|sparky mike||24/07/2020 09:06:10|
|243 forum posts|
I have to drill a 1/16" hole right through a 2BA brass screw, from end to end on the lathe..First attempt, the screw broke at a depth of half in or so. The screw is just over an inch long. I was going to drill from each end, but did not get that far !!
Any tips here, lubricant/speed etc.
|148 forum posts|
I've not drilled a brass screw but have drilled a 1/16" hole through a 1/8" stainless steel screw a little over an inch long. The trick is to back the drill completely out of the hole about every 1/16" of an inch of cut otherwise the cuttings jam the hole and tragedy ensues. Use constant pressure when the drill is cutting and don't allow it to rub.
|Andrew Johnston||24/07/2020 09:37:45|
6405 forum posts
Shouldn't be a problem, use normal feeds and speeds and no coolant/lubrication for brass. With brass pecking is less critical; I'd probably withdraw every 1/4" or so.
Use quality makes of drill. Start the hole with a spot drill. Assuming the lathe is being used ensure that the tailstock and headstock are aligned. Make sure everything is rigid; don't put the screw directly in the chuck, use a threaded split collet.
|Martin Kyte||24/07/2020 09:43:04|
2637 forum posts
Stone the rake off the drill, withdraw regularly to claer swarf, use a collet as Andrew has said and drill dry.
|John Haine||24/07/2020 09:45:38|
|4428 forum posts|
The screw broke? That sounds weird! Blunt drill?
|2314 forum posts|
Type of brass makes a huge difference to the ease with which the hole can be drilled, CZ121 will be easy to do while hard brasses can be difficult, just like some I had got from a steam rally stall.
Some weeks ago I made some small parts using 6mm OD brass, total length 20mm with a 1.6mm hole through, when drilling 1 of the pieces I could see something was wrong, the drill had run off centre and broken out through the wall at about 15mm depth but the drill did not break, needless to say I fitted a new drill.
|Dave Halford||24/07/2020 10:33:29|
|1890 forum posts|
If it's using the lathe i would
True up a random lump of round bar for at least an inch.
Cut the inch off and remount in the chuck.
Drill at 2BA tapping size right through.
Tap the hole 2BA. Mark the bar where #1 jaw is so when/if you turn it round, there's no wobble.
Make sure the centre of the threaded end of the screw is square
Insert screw and tigthen and drill 1/16" as fast as the lathe will go with light feed pressure, if the drill is long enough go right through
5508 forum posts
How did the screw break in half? Was it sticking out of the chuck? Sounds like workholding -- or lack thereof-- might be a contributing factor. Some kind of threaded collet that holds the job without crushing it hard enough to nip up on the drill could help.
You have about 40 thou wall thickness between hole and thread root so it should be do-able with suitable care.
Edited By Hopper on 24/07/2020 10:43:22
2938 forum posts
+1 - check the drill, small ones do have a tendency to be bent, roll them on a piece of glass or surface plate ,if you have one. I've found that with multi packs ( box's of 10 ) there's at least 2 + that are bent plus check the cutting edge/lip quite often the back relief is not ground properly & the drill is trying to cut on the back instead of the front cutting lip.
|sparky mike||24/07/2020 12:10:51|
|243 forum posts|
Sorry, the drill broke, not the screw. Senile moment !!
I will take on board the above comments and see what happens. I was withdrawing the drill each 1/16" or so but it did not work.
|1427 forum posts|
What did the drillings look like? Chiplets or stringy?
|Nigel McBurney 1||24/07/2020 14:03:23|
965 forum posts
A commercial screw brass material will probably be tougher than the usual brass rod, so I would not back off the drill cutting edges with a stone, and then use coolant ,its a long hole and drill runing at high speed,the drill needs some lubrication on the flutes. My experience when at work was to turn brass dry on the fast plain bed lathes,and full flood soluble oil on the capstan lathes,the coolant kept the tools cool and flushed away the chips.
|sparky mike||24/07/2020 17:43:47|
|243 forum posts|
First one now ok now, thanks to various tips. Now just one more to do.
Fingers crossed. Perhaps you get better with practice !!
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