Re: [multimachine] An observation on drilling
- Hi Adams
That's what I trying to address, the small press drill can be reworked
to run at slower speed not necessary to buy bigger drill press.
On 6/19/13, Adam Simmons <xyrthx@...> wrote:
> I pretty much have the same press for home use, the biggest downfall of it
> is that it doesn't go slow enough. It gets the job done, but destroys bits,
> and sometimes accuracy.
> Slower is better sometimes, especially when you have time to give to your
> On Tue, Jun 18, 2013 at 5:08 PM, Gordon Haag <mr.meker@...> wrote:
>> For the past couple days, I have been drilling hundreds of holes in
>> some sprockets to lighten them. They are made of plain mild steel,
>> about a quarter of an inch thick. The sprockets are 11.75" 40 pitch,
>> 72 tooth. I used DraftSight, a really good free 2D CAD program, to
>> print out a set of points spaced on a 5/8" grid. I then taped the
>> printout to the sprockets and marked each point with a centerpunch.
>> Each point was then drilled to 3/32", then 1/4", then finally to 1/2".
>> The drill press is a really small Harbor Freight type, I think it is
>> 1/4 or 1/3 HP. The slowest rpm is 760, which I used for all bits.
>> Anyway, I used 3/32" bits because I had a bunch left over from a
>> previous project. I ended up breaking them all. I switched to just
>> drilling straight in with the 1/4" bit. Accuracy doesn't really matter
>> in this application.
>> Expanding the hole from 1/4" to 1/2" was right on the edge of what the
>> drill press can do. It took all the power and would frequently bind.
>> The motor would get very hot and I would have to stop every 20 holes
>> or so to let it cool down. I found a 3/8" bit and used this in between
>> the 1/4" and 1/2". This made it easier on the press, but the bit would
>> still bind and the motor still heated.
>> All of the bits mentioned til now were HSS, the 1/4" and 3/32" TIN
>> I picked up a plain carbon steel 1/2" bit, sharpened it, and tried to
>> drill with no pilot hole, just a punch mark. Remembering what I had
>> read here about the ratchet drill, I pressed really hard. The bit not
>> only drilled, it took a much less power and was easier on the motor.
>> It did take longer for the hole to be drilled, but the press managed
>> it much better. The table did flex down a bit, but again, accuracy is
>> not important.
>> In the first case, the limiting factor of the speed of the 1/2" bit
>> was the power and torque of the motor, which is not large enough to
>> efficiently do the task. In the second case, the bit was held back by
>> how fast the center of the bit could deform the metal without a pilot
>> I think this goes to show how things must be thought of differently
>> when one is limited in resources but not in time. This is the opposite
>> of what most of the metalworking world assumes.
>> I will keep drilling with the 1/4" -> 3/8" -> 1/2" system because it
>> is faster and easier on the press. If I were out in the bush
>> somewhere, I would conserve my bits and find a way to brace the table
>> from bending.
>> This group has really been an inspiration to me! Thank you.
>> Gordon Haag