Help! > Machines, Tools and Fixtures
Sensitive Drill Attachment
JasonP:
After spending a productive weekend reading build logs for the MEM Corliss, I came across a discussion of a sensitive drill attachment. I'm new to the machining game and hadn't heard of this before, to my cost. When I was machining the engine block for my corliss I broke 3 drills trying to drill the steam ports, which caused no end of grief. It doesn't help that I'm using a bit of 1018 scrap that is quite "grabby".
So after a bit of research I hit ebay and found what I think is a nice tool, a Jacobs #0 chuck and #55 Drill attachment. It's now on it's way to me, but I'm a bit wary as it is used. Does anyone know how to evaluate how good this tool is? Where should I be concerned? Any advise on this tool and it's use would be greatly appreciated.
Jason
crueby:
I don't have much experience with a senstive drilling attachment, but have vowed to never again use 304 stainless steel, it also is very grabby and work-hardens quickly, destroyed a number of drills and taps on that. Some alloys are just not worth the trouble on models.
1018 steel is rated low for machining, though it is very popular for welding. I much prefer using 303 stainless, it machines very well, does not work harden, drills and taps very well. Not available in as many shapes/sizes, but worth looking at if you can.
steamer:
If its' not getting wet on a regular basis, consider 1144SP. It's a low alloy medium carbon steel, with excellent properties ( 100,000 psi yield ect) but is very nice to machine, drills, mills and taps very well, and is fine without heat treat, though you can case harden it very well. good stuff!
Dave
TerryWerm:
Can you tell us a bit more about the #55 drill attachment?
Sensitive drills usually require a couple of things:
1. High speed. Spindle speed in the neighborhood of 10,000 RPM or even higher work the best for these tiny drill bits.
2. The ability to hold the bit nice and square to the work
3. The ability to advance the drill bit with light pressure. They often have a bearing mounted collar on the spindle that you hold with two fingers in place of a rack and pinion with a long handle. You don't need much pressure.
The reason a sensitive drill press has that name is because using your fingers to advance the spindle allows you to feel what the tiny bit is doing in a very sensitive fashion. If the flutes of a tiny bit are starting to fill up with chips, you will feel it in your fingers long before you hear it in your ears. With some of the very tiny bits the bit will break before you ever hear things binding up.
steamer:
As Terry has described you need "feeeeel" about 20 years ago, I made a sensitive drill attachment on my lathe. It consisted of a MT3 blank arbor bored in the lathe it was going to be used in. I bored it to fit (2) 1/2ID x 3/4" long drill bushings. I then got a straight shank drill chuck arbor with a jacobs taper to match a nice albrecht chuck that I had. The shank fits very closely in the bushings. I drilled a vent hole for the air to escape. and you are done!
Later Joe PI published this video....and wouldn't you know it...
http://www.youtube.com/watch?v=PqU5wS0J4MU
I can't say i invented this, but I doubt Joe did either. I will say it works awesome! and as soon as you feel that drill do anything other than cut...just let go...stop the lathe ,and back the drill out. works great!
Dave
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