I have an application which requires a ball nose plunge cut for two
intersecting channels. The ID of the holes require precision, and are from
..130 - .190 depending on the application. First the channels are drilled
with a carbide .125 drill bit, then I was using a ball nosed end mill, 5/32
to be exact. That size was easy to find, and at first I just wanted to see
if my jigging and procedures would hold up, and things are all looking
great. Now that I need to get serious with the precision, it is time to
switch to reamers.

I could go with custom 'ball nosed' reamers, but I have a ton of standard
reamers here now, and was contemplating trying to cut the nose of the reamer
to be a nice radius. Since the pilot hole takes care of alot of the
material, I was hoping that someone might recommend a procedure that will
give a nice smooth radius tip to a standard end reamer.

Any helpful posters are invited to enlighten me!

thanks in advance,

Ryan

"Ryan" wrote in message
news:qjKjb.19667$S_.2981@clgrps13...
I have an application which requires a ball nose plunge cut for two
intersecting channels. The ID of the holes require precision, and are
from
.130 - .190 depending on the application. First the channels are drilled
with a carbide .125 drill bit, then I was using a ball nosed end mill,
5/32
to be exact. That size was easy to find, and at first I just wanted to
see
if my jigging and procedures would hold up, and things are all looking
great. Now that I need to get serious with the precision, it is time to
switch to reamers.

I could go with custom 'ball nosed' reamers, but I have a ton of standard
reamers here now, and was contemplating trying to cut the nose of the
reamer
to be a nice radius. Since the pilot hole takes care of alot of the
material, I was hoping that someone might recommend a procedure that will
give a nice smooth radius tip to a standard end reamer.

Any helpful posters are invited to enlighten me!

thanks in advance,

Ryan

It's probably not necessary for me to tell you that machine reamers are not
intended to cut to the center. In order to grind one that does, you'll
have to eliminate all the flutes in the radius area except for two or three,
to create the needed clearance. Staggering them by grinding three instead
of two could help prevent chatter if it's a problem.

If you have a cutter grinder available, you should be able to make the
cutter, but it could be a tough job, though certainly possible, freehand.
I think you can see what you must do to the reamer by studying a ball end
mill. In principle, they would cut the same way. You'd be leaps ahead if
you don't need it to cut to the center, though.

Good luck~

Harold

Thanks Harold,

I am quite intimidated by this project, but since I will be drilling a pilot
hole of .125 which will leave basically no material in the center to cut
with the reamer... then reaming to .160 (for example) the reamer will only
have to cut a bit on the nose, and not on the very tip, just on the corner
radius of the nose. Did that make sense?

Ryan




"Harold & Susan Vordos" wrote in message
...

"Ryan" wrote in message
news:qjKjb.19667$S_.2981@clgrps13...
I have an application which requires a ball nose plunge cut for two
intersecting channels. The ID of the holes require precision, and are
from
.130 - .190 depending on the application. First the channels are
drilled
with a carbide .125 drill bit, then I was using a ball nosed end mill,
5/32
to be exact. That size was easy to find, and at first I just wanted to
see
if my jigging and procedures would hold up, and things are all looking
great. Now that I need to get serious with the precision, it is time to
switch to reamers.

I could go with custom 'ball nosed' reamers, but I have a ton of
standard
reamers here now, and was contemplating trying to cut the nose of the
reamer
to be a nice radius. Since the pilot hole takes care of alot of the
material, I was hoping that someone might recommend a procedure that
will
give a nice smooth radius tip to a standard end reamer.

Any helpful posters are invited to enlighten me!

thanks in advance,

Ryan

It's probably not necessary for me to tell you that machine reamers are
not
intended to cut to the center. In order to grind one that does, you'll
have to eliminate all the flutes in the radius area except for two or
three,
to create the needed clearance. Staggering them by grinding three
instead
of two could help prevent chatter if it's a problem.

If you have a cutter grinder available, you should be able to make the
cutter, but it could be a tough job, though certainly possible, freehand.
I think you can see what you must do to the reamer by studying a ball end
mill. In principle, they would cut the same way. You'd be leaps ahead
if
you don't need it to cut to the center, though.

Good luck~

Harold

I'd be drilling a larger hole than what you are. Reamers can be done with a
taper on the nose area if so desired and the reamer goes all the way through
the material however, such shouldn't be done for that much material as a
reamer is intended for doing a final trim of the hole size rather than doing
massive cutting of the work. You're trying to take .035" of material which
is pretty thick for a reamer on one shot.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!

