The Art and Science of drilling the perfect hole...Need help from the folder makers

You are most welcome!

I do also sincerely mean best of luck with your project. Although you don't sound like a guy who leaves much to "luck" in that sense. I think I am also the same way: careful planning and precise execution. Dashiell Hammett once wrote, "The outcome of successful planning always looks like luck to saps." So I guess I actually should have said I hope the project turns out exactly like you have planned and envisioned it to be!

Really can't wait to see your knife!!

There's nothing like planning something, working diligently to creat it and finally holding the finished thing in your hand. It always seems a shame to exchange these things for money... but then there's always the next one!

Keep smiling!
 
One thing that always comes in the machine tool world, is perfect. Perfect is a theoretical concept and doesn't exist in the real world. That's why prints have tolerances.

A drill will not make a good round hole regardless what you do. It's not great on holding size or location. Reamers control size very well, but do nothing for location or perpendicularity. A good rule of thumb for reamers, is to leave 1/64 inch of material for cleanup. If you leave too much, it'll bog the reamer. If you leave too little, the cutter won't be loaded properly. Whether drilling or reaming, always use some form of coolant.

Speed and feed are important whether reaming, drilling, end milling, etc... Generally, the speed for reaming holes is 1/2 - 2/3 the speed for drilling. The shorthand forumula for calculating speed, is (4 x Cutting Speed) / cutter diameter. The formula for calculating feed, is rpms x number of teeth x chip load.

CNC circle interpolation isn't a perfect hole either. Circles on it are broken down into a bunch of little linear steps based on the linearization value of the machine. Some of them can be really good, like 0.000040 steps, but it's still not perfect. Wire edm is the same way.

In a mill, you can get really nice holes by boring. Small holes can be a challenge though.

The best quality holes are usually done with a jig grinder.

For position accuracy, is the 0.0001 referred to true position?

For the home shop, the method used for lapping holes will probably be the best.

Jamie
 
Positional accuracy on my Haas TM-1 mill is +/- 0.000402 inch or 0.0102mm
 
Wow thanks that is some great advice and opened my options along with my wallet. Have gotten to the point where my starter equipment is getting worn and not performing the way it needs to. It will get replaced!
Though not a machinist it becomes increasingly clear I need to think and work like one to achieve my goals.
 
polarbearforge said:
I've worked on Haas mills before, the brochure might say that, but I don't recall ever having parts that came close to holding that reliably.

Jamie
Click to expand...

I don't know about the details of this or that machine, but my machinist was telling me that typical positional accuracy in his field is .0005, but they would hold .0002 when necessary. He tells me there are ways of doing this that ... well ... you take seminars and do constant training to be aware of the latest techniques. He gave me an example of how you'd interpolate a hole with high accuracy and it's more than just cutting from center out, around the hole and back to the center. It's pretty involved and quite a headache, but apparently they did it a lot.
 
i dunno, on a new haas, ive worked in tenths (.0001's) boring diameters and what not, but not everyone has access to a good 3axis CNC machining center...
 
Boring diameters is pretty straight forward. We did that a fair amount. It's a good way to make a good hole. An experienced operated can hold size really well this way.

The parts that I made on the Haas didn't need to be that tight of tolerance. The tighted tolerance holes were almost always jig ground. Wire edmed holes were the second most common. For the jobs that they couldn't do, I did in sinker edm. They were blind openings that wire couldn't do and often times rectangular so that jig grind couldn't do it. On top of it all, it was usually holding 0.0005 true position(as defined in Geometric Dimensioning and Tolerance, newest version).

I'm not saying that it can't be done. It can and is done regularly. I'm just saying that the Haas mill that I worked on wasn't the greated machine in the world. It didn't repeated consistantly enough for me, nor did it have enough rigidity for my tastes.

Jamie
 
There are a lot of machine tools from different makers out there. Okuma, Mori Seki, Mazak, Haas, etc etc. It's important to choose the right one for your application and that means not only performance but price/value as well. If I had purchased a $100k VMC I would have been bankrupt the day it was delivered.

Haas alone makes many, many different models of VMCs. The one I have is the smallest, most inexpensive machine they make. And I can tell you after a year and a half working with it, for a knifemaker, it's a dream. Fantastic. The accuracy is way more than you'll ever need and way more than I can even measure. My Mitutoyu, Tesa, Steinmeyer, and other dial indicators only do 0.01mm.

