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A quick one this time.

I have a need to cut a larger dovetail than my small HSS dovetail cutter will manage (it has a max depth of 5mm). So, I'm making an insert dovetail cutter. This will take the standard inserts that I use, TCMT110402, which are about 10mm along each edge and have a 7deg relief angle. The design I came up leaves the cutting edge of the tool only just past teh center line, resulting in a very small negative rake angle. Mounting it on the center line would be better, but would increase the required diameter of the tool too much, it's a compromise. https://pic8.co/sh/PaLP7L.jpg

To start with, I turned the shank to 10.00mm and roughly turned the 60deg cone on the end resulting in a 24mm max diameter. https://pic8.co/sh/nS018u.jpg

After the shank was cut from the bar and faced, it was mounted in a V block on the rotary table. The exact location wasn't critical as the rotation is only needed to give an accurate angle for the cutout. The fixture was rotated until the bottom of the cutter was aligned with the mill Y-axis. https://pic8.co/sh/CJkT9P.jpg

The first milling operation is to drill and tap the M2.5 hole that secures the insert. First, a flat spot is milled with a 3mm end mill, then a 2mm hole drilled (should be 2.05, but I don't have that drill) and carefully tapped for M2.5. https://pic8.co/sh/bQTKUa.jpg

Next, the cutter needs to be rotated 180deg in the V block. To do this, I attached my mill vise stop block to the end and aligned it vertically. Then I could rotate it and re-align it vertically to ensure that I had a 180deg move. https://pic8.co/sh/ulPKjT.jpg

After that the table was rotated 30deg. It was just a matter of milling away material until the desired depth below the center line was reached and the desired depth was reached such that the insert would secure snuggly against the milled edge. https://pic8.co/sh/fL9BAz.jpg

This left the end of the cutter a little large (as was planned). So, it was back into the lathe with it, where the face and tapered sides were trimmed until they aligned with the rear edges of the insert. This would give sufficient clearence on the bottom and sides. https://pic8.co/sh/KUFhBd.jpg https://pic8.co/sh/ZocuJt.jpg https://pic8.co/sh/Igs8jP.jpg

That's it, now I just need to see if it works. That should happen soon enough as I use it to make yet another tool. https://pic8.co/sh/5xiwRz.jpg

A quick one this time. I have a need to cut a larger dovetail than my small HSS dovetail cutter will manage (it has a max depth of 5mm). So, I'm making an insert dovetail cutter. This will take the standard inserts that I use, TCMT110402, which are about 10mm along each edge and have a 7deg relief angle. The design I came up leaves the cutting edge of the tool only just past teh center line, resulting in a very small negative rake angle. Mounting it on the center line would be better, but would increase the required diameter of the tool too much, it's a compromise. https://pic8.co/sh/PaLP7L.jpg To start with, I turned the shank to 10.00mm and roughly turned the 60deg cone on the end resulting in a 24mm max diameter. https://pic8.co/sh/nS018u.jpg After the shank was cut from the bar and faced, it was mounted in a V block on the rotary table. The exact location wasn't critical as the rotation is only needed to give an accurate angle for the cutout. The fixture was rotated until the bottom of the cutter was aligned with the mill Y-axis. https://pic8.co/sh/CJkT9P.jpg The first milling operation is to drill and tap the M2.5 hole that secures the insert. First, a flat spot is milled with a 3mm end mill, then a 2mm hole drilled (should be 2.05, but I don't have that drill) and carefully tapped for M2.5. https://pic8.co/sh/bQTKUa.jpg Next, the cutter needs to be rotated 180deg in the V block. To do this, I attached my mill vise stop block to the end and aligned it vertically. Then I could rotate it and re-align it vertically to ensure that I had a 180deg move. https://pic8.co/sh/ulPKjT.jpg After that the table was rotated 30deg. It was just a matter of milling away material until the desired depth below the center line was reached and the desired depth was reached such that the insert would secure snuggly against the milled edge. https://pic8.co/sh/fL9BAz.jpg This left the end of the cutter a little large (as was planned). So, it was back into the lathe with it, where the face and tapered sides were trimmed until they aligned with the rear edges of the insert. This would give sufficient clearence on the bottom and sides. https://pic8.co/sh/KUFhBd.jpg https://pic8.co/sh/ZocuJt.jpg https://pic8.co/sh/Igs8jP.jpg That's it, now I just need to see if it works. That should happen soon enough as I use it to make yet another tool. https://pic8.co/sh/5xiwRz.jpg

(post is archived)

[–] • 1 pt

That's cool. I like the triple cutting bit/edge/die/tooth (whatever you call it) Should keep you in business for awhile.

[–] • 1 pt

They're ok while they last, but this is a cheapo one (if you look closely, you can see one corner is already burned out). Having said that, I'm only on my second pack of 10 of them, with the first pack being the shitty ones pictured that came with the tool holder kit.

Even when a bit blunt, they'll usually cut ok, but leave a shitty surface finish. There are hundreds (probably thousands) of different types of them though, so you can get one almost any purpose. The cheap ones are low quality carbide and are pretty fragile and don't like interrupted cuts too much which is what tends to kill them for me as I used them for all sorts of things, like on my fly cutter.