Drill your holes

OTK said:
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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I haven't drilled 110V but I drilled a lot of M4 last year using a regular HSS drill.

These are expensive parts I'm making and I'm using very conservative numbers with no regard to cycle time. I'm using an American made HSS 1/8" drill and drilling 1/2" deep in two places. 3.0 IPM and 1070 RPM and pecking every .100". I cut 40" of CPM M4 with one drill before changing it. And I'm certain it could go much longer than that but the material cost dictates I change cutters frequently.

I'm sure 110V is worse than M4, but M4 is no cake walk. I'm pretty sure your problem is under feeding, which was the purpose of this thread. If you're not pushing it hard enough to break your chip you're not pushing it hard enough. You should not be getting birds nests or chatter. Keep that cutter feeding or you'll work harden your steel. Once your cutter is dull through it away. I expect I would get at least 10" out of a drill in 110V before dulling it.

This is an application for a cobalt 135 deg split point.

Harder material requires more force to get the web to penetrate fast enough to maintain a proper chip. If you're not flowing metal over that cutting edge it is sitting there rubbing (lots of carbides in 110V) and hardening your work piece. Lean into it (within reason) and lift as soon as the web penetrates and regular HSS should cut that just fine.
 
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Nathan,

First of all, thank you very much for replying :)

Reading through your response, the under feeding point is well taken. I usually am pretty conscious to feed firmly but hey...maybe not firm enough. I may not be pecking enough and rubbing over the fines is what I'm suspecting. 110V does not form the long continuous strings like other stuff usually will, and it will harden up extremely suddenly. Once it does this it's carbide or no hole. A brand new 135d cobalt but won't touch it. It's way more difficult to drill or cut than any other material I use because of the sudden hardening.

I probably need to start out with a new/sharp bit, feed it strongly and peck often. Thanks again for the sound advice!
 
I was a machinist for 10 years before becoming a stay at home dad along with knifemaking. I have used a lot of 10V lately and I do not find it any harder on bits than any other steel when using good bits. It is more wear resistant and requires more sharpening on the larger bits. I use all 135* split point screw drills for drilling the steel. I mainly use Precision Twist brand made in the US. I have been using the same 5/32" drill for two years with no need to sharpen yet. However, my 3/8" I use needs replacing from sharpening and getting it too short. When I drill in the high Vanadium steel I run my DP at 240 rpm, the slowest it will go. I feed hard enough to break chips. I especially like how the CPM steels machine. They seem to break chips much easier to start with. This has seemed to work well for me so far.
 
OTK said:
I may not be pecking enough and rubbing over the fines is what I'm suspecting. 110V does not form the long continuous strings like other stuff usually will, and it will harden up extremely suddenly. Once it does this it's carbide or no hole. A brand new 135d cobalt but won't touch it. It's way more difficult to drill or cut than any other material I use because of the sudden hardening.
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Frequent pecking may not work in your favor if the steel work hardens that aggressively. I started to recommend a parabolic flute drill that doesn't need pecking but it occurred to me you're probably drilling blade steel no more than 1/4" deep so a regular drill will work. I suggest running it slow enough that you don't overheat the web and drill it in one shot. That is an application that would benefit from oil or coolant.

If you're turning 600 RPM and feeding at 2 IPM (hypothetically speaking), your drill would exit a 1/4" work piece in under 10 seconds of constant feeding. If it doesn't you can feed it harder.
 
It will work harden in a flash! One if these days I'm going to clamp a piece down in the mill vise and try a few different speeds at the standard auto down feed rates just to get an idea what I need to look for.

Thanks again!
 
It is very easy to sharpen a drill bit if you own a flex-shaft or Dremel machine. The side of a 7/8" separating disk makes a great miniature grinding wheel. Use a medium speed. The correct angle will be very easy to see. Works for up to 1/2" drill. I have used this technique to sharpen a .005 mm drill bit when it was the last one in the shop at 11:00 PM :) ...Teddy
 
Great info Nathan, my first job as a machinist when I finished school to be a machinist was in a guy's garage who had a government contract to drill holes I worked there for 2 weeks, I drilled an average of 2100 holes a day, for 2 weeks, you know how many holes that is?

We were taught feed and speed were dependent on material, hole size and depth. Basically it becomes a feelin' ya develop with time, we had old timers there that weren't happy unless they were blue chippin'.

We had no drill doctor back then, ya sharpened yer bits on a grinder, a lot of old timers used the side of the surface grinder back then and could adjust the angle of the bit and the width of the web by eye, took me a while but ya learn the feel and what to look for.
 
Hey Ted, it's cool to see you around these parts. That's a lot of holes to drill. That would get tedious after a while.

My first CNC mill I got from a guy who had been using it to drill holes in electrical buss bars. A glorified drill press.

You're right of course, feed and speed are dependent on material, hole size and depth. The funny thing is, in this particular forum you can almost figure on about a 1/4" drill in some kind of nasty high carbon high alloy steel at perhaps 1/4" thick. You could almost lock a person's spindle at 600 RPM and just leave it there.
 
OK Nathan, just for my own info: How does that recommendation change when most of the
holes I drill are only 1/8 - 1/16? I just don't like fat pins, though I am using Corby or Loveless
bolts for my kitchen knives now (still don't like the way they look though).
 
