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Grinding a HSS Chamfering Tool?

Alan H

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#1
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

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#2
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

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#3
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

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#4
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

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#5
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?
 

Bob Korves

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#7
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

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#8
Okay Bob - I guess the best thing to do is to hone the top so you get a good edge.
 

mikey

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#9
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

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#10
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.
 

Alan H

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#11
Mike, I think your knife tool has back rake on it doesn't it? That means you likely are not cutting too far from the tip are you (back to the off center issue)? Do you spin the post and plunge through the chamfer rather than side cutting?
 

mikey

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#13
I don't worry too much about cutting on center height when chamfering. I can get away with that because I tend to use larger relief angles than most folks do. I also slow the lathe down a bit before cutting. And yes, I bring the side of the tool into contact and feed in with the cross slide. Accordingly, the segment of the cutting edge is changing elevation as I go in. I have no chatter and the cut is done inside of a second or two at most.
 

darkzero

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#14
Check out the tool that Tom Lipton (Ox Tools) grinds, Stefan Gotteswinter also uses the same grind. It allows you to face with it also. It's really only for OD chamferring but if the hole is large enough & if you grind enough clearance you can use it for ID chamfering as well. You can also raise the cutting height/tool for ID chamfering for more clearance. EDIT: Didn't notice but Mike beat me to it. :)

I use a 45° indexable tool that is similar. Allows OD chamfering & facing. I probably have a lifetime supply of these inserts that I got for cheap. The inserts I got also has a large nose radius so they give a nice finish for OD turning as well. As you can see it doesn't have a lot of clearance like Tom Lipton's tool so it won't work for ID chamfering but that's ok. I usually use a boring bar for ID chamfering when I want a nice chamfer. My compound sits at 45° 75% of the time anyway.




I also still use these D-style brazed carbide bit for certain applications, one for OD & one for ID. They're 80° inclusive but still work fine. I've been meaning to shorten them so I can use both in one tool holder. But as of now I still have plenty of tool holders so not a big priority. Again, for ID I just raise the tool for clearance when needed.



 
Last edited:

Tozguy

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#15
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.
I'm a flunky when it comes to grinding HSS chamfer tools. The most versatile chamfering tool I own for one off jobs is this:

IMG_0240.JPG

It is a spiral carbide 45 deg burr that will chamfer the smallest hole or the largest o.d. The spiral flutes provide for chip clearing and also facilitates control of the cutting action.
 

BGHansen

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#16
I use a LH triangular insert tool. Just pop off what's on the QCTP, drop on the LH tool and chamfer away.

Bruce
 

benmychree

John York
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#17
I use style D carbide brazed on tools in both ends of my Aloris holders, with the shanks cut shorter to reduce overhang; on the tool that is used for ID chamfering, I grind more clearance on the carbide and the steel shank, so that most of the time it is not necessary to raise tool to attain clearance, only necessary for small diameters, many of which can be deburred with a twisting type deburring tool or a three cornered scraper; for back end of bores, I have a Bokum boring bar with a 90 degree included angle screw on end that can do small chamfers on the inner end and outer end of a bore.
 

Silverbullet

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#18
I don't use chamfer tools unless the print calls for it . I brake my edges with a file held on a angle to do the chamfer , inside edge on the end of the same file I have ground a sharp edge with a rounded hook to rest the hook in the bore and apply pressure will deburr and either round or chamfer as I please . In fact I get less chatter doing them this way.