Mortiser Blues

[ChrisD]

Hey guys,

What do you do to prevent your hollow mortising chisels from bluing?

I:

1.) honed all four sides of the chisel to a nice polish (up to 2000 w/d sandpaper),
2.) honed the inside with the Rockler honing cone,
3.) applied Bostik dry lubricant to the auger bit,
4.) did the "nickel trick" (which is actually a good clearance because the chips are ejecting efficiently out the slot, which is to my right when I am facing the mortiser), and
5.) plunge the chisel into the wood only by about 1/8" at a time.

And I still get a thin blue line along the length of the chisel!

Am I doing something wrong or is this generally expected of all mortisers?

I have the Delta 14-651.

Thanks in advance.

[LCHIEN]

I'm not 100% sure about what you talk, but if tool steel turns purple-bluish then it has been exposed to high heat and probably ruined because such overheated metal loses its temper and fails to hold an edge after that.

If the blue part occurs where along the whole side of the mortise chisel then the heat is not generated by the cutting but probably by excessive rubbing of the auger against the chisel. THis I would assume is caused by poor alignment of the chisel holder and the drill chuck/quill assembly.

If the chisel was being overheated by cutting then only the full width of the tip on all four sides would be blue, not a line down the entire side.

Or possible you mixed chisels and auger pairs and one auger is a tight fit in the chisel.

But the only thing I know causes tool steel to turn blue is heat. or paint.

[ChrisD]

Loring, yes, I am talking about bluing due to overheating (I'm out of blue paint ). And unfortunately, I have experienced both scenarios you describe below.

The bluing at the tip of all 4 sides was probably due to sheer ignorance, as I practically just put the thing right to work out of the box. This happened several months ago. I've learned since then.

What happened the other night was that my 3/8" chisel, after cutting a couple of mortises, developed a thin blue line along two sides. Although I am using the right auger for the chisel, I also suspect I have an alignment problem. I'll check on it tonight.

Thanks for the response.

[JimD]

Chris,

I think it also makes a difference how fast your mortiser turns. At 3450 rpm, it is easier to get high friction IMHO. I like my lower speed Jet. I put a few drops of light oil on my drill bits to reduce squeeking and friction. I also plunge into a piece of scrap first to remove any excess oil. I find that a buisness card is enough added clearance typically for chip ejection. Having the drill bit hanging out a lot could also allow it to cock a bit increasing friction - if your nickel comment means you allow that much clearance for chips you might want to try less.

Jim