What are your FAVORITE home shop machinist (HSM) tips?

[British Steel]

Dave,
Thanks. If I'm reading this right, it's like "taking a little off the top." In other words, flatten the point of the drill bit just a little (1/32 or 0.5mm)? Not completely flat, just a little less pointed? Maybe I still don't quite get it. Kinda like why I can't get the smilies to work. Lol!

Nope, not the point - the edge where it meets the sprial flute! What makes it grab is the "wedge" effect of the flute screwing into the material, so you need to "square off" the edge.

Hold the drill bit upright in front of you, and look at where the sharpened edge meets the flute - on most bits this will be about a 60-degree angle. What you need to do is stone off some of the edge *in the flute* so that there's a flat parallel with the drill axis, so that when it's presented to the work it doesn't try to dig in - this is a lot easier to do than to explain!

In industry, the drill bit of choice for acrylic etc. has straight flutes - they run parallel with the bit's axis (centre line) so they don't grab, but are crap for ductile materials as they don't clear the chips at all well and can clog up - what you would do to a standard spiral bit for acrylic, brass etc is stone the edge so you have a *very* short straight flute (the 1/32 or 0.5mm flat) where the drill's cutting into the material - no spiral, so no grabbing.

Having a *short* straight flute = *narrow* flat lets you grind it back to normal for metals etc., without sacrificing a bit to one sheet of acrylic

Hope I've explained that better this time!

Dave H. (the other one)

 

[Chucketn]

Would it be possible to post a couple of pictures of an un-modified and modified drill bit for drilling plastic?

Chuck in E. TN

 

[Frank Ford]

My number 1 tip is to use an old gym sock to pad the handle of my lathe collet closer because it gets slippery when I have cutting oil on my hands:



Numbers 2 through 407 are here:

Shop Tips

 

[Tony Wells]

Good tip, Frank. It took a while, but I have read all your other tips. You are a very creative individual. I think it's time to read through them again.

 

[churchjw]

My number 1 tip is to use an old gym sock to pad the handle of my lathe collet closer because it gets slippery when I have cutting oil on my hands:



Numbers 2 through 407 are here:

Shop Tips

Hi Frank I have been reading your site for a long time and love it. Just wanted to say thanks for all of the incites you have given me over the years. Any one who list Zaphod Beeblebrox (shop tip #368) in a post has to be one hoopy frood. :biggrin:

Jeff