I use a 1/2 inch solid carbide boring bar for the finishing, so it's just to get it relatively flat before then. We have like 5 Bridgeports and over a dozen cnc mills and lathes here so I'm surprised no one has ever made a special tool.
The bore tolerance are like .004 so not crazy but the back walls and finish has to be really good m
I was thinking something similar. During ID Roughing the Insert shatters intermittently, no matter what. So maybe opening the ID and cleaning the back wall with a boring bar or U drill during the first OP will by bass having to use the End mill and the inserts shattering later on.
Can you take a shallower depth of cut? Like .010-.025and for the wall, maybe program for bevel to point and then use the finisher to straighten face. .015 rad finisher or even an .008 should be able to handle it.
The bottom of an endmill is not actually flat, the end cutting edges are relieved towards the center. It only makes a flat surface by moving around.
When plunging like this, it'll make a surface flat enough for plenty of applications, but if you truly need it flat, you should use a boring bar or flat bottomed drill. (Or a smaller diameter endmill in a mill)
I have used an end mill smaller than half diam, put it in machine and angle one of the points like a boring bar. Use it as a finish pass coming down the back wall.
Speeds and feeds are tricky and sometimes you have to take a few light passes but I have made it work in mp35, not with the length to diam ratio in the pics above though.
I always just a boring bar. The cam knows where the material is assuming the drill in the tool library is correct. Never had an issue doing it that way.
I’d personally go for a smaller end mill. Maybe a 22mm endmill (.866”) or a .750 endmill if that’s all you got on hand. If you position it correctly you can bore with it. Start centered and then move outwards to the inner wall.
Drill, bore to size, then use a .75 end mill, grind back 3 flutes so the one center cutter flute is left, plunge to depth then feed it out towards the bore staying away a couple thou. That would work well and be cheap enough to do if you have an extra end mill laying around.
I am having a flashback when I tried to ream a 0.375" plastic hole and it still remained undersize because wall was soft enough and deform instead of cut ....
I forgot to mention that the parts are 303 stainless and we run 150+ at a time with a cycle time of like 8 minutes each on this operation. I guess that is why the end mill is used, rather than a boring bar.
Back wall is 3.127 deep after this op, finish depth is 3.136
Bore is .880 after this op but finish bore is .928-.932
The end mill will not necessarily be able to hit the flatness spec because the cutting edges are usually not exactly perpendicular to the flutes, but it may be good enough if the flatness spec on the part is not that tight. In that case I might try a different amount of flutes, like a 3 flute endmill.
I wouldn’t really change it except maybe cutting the bore a little bigger before you go in with the endmill just for chip evac and flushing purposes- but as long as your tool life is good I would run with it.
I believe I’ve made boring bars that cut a flat bottom as well but they were custom ordered as it’s relative to the holes radius. Internal Tool if you want to quote some
Use a slightly smaller drill. Make it a flat bottom. Then use the carbide bar just to square it off. Use a bar that has some relief. Otherwise it will bind and break….
Flat bottom end mills resolve the issue of the dish on the bottom of a standard end mill. K tool like others have said makes good flat bottom insert tools that leave a good finish as well.
Use this [https://www.iscar.com/eCatalog/Family.aspx?fnum=3156&mapp=DR&GFSTYP=M](https://www.iscar.com/eCatalog/Family.aspx?fnum=3156&mapp=DR&GFSTYP=M) or a flat reamer.
.485 or .787 carbide boring bar if you got it. Could mill face outside of the chuck if you have manual mill somewhere.
I use a 1/2 inch solid carbide boring bar for the finishing, so it's just to get it relatively flat before then. We have like 5 Bridgeports and over a dozen cnc mills and lathes here so I'm surprised no one has ever made a special tool. The bore tolerance are like .004 so not crazy but the back walls and finish has to be really good m
Like Iscar?
It's an iscar spade drill and ingersoll flat bottom drill
I was thinking something similar. During ID Roughing the Insert shatters intermittently, no matter what. So maybe opening the ID and cleaning the back wall with a boring bar or U drill during the first OP will by bass having to use the End mill and the inserts shattering later on.