Naturally there is a difference between a $30k machine and a $300k machine. Generalizing about "Haas machines" doesn't seem very reasonable based on experience with one model and one machine. It would be helpful to know which machine you used. But for the discussion here, the point is actually moot.

It's one thing to talk about machines they have at work and another to actually go out any lay down the cash to buy those machines.

Most knifemakers, including myself – and others reading this thread – aren't making parts for Boeing from their little workshops. I have two drill presses, one from Maxion that cost well over $1000 and the larger one from Flott that costs new almost $10,000 (I bought that one used).

I had one of those far eastern drill presses for about one hour years ago, then I packed it back up and returned it. It was crap. Then I saved my money and bought the Maxion. That was almost 10 years ago. I have never regreted it for a minute.

If you want to drill proper holes, get a proper drill press – or at least one that (as Ben instructs above) can be more or less tarted up to work like one. Some guys have a bunch of those crap drill presses set up to do particular operations, and that seems to be a good solution. But I still fail to see how they by without at least one good drill press somewhere.

I never feel I have to fight my machines to get them to operate correctly; quite the contrary, I think my machines are capable of more than I can get out of them. But I'm working on getting better every day.
 
Wow!:eek:

I've been trying to figure out holes too, now that I've started into folders. I've made (probably all of) the rookie mistakes that one bumps into without a coach.

  • I realized that jobber bits on a $59 drill press that hasn't been set up properly work in tolerances very similar to hogging profiles with a 36 grit belt.
  • I realized that a 1/8 reamer isn't going to improve a drilled 1/8 screwed up hole.
  • I realized that split point bits are a cruel trick on the user of a centre punch.
...... and I'm still learning.

I am using cutting fluid now - doing a reasonable setup of the drill press before starting and beginning with about 1/64 smaller before reaming.

I'm still looking for info on speeds and there has been some good information posted here but it has been either non specific (keep it slow) or formulas without units. Could someone offer suggested RPMs for drilling and then reaming holes - even just 1/8 and 3/16 - in typical knife steels?

I'm also fighting with a problem I've had since my first knife. Holes in wood seem to shrink back to undersize. I can use the same bit to drill a hole in for a handle pin in the steel and in the stabilized wood. The pin goes through the hole in the steel easy (sometimes too easy) :o but it threatens to split the wood. I've been answering this problem with oversize bits - F bit 1/4 inch and so on - and on fixed blade pins, this works because the wood hole is just about right and a little slop in the metal hole is filled by glue.

Of course, on folders, I want things a little more precise - especially the pivot because I hope not to fill that with glue. :)

Is there a way to get better consistency between wood holes and metal holes?

I will eventually get better equipment, but for now, I'd like to learn to properly use the equipment I have to its best capability. I'm told it's a porr cratsman who blames his tools.

Rob!
 
Rob! said:
Wow!:eek:

I've been trying to figure out holes too, now that I've started into folders. I've made (probably all of) the rookie mistakes that one bumps into without a coach.

I will eventually get better equipment, but for now, I'd like to learn to properly use the equipment I have to its best capability. I'm told it's a porr cratsman who blames his tools.

Rob!
Click to expand...

Right on the money!!

The very best equipment turns out poor work if the operator doesn't know what he's doing.

The best sign of a true craftsman is the ability to do great work with a poor machine.

I've been using one of the cheap import drill presses for over 25 years and have no problem with holes in my folders.

I recently purchased another little bench drill from Home Depot because it has a convenient spindle depth stop I use when counterboring screw holes. If you know how to line it up and use it correctly it'll do the job just fine.

Of course, I use my milling machine for precisely square and on-size holes. The mill cost me a whole $2,000.00 new about 10 years ago.

You don't need to have expensive machinery. Spend your time and money learning how to use what you have correctly. And listen to the right people.:)

I've seen some poor advise in this thread and some very good advise. The trick is learning to differentiate between the two;) .
 
Kevin Wilkins said:
... aren't making parts for Boeing ...
Click to expand...

How did you know? :eek:

Generalizing about Haas machines was my bad, I usually don't do that. I probably should have added the caveat that it applies to all their machines that I've worked on. I could look up the models (there are 3 mills and one lathe), but like you said, it's really a moot point.