"Ryan" wrote in message
news:zcUjb.5120$qh7.1723@edtnps84...
Thanks Harold,

I am quite intimidated by this project, but since I will be drilling a
pilot
hole of .125 which will leave basically no material in the center to cut
with the reamer... then reaming to .160 (for example) the reamer will only
have to cut a bit on the nose, and not on the very tip, just on the corner
radius of the nose. Did that make sense?

Ryan

Yep, it did. You might be able to simply enlarge the chamfer on the reamer
a little, changing it from the 45° angle it should be, to the radius you
desire, without going to the center. If you choose that direction, keep in
mind chip clearance. As you get closer and closer to the center of the
reamer, you'll lose any room for chips, which is one of the reasons for
altering the number of flutes. As you remove a few of them it will provide
the necessary space for chips. Keep the clearance angle in mind as you
do, too. Be very careful to not round off the cutting edge. That is a
sure recipe for a cutter that doesn't cut size. It's also important that
each of the flutes cut equally, otherwise the reamer will tend to wing on
one tooth and cut an oversized hole. .

I think you can make this work, but you may spend a little time working it
out. Well spent if you have enough holes, that's for sure.

One other thing to consider, you may desire to ream a lot less material,
which will help. Reaming much more than about .008" per side can present
some serious problems, and also increases your chance of an oversized or
poorly finished hole, mostly due to chip loading. If you can drill closer,
perhaps only ten thou under, try that to see how it goes. Drill such that
the point of your drill stops shallow enough that the drill point leaves
material for the reamer to cut the desired radius.

Good luck~

Harold

Harold & Susan Vordos wrote:

"Ryan" wrote in message
news:zcUjb.5120$qh7.1723@edtnps84...
Thanks Harold,

I am quite intimidated by this project, but since I will be drilling a
pilot
hole of .125 which will leave basically no material in the center to cut
with the reamer... then reaming to .160 (for example) the reamer will only
have to cut a bit on the nose, and not on the very tip, just on the corner
radius of the nose. Did that make sense?

Ryan

Yep, it did. You might be able to simply enlarge the chamfer on the reamer
a little, changing it from the 45° angle it should be, to the radius you
desire, without going to the center. If you choose that direction, keep in
mind chip clearance. As you get closer and closer to the center of the
reamer, you'll lose any room for chips, which is one of the reasons for
altering the number of flutes. As you remove a few of them it will provide
the necessary space for chips. Keep the clearance angle in mind as you
do, too. Be very careful to not round off the cutting edge. That is a
sure recipe for a cutter that doesn't cut size. It's also important that
each of the flutes cut equally, otherwise the reamer will tend to wing on
one tooth and cut an oversized hole. .

I think you can make this work, but you may spend a little time working it
out. Well spent if you have enough holes, that's for sure.

One other thing to consider, you may desire to ream a lot less material,
which will help. Reaming much more than about .008" per side can present
some serious problems, and also increases your chance of an oversized or
poorly finished hole, mostly due to chip loading. If you can drill closer,
perhaps only ten thou under, try that to see how it goes. Drill such that
the point of your drill stops shallow enough that the drill point leaves
material for the reamer to cut the desired radius.

Good luck~

Harold

Find a *good* tool & cutter sharpening shop and have them done. Perhaps try a
couple or three and have each do a sample to find the best at the job.

Do you really need a reamed hole? You can have special ball ends done which will
not have the clearence problems of a reamer. Ream to just shy of the bottom
profile and follow with a ball mill with relived flutes above the end and you
won't get side cutting chatter if it's a finish you want.


michael

"Ryan" wrote in message
news:qjKjb.19667$S_.2981@clgrps13...

I have an application which requires a ball nose plunge cut for two
intersecting channels. The ID of the holes require precision, and
are from .130 - .190 depending on the application.

I could go with custom 'ball nosed' reamers, but I have a ton of
standard reamers here now, and was contemplating trying to cut the
nose of the reamer to be a nice radius.


Unless you have a grinding machine or jig specifically for this type of
toolmaking, you will be hard pressed to do this with any degree of
precision. You will have to grind a perfect radius on the end of the reamer
and then custom grind two or three flutes from the periphery to the center.
On a large reamer, that would be quite a challenge without the specialized
equipment. On the small reamers you need for your application, I think it
will be outside the realm of practicality.

I would suggest either buying the specialized reamers you need, or
contacting a shop that has the equipment to custom grind these for you. But
before doing that, have you considered lapping the holes? You could ream the
holes with a standard reamer to just above where the end radius starts. Then
use a piece of correctly-sized rod--with a hemispherical profile turned on
the end--and some lapping compound to finish your holes to size.