Fine hole drilling

[Jesse Hancock 1Participant @jessehancock1]

No. 70 hole required for Sealion carb Jet tube

[Jesse Hancock 1Participant @jessehancock1]

I have read somewhere that the worst of the Sealion build is perhaps the crank. I'm not about to argue with that but I get the jitters when drilling small holes. I've drilled 1mm holes and still have the drill in the rack. Phew! However a No. 70 drill for the jet tube is in a different league!!

Have read "Small hole drilling in stainless thread."

Any tips, tools used etc that may help in a successful endevour will be much appreciated.

I'm no millionaire but I am willing to purchase a fine feel drilling rig for this job if that's what is necessary upon recommendation.

Yours truly, I must change my nappy now Jesse.

PS: On a none related topic my new milling head arrived today YAH! No instructions whatever BOO.

[JasonBModerator @jasonb]

I quite often drill 0.8mm which is about a No 67 and don't do anything special. Just run it fast, dab on some soluable oil with a brush and peck at it to remove the swarf. These are generally cross holes in pivot pins to take 1/32" split pins. Thats on the X3 mill using the quill downfeed like drill press

[Gary WoodingParticipant @garywooding25363]

I recently had to drill 45 0.6mm (a fraction smaller than #73) holes in a rather soft, gummy, metal. After drilling 7 holes the drill broke. The next 8 holes consumed a further 4 drills, so, with only one drill left I was in trouble. A friend at my ME club loaned me a 4 facet drill sharpening jig specially for small drills that he'd made to a D.A.G.Brown design that appeared in ME in 1993/1994. I sharpened one of the broken 0.6mm drills and managed to drill the remaining 30 holes without mishap. Since then I've drilled another 24 holes with the same drill, and its not required sharpening.

My next job is to make myself a drill sharpening jig.

[Jesse Hancock 1Participant @jessehancock1]

Hi Jason and Gary, are we reading off the same sheet here as a No. 70 is .028 of a millimetre is it not? Maybe I have it wrong but we are talking a jet in a carburetter for a 30cc engine here!?

The smallest drill I have used is a .5mm which to my mind is pretty small but a No 70 is less than 1/3rd of a millimetre.

Jesse

[Keith LongParticipant @keithlong89920]

Jesse

Think you've got you mm mixed up with your thou. No 70 drill = 0.70mm = 0.0276in or 28thou if you like, so not as small as you fear.

[Jesse Hancock 1Participant @jessehancock1]

Ah yes it helps to read parts of an inch not millimeters. I feel a bit more confident now cheers guys.

Jesse.

Edited By Jesse Hancock 1 on 10/02/2015 16:41:00

[JasonBModerator @jasonb]

No a number 70 is 0.028"

0.039" is 1mm so 0.7mm is 27/39 or a little over 2/3rds but yes we are talking about the same size hole

[Peter BondParticipant @peterbond14804]

It's probably not the same level of accuracy, but I do drill down to 0.5mm using a micromotor in soft metals. At those diameters pretty much everything counts as deep hole drilling… I use either Burr Life or Vaseline as a cutting lube; there are doubtless technically better ones, but they work.

I grind short twist drills from old carbide burrs too – https://www.youtube.com/watch?v=Dc-aH2G1oiI

Again, perhaps not accurate enough (but adequate for my uses). The sharpening is done with diamond-impregnated polishing wheels (hijacked from the dental industry as usual).

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