Drill your holes

Your slow cooling is your problem look for Kevin's instruction on spheroidizing in the "working with the three types of steel" stickey specifically in the hypereutechtoid section

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Nathan, I have one of those "Drill Doctor" type sharpeners, but find it is totally useless on anything less than around 3/16".

I used to watch my Dad sharpen bits (any size) on the rock of a "valve-grinding" machine (pretty fine stone). He would grind the cutting edge, then roll the bit. It would cut like crazy. I have tried it on my KMG, with mixed results. Biggest problem I have is getting it even from side to side.

Would love to hear (and see) more about your techniques.

This thread has the potential to offer great information in so many related areas of what we do. Maybe it will continue and one of our gang will figure a way to sort each segment into an informative "FAQ".

Robert
 
Patrice Lemée;11101339 said:
Thanks, great post Nathan. I do ok but still I'll try a faster feed.
First found out that going faster worked better when parting in the lathe. But that is just scary. :(
Click to expand...

Parting in a lathe is scary. Chatter can be a challenge. Chatter can be eliminated by reducing speed (not ideal), increasing speed into a stable machine harmonic (awesome if you can do it) improving rigidity (normally all the low hanging fruit is already picked there) and increasing feed rate. The last one there is the big one. Increase feed rate. Unfortunately, the first thing most first year apprentices do is back off the feed rate, which can make things worse. It is a leap of faith, but sometimes you just got to push it harder to get it to quit chattering.

I like to put my parting tools behind the work piece and upside down so the chips fall down and out of the cut. Ideally you can push it hard enough to break your chip but my little lathe doesn't have enough horse power so I often coil up big clock springs.
 
Robert Dark said:
Nathan, I have one of those "Drill Doctor" type sharpeners, but find it is totally useless on anything less than around 3/16".

I used to watch my Dad sharpen bits (any size) on the rock of a "valve-grinding" machine (pretty fine stone). He would grind the cutting edge, then roll the bit. It would cut like crazy. I have tried it on my KMG, with mixed results. Biggest problem I have is getting it even from side to side.

Would love to hear (and see) more about your techniques.

This thread has the potential to offer great information in so many related areas of what we do. Maybe it will continue and one of our gang will figure a way to sort each segment into an informative "FAQ".

Robert
Click to expand...
First thing we did as apprentices was make drill point gages.
With a hacksaw and file.
It sucked.
Teacher took them to a comparator and said "angle is wrong, file some more", many times before we were done.
Think mine took like 10 -12 hours.

You can buy them cheap.
Google it.
You will be able to make both sides even that way.

Scale and a protractor works too...
 
Thank you for this thread, I almost missed it!

I tried your technique the other day, using a pretty cheapy HSS no-name brand bit (not even sure if it was meant for metal) to drill some 7/32" holes in 3/16" O-1. Used 600 RPM and cutting oil, and got no smoking, no blue curls and nice clean holes with no tearout "burrs" on the exit side. I did the same with some 5/32" holes with a brand new cobalt bit and it was like drilling into warm butter... good tips for improving tool life and effectiveness! Thanks!
 
I was thinking about this thread today while I was drilling thru some .375wall 303 tubing. I was using a lot of federate to get thru the piece but I back off right as im breaking thru. I think that as the material gets thin when you are almost they a piece it gets really hot and can possibly work-harden a bit.

TLdr; Feed hard thru the meat but baby it during break thru.
 
At the machine shop I use to work at the general rule of thumb for various steel was.

1/8" Drill => 2000 RPM (Double from 1/4")
1/4" Drill => 1000 RPM (Double from 1/2")
3/8" Drill => 750 RPM
1/2" Drill => 500 RPM (Easy to remember 1/2" => 0.500" decimal)
3/4" Drill => 250 RPM
1" Drill => 125 RPM

For sizes in between just use your judgement. Remember these are just general recommendations!
 
here is a link to a chart that recommends cutting speed for different materials

http://www.carbidedepot.com/formulas-drills-speeds.htm

and here is a calculator to turn SFM to RPM

http://www.carbidedepot.com/formulas-turning.htm

for example a 400 series stainless says to cut between 30 and 60 SFM so on the calculator enter 45 in the sfm column and whatever drill you are using's diameter in the diameter column.

45 sfm at .125 diameter is 1375 RPM

this actually gives us a pretty big range because

30sfm= 917 rpm
60sfm= 1833RPM

but 1375 would be a good place to start.
 
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Most drill presses come with their spindle speeds listed in RPM's (Revolutions Per Minute) whereas alot of charts you'll find that list CS (Cutting Speed) for materials have it listed as FPM (Feet Per Minute) or MPM (Meters Per Minute). When CS is listed by FPM or MPM there are some simple formulas to convert those CS listings to RPM's.

