Rework cement drills to drill metal

[mr_modify1]

Inexpensive way to drill hard metals.

[cmarlow]

One of the problems with carbide masonry bits having brazed in place carbide inserts ground for drilling steel there can be enough heat generated to melt the brazing as you drill. either coolant is needed or you need to keep the actual drilling time short enough to prevent overheating.

[mr_modify1]

This has not happen to me yet but now I will know what happened if it does.

[cmarlow]

I have some carbide drills with inserted carbide bits from Bosch that are intended for both steel and ceramic material. They are very much like what you made, not like the solid carbide drills used for machining metals. Bosch seems to have used a tougher carbide and a higher temperature brazing when they were made. They are quite resistant to chipping or overheating. They are also a bit pricey.
Another style of bit that works well for harder steels are the spear pointed glass and ceramic tile drills, especially with a regrind, but you still have to be careful about overheating the brazing and about keeping an even feed to avoid chipping or fracturing the carbide.

[old kodger]

I made a post to this effect some time ago, "regrind a masonry drill to resemble a high speed metal drill" they don't get any hotter than a metal drill so the question of melting brazing does not exist. So long as you don't go at it like a bull in a china shop.

[cmarlow]

Ha ha ha. I am the kind of guy who can melt drills, even HSS drills. (and I have had carbide masonry drill come apart too). Brazed carbide inserts are funny. You would think something that can hammer its way through rock would stand up to hitting a bit of rebar, but they do not. Not only does the carbide shatter because it is brittle the brazed joint doesn't hold together either. Reshaping the bit to cut like a twist drill bit introduces other problems related to the grade of carbide and the quality of the brazed joint.

It is the same with carbide tipped circular saw blades for wood. You would think the inserts should stand up to a bit of metal but hitting a nail in the wood can take the inserts off of the blade. Yet at the same time I can buy circular saw blades designed to cut steel. Even with those you have to be a bit careful because some are designed for cutting regular mild steel, some are for hardened and cast steel, and some are for different grades of stainless.