We have a 20mm bore that needs a flat bottom. We don't have a good mill or CNC but have a good lathe in our shop. I would like to turn down the chamfer of the reamer and then resharpen the flutes. We unfortunately don't have a tool grinder either. Any suggestions on how we might be able to get the 1/4"ish chamfer off the end?
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Looking for tips on turning down a reamer
- Thread starter teemfan93
- Start date
- Replies 30
- Views 1,786
redlee
Titanium
- Joined
- Apr 2, 2009
- Location
- Beaver County Alb. Canada
Ceramic Insert.
Grind it.
Grind it.
Seesecurity
Aluminum
- Joined
- Jun 20, 2017
- Location
- Brisbane Australia
If you have a good lathe just bore it, why bother with a reamer?
john.k
Diamond
- Joined
- Dec 21, 2012
- Location
- Brisbane Qld Australia
If you have a steady hand ,you can grind a cutter freehand with a small grinder.......or even an angle grinder ....Ive done it.
Philabuster
Diamond
- Joined
- Jul 12, 2006
- Location
- Tempe, AZ
Reamers are generally not the correct tool to produce a flat bottom hole. Do as Garwood suggests and grind yourself a flat bottom drill to clean up the bottom of the hole after drilling it to depth with a regular grind drill bit.
PegroProX440
Hot Rolled
- Joined
- Mar 7, 2012
- Location
- Ormond Beach
I did the same thing your talking about about 6 months ago. Just did it on a surface grinder and hand lapped a little back taper to the bottom end of the flutes. It left a horrible finish on the walls.
EmGo
Diamond
- Joined
- Apr 14, 2018
Counterbore would probably work better than a drill. Pull the pilot out and baby it, should work okay. That's what they are made for, more or less.
michiganbuck
Diamond
- Joined
- Jun 28, 2012
- Location
- Mt Clemens, Michigan 48035
Having a surface grinder you can grind the reamer end flat, and then by hand bring the clearance up to the edge. Up sharp for steel about 10 to 12*.
*Pre-ream so only taking the 1/4" with the hand-sharpened tool, slow RPM, cutting oil can help.
You may need to angle dress your bench grinder wheel so as to miss hitting that next (below) tooth. An easy job for a local grinder shop so should not cost much to send the job out.
Being handy you might do the reamer with only using a bench grinder for snubbing and back-off clearance.
*Pre-ream so only taking the 1/4" with the hand-sharpened tool, slow RPM, cutting oil can help.
You may need to angle dress your bench grinder wheel so as to miss hitting that next (below) tooth. An easy job for a local grinder shop so should not cost much to send the job out.
Being handy you might do the reamer with only using a bench grinder for snubbing and back-off clearance.
Last edited:
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi teemfan93:
As others have already remarked, bodging a reamer to make a flat bottom hole is a problem on several fronts.
The two main ones are:
1) If you plan to make a dead sharp corner where the wall and floor meet, you will also scarf up the sidewalls of the hole when you run the reamer down the hole as PegroProX440 points out in post #7.
2) If you don't gash the end flutes and put center cutting geometry on the business end, you won't have enough room for the chips to form...the tool will buck at the bottom of the hole and the finish will be shit.
So you need to make the end geometry sophisticated enough to get it to work.
You don't have a T&C grinder so that is out.
A flat bottom drill is the poor man's way of "solving" the problem but you still need to get the end geometry right for it to work, and the corners of the drill will dig into the sidewalls just like the butchered reamer would.
Back when I was a mold maker in the 1980's, before we had sinker EDM, we would make a "D" bit to do stuff like this.
Now you only have one flute to worry about, and you can stone a tiny (0.005"ish) radius on the corner and give it clearance only on the bottom half of the rad.
If you undersized the D bit by 0.001" or so and stoned that rad with care, you could make a beautiful hole but you had to be patient when you nibbled out the bottom of the hole and I found it worked better if you relieved the sides of your D bit, but left the first 1/2 inch or so unmolested.
Of course we had a whole range of cutter grinders to help us...things you don't have.