It's always hard comparing machines in at the work versus machines at the home. Some companies treat their machines properly and some don't. Some home shops treat them right and some don't. Improper techniques on any machine, regardless of cost won't yield optimum results.

I really haven't started on folders yet. My experience has been in the machine tool industry. Tolerances at machine shops are tighter than most of us will ever need on a knife. With this in mind, I've always wanted to see a folder print with appropriate tolerances.

Jamie
 
I totally agree with you on that one Jamie.

Over on the Practial Machinst Forum you can read some real horror stories about the way some employees treat machine tools. And you can get a lot of advice from people who have used a lot of differrent machines. I only have experience with Haas, so I have nothing to campare against based on personal experience. If I had the $40k I would buy one their Office Lathes tomorrow!

Don,
I have to say it, but I think your last post above belongs in the "bad advice" catagory you mentioned.

It's not a poor craftsman that blames his tools... IF the real problem is that his tools are crap. of course if he's the one who purchased the tools, then it's still his fault and he gets to buy them all over again.

Why do you think you don't go into successful, professional machine shops and see them full of crappy machine tools? Why do machine shops spend 100s of thousands of $ on the kinds of machine tools we've been talking about in this thread? Answer: because they're better than the crap ones; because they make more money for their owners; because they're a better investment over time and easier to use. Tools shoud work FOR you, not AGAINST you.

Telling people to expect the same quality from a crap drill press as from a good one is nonsense and I hope people reading will understand the inherent flawed logic in that argument.

Good tools make getting the job done that much easier. If you buy a crap drill press you not only need to be skilled in operating it you must understand exactly how it works so you can rebuild/refit it to produce passable work. Buy a good drill press and all you have to do is use it properly. No need to try and first figure out the weaknesses of the machine and either correct or work around them. Of course for most part time users there will be a trade off; some far eastern goods are pretty good. Do some reasearch and try and buy the best you can afford.

I learned this lesson over 20 years ago working in the auto workshop: I came in with some Craftsmen wrenches ... soon I realized I was the only guy using that quality of wrenches. Everyone else used Snap On.

I borrowed a few Snap On wrenches and compared using them against the Craftsmen stuff. Pretty soon I was buying Snap On wrenches because the differences were really quite obvious. The price was also obvious: the Snap On wrenches were like 5 times more expensive, but they were 10 times better.

"Always buy the best tools you can afford. That way you'll only have to buy them once." Thats another old saying, and it's one with a lot of truth in it. I hope those considering buying tooling will give it some thought.
 
Perhaps I did... in any case, your last post really has me puzzled... hopefully my comments have been easily understandable.
 
Thanks all. I do get the idea. The craftsman should aspire to the best he can get out of the tools available to him.

Still looking for advice of drill speeds and materials that seem to "close up" leaving a tighter hole than drilled.

Rob!
 
Someone has already posted the formula for finding the correct spindle speeds.

RPM=CSx4/diameter of tool.

For instance use a cutting speed of 50 for the steel blade materials you use.

200 for wood and most other handle speeds.

150 to 200 for brass and aluminum.

A cutting speed of 100 is based on drilling mild steel.

So, for example if you're drilling a 1/8" hole in ATS34 or other blade materials using a HSS drill, your RPM should be 50 x 4 = 200. 200/.125= 1600 RPM. Consider that the maximum RPM. Go down to the closest RPM your machine has available.

To ream the hole, use no more than 800 RPM and if you want a straight, close fit, use tapping fluid.

I have no answer for wood closing up on pins when the pin slides thru the steel.

Here's what I do. After all the holes in the tang and both scales are drilled, I put both scales on the tang and place pins in all the holes except one, then run the reamer all the way thru the handle using a battery hand drill, holding the knife in one hand so the reamer can follow the holes. After reaming all the way thru the first hole, put a pin into that hole, remove one of the other pins, and repeat, reaming and pinning until all the pin holes have been reamed.

Works fine for me.:)
 
Thanks Don

The 50 and 200 cutting speeds were what I was missing and also the units (imperial) for tool diameter. I can figure it out from there.

Don't know why I hadn't tried reaming wood and synthetic scales - but I will now. Thanks VERY much.

Rob!
 
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