Inside out reamer?

[Neil]

We 3d print some parts that are short stubby cylinders (about .25 diameter and .500 long). We need something like an inside out reamer to ream to final size and shape. What I mean by inside out is the internal bore is where the teeth are. Probably virtually impossible to make, although it could be open bore at both ends, and wire edm teeth? Probably very expensive to make.

Does such a tool exist??
This problem could be solved if my boss used support while 3d printing, but he doesn't want to for whatever reason, so this is the solution he is asking for. I ask pointed questions, but I stopped challenging him long ago. Not worth the effort.

 

[memphisjed]

rota-broach without the ejector pin.

 

[gusmadison]

Hollow mill perhaps? - fixed or adjustable

 

[M.B. Naegle]

turret lathe box tool?

 

[swarfless]

Try CDTooling.com for hollow mills. No affiliation here, just first one to come up with Google. Hollow mills used to be used on Capstan/turret lathes to quickly cut down spigots. Also extremely handy for producing round spigots on milled work. Gus beat me to it.

 

[Metalurgent]

Regular boring head with the tooling reversed?

 

[michiganbuck]

or buy the correct Od and run a drill through on a lathe.
Feeding long round stock through a steady rest might be good.
*Sketch of the needed part would be good.

 

[sfriedberg]

Another vote for hollow mills. However, all these tools are designed to remove metal. You need to think about tool angles (like rake) that would be more appropriate for plastic (you didn't state, so I am assuming). Also beef up the perimeter on your prints so they can stand up to the material removal.

 

[Neil]

Thanks everybody!!

 

[mhajicek]

We 3d print some parts that are short stubby cylinders (about .25 diameter and .500 long). We need something like an inside out reamer to ream to final size and shape. What I mean by inside out is the internal bore is where the teeth are. Probably virtually impossible to make, although it could be open bore at both ends, and wire edm teeth? Probably very expensive to make.

Does such a tool exist??
This problem could be solved if my boss used support while 3d printing, but he doesn't want to for whatever reason, so this is the solution he is asking for. I ask pointed questions, but I stopped challenging him long ago. Not worth the effort.

I've been asked several times to clean up and fix tolerance on 3D printed parts. In most cases I've seen it's faster, cheaper, and easier to just machine the part from scratch.

 

[Limy Sami]

I've been asked several times to clean up and fix tolerance on 3D printed parts. In most cases I've seen it's faster, cheaper, and easier to just machine the part from scratch.

BTDT (almost) heard the tale of woe and asked the customer to take them away.

 

[kenton]

My personal experience with 3D printed gears in PLA is to jam a twist drill through the center hole as fast as possible rather than try to use a straight flute reamer to bring the center hole to size. Might tell you something about the needed cutter geometry and chip load.

 

[Conrad Hoffman]

They sell cutters for making wooden dowel pins that are basically inside out cutters.

 

[EPAIII]

Beat me to it.

But just how are you going to hold a 1/4"x1/2" cylindrical part to use that or any kind of cutter on.

I think a better way would be to force them through a 1/4" diameter hole in hardened, tool steel; aka, a sizing die. You would need a slightly larger diameter hole in a guide that sits a small distance (1/16"?) above the top of that die to allow an opening for the shavings to exit to the side. A lever activated pin, slightly smaller than 1/4", to apply the pressure to force them through. And a bucket below to catch them as they drop.

The thickness of both the die and the guide should be a significant fraction of the 1/2" length of the parts to insure proper guidance both before and during the sizing process. If the guide is around 3/4" thick the bottom 1/2" of the guide hole can be just slightly larger than the 1/4" diameter so the parts will be guided and the top 1/4" of the hole can be tapered/chamfered to allow easy insertion of the parts. A tapered reamer might be used for that part of the hole.

If you have a lot of them to do, some kind of powered activator on the drive pin would be nice.

They sell cutters for making wooden dowel pins that are basically inside out cutters.

 

[swarfless]

Beat me to it.

But just how are you going to hold a 1/4"x1/2" cylindrical part to use that or any kind of cutter on.

Right On! I didn't read the OP's post properly. AND we don't know what material is involved .. could be anything from wax to metal. But since his boss is into Value Adding rather than efficient production, instead of EPA's female broach how about centreless grinding the little beggars?

 

[Illinoyance]

Look for hollow mills.

 

[triumph406]

We 3d print some parts that are short stubby cylinders (about .25 diameter and .500 long). We need something like an inside out reamer to ream to final size and shape. What I mean by inside out is the internal bore is where the teeth are. Probably virtually impossible to make, although it could be open bore at both ends, and wire edm teeth? Probably very expensive to make.

Does such a tool exist??
This problem could be solved if my boss used support while 3d printing, but he doesn't want to for whatever reason, so this is the solution he is asking for. I ask pointed questions, but I stopped challenging him long ago. Not worth the effort.

something like McM 3323A29 with the tang on the backside ground off

Or McM 3438N25

 

[EPAIII]

OK, so I don't know. I am just asking. Can you actually centerless grind something that small? I thought centerless grinding was done on long stock. Grind, then cut them off?

Right On! I didn't read the OP's post properly. AND we don't know what material is involved .. could be anything from wax to metal. But since his boss is into Value Adding rather than efficient production, instead of EPA's female broach how about centreless grinding the little beggars?

 

[Neil]

The part is PDA I think. Some kind of 3d printing plastic.

 

[Illinoyance]

If you have a small geometric die head, there are cutters available that convert it to a hollow mill. They are probably custom-made and spendy.

BTW, what is your diameter and tolerance? I may have a hollow mill of the correct size. I also have an adjustable hollow mill that I might part with.