Counterbores, End Mills, Bits... How do you drill holes on your folders?

[Daniel Fairly Knives]

Lets talk folder making!

I am curious how everyone does the holes on their folders. What exact process do you use?

I just got a mill and am trying to dial in my process to get perfect holes... the right size and perfectly square.


I'll go first

- find starting point with a center finder
- start hole with a center drill
- drill undersized
- ream


Should I change from a collet to a chuck at any time? Use a chuck except on end mills?

Drill with end mills?

For counterbored holes (like a pivot) should I use a combined counterbore or smaler then larger end mill?

Do you stack the frame sides and drill both at once? Index?

Coolant? I'm using Titanium here...


Thanks in advance! I hope we have a fun discussion.

 

[Nathan the Machinist]

I hope some experienced folder makers will chime in here, I'm currently delirious and loopy with a bad cold, cough syrup and some strong beer but I'll put in my .02...

The "correct" way to cut an accurate hole (I don't know anybody who actually does this on a regular basis):
Locate the hole (lots of ways to do that)
Spot the hole (with a spotting drill, not a center drill or you'll go to hell)
Drill an undersized hole, .015 under for 1/4" is good
Bore that hole, single point (.005 under for 1/4 is good). At this point you're square, round and accurately placed
Install a reamer and tweak out the run out and then ream that hole. Reaming is done with low SFM, lubricant, and high feed in, and the same controlled feed back out.

If you follow these steps correctly you will have an accurate hole. This is old school here.

A more common approach is to substitute an undersized endmill for the bore head or replace it all together with circular interpolation.

Reamers will cut over sized bell mouthed holes if they're wobbling. You can usually use an indicator and some hand tweaks to get the runout under a thou for good results.

For counter boring, the end of endmills are not square, they're an inverted taper. You can use them for counterbores (lots of people do), but really they're not correct. I use circular interpolation, which is probably not on the table here...

For coolant I like Trim Microsol 585. It was designed for titanium, but it works so well I have it in all my sumps.

 

[Patrice Lemée]

Interesting about spotting drills Nathan. Never heard of them and I an tired of breaking center drills.

 

[Nathan the Machinist]

Interesting about spotting drills Nathan. Never heard of them and I an tired of breaking center drills.

Center drills are short rigid necked drills used to drill "center holes". They're common in machine shops because they're used on lathes to make holes for dead and live centers. Center holes are typically a 60 degree included angle cone used to "center" a part on a lathe. Typically this is in one end where the workpiece is supported with a live center to prevent long work pieces from deflecting in a cut and cutting tapers, though it is not uncommon to run a part between two centers, with a dead center in the spindle. Anyways, being short and stubby they're stiff so they can be used to start a hole without walking around on you.

Here is a common misconception:
If you start your hole with a center drill, the 60 degree cone will help "funnel" your drill into the work piece. This is incorrect. It only works because the small pilot hole (which is actually intended to create clearance for junk when used properly with a center) acts as a guide for the web of the drill. It is the web of the drill that walks when starting a hole. By contacting on the corners of the drill first, your 60 degree center hole is not "funneling the drill", they grab and get that unsupported tip wandering everywhere trying the drill a triangular lobe shaped hole. Think about it for a minute and you'll visualize the mechanism at work here.

This is such a common misconception that I have seen it in college text books, and it is wrong. A center drill is better than nothing and can be used to make a shallow dimple to start your drill without much wandering, but the correct tool is a spot drill.

A spot drill is also short and stubby and sometimes has a special web. You start a 118 degree drill with a 120 center spot. Then the web contacts first, stabilizes the cut in an accurate location and you drill a nice straight round hole. And the more accurate a hole you start with, the less uneven the cutting forces will be when you go to single point bore that hole (as if anyone is actually doing this) so the more accurate that will be and so on.

 

[Bill DeShivs]

I use a flexible shaft machine and drill most holes by hand. If I need a bigger hole, I go to my cheap drill press.
I make my folders by hand, and have found that the holes don't need to be precise. I guess if you are machining the knives, precision is required.

