Drilling/Boring a deep hole

Although it's time consuming, in cases like this, I drill with two different diameter bits. Start with a 50% smaller diameter than needed then drill no more than about 4 times it's diameter. Peck the bit as you go. Switch to the desired diameter and drill up to depth of the first hole. Keep repeating until you're done. The theory here is that smaller hole is drilled a depth safely in the limit of it's depth to diameter ratio. Following-up with the bigger one opens a "tunnel" so the next time around, the smaller bit can later eject it's chips easily.

Also, both bits need to have properly and evenly sharpened tips. Uneven flutes cause the hole to wander off track.

Using this technique, I have "successfully" flipped a part in the lathe, using a collet chuck, and met the hole in the middle. It was 0.25" hole about 5" long in 316 stainless. There was a very slight mis-match where the holes met but, it was surprisingly close. I've done this a handful of times. It's always a crap-shoot but, I've managed to pull it off with more successes than failures.

Ray
 
The_Apprentice said:
Hey Jim, I did try experimenting with going past the flutes. But there is a problem with this. Even though the shank doesn't look thicker than the flute edges, I get a lot of restriction and a hell of a lot of rubling and chatter, etc. the second I reach the end of the flutes. Not to mention, everything gets VERY hot quick.

Maybe my Titanium Coated MasterCraft drill-bits just are designed a bit unorthodox from the norm. I'll see about picking up another brand. Now that I think of it, I should have done so while at Harbor Freight this morning. Doh!
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Normally drill bits drill slightly oversize because of unequal grinding, but yours may actually be properly sharpened and drill on size. It wouldn't be impossible that the flutes are slightly small. Grinding a little relief on the shank might work also.
 
I have no idea what this is for, so just thinking outside the box here.

Since a long 1/8" hole is a challenge, how about finding a piece of thick wall tube with a 1/8" I/D and as large an OD as possible. It seems like it would be easier to drill the larger diameter hole then insert / press in the tube. ??

David
 
I checked for something like this in the past with a local metal supplier. But there are only very limited options for the distance between ID & OD.

In any case I'll put this aside for a side-project for now. It's not the end of the world at the moment.

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Update!

What is the material?
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Stainless...

I finally found some longer bits that MAY work out. Have ordered them and we'll see how it works out when they finally arrive. And now, onto other things....
 
I like David's suggestion.
I don't know if this helps or not but while I was working on a pressurized coolant mister project , I had to order some copper tube 4mm OD ,3mm ID which is .118" (.007" smaller than 1/8"),this seller has tubes in stainless steel, copper and Brass ,the length can be ~ 250mm to 300mm. here's the link :

https://www.ebay.ca/sch/m.html?_odk...l+tube.TRS0&_nkw=stailess+steel+tube&_sacat=0

https://www.ebay.ca/itm/2pcs-304-St...692986?hash=item2cce00637a:g:iE8AAOSw8A1aZbfC
https://www.ebay.ca/sch/m.html?

https://www.ebay.ca/itm/Brass-Tube-...hash=item3f8fa9092f:m:mVK_zPNJo2r93wSmqeAf_Qw
 
These finally arrived today... now I will try to get an hour or two in on giving them a test-drive tonight... Stay tuned-in for an update...lol


drills.jpg
 
Update!

Well that was total FAIL.

The HSS refuses to bite into the stainless no matter what I do... cutting fluid no help.

I'll just wait for the other pack I ordered to arrive, and hope for the best with that one
 
Did the stainless work harden?
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This is one thing that had been going through my head of possibilities. But I did some checking today, and perhaps the issue is with just the bits themselves. The stats said they were great for non-ferrous metals, nothing much said on how they performed for the rest.

I have another set arriving in a few days that I will be very curious on how they behave.

What's you TS taper?
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I'm not 100% sure on the question, which could be due to my newbieness with drills.
 
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