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epicfail48
07-01-2019, 04:42 AM
Bit of an issue, im working on a butterfly knife design, and said design has the blade running on a bushing that sits in a 3/16 hole in the blade. Ive been drilling and reaming these before heat treatment, but after all is said and done the bloody things have opened up by about .004", as well as being slightly ovate. My question is, is there any sane way to ream these holes out after heat treatment, with the steel sitting at about 61rhc? The present best idea ive got is to drill the holes to .182" or thereabouts before heat treatment, then go back to the mill afterwards and finish off those holes with a carbide tipped 3/16" reamer.

Am i insane for thinking this would work? Can i reasonably expect carbide to cut through material at that hardness, or will i just smoke a reamer?

DATo
07-01-2019, 05:19 AM
I think the reamer idea would work provided you run it slow, but given that you have that "slightly ovate" hole after hardening you might still have some problems.

Another idea might be to use a 3/16 carbide end mill with a very slow upfeed on the mill knee rather than using the quill. I think you can control the upfeed on the knee, even by hand, easier than the quill. If I HAD to use the quill I'd put a bit of tension on it by tightening the quill lock a little. On a hard irregular shaped hole the reamer/mill cutter would have a tendency to bounce when it engages the workpiece or it could chip the carbide. By having a very rigid set up like this there is abetter chance of getting good size and a round hole.

MattiJ
07-01-2019, 06:21 AM
Carbide reamers are quite pricey to lea(r)n on.
Since the hole is so short you could grind it with small diamond stone and toolpost grinder in a lathe. Or maybe even bore with small carbide boring bar but getting the hole round and to correct size by boring can be tricky at 61hrc

JoeLee
07-01-2019, 07:27 AM
I would try the carbide reamer. I would also cut the shank as close to the reamer flutes as you can leaving just enough to chuck up in the collet. This will eliminate any deflection from the shank.

JL............

wdtom44
07-01-2019, 07:36 AM
There are carbide drills advertised as being able to handle low 60 rc. You need a rigid setup (milling machine) and a lot of nerve to feed the drill into a hard piece of steel but it works. I would think a carbide endmill would work too.

cameron
07-01-2019, 07:55 AM
Do you really need the pivot area that hard? Seems to me that would be pretty brittle and it annoys the hell out of me to break a blade off at the end I don't even cut with.

I don't know anything about fancy knife steels, though, maybe it can't be softened locally.

Mcgyver
07-01-2019, 09:12 AM
A carbide reamer might work, but its an expensive experiment if not. One should expect tool steel to move a bit on heat treating and you usually deal with it afterwards by grinding .......or in the case of small holes, lapping. The laps don't necessarily have to be adjustable, just a piece of brass that is a tight fit with some medium compound on it can do the trick.

George Bulliss
07-01-2019, 09:24 AM
One should expect tool steel to move a bit on heat treating...

That fact can spell doom to a carbide reamer – they don't follow a hole like a HSS reamer will and any deflection will snap them. Whenever I used a reamer in hardened steel I would plunge an undersized (reground) carbide cutter through first to re-establish the hole location.

In your case, I would be tempted to just try plunging with an end mill. Note that unless your mill is very rigid, it will likely cut a little oversize.

RB211
07-01-2019, 09:25 AM
My thought is if you're doing many of these, as your own product, to change the method of heat treat. As others said, does the entire blade shank need to be hardened? I don't make knifes, I don't know.

Sent from my SM-G950U1 using Tapatalk

Toolguy
07-01-2019, 10:03 AM
When making precision dowel pin holes in hardened die blocks, we always drilled and reamed them enough undersize before heat treat, then lapped out the last thou. after. If you use an air hardening tool steel like D2 or S7 (my preference), the steel doesn't move as much during quenching. This is because air quenching is cooling much more slowly than liquid quenching. It all expands when heated, cooling slowly gives it more of a chance to go back closer to where it started out before it solidifies. You don't say what alloy you're using.

As for reaming the hole after heat treat, I agree with those that said the tang/hinge area could be drawn back some. Even at 50Rc for the tang, the blade would still be very strong. I would still want the cutting edge to be 58 - 60 or so to hold an edge. At 61Rc you're going to go through a lot of carbide reamers. I would use a carbide spade drill for that, they are way cheaper and tougher. Run any of them dry. If you use cutting oil, the carbide will just skate off the steel till you get enough pressure to rupture the carbide. If dry, it will bite in right away.