 

[Nathan the Machinist]

^
Yeah, precision would be required if you were machining them and wanting to achieve a certain level of accuracy for fixturing from existing features and minimizing hand fitting while maximizing interchangeability. That is one approach. Another build approach is folks like Bill who can achieve a fine fit and finish without the big tools. I approach things the first way because that is the only way I know, but I acknowledge the validity of the second approach. The worlds first precision surface plates were essentially made by hand and were probably more accurate than mine.

If you want to know how to drill a precision hole, I just told you. If you want to know how to make a folder you should talk to folks like Bill.

 

[JBS TOOLMAKER]

For the pivot hole, on frames and liners. I bore through with an undersized end mill as Nathan described. Then ream the lock bar side for a press fit to the pivot, the other side slip fit ( makes assembly and dis assembly easy) and trust me just starting out you're gonna do that a lot. For everything else I use counter bores, check out Mcmaster Carr and order 2 of every counter bore you need to fit your pivot, screws etc. Why 2 ? Cause you're going to fry one or dull it. They can be resharpened but it's tedious without the right equipment. The other thing you will need is some carbide drills for your detent work. I use a #56 for the blade and a #53 to press fit a .0625 ball, that's for a .015 washer / bearing. Also, a carbide reamer for the pivot hole in the blade. For a good perpendicular hole you should ream after heat treat and surface grinding. You don't have to ....but it's a more accurate method.

 

[Don Hanson III]

Folder holes, I just drill undersize and ream on a cheap ass drill press.

No thought and very little time spent.

 

[JBS TOOLMAKER]

Listen to Don.

 

[Frank Niro]

Well I'm pleased I'm doing that right, Don, and it does work for me. Frank

 

[Don Hanson III]

Listen to Don.

No, don't listen to me. I just find the simplest way to do stuff and still have it work.

 

[JBS TOOLMAKER]

Nothing simple here Sir. That's pure awesome.

 

[Alpha Knife Supply]

Daniel, what kind of folders do you want to build? The tools, processes and tolerances are different depending on the kind of folder you make. For example, flippers using IKBS have different requirements than slipjoints.

Chuck

 

[roblockwood]

I concur with everything nathan said. We regularly use the method he outlined to hold hole tolerances of +/- .0003" on diameter. I would say though, that it would largely be overkill on anything knife related. I don't start pre-boring until a hole reaches a 2:1 length to diameter ratio, and rarely do it on holes under 3/8" of an inch anyhow.

 

[Patrice Lemée]

Good stuff Nathan! Thanks. :thumbup: Spot drills just made it to the top of my ToBuy list.

 

[Daniel Fairly Knives]

I hope some experienced folder makers will chime in here, I'm currently delirious and loopy with a bad cold, cough syrup and some strong beer but I'll put in my .02...

The "correct" way to cut an accurate hole (I don't know anybody who actually does this on a regular basis):
Locate the hole (lots of ways to do that)
Spot the hole (with a spotting drill, not a center drill or you'll go to hell)
Drill an undersized hole, .015 under for 1/4" is good
Bore that hole, single point (.005 under for 1/4 is good). At this point you're square, round and accurately placed
Install a reamer and tweak out the run out and then ream that hole. Reaming is done with low SFM, lubricant, and high feed in, and the same controlled feed back out.

If you follow these steps correctly you will have an accurate hole. This is old school here.

A more common approach is to substitute an undersized endmill for the bore head or replace it all together with circular interpolation.

Reamers will cut over sized bell mouthed holes if they're wobbling. You can usually use an indicator and some hand tweaks to get the runout under a thou for good results.

For counter boring, the end of endmills are not square, they're an inverted taper. You can use them for counterbores (lots of people do), but really they're not correct. I use circular interpolation, which is probably not on the table here...

For coolant I like Trim Microsol 585. It was designed for titanium, but it works so well I have it in all my sumps.

