Re: Digest Number 8972


arved_grass
 

Good, but I personally think that if the OP had a mill or drill press with an cross slide vise (http://www.amazon.com/Cross-Slide-Drill-Milling-Machine/dp/B001FGAJTA) he wouldn't be asking this question. If I may add:

1. Be careful about backlash. Approachng a dimension from one side is not the same as approaching the dimension from the other if you are relying on the hand wheel markings. Unless you have a Digital Read Out (DRO). DROs measure actual table or vise movement.

2. If you must use a jobber bit, I highly suggest using a "sensitive drill feed" instead of a pin vise. I have this one (but less expensive ones are available if you go with a keyed chuck rather than a keyless chuck):

https://littlemachineshop.com/products/product_view.php?ProductID=3790

Brian Banna has a video (on youtube) demonstrating it's use, although I can't presently find it.
However, every time you add another holding device (chuck and/or pin vise), you tend to get more and more runout, which can be very critical, especially with finer drill bits.

3. Carbide drills are available that have a 1/8" shank from 1/4" down to 0.0059" (#97). I buy resharpened bits from Drill Bit City. Their costomer service has been excellent. I find carbide bits to be stronger but more brittle. However, they stay sharper considerably longer. If you haven't tried these, I suggest getting the 25 peice starter set, containing all wire sizes from #80 through #56:

http://drillcity.stores.yahoo.net/25stardrilbi.html

I gave a set to a good friend about 20 years ago, and he never bought another jobber bit again.

Although not STMFC, here's a photo of me using a #91 drill bit to install BLMA grab irons in an N-scale SD50:

http://arvedgrass.com/wp-content/gallery/sd50-mill/2011-10-22_d70s_7670-e.jpg

That's a 0.0083" drill with a 1/8" shank in a 1/8" R8 collet in my Microlux Mini-Mill (rebadged Sieg SX-2). My DRO was critical to getting the locations right. I couldn't have done this with a drill press and cross slide vise. I tried, and gave up, eventually making the commitment to buying the mill, if for nothiing else, to be able to drill accurate holes.

Even if you don't have a Mill or Drill Press, since all these bits share the same shank, it becomes very easy to use these and change them out on a rotary tool (Dremel, etc.). I find them much easier to chuck than jobber bits.

Sometimes you just need the right tool for the job. But only sometimes. :-)

I sincerely hope this helps. All the best,
------------------------
Arved Grass
Fleming Island, Florida

--------------------------------------------

On Thu, 9/4/14, jimbetz jimbetz@jimbetz.com [STMFC] <STMFC@yahoogroups.com> wrote:

Subject: Re: [STMFC] Digest Number 8972
To: STMFC@yahoogroups.com
Date: Thursday, September 4, 2014, 2:29 AM

Hi Scott,

   I have a mill/drill with a vise.  I'd
put the
styrene in the vise and use the x+y of the
vise to position the drill ... and drill without
ever scribing and with no hand positioning.

   Really small drill?  Put the drill in
a pin vise
and put the pin vise in the drill chuck.  Check
that it is turning true before drilling!
   BTW - a #78 drill is about 10 times less
likely to break than a #80.  I challenge
anyone to see the difference in the size
of the hole.

   By using the table of the mill/drill you
can
move the work in perfectly aligned rows
and drill perfectly spaced holes on those
perfectly spaced rows.
   You can do the same thing with an X+Y
table on a drill press.

   Make the piece at least 25% larger than
you need - and adjust the size of the piece
after you have the rows of holes drilled.

               
               
               
           - Jim Betz

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