What's the right tool to cut the inside of a 60° cone?

[CMV]

Making powder funnels as practice and have lots of options that work for the outside part, but nothing I have come up with so far does well on the inside part of the cone. I read Mongo's tutorial & like the countersink method, but don't want to spend $70+ on a big countersink that won't see that much use - esp if there's something in all my current tooling that will work. So far, I can get about 3/4 of the depth & everything is perfect, then the tool gets it it's own way. Tried grinding a HSS bit & kept adding relief, but I end up getting to a point where the tip is too fragile. I have a small insert type boring bar that looks like it should work, but no inserts (I suck). Takes one that looks like a smaller version of the CCMT 32.51 my other stuff uses but no idea which one exactly.

Maybe I'm going at it wrong. I have the compound set at 30° and the tool inline with the compound. Even if I offset (turn the tool holder a bit counterclockwise) I either still end up dragging on the cutting side (closest to me) or interfering with the other side deep in the cone. And no matter what, the bottom of the tool eventually interferes with the bottom of the cone once I get some depth.

I'm kind of thinking now that i could get a smaller countersink - maybe 1/2" - and use that as step 1. That would leave clearance deep in the cone where I'm having trouble. Then I could just meet that with what i'm doing now. It would work & only require a $30 tool, but seems like a shitty workaround for not knowing the right way/using the right tool.

Pics of tools/grinds that work well would be awesome!

[wolf]

A stink normal HSS drilllbit

grind the end flat ,grind a small portion of the cutting egde flat like a normal cutting tool
the cutting point have to be at 3 o clock when the tool points at you (just like a normal inside cutting tool )

the twist in the drill will let the long ribbons that you get when cutting flow nicely out of the hole/cone when cutting

set the drill so that it points straight into the center NOT at a angle (if a hole you have to give a slight angle to prevent the tool from rubbing on the parallel sides of the hole)

if the drill is smaller than the hole in the funnel/cone , nothing can interfer

dont make it longer than needed

its HSS , so it will cut like a HSS big surprise ,,huh

[jus2311]

I have counter bored, bored and then used counter sink to clean up the smaller diameter inside

[CMV]

Thanks - will try the drill bit tool this afternoon

[Bendersquint]

I use an indexable cutting tool and get a perfect finish everytime.

[CMV]

I use an indexable cutting tool and get a perfect finish everytime.

Can you link to the tool you're using? My indexable tools are way too big to get in there. I thought my boring bar would but now that i have something to gauge it with, it looks like it would get about 85% of the way there. Could just finish that last bit with a countersink

I'm getting nice finish on 316L, just can't get the depth.

Tried the drill bit using a 7/64. Only extended as much as I needed from the holder, but it kept snapping.

Have a 1/8 square HSS blank that worked, but took forever & didn't get a good finish - too small. A 1/4" blank might be the right starting point.

[redtazdog]

Mini boring bars work good
http://www.shars.com/product_categories ... 20_Inserts

[Bendersquint]

Mini boring bars work good
http://www.shars.com/product_categories ... 20_Inserts

Any of those will work fine. There are others out there that are more rigid, but they cost a pretty penny.

These will vibrate when working steel or titanium.

[57fairlane]

what you need is called a face grooving tool

[Bendersquint]

what you need is called a face grooving tool

For the inside of the skirt? How would a face grooving tool work for that? I can see the face of the plate but the skirt? Thats really deep and tight to use that, the radius would be insane.

[Historian]

Mentioned many times on this site a possible candidate:

1" 60 DEGREE ANGLE SINGLE FLUTE HSS COUNTERSINK

[wolf]

He DID write

but don't want to spend $70+ on a big countersink that won't see that much use - esp if there's something in all my current tooling that will work.



that's why i did suggest a simple drill bit used as a boring bar ,i DID assume he had one

I got the feeling he couldn't sit on his hands and wait for tooling

now i DID hope he would show some pictures of his work

[CMV]

Too embarrassing for pictures. When I get something looking halfway decent, I'll post a pic. You've all seen enough scrap by now to not be interested by any more

After looking closer at a lot of pictures I think part of the problem is I'm trying to go too deep. Should I be taking the taper all the way down to where it meets the bore hole? Some pictures look like the taper is stopping short of that point.



Lower left is looking straight in - lt gray is the tapered wall, black is bore, dark gray is area around the bore where the taper doesn't reach.

Other 2 are showing the taper on my funnel going all the way to meet the bore or stopping short. Which method is correct? I think trying to get all they way down there to meet the bore with the taper is what's boogering things up.