Nathan - I can't say enough about how helpful that is! Much appreciated

How do you tweak around the reamer, mine was wobbling for certain.

I'm adding a spotting drill to my list...

For the pivot hole, on frames and liners. I bore through with an undersized end mill as Nathan described. Then ream the lock bar side for a press fit to the pivot, the other side slip fit ( makes assembly and dis assembly easy) and trust me just starting out you're gonna do that a lot. For everything else I use counter bores, check out Mcmaster Carr and order 2 of every counter bore you need to fit your pivot, screws etc. Why 2 ? Cause you're going to fry one or dull it. They can be resharpened but it's tedious without the right equipment. The other thing you will need is some carbide drills for your detent work. I use a #56 for the blade and a #53 to press fit a .0625 ball, that's for a .015 washer / bearing. Also, a carbide reamer for the pivot hole in the blade. For a good perpendicular hole you should ream after heat treat and surface grinding. You don't have to ....but it's a more accurate method.

Much appreciated!

Great call on getting two of everything.

What kind of counterbores do you recommend? I have been staring at the McMaster page every night for a week now, lol.

Your folders are looking top notch by the way.

Folder holes, I just drill undersize and ream on a cheap ass drill press.

No thought and very little time spent.

I do have the equipment for that...

I use a flexible shaft machine and drill most holes by hand. If I need a bigger hole, I go to my cheap drill press.
I make my folders by hand, and have found that the holes don't need to be precise. I guess if you are machining the knives, precision is required.

I am familiar with your work and whatever you are doing is right I know that!

I am mostly worried about keeping everything precise for no blade play or uncentered blades. I have only made a few folders though and have a long ways to go.

No, don't listen to me. I just find the simplest way to do stuff and still have it work.

The simplest way is usually the best!

You make some pretty good pocketknives too...

Daniel, what kind of folders do you want to build? The tools, processes and tolerances are different depending on the kind of folder you make. For example, flippers using IKBS have different requirements than slipjoints.

Chuck

Type - Tactical Framelock, .190" Ti Frames and a .203" CPM D2 blade. My goal is a clean or simple look with overbuilt features.

I am using phosphor bronze washers and want the smoothest action possible. Hopefully it will flick open if I get everything right.

1/4" AKS Pivot - 1/4" standoffs - 1/4" Press Fit Stop Pin


Thanks for the help and the pivots you guys make are awesome!

I concur with everything nathan said. We regularly use the method he outlined to hold hole tolerances of +/- .0003" on diameter. I would say though, that it would largely be overkill on anything knife related. I don't start pre-boring until a hole reaches a 2:1 length to diameter ratio, and rarely do it on holes under 3/8" of an inch anyhow.

That sounds good... especially on the overkill part!

Thanks!

 

[Daniel Fairly Knives]

Here's what I am making

The holes are undersized in this sketch, they represent where the pivot, stop pin and lanyard hole will be placed. I'll be adding a .25" standoff to either side of the lanyard hole as well.

 

[Nathan the Machinist]

How do you tweak around the reamer, mine was wobbling for certain.

You can improve the quality of reamed holes by aligning the spindle with the bore of the hole and by minimizing runout. These things causes bell mouthed holes. For many classes of work, the flexibility in a long skinny reamer and a free floating work piece allow the reamer to follow the existing hole reasonably well. I'm sure this is good enough for knife making, I'm not trying to imply that makers who stop there are taking shortcuts.

That said, a precision hole is first drilled accurately, then bored, then properly reamed. "Precision" holes are not necessarily of benefit here, but if you want an accurately cut hole you will want to minimize reamer runout.

A high quality American made reamer held in a precision collet chuck mounted in a precision spindle will generally have runout under a thou, but not always. If not, I give it a tweak. Most reamers are finish ground after HT between centers and if you'll indicate just above the flutes you'll get a good picture of what is happening down where the cutting is happening. If I need a tweak I'll use an indicator to find the "low spot" and simply give the cutter a stout tug with my hand. Most of the time that will bring a reamer moving one or two thou in under a thou.

