Custom reamer

[sparky961]

I got on this idea after the recent (?) posting about chambering reamers.  I have always considered that it would be fairly simple to make something like this, but it's always great to see someone else go through the steps before attempting something yourself.

That said, I have an internal profile that I'd like to cut using a drill/reamer type of tool.  Material to cut is 6061 AL, and I'd be making the tool from drill rod (silver steel), probably O1 or something like that.  I'd prefer to cut everything in one shot but it might be easier on the tool to hog out material with a big drill first.





After trying to visualize how to cut the flutes both in my own imagination and 3D software, I'm at a loss.  I can't seem to figure out the best way to cut the flutes while getting decent chip extraction, keeping enough material for strength, and limiting it to methods compatible with my equipment.  I was going to mount in a 3-jaw on a rotary table, then cut the shape of the flutes with an endmill.  I'd love to be able to cut the flutes somehow straight, thus not requiring that I get all of my CNC stuff put together but that too is on the table.

Eagerly awaiting your helpful suggestions...


Thanks,
-Sparky

[bp]

I made something similar to profile the venturi for a model aeroplane engine.  Not quite as big as the one you have shown, it was out of 0.5" silver steel, like your drill rod.  I simply turned the profile I wanted....a shallow taper starting at about 1/8" diameter, something like 10 or 15 degrees, finished with a big radius 0.25" if I remember.  Then parted it off, milled down to 1/2 diameter plus a bit, filed in some clearance, filed away the "back" of the tool, and hardened it.  Cleaned up and honed it works a treat.  I just drill a 1/8" diameter hole, stick the reamer in the tailstock chuck and gently crank it in, with lots of kero, and frequent withdrawals to clean off swarf.  Not too fast.  Because I went to some trouble to hone the cutting edge, it leaves a beautiful finish.
Don't stress over it, give it a go, they are very quick and easy to make.
best of luck
Bill Pudney

[Fergus OMore]

All that is happening is 'Making a D Bit' but it is not a half diameter left but a half plus .002" The redoutable Bradley covered it in- if I recall in several of his books. George Thomas has one ( or more) in Model EngineersWorkshop Manual and old Sparey certainly had a variant.
That leaves the World of Musical Instrument people who make D bits  boring some 13" and more deep. The Scottish bagpipe and half long brigade use-- French Napoloeonic bayonets- seriously. Me, I am dead lazy. I make up reamers to bore through brick walls - and don't even temper them. However, if you have have something capable of grinding, you introduce a 10 degree chip breaker to bore metal.

My reamer jig( I got it given) is rusting away. Frankly, if it a 'one off' in ally, I'd temper it by getting it red hot and sticking it in a 'tattie'

[sparky961]

Thanks for the suggestions gentlemen.

So, if I'm getting this straight the goal is to make a tool with a single cutting edge that has the profile you wish to cut?  Was I just trying to make my life more difficult than need be by thinking multiple flutes? (yes, I do tend toward that...)

I will look more at D-bit geometry before going at it.  I recall reading a few posts on the subject a while back.

Thanks,
-Sparky

[bp]

Yep, that's it, a single cutting edge.  The one I described above has a cutting edge about 1" long and as long as the feed and speed is kept sensible there's no chatter.
Good luck!!
cheers
Bill Pudney