So can you farm this job out to a shop with a sinker?
Alternatively if you don't care about the finish in the hole, can you do as others suggest and run a flat bottom drill, even if you have to get a grind house to make you one?
The whole challenge with flat bottom drills in blind holes is to get them to center cut...if you plan to try to fake it, put a center cutting endmill on the bench beside you and try to copy the end flute geometry.
Another way you can try is to buy a 20 mm 4 flute endmill and deliberately dull the side flutes.
It might make you have to cry a bit to fuck up a brand new endmill this way, but sometimes you gotta break eggs to make an omelette.
Ream the hole with a normal 20 mm reamer first...as deep as you dare to go, then go down with your custom tool.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
As others have already remarked, bodging a reamer to make a flat bottom hole is a problem on several fronts.
The two main ones are:
1) If you plan to make a dead sharp corner where the wall and floor meet, you will also scarf up the sidewalls of the hole when you run the reamer down the hole as PegroProX440 points out in post #7.
2) If you don't gash the end flutes and put center cutting geometry on the business end, you won't have enough room for the chips to form...the tool will buck at the bottom of the hole and the finish will be shit.
So you need to make the end geometry sophisticated enough to get it to work.
You don't have a T&C grinder so that is out.
A flat bottom drill is the poor man's way of "solving" the problem but you still need to get the end geometry right for it to work, and the corners of the drill will dig into the sidewalls just like the butchered reamer would.
Back when I was a mold maker in the 1980's, before we had sinker EDM, we would make a "D" bit to do stuff like this.
Now you only have one flute to worry about, and you can stone a tiny (0.005"ish) radius on the corner and give it clearance only on the bottom half of the rad.
If you undersized the D bit by 0.001" or so and stoned that rad with care, you could make a beautiful hole but you had to be patient when you nibbled out the bottom of the hole and I found it worked better if you relieved the sides of your D bit, but left the first 1/2 inch or so unmolested.
Of course we had a whole range of cutter grinders to help us...things you don't have.
So can you farm this job out to a shop with a sinker?
Alternatively if you don't care about the finish in the hole, can you do as others suggest and run a flat bottom drill, even if you have to get a grind house to make you one?
The whole challenge with flat bottom drills in blind holes is to get them to center cut...if you plan to try to fake it, put a center cutting endmill on the bench beside you and try to copy the end flute geometry.
Another way you can try is to buy a 20 mm 4 flute endmill and deliberately dull the side flutes.
It might make you have to cry a bit to fuck up a brand new endmill this way, but sometimes you gotta break eggs to make an omelette.
Ream the hole with a normal 20 mm reamer first...as deep as you dare to go, then go down with your custom tool.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Last edited:
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
This is another one of those threads with poor/incomplete outlining of information. The suggestion of reamer use by OP indicates to me that the hole has a fairly tight tolerance and needs a good finish. If it does, we need to know that to give good suggestions. Will the part fit in a lathe? (More info we don't have...). You could follow the suggestion to just bore it there. Do you have a rotary table on the mill? You could use an endmill and spin the rotary. You could also buy a 20mm endmill and just plunge the hole after it's roughed out with say a ¾" endmill. Do you need a perfectly flat bottom or is "pretty flat" good enough? etc. etc. etc.
If the hole does not need a tight size and good finish, for sure use the suggestion of a flat bottom drill.
If the hole does not need a tight size and good finish, for sure use the suggestion of a flat bottom drill.
Bill D
Diamond
- Joined
- Apr 1, 2004
- Location
- Modesto, CA USA
Why does the hole need to be flat? How flat and smooth does it need to be? How will that flat get measured by the customer? Why not just drill it a bit deeper.
Boring head in a drill press ?
BilL D
Boring head in a drill press ?
BilL D
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi eKretz:
You wrote:
This is another one of those threads with poor/incomplete outlining of information.
Yeah, but they're pretty much ALL like that...part of the questioner's question is that he/she doesn't know enough about the problem to solve it themselves, so there will be bits missing in the narrative.