Doozer
07-01-2019, 10:18 AM
.... 3/16 hole in the blade. Ive been drilling and reaming these before heat treatment, but after all is said and done the bloody things have opened up by about .004", ...



Why is +.004" a problem?
It is a knife.
Does not a rivet go through that hole anyways?
As in peen until tight??

-Doozer

old mart
07-01-2019, 10:26 AM
Could the hole be finished by lapping? If the hole is for the hinge pin, the frames could be reamed larger to suit a bigger pin.
If you have a rigid clamping and drilling setup, then a 5mm solid carbide drill for hard steel with a slow controlled feed would give as good a finish as a reamer at less cost, allowing a 5mm pin.

MrWhoopee
07-01-2019, 10:38 AM
The answer would depend on the alloy used. What are the blades made of?

Tim The Grim
07-01-2019, 11:04 AM
I don’t know what kind of mill you have, but most mills have a threaded quill stop. If you’re plunging and need to maintain good control of your downfeed you can use the quill stop nut to increment your plunge depth and repeat. Left thumb on the nut...

Set your surface, rotate 1/5 turn, plunge .010, draw back to cool, repeat.

You won’t risk an over deep cut or screwing in. Just get into a rhythm and your new carbide end mill should have no problem

There are also carbide spade drills that have a tip designed to “anneal” hardened steel as it cuts through. With those you could drill through the hard steel from scratch with an accurate sized hole. I’ve used them on 1/4” D-2 and was able to get a couple good holes before I got nervous.

epicfail48
07-01-2019, 03:10 PM
Addressing a few major questions at once:

Yes, the blade needs to be hardened all the way through. Its a small pocket knife blade, and while I certainly could locally soften the area around the pivots, its not something I want to do because of the extra time and materials needed to do so. Adding to that, some of the alloys I use don't lend themselves to spot annealing very well

Yes, the pivot holes do need to be accurately sized. Its not a fixed blade knife and the holes are for the movement bushing. If the holes are sloppy, the fit of the entire knife is. Riveting isn't an option here either, the knife needs to be able to be taken apart.

Steels vary on the exact knife, but the most used allows are 1095 and AEB-l, with some O1, A2 and 440c mixed in on occasion.

I had thought about lapping, but I'm not sure how well that would work in this case. To my understanding, lapping is only supposed to be used to take out a few thousandths at most, yes? Not sure exactly how of go about managing that with the movement from heat treatment

I was thinking more carbide tipped reamer than I was solid carbide, to reduce the risk of snapping if the holes slightly misaligned. I did consider using an end mill, but I would really like these holes to be on-size, so the risk of cutting oversized is a bit of a non-starter there

Mcgyver
07-01-2019, 03:20 PM
single point bore it with a carbide tool you grind to fit?

lapping will take off more than few thou, its matter of how course a compound and how long you lap for

Norman Bain
07-01-2019, 04:53 PM
Would it work to make the hole oversized from the start. Then harden the blade, then put in (peen, drill, ream) a mild steel insert.

epicfail48
07-01-2019, 06:01 PM
Would it work to make the hole oversized from the start. Then harden the blade, then put in (peen, drill, ream) a mild steel insert.

Strictly speaking yes, that would work, but adds way more complexity and work that im looking for. Im more asking if a carbide tool can reasonably be expected to cut through hardened steel

RichR
07-01-2019, 06:05 PM
Strictly speaking yes, that would work, but adds way more complexity and work that im looking for. Im more asking if a carbide tool can reasonably be expected to cut through hardened steel

Instead of peening the insert, you could secure it with retaining compound.

garyhlucas
07-01-2019, 06:52 PM
Break out the jig grinder!

Yondering
07-01-2019, 08:03 PM
Strictly speaking yes, that would work, but adds way more complexity and work that im looking for. Im more asking if a carbide tool can reasonably be expected to cut through hardened steel

If it were mine - I'd try drilling the hole after blade tempering with a straight flute solid carbide drill, no reaming needed. In hard steel those seem to leave a very precise hole size with reasonably good finish. I think it would be best to do this with either a very small pilot hole (drilled before hardening) or none at all; I'm not sure it would work well to fix a hole that's already drilled and warped.

Your blade may be too hard for the type of drill I'm thinking of - I've seen them listed as only good for ~50 Rc - but I've drilled through fully hardened O1 tool steel with these so it might be worth a shot.

