Progressing on drilling holes in Backsaw plates

[C. in Indy]

Hey, it's getting easier!

Brief history:
- 3 years ago, bought a fine USA-made carbide bit from Blackburn tools, broke it on the first hole.
- Last 2-1/2 years, used some cheapo Craftsman carbide glass-cutting bits; these did OK for starting holes in spring-steel plates.  Additional clean up with round files.
- Last 1 day, the "center punch method" described here by Don Williams and credited to "Chris Cianci"  (I wonder if he meant Matt Cianci ?):
http://donsbarn.com/dovetail-saw-making-workshop-day-2/

Chris

[Timberwolf]

Hey, it's getting easier!

Brief history:
- 3 years ago, bought a fine USA-made carbide bit from Blackburn tools, broke it on the first hole.
- Last 2-1/2 years, used some cheapo Craftsman carbide glass-cutting bits; these did OK for starting holes in spring-steel plates.  Additional clean up with round files.
- Last 1 day, the "center punch method" described here by Don Williams and credited to "Chris Cianci"  (I wonder if he meant Matt Cianci ?):
http://donsbarn.com/dovetail-saw-making-workshop-day-2/

Chris

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Spot annealing.........

Take an old drill bit and chuck it upside down in a drill press. Make sure the bottom is flat. Put your drill press to the fastest speed it can go. Put the metal you want to spot anneal under the drill and press down while running at full speed. You will need to clamp it. Press fairly hard to create friction and heat things up. It doesn't take very long to get pretty hot in that spot, turn blue and soften it up. it is then ready to drill..Clamp the blade for safety...Make SURE the bit you are using to drill the holes is high speed steel...not carbon steel like many WW's are used to....HSS should be marked on the shank...otherwise I consider it carbon steel..I usually take a small slip stone and "back off" the rake angle of the drill bit a small amount, to strengthen the edge...Use a coolant when drilling.

[Admiral]

.................................
Spot annealing.........

Take an old drill bit and chuck it upside down in a drill press. Make sure the bottom is flat. Put your drill press to the fastest speed it can go. Put the metal you want to spot anneal under the drill and press down while running at full speed. You will need to clamp it. Press fairly hard to create friction and heat things up. It doesn't take very long to get pretty hot in that spot, turn blue and soften it up. it is then ready to drill..Clamp the blade for safety...Make SURE the bit you are using to drill the holes is high speed steel...not carbon steel like many WW's are used to....HSS should be marked on the shank...otherwise I consider it carbon steel..I usually take a small slip stone and "back off" the rake angle of the drill bit a small amount, to strengthen the edge...Use a coolant when drilling.

Excellent tip Jack.  I'd never have thought of doing that, but it makes incredible practical sense.  You da' MAN!

[Timberwolf]

Excellent tip Jack.  I'd never have thought of doing that, but it makes incredible practical sense.  You da' MAN!

........................
Rich, reducing the rake angle a bit and thinning the web on a HSS bit may make it possible to drill the plate without spot annealing at all...I did it on the last saw I made....I have also drilled out grade 8 bolts with a HSS bit that I hardened {the bits are not as hard from the factory as they "can" be...I suppose that is because they are more prone to breaking and the maker does not want a bad reputation in that regard..Grade 8's are harder than the average saw plate. But they still want the web of the drill bit thinned and the rake angle reduced a tad...The web can be thinned using the appropriate burr in a Dremel...As you know, the web is tapered and gets thicker as the bit is sharpened, making it more difficult to get "started"..

The "tool" for annealing can just be a short piece of any steel, preferably twice as large as the hole you want to drill and with a flat bottom on it to generate the most friction...You can actually see the saw plate "glow" red in color if you stay on it long enough.,.Sometimes friction is your friend !


Here's a good explanation of modifying the rake angle...The method he uses for brass also strengthens  the edge for steel as well..

https://www.youtube.com/watch?v=pAngKHIZgyA

and another on web thinning by Lyle Peterson..He has about a thousand tutorials on Youtube and you can't go wrong taking his advice...

https://www.youtube.com/watch?v=cqn2VPGYA9c

[bandit571]

There are some out there, that use a step drill bit......I have used a masonry bit as well....

[TraditionalToolworks]

I have punched them with a Roper Whitney Jr. Much cleaner.

When I did it, I center punched with the plate in the handle, then punch it out with a Roper Whitney.

Alan