Often, I use my imagination and the guesses I make turn out to be wildly off base...if the OP with the question can live with that, all is good.
If, however, they expect us to read their minds and get pissy with us when we can't...well you know how that typically works out for them in a place like this one.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
You wrote:
This is another one of those threads with poor/incomplete outlining of information.
Yeah, but they're pretty much ALL like that...part of the questioner's question is that he/she doesn't know enough about the problem to solve it themselves, so there will be bits missing in the narrative.
Often, I use my imagination and the guesses I make turn out to be wildly off base...if the OP with the question can live with that, all is good.
If, however, they expect us to read their minds and get pissy with us when we can't...well you know how that typically works out for them in a place like this one.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
michiganbuck
Diamond
- Joined
- Jun 28, 2012
- Location
- Mt Clemens, Michigan 48035
Agree that a 20mm hand-made flat bottom drill Philibuster mentioned in post #6 should do fine in a pre- reamed hole so just taking out the bottom. Push it back to be the desired size, perhaps .0003 /.0004 smaller than the reamer, and perhaps use some oil in the bore...if the spec allows .0003/.0004.
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
Yes, you are right. I sometimes do the same as you, but I generally prefer to type messages similarly to the way I speak. I don't mince words, and I'm generally pretty sparing with them. I don't want to cover 20 options because of incomplete info, heh. You are much more verbose than me when it comes to that, and it's generous of you.
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi again eKretz:
Are you telling me (politely) that I can talk the ass off a donkey?
Funny...my Lovely Wife says exactly the same thing, but she's often much blunter about it.
Sadly, I can't help myself...once I get my teeth firmly into a topic, I can just go and go and go, until everyone is rolling their eyes.
Like right now!
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Are you telling me (politely) that I can talk the ass off a donkey?
Funny...my Lovely Wife says exactly the same thing, but she's often much blunter about it.
Sadly, I can't help myself...once I get my teeth firmly into a topic, I can just go and go and go, until everyone is rolling their eyes.
Like right now!
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
eKretz
Diamond; Mod Squad
- Joined
- Mar 27, 2005
- Location
- Northwest Indiana, USA
Hi again eKretz:
Are you telling me (politely) that I can talk the ass off a donkey?
Funny...my Lovely Wife says exactly the same thing, but she's often much blunter about it.
Sadly, I can't help myself...once I get my teeth firmly into a topic, I can just go and go and go, until everyone is rolling their eyes.
Like right now!
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
In a word, yes.
But it's not a bad thing in this case.
EmGo
Diamond
- Joined
- Apr 14, 2018
So you guys never used one of these ?
michiganbuck
Diamond
- Joined
- Jun 28, 2012
- Location
- Mt Clemens, Michigan 48035
Considering what Implmex/Marcus said: "the corners of the drill will dig into the sidewalls."
You could ream the hole to depth..and then start the flat nose drill (or whatever flat nose tool) deep in the hole..finish to the depth..and park the tool before pulling it out of the hole..
The circle grind OD land/margin on a drill or like tool will keep it from digging into the side wall of the bore.
or hone a slight radius on the Flat-nose whatever tool.
An end mill is sharp on the OD so is not good for a precision hole, or the bottom hole finishing.
You could ream the hole to depth..and then start the flat nose drill (or whatever flat nose tool) deep in the hole..finish to the depth..and park the tool before pulling it out of the hole..
The circle grind OD land/margin on a drill or like tool will keep it from digging into the side wall of the bore.
or hone a slight radius on the Flat-nose whatever tool.
An end mill is sharp on the OD so is not good for a precision hole, or the bottom hole finishing.
Last edited:
implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi EmanuelGoldstein:
Yeah, I've used one of those.
Quite often in fact.
But not on a blind hole with a flat bottom.
Also not on a hole that I needed to be on size with a nice finish.
I could probably make it do those things too.
But not without a cutter grinder.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Yeah, I've used one of those.
Quite often in fact.
But not on a blind hole with a flat bottom.
Also not on a hole that I needed to be on size with a nice finish.
I could probably make it do those things too.
But not without a cutter grinder.
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
