Question for folder makers(Machinists)...pivot pins?

Hankins

Hankins

Joined
Dec 7, 2008
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Who has the best tolerance on there folder pivots?
Looking for a smooth consistant pivot where you dont have to measure every one.
Also looking for the same in washers for folders. Many of the ones advertised are not the thickness advertised or the exact hole size either...
Some advertised as 3/16" measure out at .176 in diameter Etc. Frustrating and expensive to keep buying reamers that make the proper hole size blah blah blah.

Someone with more machining knowledge please enlighten us to the ART of getting the right sized perfect hole!!!
Rant Over:confused:
 
Hi,

You want to know how to hit your tolerances yourself? Or why are your supplier's tolerance so loose?:) How tight a tolerance do you want or do you thing you need? There is a big difference between those two questions.

dalee
 
Refering to the suppliers tollerances...mine are somewhat under control;)
Can you explain what happens when a drill bit makes a hole, on a micro level?
My visualization is that it rips pieces of metal out leaving a jagged edge on the sides.
I have found that by using a two step reamer process the holes seem to clean up better. IE: For example to get an exact 3/16" hole--- original hole drilled to .175, first reamer .180, second reamer .1875 just a reference point.

What I find is that different steels and materials will leave a different sized hole even when using the same drill bit or reamer.
Explain...
 
Hi,

Well, after 20 years as a machinist I still don't have down exactly what the physics are right at the very tool/material interface myself.:) But for a reamer and drills, (and I consider reamers to be a second best option for tight hole tolerances only marginally better than a drill bit for size and finish), the material isn't quite "ripped" out of the way. But rather it is supposed to have "plastic deformation" and then it flows over the cutting edge and then "chips". This phenomena is why coated tools are the rage right now. Those coating are supposed to be slippery and wear resistant. There by reducing friction and heat build up and the inevitable breaking down of your tool edge due to the heat.

But what could be causing your supplier to have such a variance could be quite few different things. Things that often go wrong are incorrect speeds and feeds for the tool size and material. Improper lubrication/coolant. Lack of rigidity in the work holding set-up. Lack of rigidity in the machine tool itself. Miss-alignment of the spindle to work. The spindle being canted to the work plane. Loose or worn spindle. Poor tool holding. Improper pilot hole size. Flexing of the tool and work. Oh, and dull/damaged tooling.

Don't think I missed too many things. But you can mix and match any or all of those things and mess up your hole. It's amazing we can get anything right at all isn't it. But without actually seeing how they do the work, it's pretty hard to determine where there trouble lays.

dalee
 
You missed one thing. The "made in China" markings.:rolleyes: Seriously, AKS pivots are dead-on what the measurements are on their site.:thumbup:
 
i tend to under size drill the hole in a pivot and the after heat treat use a carbide ball endmill to "clean" the hole
so far as pivots them selves being over sized (they can be ) i have a screw thats the right thread and thread to together and lightly sand them to size in my mill
works for me
i would rather mess up a 2 $ pivot then to have to restart a blade in high $ steel
thats been heat treated

OOO also i use a mill to drill all my holes


so far as why you can get a clean hole with a drill its all cause of the cutting edges
a mill bit most times has at least 3 flutes and more often then not 4 or more. drill bits "wobble " more in the hole making a tringlar hole
 
dalee100 said:
It's amazing we can get anything right at all isn't it.
Click to expand...

No kiddin, this is one reason why I make fixed blades and not folders yet. I don't have the skills/knowledge/tools for that kind of tolerance... on a straight knife, a mil of "slop" around the pins is a good thing, makes room for the epoxy.

As for different materials getting different holes from the same tool, maybe it's due to different density/toughness/wear resistance? Allowing the bit to "wobble" more or less depending on those factors? I'm only guessing.
 
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I drill ream and then use a barrel lap with 600 grit diamond paste to make round hole that fit the bushings that i use. oh I make them too. the pivot pins that chuck sales are the best that I have found to date.
 
greatlakeswaterjet said:
You missed one thing. The "made in China" markings.:rolleyes: Seriously, AKS pivots are dead-on what the measurements are on their site.:thumbup:
Click to expand...

Hi,

I purposely omitted the Made in China. Poorly made parts don't know geographical boundaries and can be bought from anywhere. All I will say is, accuracy costs money. The more accurate, the more it costs.

Bucher_ block, while end mills are very accurately sized, what maybe more important to your process of sizing the hole is the final machining step after H.T. Many types of steel aren't very dimensionally stable during H.T. And heating and quenching can do bad things to holes. And using a mill, (far more rigid and has more mass that a drill), is a good way to do it.

Bill, you are probably doing the best way in my opinion. Drill, ream, and lap for the ultimate accuracy and surface finish. A bit over-kill for this application, perhaps. But it will give the best end results.

dalee
 
butcher_block said:
drill bits "wobble " more in the hole making a tringlar hole
Click to expand...

You hit that one on the head there Butch.

The "proper" way to make a hole is to center drill, drill, bore, then ream. Followed in this order the hole will be accurately located, straight walled and square to the work piece, round and dimensionally accurate. You can use tooling buttons before boring to be sure it is where you want it relative to other stuff if it has been off the machine. I don't know anybody who actually does it that way...

Reamers cut different sizes depending on how sharp they are, the hardness of the material being cut, lubricant used, the condition of the hole before reaming etc. Two common mistakes while reaming is not controlling the run out (if you can see it wobbling, it isn't going to work right) and pulling it out of the hole too fast. fairly low RPM, fairly high feed in, and the same feed back out and I'll get near mirror finishes that are round to a .0001 (measured TIR) and sized accurately under a thou.

I think Butch's idea of leaving the hole undersized until after HT and chasing the hole with a carbide ball mill (4 flute, not two or you'll get a triangular hole) is a good approach for most folks. You'll get a good finish and a fairly accurate hole.

I can circular interpolate accurate in size, roundness and location to within .0003". When I need it better I ream. When I need it better than that I'll chuck up a plate in the lathe, face it and bore a hole. Put my part on a pin and pin it to the hole and clamp it to the plate. I remove the pin, put a 40,000 RPM live tool (think tool post grinder with ceramic bearings) in the tool post and grind that baby. That hole is perfect within my ability to measure. Also overkill. But you asked....
 
quick side question, is is better to use a straight reamer with power or a spiral reamer with no power? (or is it the other way around)
 
Vary helpfull gentlemen...
Don't have a mill yet but am wondering: Can the drill bits used in a mil also work in a drill press?
 
Any side pressure in a drill press will wear out the bearings extremely fast, not to mention the press is not as rigid as a mill. I have done that to my drill press and it now has a lot of side to side play. When I turn it on full speed the bearings scream for mercy also.
 
Gix
Was asking if I can use the drill bits to make holes not do any real milling, sorry if it was not clear
 
in short yes
you just have to make sure every thing is lined up and clamped as tight as you can the only
i would not use std mill bits tho (ball end would "drill" better in a drill press) least i would think

other thing to think about is if the drill press table is "tramed out" so your holes are not gettign off 90 degree and making the blade in the folder swing badly when its finished

lots of little things make the best folders the best but you can get buy with a worker if you need to
you might always chase that last little play or fit and finish that's what makes folders fun and maddening at the same time
 
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