RB211
07-01-2019, 08:10 PM
Maybe get a D-bit grinder and start making your own carbide D-bits for this.

Sent from my SM-G950U1 using Tapatalk

Doozer
07-01-2019, 08:28 PM
... If the holes are sloppy, the fit of the entire knife is...

4 thou, right?
For real, 4 thou??
That is too loose???
That is 4 thou radial location.
I assume you can get the pivot
bolt tight, so you can have almost
zero axial play. If that is the case,
then 4 thou radial play is nothing for
a folding knife. If it is spring loaded locking
then you will notice it even less. It seems to me
that someone's OCD medication ran out of prescription.
Design it with a countersunk hole and let the taper be your
friend, and make a tapered bushing to suit the pin. Then achieve
zero fit with the tapered bushing in the tapered hole. Split the busing
if you want, and tighten to remove all play. That ought to get your man
boobs out of a bunch, and cheaper than therapy any day of the week.

-Doozer

Bented
07-01-2019, 09:58 PM
I made a part in O1 for a labeling company last week, the OD is 2.150" -.0007 -.0002 (ISO GD&T tolerancing) and the bore was .630" + .0000 -.0005, it is 8" long.
I told my employer that I would leave .010" per side for finish grinding after hardening. He did not like that idea and told me to turn it to size so I did as told.
After hardening he had me measure it and it grew .004" on the OD and .002" on the ID. I told him that it will be rejected but he shipped it anyway.

Sure enough a day later it returns with a Notice Of Nonconformity.
I told him that we can grind the OD smaller but we can not grind the ID smaller. I believe that it is scrap.

Yondering
07-01-2019, 10:44 PM
4 thou, right?
For real, 4 thou??
That is too loose???
That is 4 thou radial location.
I assume you can get the pivot
bolt tight, so you can have almost
zero axial play. If that is the case,
then 4 thou radial play is nothing for
a folding knife. If it is spring loaded locking
then you will notice it even less. It seems to me
that someone's OCD medication ran out of prescription.
Design it with a countersunk hole and let the taper be your
friend, and make a tapered bushing to suit the pin. Then achieve
zero fit with the tapered bushing in the tapered hole. Split the busing
if you want, and tighten to remove all play. That ought to get your man
boobs out of a bunch, and cheaper than therapy any day of the week.

-Doozer

I'm getting the strong impression you've never built or even re-assembled a quality folding knife.

mattthemuppet
07-01-2019, 11:10 PM
I do like the formatting though

epicfail48
07-02-2019, 12:12 AM
I'm getting the strong impression you've never built or even re-assembled a quality folding knife.

You beat me to the punch with that comment. I also get the impression that the "butterfly knife" part was missed. This aint a friction folder or a fixed blade, it requires precision. If i could get it done with a backyard hackjob, i wouldnt be asking the question.

Ill see about ordering in a carbide tipped reamer before i do the next blade, the few useful responses have indicated thats where i should be looking, unless i want to completely redo the design (which i dont), or settle for crappy tolerances (ditto)

epicfail48
07-02-2019, 12:14 AM
Also, Mr. Doozer, you missed the "pivot bushing" portion of things as well. Theres a bushing in the joint of this knife so you cant tighten the screws down so much they affect the action. May want to do some research on the style of knife before making insulting remarks about my medication status

J Tiers
07-02-2019, 12:59 AM
OK, you have a size problem, and a machining problem. Both are the result of heat treating that has to be done, so that part is a "known".

DOES that part of the blade have to be RC61, or would it work as well if it was "only" RC45 or RC50? Something that would be more readily machinable to tolerance with good results.

If you say "no, it has to be RC61", can you share why a still hardened but not "as" hard material in that portion of the part is not usable?

If you agree that the somewhat less hard part is fine, then you have a choice of either not hardening that area so much, or of drawing that area back. I suspect drawing that area back is easier and more controllable.

You said that it adds steps and time. OK. Now, how much time does it add to fiddle-fart around with trying to precisely size a hard as heck part without the proper equipment? Likely more than the drawback process.

You would be money and time ahead if you just did a controlled draw-back of that area, probably by dipping it in a bath of molten material at a particular temperature to a specific distance for a specific time. The temp will give you the draw-back hardness result assuming you follow your process. The specific depth will allow you to avoid any drawing back of the cutting part of the blade.