[Bendersquint]

Too embarrassing for pictures. When I get something looking halfway decent, I'll post a pic. You've all seen enough scrap by now to not be interested by any more

After looking closer at a lot of pictures I think part of the problem is I'm trying to go too deep. Should I be taking the taper all the way down to where it meets the bore hole? Some pictures look like the taper is stopping short of that point.



Lower left is looking straight in - lt gray is the tapered wall, black is bore, dark gray is area around the bore where the taper doesn't reach.

Other 2 are showing the taper on my funnel going all the way to meet the bore or stopping short. Which method is correct? I think trying to get all they way down there to meet the bore with the taper is what's boogering things up.

Most are a full taper, some of the more advanced have the stopping point as you describe.

Why don't you use a mini/small boring bar like suggested, it will get the job done, you will get some vibrations but nothing that you can't deal with.

[CMV]

Thanks everyone.

Why don't you use a mini/small boring bar like suggested, ...

Because I don't have one. My small one is 3/8" and can not go all the way in to meet a 17/64" hole. At least not with a typical CCMT 21.51 insert.

Kept messing with grinds. Got good results on the 316. Did one in 6AL4V and it cut the inside perfectly but my outside tool had issues about 3/4 of the way in. Stopped cutting and pushed the work into the chuck a little. Ended up boogering it all up after that, but up to that point it was bright, shiny, & smooth. Probably went a little to slow or dwelt a bit to long.

This is what i have so far inside & out and the tools I used.

[CMV]

Underside of little tool for the inside with relief:

[Bendersquint]

Mini boring bars from Shars as linked above is like $30 bucks and inserts are cheap and you won't run into the issues with the Ti.

What was your speed and feed with the titanium?

Were you using coolant?

How deep was your cut?

[57fairlane]

what you need is called a face grooving tool

For the inside of the skirt? How would a face grooving tool work for that? I can see the face of the plate but the skirt? Thats really deep and tight to use that, the radius would be insane.

Huh? We must not be talking about the same part.

I did these for a 2" O.D. shorty can

Its a crappy cell phone picture but the material on the bottom 3 is 316. tops are 7075.



Carmex makes the high dollar ones:

http://www.ebay.com/itm/Carmex-MFR-6-B2 ... 1123689354

you can find cheaper on msc through various other dealers.

being able to hang the tool out ~.750 and cut .040" depth of cut is nice. Just keep the feed to .0015 or less per rev.

[Bendersquint]

what you need is called a face grooving tool

For the inside of the skirt? How would a face grooving tool work for that? I can see the face of the plate but the skirt? Thats really deep and tight to use that, the radius would be insane.

Huh? We must not be talking about the same part.

I did these for a 2" O.D. shorty can

Its a crappy cell phone picture but the material on the bottom 3 is 316. tops are 7075.



Carmex makes the high dollar ones:

http://www.ebay.com/itm/Carmex-MFR-6-B2 ... 1123689354

you can find cheaper on msc through various other dealers.

being able to hang the tool out ~.750 and cut .040" depth of cut is nice. Just keep the feed to .0015 or less per rev.

Yes we were talking about the same tool. You just used a long face grooving tool as a boring bar.

Face grooving tools are meant for making grooves(like for o-rings etc) not boring material, thats why I thought you were talking about something else.

[57fairlane]

Face grooving tools are meant for making grooves(like for o-rings etc) not boring material, thats why I thought you were talking about something else.

ah. I use it very frequently as a boring bar when the start hole is small. Boring bars flex much easier.

[CMV]

Mini boring bars from Shars as linked above is like $30 bucks and inserts are cheap and you won't run into the issues with the Ti.

What was your speed and feed with the titanium?

Were you using coolant?

How deep was your cut?

Speed was 180 rpm, 300 for the finish pass

Yes, flood coolant. SynKool (of which I'm not a fan but is what I have)

Depth of cut - for inside the passes were about .060 each with a .003 finish pass. For outside (and here is the problem) 1 pass full depth and 1 .003 finish pass. On the stainless that was fine, but on the ti once the 'flat' part was around 0.275 that was asking too much. Maybe if I clamped the jaws down a little tighter I'd have gotten away with it, maybe not.

But for the outside I'm doing 1 cut - starting the tool at the end and feeding in with the compound deeper & deeper until I'm at the right depth. Pretty hefty cut for my 2 hp machine and 1/2" tool once its near the end.

[OnyxSkyDV]

I used an inexpensive braised carbide lefthand tool, and ground a very generous radius'ed relief under it. Probably weakened the carbide some, but still takes a decent bite without much issue.

http://s18.photobucket.com/albums/b108/ ... G_0965.mp4

Onyx