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Shop made chamfer insert tool

Janger

Janger

(John)
Vendor
Premium Member
I tried to use my carbide center drill as a router bit and broke it. First it neatly drilled through a strap clamp. CNC... look away for a few seconds and the machine does exactly what you told it to do. So I ordered a index based chamfer tool from china and now i'm waiting for it to come. probably a month out still. So I decided to try to make one. Results are ok - not super - but the tool does work. It's noisy though. The tool has a bit of a gap from the side wall to the insert. Perhaps 0.010". I'm not sure if the screw hole is located out a bit or I measured the insert wrong. I only have a really crappy metric drill of the right size. I made the tool 3 times, funny the last one was the worst.

Diameter is 0.73". The triangle insert has a 3/8 inscribed circle.

CAD Drawing...
1587952104407.png


IMG_4935.JPG
 
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Results... the four 1/2" holes in the middle...
IMG_4938 2.JPG
You can see the tool leaves a big burr. @Alexander our resident expert suggests trying a faster RPM. I'll try some more combinations. This is about 1500 RPM and 0.001" per rev.

After clean up it looks better. It's ok.


IMG_4940 2.jpg

I hope you find this interesting :)
 
What's it made out of? In your milling images it looks like aluminum, but the finished product looks like steel?
 
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Ah it's just rusty basic 0.75 hot roll from federal metals. I did the vinegar thing and skimmed off the rest on the lathe to clean it up. Tool steel or something would probably be better - I imagine this is too soft for long life.
 
Janger said:
Ah it's just rusty basic 0.75 hot roll from federal metals. I did the vinegar thing and skimmed off the rest on the lathe to clean it up. Tool steel or something would probably be better - I imagine this is too soft for long life.
Click to expand...
I was thiking it was aluminium .
 
Does that vinegar pickling process take that hard crusty layer off that hot rolled or just the soot?
 
Can’t remember which Youtuber (maybe Robin Renzetti?), but they mentioned that the hole for the screw should be some distance off of perfect center to “draw” the insert into the pocket. I presume the countersunk bolt deforms or unevenly snugs into the insert to do that. They also used an appropriate tapered endmill to give the pocket sidewalls the same angle as the insert‘s relief.
 
Good info Rudy I’ll think about that. I wonder how many thousands over I should move the hole? 0.010?
 
Way to go John - that looks great.
Rudy beat me to it. I know Stefan has talked about this too.

I've had a few similar insert tool ideas kicking around, but always back burner mode. I've dodged the bullet thus far by modifying cheapo AliExpress tools where they have done the insert relief. But that only works in certain configurations & it would be nice to make some custom jobbies. FYI recently I discovered KBC sells tapered end mills in various included angles & diameters. Never even thought to look that up. Even my cheapo boring bars have tapered pockets so I'm guessing this might be the 'right' way to support the insert. Although I don't really know how bad the downside would be for hobbyist tools - risk cracking the cutter/supported edge since a 90-deg pocket would only be line contact?
 

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About the rpm, FWIW I was getting hit & miss results with countersink tools. Steel worse than aluminum. Usually rough looking finish or chatter that sometimes could develop into harmonic 'bumps'. I tried the single edge style & the usual multi edge thinking it was the cutter. Somebody finally mentioned to slow the rpm way down. I did that & problem solved. Much nicer results. I think my issue was for the most part I was just walking the part over to my drill press since the operation was quick & basically self centering. But because I was too lazy to change the belt it was inevitably too fast, at least for larger holes.
 

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I think it was Rob in this two part series that has the info you are after... I can’t remember how far offset he made the hole....


what size metric drill are you after? I probably have one.
 
Just a thought on the off centre hole for an insert. Every threaded hole has clearance. For the small screw used foir a 3/8 insert, it should be in the order of .005 - when you make the screw hole .005 off centre, your are sucking up the clearance on only one side of the hole, making a much more secure hold.

-- you can measure your particular hole by screwing the screw to the same depth as the hole, setting up your brand new .0005 indicator and pushing the screw in both directions using a tiny screwdriver. remember that this is a relative measurement and you have to take in account the geometry of where you are measuring versus the top of the hole.

-- in 3mm holes using cheaper but more available screws, i usually get .007 inches (yes mixed units - i love them!)
 
Janger said:
I tried to use my carbide center drill as a router bit and broke it. First it neatly drilled through a strap clamp. CNC... look away for a few seconds and the machine does exactly what you told it to do. So I ordered a index based chamfer tool from china and now i'm waiting for it to come. probably a month out still. So I decided to try to make one. Results are ok - not super - but the tool does work. It's noisy though. The tool has a bit of a gap from the side wall to the insert. Perhaps 0.010". I'm not sure if the screw hole is located out a bit or I measured the insert wrong. I only have a really crappy metric drill of the right size. I made the tool 3 times, funny the last one was the worst.

Diameter is 0.73". The triangle insert has a 3/8 inscribed circle.

CAD Drawing...
View attachment 8805

View attachment 8806
Click to expand...
That looks like a dandy tool. I have some inserts I purchased that were incorrect for one of my tools. i think I might have a go at making a holder for them. What steel did you use for the holder? (sorry, I should have read through the comments first) Could a person use a HSS tool blank?
 
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I think you could shape the HSS with carbide tools. You would need carbide drills and taps too I think?
 
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