It sounds to me like a practical solution, that might actually have advantages to the user.

cameron
07-02-2019, 07:58 AM
Just me and my crude methods, but if the blade was O2 or other simply treatable steel I would stand the blade upright in a container of water with enough of the shank exposed (we can debate "How much is enough" later , of course.) and play a small torch flame on the pivot area until the color looked right.

Can't help but be just as good as or a little better than all hard when the owner puts a bit too much prying force on the knife.

And of course you've added value to the product because now you can advertise the blades as "differentially hardened".

J Tiers
07-02-2019, 08:18 AM
Of course the water would work.

It might be harder to hit a specific hardness for the pivot area that way. I suggested the other approach as one that would be consistent, because the general approach of the OP seems to be "quality" in a professional manner, from a production viewpoint.

It would be possible to get the same result from the water-moderated tempering process also.

RichR
07-02-2019, 09:00 AM
Just me and my crude methods, but if the blade was O2 or other simply treatable steel I would stand the blade upright in a container of water with enough of the shank exposed (we can debate "How much is enough" later , of course.) and play a small torch flame on the pivot area until the color looked right. ...

Or if you want to go a little high-tech, use an induction heater for some fast localized heating.

cameron
07-02-2019, 09:07 AM
The specific hardness required for the pivot area is "just soft enough that you don't wreck too many expensive carbide drills or reamers".

Hey, it's a butterfly knife. It's probably not the tool you're going to choose for a critical mission like making violins or fending off grizzly bears.

Toolguy
07-02-2019, 10:29 AM
I would use a straight 2 flute solid carbide drill to drill from solid, or a solid carbide spade drill to finish an undersize hole, both after hardening. Both of these are inexpensive and should do the job.

BCRider
07-02-2019, 11:05 AM
Late to the party because I was away. But my own thoughts were similar to Yondering's on the idea of no pilot and then drill the hardened part with carbide drill of the proper size. Any sort of pilot that gets distorted out of position or shape would make it really hard to ensure that a brittle but very hard carbide tool will not be pulled to the side or shocked and end up snapping. Doing all the drilling after the hardening or hardening and tempering would avoid any possible issues. I believe (from reading not doing) that carbide drills in this situation will drill pretty true and very close to size. Or if it turns out they don't then finish with a carbide reamer using the same setup?

Depending on the steel too I'm also on board with those that are suggesting to draw the tang end with the holes back to more of a good spring mode hardness if the steel you are using is the sort which can be done so. I'm guessing that butterfly knives (illegal up here in Canada as it happens) in learning to use them in a flashy manner get dropped quite a lot. So a little more durability from being tempered back a little would not be a bad thing anyway? In particular the tang end?

Lapping has been mentioned a few times. But you're looking at lapping a rather small hole here. That's going to make life a bit harder since it will want to flex over to the center of any ovoid shape instead of staying where it needs to stay. The good news though is that a lap for a small hole like this is pretty easy to do. It would be size for size or perhaps just a hair under and have a tapered end. The taper and size for size portion would be charged with compound and the taper pushed into the hole. Or perhaps a liquid slurry of compound and light oil? Either way the idea is that the tapered point laps the hole out to where the parallel portion an finish and leave the hole very round and hopefully very accurate for size. I'm thinking that a light touch will be needed for this operation. And perhaps the laps would wear over some number of holes? Some trials would be needed.

mattthemuppet
07-02-2019, 11:11 AM
quick question - wouldn't it be better to draw back the tang a little anyway to give that part of the blade a little more ductility? (ductilaciousness?) It's the part subject to the most leverage, so I would have thought it would benefit from toughness more than hardness. Don't know much about it though, hence the question :)

Bob La Londe
07-02-2019, 12:13 PM
Bit of an issue, im working on a butterfly knife design, and said design has the blade running on a bushing that sits in a 3/16 hole in the blade. Ive been drilling and reaming these before heat treatment, but after all is said and done the bloody things have opened up by about .004", as well as being slightly ovate. My question is, is there any sane way to ream these holes out after heat treatment, with the steel sitting at about 61rhc? The present best idea ive got is to drill the holes to .182" or thereabouts before heat treatment, then go back to the mill afterwards and finish off those holes with a carbide tipped 3/16" reamer.

Am i insane for thinking this would work? Can i reasonably expect carbide to cut through material at that hardness, or will i just smoke a reamer?

Rather than read 4 pages of replies where this has most likely been suggested I'll just risk being repetitive.

How about just letting it be over sized... a lot. Pressing in a bushing, and then reaming the bushing to exact size. The bushing will be trapped between the plates so there is no risk of it coming out.

