Blade smithing

[trevj]

Check ebay for Counterbore cutters or new, like https://www.aircraft-tool.com/detail?id=4000-1034

Also search for spotfacer cutters. https://viewer.ipaper.io/sna-europe/snap-on-industrial/ati-catalog/ati-tools-catalog/?page=62

They make a clean, flat bottomed recess, and use a pilot hole for alignment.

If you saw a picture of the mandrel that the aircraft spotfacer type use, you could make one in a couple minutes.

Used in a drill press, they work really well for making an accurately sized well finished socket, where you want one.

 

[Chris Cramer]

Can I sharpen these dull tools? Unless they aren't made for stainless steels or tool steels the first one did not cut well at all into my shear blade. It could also have been that the heat from welding and plasma cutting the blades hardened them too much; but even when I tried cutting some old AEBL stainless steel which is not hard the tool still did not cut well. The first sew seconds are fine but even when working slowly it doesn't last.

 

[trevj]

Can I sharpen these dull tools? Unless they aren't made for stainless steels or tool steels the first one did not cut well at all into my shear blade. It could also have been that the heat from welding and plasma cutting the blades hardened them too much; but even when I tried cutting some old AEBL stainless steel which is not hard the tool still did not cut well. The first sew seconds are fine but even when working slowly it doesn't last.

Yes, you can, but it will take some amount of either skill or intuition to make it all work out!

Figure between 1 and 3 degrees of angle, to ensure that the cutter has a chance at actually cutting.

Then factor in, that there may well be, a bunch of really miserable hardened bits as a result of, well, 'circumstances'...

 

[PeterT]

You might have some harder material there. But another common thing is spinning too high an RPM on multi flute counterbores & countersinks. Try bringing the RPM way down & adjust feed. Oil helps but is not a remedy to RPM, feed & obviously cutting tool geometry.

 

[Chris Cramer]

You might have some harder material there. But another common thing is spinning too high an RPM on multi flute counterbores & countersinks. Try bringing the RPM way down & adjust feed. Oil helps but is not a remedy to RPM, feed & obviously cutting tool geometry.

Yeah, I started out at only 800rpm on my drill press and I made sure I used cutting oil. The other flutes in the set that haven't been used don't feel very sharp either. By the geometry of the flutes can these tools only cutt into a perfectly level flat surface?

 

[PeterT]

Even 800 rpm sounds high. Reduce it to half that or less, it might improve significantly. I all but gave up on chamfering countersinks but low RPM was the key. In your case the pilot pin keeps the cutter centered. . The tools @trevj mentions are specifically intended for this purpose. There are flat bottom end mills too, you have to look for them specifically. IMO they benefit by having a center hole pre-drilled because there is little to no EM cutting action near the center so they advance into the work better.

The trouble with some of this tooling is sometimes theoretically it should work, but if the grind is off, you have unequal cutting & it will skate off path for that reason alone. That's kind of like what a tool cutter grinder is all about to dress the edges consistently being held by the shank. But TCG is a whole nuther level of money.

I have made low brow grinder dressers using a collet block & just advancing into some kind of abrasive wheel or belt sander to a fixed stop. The 2-4-6 block sides means you can just flip the block & get quite consistent results. In fact I'm just about to try something along these lines on my Chinese TCG using the setup yoke as more or less an angled platform vs the indexing work head. To be continued.

 

[Chris Cramer]

This dimond file is the perfect shape and size for sharpening the edges of the counterbores. The flat bottom when made flush with the surface of one flute also lines the curved top fush with the curve on the bottom of the flute behind. This makes it easy to keep it straight at the proper angle and sharpens both the top and bottom of each flute.

 

[Chris Cramer]

Figure between 1 and 3 degrees of angle, to ensure that the cutter has a chance at actually cutting.

Im thinking that is why the tools don't cut well straight from the box. The bottom face of the tips are level with your work, so the tips don't have a steep enough angle to cut into the metal.

 

[trevj]

Im thinking that is why the tools don't cut well straight from the box. The bottom face of the tips are level with your work, so the tips don't have a steep enough angle to cut into the metal.

If you get a good look at a new unused edge, likely it has a fairly pronounced secondary relief from the rear of the edge, forward, with a much narrower primary relief to the cutting edge itself. The primary relief will be on the order of a couple degrees, the secondary is usually much steeper an angle.

If you think about it, you are trying to engage the total length of all the edges, at the same time, so low speed and ample torque are gonna be the order of the day!

 

[Chris Cramer]

so low speed and ample torque are gonna be the order of the day!

Yeah that started to work a bit after I sharpened the edges of the first bit. Instead of creating too much heat by applying high pressure at high speed I ran it as slow as possible which is 500rpm. The problem then was the fact that they are brittle. The blade shattered when I applied more pressure. It did cut fairly well into a mild steel plate, but I still had to apply more pressure than I should. Excessive pressure is dangerous and most tools at their high hardness are brittle.

 

[Chris Cramer]

This bur happens to have teeth on the end of the cylinder as well as the face around it. They did a much better job of grinding the hole around the link of the new bade I just cut.

 

[trevj]

I gotta suggest, that the issues you are dealing with, have a LOT to do with the varying hardness levels that come about from the welding of high and low carbon steels together.

Aka: "Much Misery".

Would suggest, as an easy route, looking at the most miserable alloy you may have created in the weld, and using that as the point of reference, from the perspective of trying to find a solution that just works. I say "Try", because, sometimes, that is pretty much all you can do. Try.

Counterbore and Countersink cutters are pretty handy tools to have, but there are no tools that can cover all the options!

No matter what, you really DO, have to fit the tool to the task at hand.

Carbide tools make life easier, but they don't always solve ALL the problems. Sometimes a fella has to look at the heat cycles that the work has endured.

 

[Susquatch]

Can I sharpen these dull tools? Unless they aren't made for stainless steels or tool steels the first one did not cut well at all into my shear blade.

Hey Chris, take a boo at the video I linked below. A short clip of the process is featured at the very beginning so you don't have to watch the whole thing. It simply isn't true that all metal cutting edges need to be sharp. Cutting most metals at the grain boundaries can sometimes be better described as ploughing or tearing instead of cutting. At the microscopic level, the tool compresses the metal ahead of the blade and causes it to tear along the grain boundaries.

If you have a lathe and carbide insert tools, look at the cutting edge under a magnifying glass. You will see that the edge cannot really be called sharp. your photo looks like it has carbide on the cutting edge. Carbide is particularly good for ploughing and doing so often requires a rounded edge that won't break off as easily as a sharp edge will.

I'm not suggesting that all carbide is dull or that it must always be dull. Just that it doesn't always have to be. I'm pretty new to carbide insert tooling so I could be wrong, but it is my impression that the majority of carbide inserts are actually quite dull even when brand new. It's also my observation that carbide inserts for cutting aluminium are usually quite sharp by comparison and surprisingly, these sharper inserts often work quite well in steel too - especially at low depth of cuts and low feed rates.

Just some info for your mental tool box. Hope you enjoy the video as much as I did. It adds another whole dimension to the process of metal working.

 

[Chris Cramer]

So far I think I've done pretty good designing and cutting these more heavy duty shears. The link works well, and I can feel that the inner edges come in contact with each other when I close them. However there hasn't been any heat treatment and the straightening was done by bending and with a hammer. There is a chance that the heat treatment will cause warping which is probably why they say it is so hard to assemble them when they are harder and more brittle.
I'm not really worried about them breaking, because I used AEBL stainless steel which is the most tough and flexible; but that may make it more difficult to make any changes afterwards without them flexing back.