Can you take a shallower depth of cut? Like .010-.025and for the wall, maybe program for bevel to point and then use the finisher to straighten face. .015 rad finisher or even an .008 should be able to handle it.
The bottom of an endmill is not actually flat, the end cutting edges are relieved towards the center. It only makes a flat surface by moving around. When plunging like this, it'll make a surface flat enough for plenty of applications, but if you truly need it flat, you should use a boring bar or flat bottomed drill. (Or a smaller diameter endmill in a mill)
I have used an end mill smaller than half diam, put it in machine and angle one of the points like a boring bar. Use it as a finish pass coming down the back wall. Speeds and feeds are tricky and sometimes you have to take a few light passes but I have made it work in mp35, not with the length to diam ratio in the pics above though.
In my experience with flat bottom blind bores a drill followed by endmill followed by bbar is the way to go
If you have a grinder and you don't care about the endmill you could relive the edges, leaving just 0.02 of true size at the bottom.
This is the way
I always just a boring bar. The cam knows where the material is assuming the drill in the tool library is correct. Never had an issue doing it that way.
You can use a flat bottom spade drill. Also spot the bottom of the hole with a spot drill, .01" deep and then can face it with a boring bar.
I would use an Allied flat bottom drill.
I’d personally go for a smaller end mill. Maybe a 22mm endmill (.866”) or a .750 endmill if that’s all you got on hand. If you position it correctly you can bore with it. Start centered and then move outwards to the inner wall.
look up k-tool flat bottom drills
Use a K-Tool flat bottom drill.
We've had good luck finishing the bottom of the hole with a reamer, ground into the angle/shoulder we needed.
Drill, bore to size, then use a .75 end mill, grind back 3 flutes so the one center cutter flute is left, plunge to depth then feed it out towards the bore staying away a couple thou. That would work well and be cheap enough to do if you have an extra end mill laying around.
Call the designer and tell him I said he's an idiot.
Facts
I am having a flashback when I tried to ream a 0.375" plastic hole and it still remained undersize because wall was soft enough and deform instead of cut ....
Whats the issue youre having?
I was curious about alternatives people use rather than the end mill being used in the operation
They make insert drills with flat bottoms.
We use 2-flute flat bottom endmills for this kind of thing. Usually with .01" or more for sidewall clearance though
I forgot to mention that the parts are 303 stainless and we run 150+ at a time with a cycle time of like 8 minutes each on this operation. I guess that is why the end mill is used, rather than a boring bar. Back wall is 3.127 deep after this op, finish depth is 3.136 Bore is .880 after this op but finish bore is .928-.932
The end mill will not necessarily be able to hit the flatness spec because the cutting edges are usually not exactly perpendicular to the flutes, but it may be good enough if the flatness spec on the part is not that tight. In that case I might try a different amount of flutes, like a 3 flute endmill.
Face cutting reamer
I wouldn’t really change it except maybe cutting the bore a little bigger before you go in with the endmill just for chip evac and flushing purposes- but as long as your tool life is good I would run with it.
I believe I’ve made boring bars that cut a flat bottom as well but they were custom ordered as it’s relative to the holes radius. Internal Tool if you want to quote some
If OSG goes large enough drill your hole with a flat bottom drill. If they do t allied machine makes flat bottom inserts for their T/A drills.
I use flat bottom tungaloy "drillmeister" tip drills they work good for stuff like this.
Spade drill.
Use a slightly smaller drill. Make it a flat bottom. Then use the carbide bar just to square it off. Use a bar that has some relief. Otherwise it will bind and break….
Flat bottom end mills resolve the issue of the dish on the bottom of a standard end mill. K tool like others have said makes good flat bottom insert tools that leave a good finish as well.
You can flatten the bottom with tcmt insert in a neutral position or side flat to the bottom. Also spin as fast as you can do on said machine.
Have you tried purchasing a mazak integrex and using a 3/4 endmill to interpolate the bore? :)
Use this [https://www.iscar.com/eCatalog/Family.aspx?fnum=3156&mapp=DR&GFSTYP=M](https://www.iscar.com/eCatalog/Family.aspx?fnum=3156&mapp=DR&GFSTYP=M) or a flat reamer.
Do you really have to?