I do sometimes ream 4140HT or even 304 stainless with a carbide chucking reamer when making specialty tool holders, but neither of those is anywhere near knife hard. Well, not good knife hard. LOL.

epicfail48
07-02-2019, 08:55 PM
quick question - wouldn't it be better to draw back the tang a little anyway to give that part of the blade a little more ductility? (ductilaciousness?) It's the part subject to the most leverage, so I would have thought it would benefit from toughness more than hardness. Don't know much about it though, hence the question :)

This is a question thats come up a lot now, and rather than quote it every time it gets asked im just going to respond to this one as the overall example;

Knives arent screwdrivers. Knives arent prybars. Knives shouldnt have much in the way of any side-to-side leverage, being that knives are cutting tools, not levers. The force on a knife should be in-line with the cutting edge, and thats what i plan my knives to work with. I heat treat them to hold an edges and be flexible enough to not chip the edge, and if someone wants to snap one by using it to pry out a nail, thats not a use case im particularly interested in.

Again, im not looking to upend the entire process i have by selectively drawing back the temper on every blade, because the advantages arent there. In addition to the advantages not being there, as i already mentioned at least once, several of the alloys i use just dont lend themselves to spot annealing or differential hardening. Its not that im incapable od doing it, not by a long shot, its something that ive done before on other knives.

The question at hand isnt "should i make my knives to serve double-duty as a crowbar", the question is "can i expect a carbide tool to cut through hrc60-61 steel". Demanding justifications to my design or insulting my mental capabilities do nothing to answer that question.

And again, sorry if it seems ive singled you out mattthemuppet, this entire thread has just been an exercise in frustration. I figured itd be a relatively simple question, but 4 pages in and theres about 4 responses that actually address the question, or at least focus on the "i need to put a hole in hardened metal" part, and not "oh, just soften the metal". Had i said "i need to put a hole for a dowel pin in an injection mold thats got a mandated hardness of 60rhc", i bet the answers wouldve been a lot different


Rather than read 4 pages of replies where this has most likely been suggested I'll just risk being repetitive.

How about just letting it be over sized... a lot. Pressing in a bushing, and then reaming the bushing to exact size. The bushing will be trapped between the plates so there is no risk of it coming out.

I do sometimes ream 4140HT or even 304 stainless with a carbide chucking reamer when making specialty tool holders, but neither of those is anywhere near knife hard. Well, not good knife hard. LOL.

Thats actually what i already do, with the bushings. It works fine for a one-off, but its too much hand-fitting for multiple blades. I want to hit the point where i can make everything to a print with a specified tolerance, so if i get to the point down the road where im selling these and a customer loses a part or snaps a blade or dents a handle, i can ship them a replacement part that they can put on themselves and have everything working as it should. Were i to stick with press fitting the bushings, swapping one of those in the event of wear or similar would require the same hand-fitting, which would require a machinist and not a screwdriver. Thats why im looking to ream the holes, so i know that knife blade A and knife blade ZZ have a 3/16th hole with a +-.001" or whatever tolerance, and i can just turn a 3/16" bushing for both


Late to the party because I was away. But my own thoughts were similar to Yondering's on the idea of no pilot and then drill the hardened part with carbide drill of the proper size. Any sort of pilot that gets distorted out of position or shape would make it really hard to ensure that a brittle but very hard carbide tool will not be pulled to the side or shocked and end up snapping. Doing all the drilling after the hardening or hardening and tempering would avoid any possible issues. I believe (from reading not doing) that carbide drills in this situation will drill pretty true and very close to size. Or if it turns out they don't then finish with a carbide reamer using the same setup?

Depending on the steel too I'm also on board with those that are suggesting to draw the tang end with the holes back to more of a good spring mode hardness if the steel you are using is the sort which can be done so. I'm guessing that butterfly knives (illegal up here in Canada as it happens) in learning to use them in a flashy manner get dropped quite a lot. So a little more durability from being tempered back a little would not be a bad thing anyway? In particular the tang end?

Lapping has been mentioned a few times. But you're looking at lapping a rather small hole here. That's going to make life a bit harder since it will want to flex over to the center of any ovoid shape instead of staying where it needs to stay. The good news though is that a lap for a small hole like this is pretty easy to do. It would be size for size or perhaps just a hair under and have a tapered end. The taper and size for size portion would be charged with compound and the taper pushed into the hole. Or perhaps a liquid slurry of compound and light oil? Either way the idea is that the tapered point laps the hole out to where the parallel portion an finish and leave the hole very round and hopefully very accurate for size. I'm thinking that a light touch will be needed for this operation. And perhaps the laps would wear over some number of holes? Some trials would be needed.

