Shopsmith Forums

berry wrote:But I wasn't careful with them and 'blued' a number of them.

Sorry for my ignorance but what does 'blued' mean?

dgale wrote:Sorry for my ignorance but what does 'blued' mean?

'blued' means burnt or they got to HOT and lost their temper.

Cutting tools can get 'blued' by excessive heating both when using them and when grinding them.

Color is caused by oxidation of the steel when elevated to a high temperature.

That temperature is sufficient to cause the tool to become non-tempered.

Becoming non-tempered causes them to get dull more quickly.

is cobalt treated drills worth the price?

JPG40504 wrote:Cutting tools can get 'blued' by excessive heating both when using them and when grinding them.

Color is caused by oxidation of the steel when elevated to a high temperature.

That temperature is sufficient to cause the tool to become non-tempered.

Becoming non-tempered causes them to get dull more quickly.

Thanks for the edification

dgale wrote:Thanks for the edification

P.S. different steels produce different colors. That 'blue' can be black to brown also.

i.e. if it looses 'shiney' it probably looses temper!

One last 'detail'. The temper loss is 'local' to the area of color change.


Case hardening is a different animal.

So I assume when this happens when a bit is being used, it's a matter of trying to drill too quickly and/or through a fairly dense material? More importantly, I assume the way to avoid this happening is take your time, especially with dense materials?

dgale wrote:So I assume when this happens when a bit is being used, it's a matter of trying to drill too quickly and/or through a fairly dense material? More importantly, I assume the way to avoid this happening is take your time, especially with dense materials?

RPM's and feed rate. Too slow will not cause 'blueing'.

We are conditioned to drill at way too fast a speed because of hand drills that run very fast.

Steel cuts very nicely at 'jig saw' speed range even down to the smallest bit the chuck will hold!


Wood cuts more easily so faster speeds are appropriate. Forstner bits really really need slow.

JPG40504 wrote: Tools can get 'blued' by excessive heating both when using them and when grinding them.

I thought that using and grinding eliminated the blues.

Color is caused by oxidation of the steel when elevated to a high temperature.

That temperature is sufficient to cause the tool to become non-tempered.

And I thought that higher temperature increased stiffness aka-temper.

Becoming non-tempered causes them to get dull more quickly.

That is absolutely correct.

However, you are speaking of blue bits and I was thinking of blue balls (which many on this site will have to Google to find out what that means.)

Irreverent, obscene and unacceptable and not politically correct I know. But it is multicultural and diversity oriented as men from all nations will testify.

db5 wrote:However, you are speaking of blue bits and I was thinking of blue balls (which many on this site will have to Google to find out what that means.)

Irreverent, obscene and unacceptable and not politically correct I know. But it is multicultural and diversity oriented as men from all nations will testify.

Grinding/wear will remove the blue part. Question is, how much deeper did the 'distempering' go?

Truth be told, getting tools 'hot' actually is 'tempering' them(making them softer). They 'lose temper' because the result is softer than when originally 'tempered'.


Are you referring to the 'blue balls of Scotland'?:D





P.S. If you want to talk plumbing, go over to the Ridgid forum.