Grinding a HSS Chamfering Tool?

[Alan H.]

Interested in grinding a dedicated HSS tool bit for chamfering. What would the profile look like?

It would be used in a BXA tool holder. I have plenty of blank stock available ( 3/8" to 5/8").

 

[Karl_T]

If i understand correctly, you want a 45 on the ID at the beginning of a bore??

Best tool for this is a broken two flute end mill. grind one flute away. grind a 45 on the other side.

You can do all sorts of combinations with old two flute end mills in the lathe. they make great small boring bars too.


OR if you are just chamfering holes, use a very large drill ground to the angle you need and put it in the tail stock.

 

[Alan H.]

Thanks Karl, actually want something for both ID and OD. Perhaps it is two different tools. I am looking for a shape to grind for use on the QCTP.

I have lots of carbide inserts variations but am getting into grinding my own HSS bits.

 

[Bob Korves]

I would make the tool more pointed so it could also work inside smaller holes. For the tool to work well for inside chamfers, plenty of relief is needed below the cutting edges, or they will rub. The back rake on the top is optional.

 

[Alan H.]

Thanks Bob, I am reminded of that youtube now that I see it again.

I wasn't sure about that one. I was assuming you do not want a back rake for a chamfer bit. You will be side cutting on the bit. Wouldn't the bake rack cause you to cut below center as you cut further back from the nose?

 

[kd4gij]

Just grind a 45deg triangle with standard relief. Just lift it up above cent for ID chamfer. I use a square natural insert that way all the time.

 

[Bob Korves]

Thanks Bob, I am reminded of that youtube now that I see it again.

I wasn't sure about that one. I was assuming you do not want a back rake for a chamfer bit. You will be side cutting on the bit. Wouldn't the bake rack cause you to cut below center as you cut further back from the nose?

I do not make my chamfer tools with back rake.

 

[Alan H.]

Okay Bob - I guess the best thing to do is to hone the top so you get a good edge.

 

[mikey]

I normally just use my knife tool for chamfering because I don't require a strict 45 degree chamfer and my knife tool lets me get inside pretty small bores for ID chamfering. I also prefer a 30 degree chamfer on the end of a threaded section so I use the knife tool instead of a dedicated chamfering tool. These angles are estimated by eye but unless I'm working to a print, none are critical.

If I did grind a dedicated tool, I would use about 12-15 degrees of side relief and I would leave the top flat. The reason for a zero rake tool is to allow it to cut on either edge equally well. It also puts all the cutting forces at the side cutting edge, right where a chamfering tool cuts. Of course, with zero rake tools you need to reduce cutting speed but that's no big deal.

Tom at Oxtools did an interesting chamfering/facing/turning tool. If you're doing a lot of tubular cuts in a production run, it looks like it might work pretty well.

 

[chips&more]

I leave the top of the bit flat. The bit has two 45’s on the end, one left- one right. If I’m chamfering a small hole, I raise the bit up from center so it does not rub. It’s not on center, but still cuts, this is not a big deal. If the chamfer is a big deal, like for looks, then I cut the chamfer with the compound…Dave.