Thats a good suggestion on the carbide drills, and i know that some bladesmiths use them to drill holes after hardening already. The one worry that i have there is ive always heard that you dont grab a drill when you need a hole with a critical tolerance, because its likely to be out of round or off-size. If the carbide drills can be expected to drill a hole with good tolerances theyd be something to look into though. Then again, given that carbide drills work fine in hardened steel, it occurs to me that there shouldnt be any issue with a carbide reamer, so i may have answered my own question.

I havent ruled lapping out completely, i was just worried about the out-or-round condition affecting the outcome, as well as needing to replace the lap somewhat frequently to keep it on-size. Most of the laps ive seen for small holes have been shop-made, and im more likely to trust that 3 reamers bought from a company are going to be more identical to each other than 3 laps made by me

Oh, and strictly speaking butterfly knives are illegal to carry in the States too. Not illegal to own though, and theyre fun pieces

Mcgyver
07-02-2019, 09:31 PM
The question at hand isnt "should i make my knives to serve double-duty as a crowbar", the question is "can i expect a carbide tool to cut through hrc60-61 steel". Demanding justifications to my design or insulting my mental capabilities do nothing to answer that question.


100% agree. I'd demand a full refund :D. I mean I do agree, instead of technical help with one's questions it often becomes this cross examination and bun tossing.....but one must put up with that because the free consulting can be oh so worth it. I don't agree with insulting and there's some miserable sorts that only show up to point out the shortcomings of others....that aside, I do feel in volunteering time to help someone for free it entitles me to ask and get context and a fix for my curiosity

J Tiers
07-02-2019, 11:02 PM
Frankly, it is "doing a Milacron" and just a little bit of "pre-insulting" the folks you want answers from, to demand that everyone either shut the F up, or click our heels, salute, and agree that "Yes, Sir" the singular solution that you have come up with is the only one possible so that, yes, indeed, you are "right".. To which the only answer is , of course, YARC, YARC.....

Yah know..... MOST folks of the "problem solving" type will try to solve the problem, which is, "I need a precise sized hole in the tang of a knife blade that is pretty hard when it comes from heat treat". There are many very valid answers, but you threw all of them out before coming to us, but did not quite say so.

Basically, it seems you came to us with a problem that you already determined had only one answer, and apparently wanted confirmation of your pre-selected solution. Oooooooooo-KAAAaaaayyyyy....... but it would save time to say so.

epicfail48
07-03-2019, 05:41 AM
Frankly, it is "doing a Milacron" and just a little bit of "pre-insulting" the folks you want answers from, to demand that everyone either shut the F up, or click our heels, salute, and agree that "Yes, Sir" the singular solution that you have come up with is the only one possible so that, yes, indeed, you are "right".. To which the only answer is , of course, YARC, YARC.....

Yah know..... MOST folks of the "problem solving" type will try to solve the problem, which is, "I need a precise sized hole in the tang of a knife blade that is pretty hard when it comes from heat treat". There are many very valid answers, but you threw all of them out before coming to us, but did not quite say so.

Basically, it seems you came to us with a problem that you already determined had only one answer, and apparently wanted confirmation of your pre-selected solution. Oooooooooo-KAAAaaaayyyyy....... but it would save time to say so.


Bit of an issue, im working on a butterfly knife design, and said design has the blade running on a bushing that sits in a 3/16 hole in the blade. Ive been drilling and reaming these before heat treatment, but after all is said and done the bloody things have opened up by about .004", as well as being slightly ovate. My question is, is there any sane way to ream these holes out after heat treatment, with the steel sitting at about 61rhc? The present best idea ive got is to drill the holes to .182" or thereabouts before heat treatment, then go back to the mill afterwards and finish off those holes with a carbide tipped 3/16" reamer.

Am i insane for thinking this would work? Can i reasonably expect carbide to cut through material at that hardness, or will i just smoke a reamer?

The original post for this thread, where i presented the idea of using a carbide reamer, and the question i asked was "Can i reasonably expect carbide to cut through material at that hardness, or will i just smoke a reamer?". So, i did ask for confirmation of the solution i found that seemed to be the best fit, which i very clearly stated in the original post. Seems like plenty of time that i tried to save, in a post that seems to have been mostly ignored.


