit slip across the surface you’ll harden the metal to more than the bit.

So you need to use hard bits like a cobalt alloy, less than 500 rpm and cutting lube with high sulfur content to keep the surface friction to a minimum.

 

[Nutball]

Yes, I was able to finish drilling at lower rpm. I dulled one more bit at 500, then didn't have any trouble after going down to around 260-350rpm. I did wonder if the metal was occasionally work hardening or tempering. At 350rpm or less I was able to get good thick long coils of steel coming off the bit.

 

[davidwyby]

Low rpm, pretty heavy feed, coolmist…do not let it get hot.

 

[Stump Shot]

Instead of regular cutting fluid I use a product called "Magic Tap" instead. Makes all of the drilling and threading jobs go easier.

 

[Squareground3691]

This stuff worked well , good on various stainless steels and harder steels . Go with a stubby carbide drill if you can .

 

[Moparmyway]

Instead of regular cutting fluid I use a product called "Magic Tap" instead. Makes all of the drilling and threading jobs go easier.

This stuff ????



I use “Light Cutting Oil” or this Tap Magic …….. SLOW !!

 

[Stump Shot]

This stuff ????

View attachment 358365

I use “Light Cutting Oil” or this Tap Magic …….. SLOW !!

That's the stuff.

 

[AVB]

Here the use of 70+% rubbing alcohol works better when drilling and tapping aluminum.

 

[Nutball]

What rpm is best for 1/2" and larger? I haven't tried 200rpm (the minimum of my drill), and I rarely drill larger than 1/2", but I feel like it could get quite hot at 200rpm with large bits.

This stuff ????

View attachment 358365

I use “Light Cutting Oil” or this Tap Magic …….. SLOW !!

It smells good too

Here the use of 70+% rubbing alcohol works better when drilling and tapping aluminum.

Interesting. It is thin with a low boiling point.

 

[Moparmyway]

What rpm is best for 1/2" and larger? I haven't tried 200rpm (the minimum of my drill), and I rarely drill larger than 1/2", but I feel like it could get quite hot at 200rpm with large bits.

The larger the drilling operation, the slower I go

2nd R.O.T., the larger it is, the wetter I keep it

To me, you can NEVER have too much cutting fluid, it doesn’t hurt anything to have a bath of cutting fluid on it. The cleanup is a different story

 

[Wilhelm]

"Slow the F down!" is the rule for processing high alloyed steel, even more so if it is quenched/hardened.

Do You utilize a drill press or free hand?
Low rpm, get the drill bits cutter to bite and keep a steady feed from that point on.
When You feel or hear that You are punching through ease up on the feed or You'll chip Your drill bits cutter edges.

HSS and HSS-Co can go through a fairly hard steel medium, but You should consider grinding/sharpening the bits preemptively instead of forcing them through and causing more severe cutter damage as seen in Your 4th picture 1st post.

Solid-Carbide drill bits are a dream to work with as they go through nearly anything - BUT , they are not almighty and shatter easily due to their high hardness.
And getting a severely damaged Carbide drill bit back to sharp is a whole different story!

HSS-Co drill bits are good bits, although just because the packaging says "Co" on it doesn't mean it is a high quality product.
I have had the pleasure of using drill bits of countless manufacturers and various alloys, the quality, performance and most importantly durability vary extremely.
Also, the most expensive drill bits aren't always the best ones for the intended application.

 

[Wilhelm]

View attachment 358306

This bit almost looks as if it got run at too high rpm's, yet there is no thermal discoloration.
Still, lower rpm might have caused less damage.
I like the bit, seemed to have had a good cutting edge from the factory - although the high "shoulder" right behind the leading cutting edge makes for fast dulling. This said "shoulder" is technically a dept limiter so the bit doesn't corkscrew itself into the medium being drilled - I personally regrind brand new drill bits and make them more aggressive.

This is "my normal" free hand grind which works wonders on 90% of what I drill at home.

 

[Wilhelm]

And this is "my special" grind - same drill bit and grind as pictured above, but with the cutters corner ground to another cutting surface.
It is basically a "semi-chisel drill bit cutting edge" and it is a thing that I picked up from industrial grade WiDia Solid-Carbide drill bits I had the pleasure to test.
This grind helps reduce the probability of the outer cutting edge from melting/chipping/wearing/dulling as fast as a regular ground drill bit would.
Again, it is a matter of what You use Your drill bit for so You don't need this mod all the time even though it doesn't hurt cutting performance at all.

This grind is excellent for processing hard steel and thin materials as there is no sharp cutter corner to get damaged or catch too big a bite while punching through the medium being processed.

 

[Wilhelm]

Tip on regrinding drill bits:

- the cutting edge must be HIGHER than its trailing shoulder
- the drill bits cutting edges must have identical length and hight
- if it is a drill bit that will be utilized for drilling without a pilot hole try and learn to grind a "crosscut" into the tip without damaging the cutting edges
- learn freehand grinding with a sharp good quality drill bit , use the factory grind as a way point and follow it
- Your grinders wheel should have a sharp corner (in my case, right side wheel, wheels right/outer corner) and a mild convex "belly" , this helps me greatly to get a good grind
- it is easier to grind a shallower drill bit tip than it is to grind a pointy tip (see my pictures above, I find it easier to match cutter lengths and heights)

 

[Wilhelm]

You don’t “need” carbide, but they sure make life easy. The bits from @Wilhelm will drill a 6mm adjuster hole through a Cannon belly bar in 40 seconds.

Hello Kevin
As always, I sincerely hope You are getting some use out of our deal and are happy with it.
I have no regrets.
Thank You very much!

 

[Wilhelm]

Green, dull needs sharpened.

Red, I can't tell whether it is cutter chipping or steel chips from drilling the workpiece.
If it is cutter chipping it needs to be ground back all the way to an undamaged area - same deal as with a dull chainsaw chain.

That drill bit has a very conservative factory grind and at 1/4" (6.4mm) there is no true need for a step unless You make a countersink with it.
Grind the stepped section out when re-sharpening those bits.

 

[huskihl]

Hello Kevin
As always, I sincerely hope You are getting some use out of our deal and are happy with it.
I have no regrets.
Thank You very much!

Almost daily.
Me neither