A reamer held in a drill chuck can be done the same way. However, runout in a drill chuck can easily be .010 down at the end of the reamer. If that is the case, simply loosen the jaws a little, tweak the cutter by hand and then re-tighten the jaws. You can usually get in down under a thou this way.

edit: this is true on a mill, however some drill presses have runout that varies from rotation to rotation and it is possible to be pissing-up-a-rope here.

This all sounds way more complicated than it is. It doesn't take one minute to setup an indicator and make your tweaks. However, if you're doing one hole at a time this way it might get tedious. I'll tweak a reamer in a tool holder and leave it there, and that tool holder repeats in my spindle generally within a fraction of a .0001" so I'll tweak once and not worry about it. I'm not saying this should be "the way", I'm saying it is a way. YMMV.

 

[elementfe]

The other thing you will need is some carbide drills for your detent work. I use a #56 for the blade and a #53 to press fit a .0625 ball, that's for a .015 washer / bearing.

Everyone works out a method or ten that works great for them.
I do the assembly on my folders one at a time, and have found that just drilling the detent hole through the lock tab into the blade with a #55 bit, then drilling the tab at #53 is working great. Pre Drilling with a 55 means you're not risking getting that 53 hole too big or egged out.
I do it before heat treat and so don't need carbide.
Of course, you have to establish the blade's closed position first, so that the hole in the blade is in the right place.

 

[Daniel Fairly Knives]

You can improve the quality of reamed holes by aligning the spindle with the bore of the hole and by minimizing runout. These things causes bell mouthed holes. For many classes of work, the flexibility in a long skinny reamer and a free floating work piece allow the reamer to follow the existing hole reasonably well. I'm sure this is good enough for knife making, I'm not trying to imply that makers who stop there are taking shortcuts.

That said, a precision hole is first drilled accurately, then bored, then properly reamed. "Precision" holes are not necessarily of benefit here, but if you want an accurately cut hole you will want to minimize reamer runout.

A high quality American made reamer held in a precision collet chuck mounted in a precision spindle will generally have runout under a thou, but not always. If not, I give it a tweak. Most reamers are finish ground after HT between centers and if you'll indicate just above the flutes you'll get a good picture of what is happening down where the cutting is happening. If I need a tweak I'll use an indicator to find the "low spot" and simply give the cutter a stout tug with my hand. Most of the time that will bring a reamer moving one or two thou in under a thou.

A reamer held in a drill chuck can be done the same way. However, runout in a drill chuck can easily be .010 down at the end of the reamer. If that is the case, simply loosen the jaws a little, tweak the cutter by hand and then re-tighten the jaws. You can usually get in down under a thou this way.

edit: this is true on a mill, however some drill presses have runout that varies from rotation to rotation and it is possible to be pissing-up-a-rope here.

This all sounds way more complicated than it is. It doesn't take one minute to setup an indicator and make your tweaks. However, if you're doing one hole at a time this way it might get tedious. I'll tweak a reamer in a tool holder and leave it there, and that tool holder repeats in my spindle generally within a fraction of a .0001" so I'll tweak once and not worry about it. I'm not saying this should be "the way", I'm saying it is a way. YMMV.

Thanks again, that helps a ton.

EDIT - Who's reamers do you like?

I have been reading for months now but your explanation makes a lot more sense than the books!

Now that I am using my mill a lot of the information is falling into place but it also brings up a ton more questions. I practiced doing some actual milling and it was much easier for me than drilling holes correctly, lol...

Everyone works out a method or ten that works great for them.
I do the assembly on my folders one at a time, and have found that just drilling the detent hole through the lock tab into the blade with a #55 bit, then drilling the tab at #53 is working great. Pre Drilling with a 55 means you're not risking getting that 53 hole too big or egged out.
I do it before heat treat and so don't need carbide.
Of course, you have to establish the blade's closed position first, so that the hole in the blade is in the right place.

There are a lot of ways to get there that is for certain. I have gotten lucky on my first detent but it can make or break a knife.