How To Unable to drill Tang Holes

[SoManyQuestions]

Created a knife from leaf spring steel. Did not quench yet. Drilled pilot holes using drill press and oil and 1/8 drill bit. Now I cannot get the 1/4 bit to drill through. Tried slowest rpms on drill press (750 is the lowest it will go). Using oil and brand new drill bits. Tried heating it to orange and air cooling (saw that on another forum suggestion). How can I get this to go through? .. what is the problem? What am I doing wrong? Im brand new and getting more than a little frustrated. Thanks.

 

[Contender Machine]

As a general rule it is best to avoid drilling pilot holes with smaller drills. If you do drill a pilot hole the proper size is the diameter of the tip of the larger drill between the cutting edges. With split point drills this is a non existent problem.

Take a close look at your 1/4 inch drill. My guess, without seeing the setup, is that the outer 1/16 of either side is very dull. This could have happened immediately on the first hole you tried drilling making any subsequent attempts futile.

A leaf spring should be fully annealed before you attempt to drill through it with a steel drill as it is a spring hardness in its current state. 750 rpm with a steel drill in a non-annealed leaf spring is likely too fast and burned it up. The 1/8 drill would have half the surface footage so that is probably why it didn’t burn up. This would all depend on the type and quality of the drill.

The best coarse of action would be to fully anneal the spring. Then use a new drill bit or sharpen the one you have (if you know how to properly do that). Turn it at 750 rpm and feed with a constant pressure, avoid dwelling in the cut. If the tool is in contact with the material and no chips are being made then all you are doing is building heat. Which is the enemy here.

Edit to add: A carbide drill would work as well but they are expensive and you will likely ruin it quickly. You may get through this blade but the potential life expectancy will be reduced big time.

Also keep using your cutting oil.

 

[Glen Juntunen]

As mentioned, anneal before drilling. Heat the whole knife until it’s cherry red then cover it up in vermiculite or dry sand and then let it sit and cool down.

 

[Linus Knives]

As already said, annealing is very important. I had this struggle when I first started out and was working with leaf springs as well. I bought some Vermiculite on amazon for really cheap and put it in a metal drywall bucket. Perfect size for most blades.

 

[Hengelo_77]

I had a simular problem.
Try more speed, that worked for me

 

[Tom Lewis]

You might try carbide masonry bits. I have had some success with them. For really hard steel I have used carbide endmills in my milling machine.

 

[Stacy E. Apelt - Bladesmith]

For a cheap and dirty carbide drill, use a 1/4" masonry spade bit. By no way will it drill a perfect hole, but it will work for your task.

Another thing that makes drilling a problem is the wrong bits. You want good metal drilling bits. Cheap sets are often useless for metal drilling. Most are "universal angle" which is 118°. That works for wood and soft metal, but will do poorly on steel and not at all on stainless steel. You would want a 135° tip angle for knife work in steel. A set of Drill Hog bits isn't cheap, but will last a long time. If you only need drill bits for knife work, buying 10-packs of stub-length bits in three sizes is the smartest thing to do -1/8", 3/16", 1/4"

If you get carbide bits, 118° is the norm. That is fine, as they don't dull.

There are suppliers on eBay who sell them really reasonably. Search, "SGS 3 Solid Carbide 3 Flute Twist Drill ". They run less than half the regular price. Regular carbide bits are 25 cents on the dollar.

IMHO, a solid carbide three-flute 1/4" bit is worth it's weight in gold in a knife shop. No need for a pilot hole and with proper pressure and bit speed, it cuts straight through steel. They last a long time compared to two-flute bits.

 

[Contender Machine]

If you get carbide bits, 118° is the norm. That is fine, as they don't dull.

Actually 118 deg carbide drills are almost unheard of. 140 degrees is the most common by far and the SGS 3 fluters are 150 degrees.

The closer you get to 180 degrees the straighter and more accurately located the hole will be. (Less wondering upon starting) Carbide drills are made for high performance and accuracy so they tend to be flatter. This isn’t a concern when using a drill press though as there are many other factors limiting the performance of the drill.

118 degree drills tend to not perform as well because they typically are not split point drills. So it doesn’t have as much to do with the angle as it does the grind of the cutting edge. 118 degree steel drills can punch holes in stainless steel all day long in the correct application.

It’s funny how the standards of things change drastically from one industry to another. In the machining world if a carbide drill is wearing out with less than 2000 inches of drilling then there is a problem. 5000 inches of material removed with a single drill is not unheard of at all.