Tricky Hole

[taperlength]

Here is a job I don't come across often.  There is an existing hole and I have to enlarge it but off center.  And it is small diameter and deep in stainless.  So let's say the existing hole is about .180 and the new hole is .230 but it is .025 off center of the existing hole, so we can't just drill it.  Would not be a problem but it is over 2 inches deep in steel.  

[jeff]

can you press a plug in, and then drill it on center?

[Guest]

Helix it with a long Harvey endmill and be prepared for it to take a bit of time

[Tim Johnson]

Harvey has flat bottom counterboring tools that works nicely in aluminum. I haven't tried them in stainless but they should do well.

 

pages 38 & 39 in their last catalog.

 

opps, missed the over 2 inches. nevermind

[taperlength]

I considered plugging the hole but pressing a 2 inch long plug into the hole was not appealing.

 

I did try it with a long 3/16 endmill but the tool gave up when it was about 1.5 deep. It must have been recutting chips.

I might try it again with a shorter endmill to cut half way down and then the long endmill to do the other half.

[Tim Johnson]

How small is "small"? Guhring has 7d &10d coolant thru straight flute drills starting at 3mm. You could pilot bore your diameter with an end mill and finish the depth with a similar drill.

[taperlength]

How small is "small"? Guhring has 7d &10d coolant thru straight flute drills starting at 3mm. You could pilot bore your diameter with an end mill and finish the depth with a similar drill.

A 10d straight flute carbide drill might work.  Do they stock them, or is there a lead time? This has to be done right now.

[gcode]

I'd look at EDM... by you're  time you're done buying endmills and screwing around with this,

the EDM's shops lot charge will look very reasonable

[Tim Johnson]

A 10d straight flute carbide drill might work.  Do they stock them, or is there a lead time? This has to be done right now.

 

I would presume yes. We had some 4d and 10d 9.52mm drills brought in next day about a year ago for a casting job.

[mkd]

Lots of workable ideas here.

I'll add one:

You might be surprised what you can get away with using an old beat up .250 endmill. If your shop regularly uses regrinds find one at .230.

The reason a drill won't work is because the tip angle is going to push radially. The dish on and endmill totally prevents that. Works equally well starting a hole on an angle wall or punching holes in stainless tubing for space x lobby desplay models ( lol, inside joke)

Edit. Ok it's silly to regularly regrind down to .25 dia, but getting a custom grind for this one application using a beat carbide em that would otherwise be thrown away, is not a terrible idea.

 

[taperlength]

I'd look at EDM... by you're  time you're done buying endmills and screwing around with this,

the EDM's shops lot charge will look very reasonable

Believe me, I would do that if I could.  But those choices are not in my job description    The traveler says machining center so that's where it will be done.

[jeff]

I considered plugging the hole but pressing a 2 inch long plug into the hole was not appealing.

 

Make the plug a press fit only on the one end for about the last 1/4", and slip fit for the rest.

[taperlength]

Make the plug a press fit only on the one end for about the last 1/4", and slip fit for the rest.

That's might work.

[taperlength]

Lots of workable ideas here. I'll add one: You might be surprised what you can get away with using an old beat up .250 endmill. If your shop regularly uses regrinds find one at .230. The reason a drill won't work is because the tip angle is going to push radially. The dish on and endmill totally prevents that. Works equally well starting a hole on an angle wall or punching holes in stainless tubing for space x lobby desplay models ( lol, inside joke) Edit. Ok it's silly to regularly regrind down to .25 dia, but getting a custom grind for this one application using a beat carbide em that would otherwise be thrown away, is not a terrible idea.

Might try that.

[jlw™]

I was thinking what Tim was thinking. I've had good luck with this process in the 0.375in range on more than one occasion. The pilot hole needs to be on the money.

[taperlength]

I was thinking what Tim was thinking. I've had good luck with this process in the 0.375in range on more than one occasion. The pilot hole needs to be on the money.

Just like with gundrilling, I've done that.

[taperlength]

Harvey has flat bottom counterboring tools that works nicely in aluminum. I haven't tried them in stainless but they should do well.

 

pages 38 & 39 in their last catalog.

 

opps, missed the over 2 inches. nevermind

I just looked in their catalog.  That might work if we grind clearance on the shank.

[Charlie Pierson]

http://www.nachiamerica.com/c-1/Cutting-Tools/Drills/

[Tim Johnson]

I read the Nachi flat bottoms won't be released until May. Kennametal has them also but they're too short.

[?Mark]

Coolant thru center cutting relieved neck end mills. You can peck with them

[taperlength]

UPDATE:  I used the Harvey  long reach counterbore.  Had to grind some more clearance for depth but it worked great. Hole location stayed +/- .0005 in X and Y despite the existing hole varying in location.

[jlw™]

Nice.

 

Harvey makes some good stuff.

[mkd]

thanks for the feedback/ glad it worked out