SunsetFisherman said:
a hair smaller bit would make the standard spindle speed a hair faster, IF the lower speed isn't cutting well
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Well "technically" only increasing the spindle speed will increase the spindle speed, and using a smaller bit will decrease the surface foot per minute of the cutter, not increase it, unless I"m drunker than I realize?
 
I agree with everything Nathan said (my opinion is next to worthless in this discussion, except to compliment Nathan). However, I do have some techniques that will make Nathan and other machinists cringe, but in some ways support everything Nathan said. I have a crap (but rigid) drill press with a machinist table. I use disposable drill bits, but sharpen the larger ones on a Drill Doctor. Every hole I drill in steel is punched, then pre-drilled with a smaller bit and then drilled to size with Tap Magic or some other cutting fluid. To make sure my drill is centered, I plunge it into the punch mark or pre-drilled hole and manually turn the chuck backwards. I can see if I'm off when the bit runs, the piece moves or the marks are not centered. When I'm centered, I clamp it down hard, while holding light downward pressure, oil it, and start it up. If it chatters, I press harder. I always have success without chatter at 400 RPM with a drill up to 1/2", but can run up to 3 or 5 times faster with anything smaller than 3/8". All of my blades are stainless, and I often have to press my pins/bolts in and out during dry fit. I'm not making folders, but of all the areas I concern myself over, hole tolerance has not been one of them.
 
Dan Pierson said:
OK Nathan, just for my own info: How does that recommendation change when most of the
holes I drill are only 1/8 - 1/16? I just don't like fat pins, though I am using Corby or Loveless
bolts for my kitchen knives now (still don't like the way they look though).
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Dan,

When you get down to the fundamentals it is directly proportional, everything scales. When done "correctly" the actual feed rate in IPM doesn't change.

For example, lets say you have a 1/4" drill and you will be drilling a high carbon steel that should be drilled at 40 surface feet per minute (slow RPM). You would spin a 1/4" drill at 600 RPM to get 40 SFM. That drill is fed .002" per tooth, which is .004 per revolution which gets you a feed rate of 2.4 IPM.

so, a 1/4" drill at 40 SFM gives you 600 RPM and a feed rate of 2.4 IPM
So, an 1/8" drill at 40 SFM would be 1200 RPM and a feed rate of 2.4 IPM
A 1/16" drill would be 2,400 RPM and feed at 2.4 IPM
a 1/2" drill would be 300 RPM and 2.4 IPM

The RPM scales with the cutter diameter. The feed per tooth scales with the cutter diameter. The actual feed rate stays the same because as the allowable feed per tooth goes up or down, the RPM is going up or down also.

This is a fundamental aspect of machining that applies to most cutting tools.

The reality is that the fundamentals get you in the right ballpark, but an experienced machinist knows certain exceptions that allows them to bend some of the rules. For example, in reality, you can run a drill much faster than recommended when run over a short distance if you feed it hard enough to prevent heat build up. So you can run that 1/4" drill at 1,200 RPM and feed it at 6 IPM when drilling an 1/8" knife blank. You'd burn it up drilling a thick piece like that but it is in and out so quickly in a thin part you can get away with it. However, unless you're in production there is little to be gained by flogging the tooling beyond the recommended setup parameters that I gave in those figures above. What is important is you maintain an appropriate chip load, regardless of the RPM you choose.

Different materials have different recommended SFM numbers. 40 SFM is on the low side and is used for the steels we play with. Regular mild steel is processed at twice that SFM and 150% that feed per tooth. A 1/4" drill in aluminum would be 4,500 RPM and 41 IPM.

Remember this: you have a lot of leeway in the RPM you choose, but your feed per tooth needs to be in the correct window where it isn't rubbing and stewing in its fines. In practice, if you'll lean into your cutter hard enough that you force it to cut smoothly and lift as the web is exiting the back side of your work piece you'll get good cutter life.
 
javand said:
Well "technically" only increasing the spindle speed will increase the spindle speed, and using a smaller bit will decrease the surface foot per minute of the cutter, not increase it, unless I"m drunker than I realize?
Click to expand...

exactly, I meant say a hair smaller bit NEEDS a hair faster speed, not that it creates it. Nathan explained quite well
 
When I first started watching machinists work an old man told me that witout speaking to a machinist you can tell if he is pretty good by checking his machinery.

Is it clean, and
What do the cuttings look like.

Proper feed and speed will result in very nice clean and uniform cuttings on the floor and in the bed of the machine. The sounds the tooling makes are also indicative of improper/ proper action.

Don't forget to use different bits (grinds on the bits) for your soft metals and composite materials. Aluminum, brass, and the like it is recommended to modify your bits for them. An old Machinery Repairmens book from the Navy said to grind flats to the outside of the clean out flutes nearest the end to prevent it from bitting and shearing material. Then relieve the back side to make a more chisel like tip. Cuts like a knife through butter and won't take your stock away from the machine.
 
I still have my Machinist Handbook from 30 years ago, it's all dogeared and marked up with note.

I was in a local machine shop talkin' to the owner when I saw Hand Book sittin' by the reference books, we got to talkin' about how none of the younger machinist even know what it was. Just then a 20 something kid showed up to ask a question about a print and I asked him if he ever used the handbook, he said . ,"...nah, I can get anything I need from here..." as he tapped his iPhone, I asked what did he do if his battery went dead, " ask the boss..." was his reply.

Kinda reminds me of when the digital cash registers came out how all the kids forgot how to make change, the damn machine would tell exactly how much change to give back. When the power went out or the register broke they couldn't make change.
 
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