Tool Tip #24: Hollow Chisel Morticer chisel sharpening angles found!

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Blog entry by robscastle posted 04-28-2016 08:20 AM 780 reads 2 times favorited 3 comments Add to Favorites Watch
« Part 23: Yonico router Bits Technical information Part 24 of Tool Tip series Part 25: Making Architrave Corner Blocks »

Well I have eventually tracked down some documented information on the elusive sharpening angles, and the vague references to the mystery two cutting edge type Augers.

This is the latest doctrine available to my knowledge, however as always if I am incorrect please let me know!

Here we go breaking News!

Page 135
Note: There is also a reference to enlarging the chip extraction port. (it must have been originally small and evolved to what we see today) possibly from users enlarging them!

Some images of different augers and in particular some with two cutting edges and one with no center tip at all.

Page 136

Here is the cutting angles of the primary 60 deg and a surprise of 80 deg secondary finishing, not that its unexpected but I would doubt if ever done this day.

Also some diagrams on the cutting sequence of which I guess we all know any way, I could have edited it out but it complements the article.

So all you HCM owners its now fact!

-- Regards Robert

3 comments so far

View Joe Lyddon's profile

Joe Lyddon

9325 posts in 3474 days

#1 posted 04-28-2016 06:50 PM

Good “FIND”!

You really had to dig for this one!

Very interesting… A MUST to remember…

Thank you!

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: ... My Small Gallery:"

View PhilBello's profile


389 posts in 1388 days

#2 posted 04-29-2016 12:12 AM

I love reading these old articles in Popular Mechanics, I used to have one of those ┬┤standard bits’, it gave you a flat bottomed hole, without fear of the brad point coming out of the other side.

-- If you want the rainbow, you got to put up with the rain - Steven Wright

View robscastle's profile


3315 posts in 1626 days

#3 posted 04-29-2016 01:53 AM

Hi Phil, its interesting you say that, as there is from what I can see just about every Popular Mechanics mag is available on the net, and the articles are entertaining as well as informative.
Printing went on during WWII as well by the looks.

The brad point on HCM augers is a bit of a waste as its some times its ground off center at manufacture and will cause errors in positioning if used as a reference.
I should grind one off and do a test run to see if there is any difference, apart from no small hole.

Check this out as an example.

Its 1mm off center to the right so 2mm at full rotatation, 2mm over a 10mm bit! either way a poor mortice will result for sure!

-- Regards Robert

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