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Post by Workshopshed on Jan 3, 2009 9:15:54 GMT
When drilling in the lathe with drill bits around 1mm I find they have a tendency to wander rather than drilling straight.
Any ideas as to why this happens? It's happened a couple of times now with both steel and brass.
Is it an issue with the drill bit? Or perhaps the alignment of the lathe? Is there anything I can do about it? If it was a bigger drill I'd centre drill first but I don't currently have a centre drill that small.
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Post by Deleted on Jan 3, 2009 9:23:38 GMT
Sorry my friend, but unless you are very good with a centre punch I wouldn't dream of drilling at any size without using a centre drill first. You only need the tiniest pip so try the larger drill anyway. It's usually to do with the weaknes of the drill and the lack of a truly sharp point to 'bite' into the desired start point. In the absence of a centre drill you could try making a 'stub drill' from, say, a 1/16" drill, cut very short. The chuck may not do a good job of gripping though, as it may be grabbing the drill flutes. In that case you would have to shorten it from the cutting end, which, of course, defeats the object as the web thickness increases towards the base!
Best of luck.
JB
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Post by weldsol on Jan 3, 2009 9:24:00 GMT
If you have no location (centre pop / centre drill) the drill will decide to wander. If you don't have a small enough centre drill you could try and just mark the end deep enough with a larger one this would help to start the smaller drill.
Paul
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Post by Workshopshed on Jan 3, 2009 9:33:26 GMT
Thanks, that makes a lot of sense. I wonder if anyone has ever tried to mount a centre punch in the tailstock?
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Post by alanstepney on Jan 3, 2009 9:39:36 GMT
The other way is to make a simple spade drill with the point truly central, and use that to get the centre from which to drill the hole required.
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Post by dickdastardly40 on Jan 3, 2009 9:39:48 GMT
Thanks, that makes a lot of sense. I wonder if anyone has ever tried to mount a centre punch in the tailstock? You could use a dead centre (which is hardened) and just wind it up enough to 'pop' the job. Should be OK and not flatten the tip of the centre on brass and mild steel of you're careful. Spilt point drills don't need a centre pop to stop them wandering as they don't have a chisel tip flat on the end. They are spendy though and difficult to grind yourself, even more so in very small sizes. |
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Post by drjohn on Jan 3, 2009 11:14:13 GMT
For smallish holes like that, I use a stellite scriber in the tailstock and make a tiny pip in the workpiece.
Then do what my mentor used to say - "stab drill" - that is whack the drill in, pull it out and whack it in again for another half of the diameter of the drill - if it's 1mm, go in 0.5mm then pull it out and keep repeating the process.
As that tends to flare the flutes and drill oversize, start a few thou undersize then clean up with the desired size at the end. But beware, make sure the tailstock is no too free or the final drilling may grab, especially in brass.
But then, I'm just an old doc - no engineering background ;D
DJ
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Post by Workshopshed on Jan 3, 2009 12:43:42 GMT
thanks all. I found a smaller centre drill in the bottom of the draw with approx 1mm tip which worked a dream, no wobbles. Will try the other techniques next time if need even smaller holes.
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Post by baggo on Jan 3, 2009 12:52:36 GMT
I use a similar method to DJ when drilling injector cones which often entails using drills down to No 80 (0.014"). I use a piece of silver steel rod with a 60° point turned on the end and then hardened. Normal centre drills, even the smallest, tend to leave a flat bottomed hole which is no good for very tiny drills.
John
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redmog
Part of the e-furniture
Not Morgan weather
Posts: 461 
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Post by redmog on Jan 3, 2009 13:02:47 GMT
I use a broken 2mm slot drill that I ground to about
60 degrees ish.
Grind off-hand by eye - insert in a collet on the lathe.
Set up a small toolpost grinder at about 60 degrees,
- one concentric point in HSS.
Also use it for marking out centres on the miller before centre drilling.
Chris
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Post by alanstepney on Jan 3, 2009 13:11:23 GMT
Somewhere on one of the photo hosting sites, is a short video os an American guy drilling small holes (for injectors I believe).
His technique is one that is well worth trying and practicing with.
Now, if only I could find that video again....
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lancelot
Part of the e-furniture
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Post by lancelot on Jan 3, 2009 14:13:21 GMT
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Post by baggo on Jan 3, 2009 14:29:01 GMT
I use the 'pecking' method but hold the drills in a pin chuck which has a spindle on the end. This runs in a brass bush held in the tailstock so that the chuck can be moved backwards and forwards. The drill is fed in by finger pressure and can easily be withdrawn to get rid of the swarf. I find it takes very little time to drill through a cone. If the drill does snatch, you can just let go of the chuck and the drill spins with the work rather than breaking.   One of the comments on the first video in the post above makes a very good point. You are working in very close proximity to revolving bits and need to be VERY careful! |
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Post by Deleted on Jan 3, 2009 14:49:27 GMT
Sorry chaps, I haven't gone yet! I just watched the two videos and just can't resist a few words: the first demo appears downright dangerous to fingers and drill bits, the second seems to go to a lot of trouble to drill a not very small hole. Like a lot of people here, a simple keyless chuck mounted a close fit on the same tailstock arbor as used for your dies does the biz for me, pecks and all. £3.50 at the DIY store plus a bit of brass hexagon! This one is holding a 0.8mm drill, the smallest it will take. I use it for tapping too. Touch wood, never had a breakage...... JB EDIT: Baggo must have beaten me to the same post by about 30 seconds!  |
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Post by alanstepney on Jan 3, 2009 16:56:26 GMT
That first video is the one I was thinking of.
Yes, one does need to take care with the pecking method, or you can damage your beak!
I still say that a spade drill is worth considering. Watch and clock makers use them frequently.
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Post by Tel on Jan 3, 2009 19:11:27 GMT
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Post by Staffordshirechina on Jan 3, 2009 20:17:40 GMT
Once I have centre-drilled, if the hole is one that 'matters', I will use a 4 or 6 facet sharpened drill. They cut neatly on both edges and leave an exact size hole. You cannot really hope to get good sizing if you sharpen your drills by hand, especially larger sizes. Only those who practice very regularly can manage good freehand sharpening. If you make one of Derek Brown's little gadgets you can sharpen down to No 80 without too much trouble. Here's two I prepared earlier.. Les ![]() www.staffordshirechina.com/Pics/Drill Sharpen 2.jpg[/img] |
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Post by drjohn on Jan 4, 2009 14:52:13 GMT
Those two look as if you might get a wee bit more than a 1mm hole! ;D
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Post by drjohn on Jan 4, 2009 14:56:35 GMT
How far can you stretch your $1,400 government handout Tel? over 10 ozzy a piece - wow, the sporran cringes  |
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Post by Tel on Jan 5, 2009 8:48:21 GMT
They'd be cheap at 'arf the price DJ  Seriously tho' - they are very good value - you only use 'em to spot a little crater, don't go beyond the point, and most times considerably less than the depth of the point. |
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Seriously tho' - they are very good value - you only use 'em to spot a little crater, don't go beyond the point, and most times considerably less than the depth of the point.