For FPM the formula is the following.

Multiply 4 by CS (Cutting Speed) then Divide by the Diameter of the Decimal Equivelent of the Fractional Drill. (RPM = 4 x CS / D)

For MPM the formula is changed to the following.

Multiply CS by 1000, then Divide the product of those two variables into the Product of the Diameter of the Metric Drill (Converted to Millimeters) Multiplied by 3 (Pi rounded down from 3.14)( RPM = CS x 1000 / D x 3)​


For example, the CS listed for Aluminum and Aluminum Alloy's is 200-300 FPM. To Find the RPM's I'll Multiply 300 by 4 which give's me 1200, then I'll Divide 1200 by .500 since I've selected to use a 1/2 drill bit. Dividing 1200 by .500 gives me 2400 RPM's.

These formula's assume that you're using standard HSS (High Speed Steel) drill bits and proper cutting fluid for the material, If you're using carbon steel drill bits reduce the speed by one-half of your original calculation.

That information is meant to be used as a simple guideline for spindle speed, nothing more.

As for feed rate on a drill press, since the feed controls on a drill press are manual it isn't an exact science and I can only offer some simple advice. A feed that is too light will cause the drill to scrape, chatter, and dull quickly. Whereas chipped cutting edges, drill breakage, and drill heating (even with the proper application of coolant) usually means that your feed rate is too great.

Also I would recommend that you always make sure your drill bit is properly sharpened and in good working order, then center drill first before going to your conventional drill. That should eliminate your drill from walking altogether.
 
Sorry if my response was hard to follow, I'm feverish and on medication right now so it's somewhat hard to form a coherent statement. Also being an apprentice machinist going for an associates degree in the field, I am by no means a authority on the subject but I'll happily share what knowledge I have acquired on the subject of machining when I'm not studying or in the shop. Hope someone found the previous post useful!
 
I know I'm "necro-posting" but I wanted to say that IMHO, the biggest problem Peter is facing is the forge scale.

Forge scale is ridiculously hard and tough. It eats drills, bandsaw blades, and grinding belts.

If you zip the forge scale off of your tang, it will make drilling the hole 90% easier. :)


Also, major thumbs up to Nathan for doing this in the first place. For someone trained in the machining industry like Nathan and Brian, this stuff is kindergarten stuff. But for a guy who just goes out and drills holes without having ever had someone show them how, it's REALLY easy to do just about everything wrong.
 
orangehero said:
Any tips on drilling with carbide bits?
Click to expand...

For most home shops, I generally recommend you don't because cutting with carbide is a bit like cutting with glass.

In an industrial setting you have a machine whose spindle alone weighs more than a small drillpress and whose runout is measured in microns, attached to a casting that weighs more than a small car with a work piece that sits in a heavy vice clamped to a stout table that is as solid as the concrete floor under your feet.

Under these conditions a carbide drill can be turned up to its recommended SFM where Built Up Edge becomes less of a problem and the machine controller can feed that drill into the work piece within tightly controlled parameters that fall within a narrow window and everything works out okay.

In a home shop those speeds lead to chatter that would damage the cutting edge. At lower speeds the BUE builds up and breaks off continuously at a microscopic level dulling the drill. A ham handed move such as slightly overfeeding the drill during exit (easy to do once the web is cutting air) and the corners chip off.

So, at the end of the day, most folks will find carbide drills don't last longer than a quality HSS drill and they cost much more. And you can't readily resharpen them.

There are a few variations of the carbide drill. Perhaps the most common in industry are "circuit board drills" which are free cutting and designed to cut abrasive material like fiberglass. These can not cut steel. I use them for plastics. There are straight flute that have an almost 90 deg cutting edge. These are used to cut hardened steel. They're expensive and don't cut as well as a regular drill. And there are carbide drills with conventional grinds. When used properly on industrial tools they can cut a hole faster and more accurate than HSS. But most industrial users use HSS due to a lower cost per hole.

I only use carbide drills when cutting soft abrasive materials.
 
I am one of those ham handed guys. I have a small mill and it is very easy to break a small carbide cutter. Just a tiny bit to much side pressure. After a couple tries I never use them in my drill presses.
 
thank you for all this info (and i know i need a speed and feed app on my phone or one of thos handy calculators )
i got a bridgeport now and what a step up from my mini mill but i am relearning things (and learning to do things right this time )
 
Long shot question of the day: anybody got advice for drilling 110V? It is very difficult to drill without the material work hardening very hard. I think this stuff comes in the door in the low mid 40s rc.

I have the best luck with carbide but it is very easy to ding them up.
 
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