100% agree. I'd demand a full refund :D. I mean I do agree, instead of technical help with one's questions it often becomes this cross examination and bun tossing.....but one must put up with that because the free consulting can be oh so worth it. I don't agree with insulting and there's some miserable sorts that only show up to point out the shortcomings of others....that aside, I do feel in volunteering time to help someone for free it entitles me to ask and get context and a fix for my curiosity

I do agree with this, and i apologize if it seems like im not willing to provide context or answer questions. Im more than happy to go into details on the design, but so far "i need to put a precisely dimensioned hole in hardened steel, can i reasonable expect a carbide tipped reamer to do so" has turned into insults as to my mental stability for wanting to do so. Not an excuse, just an explanation, but its irritating having people tell me i dont know what im talking about, despite not listening to what im talking about.

If anybody wants more context, wants to see the designs, wants to see the finished product to satisfy their curiosity im more than happy to oblige. God knows i need a fix for the same curiosity from time to time. But, at the same time, i shouldnt need an attorney to defend me from a cross examination when im asking if a method will function.

Mcgyver
07-03-2019, 07:27 AM
I do agree with this, and i apologize if it seems like im not willing to provide context or answer questions.
.

you've not come across as unwilling, nothing to apologize for, just trying to be positive and point out the half full part

DrMike
07-03-2019, 08:24 AM
Bit of an issue, im working on a butterfly knife design, and said design has the blade running on a bushing that sits in a 3/16 hole in the blade. Ive been drilling and reaming these before heat treatment, but after all is said and done the bloody things have opened up by about .004", as well as being slightly ovate. My question is, is there any sane way to ream these holes out after heat treatment, with the steel sitting at about 61rhc? The present best idea ive got is to drill the holes to .182" or thereabouts before heat treatment, then go back to the mill afterwards and finish off those holes with a carbide tipped 3/16" reamer.

Am i insane for thinking this would work? Can i reasonably expect carbide to cut through material at that hardness, or will i just smoke a reamer?

Having had to specify reaming similar small, sometimes starting slightly oval, precise holes in very hard, tough materials in the past, I can say that it does indeed work. It is very fussy/tricky in terms of speeds, feeds, coolant, etc., and may produce an unacceptable level of scrapped reamers and blades, depending on how uniform the hardness and out-of-round holes are, and how you define unacceptable.

If it were me (and it's not, but it was), I'd have several new, sharp, perfect reamers on hand before going at a pile of blades, at least 1 for each blade.

J Tiers
07-03-2019, 08:40 AM
The original post for this thread, where i presented the idea of using a carbide reamer, and the question i asked was "Can i reasonably expect carbide to cut through material at that hardness, or will i just smoke a reamer?". So, i did ask for confirmation of the solution i found that seemed to be the best fit, which i very clearly stated in the original post. Seems like plenty of time that i tried to save, in a post that seems to have been mostly ignored.



I do agree with this, and i apologize if it seems like im not willing to provide context or answer questions. Im more than happy to go into details on the design, but so far "i need to put a precisely dimensioned hole in hardened steel, ........' but its irritating having people tell me i dont know what im talking about, despite not listening to what im talking about.



I am not the one questioning mental ability or stability......

There was discussion of precision, of non round holes, which a reamer might not follow..... threatening the normal precision of the reamer.

Besides spot temperin to allow other methods, the usual precise hole finishing tool for hard materials is abrasives, the "jig borer advocates" have a point, and it ain't just on top of their head.

You do not want to get a jig borer, and neither would I. But the various abrasive methods ought not to be dismissed out of hand. There may be a version that works. Your list of demands and problems makes grinding a natural.

Did you mention the amount to be reamed? Seems like the location is not critical, so the more to be reamed, the less critical the "hole following" is, you just want a round hole.

But it does still seem as if you want to find out how to make reaming work, no matter the problems, no matter the hassles.

mattthemuppet
07-03-2019, 10:32 AM
This is a question thats come up a lot now, and rather than quote it every time it gets asked im just going to respond to this one as the overall example;

Knives arent screwdrivers. Knives arent prybars. Knives shouldnt have much in the way of any side-to-side leverage, being that knives are cutting tools, not levers. The force on a knife should be in-line with the cutting edge, and thats what i plan my knives to work with. I heat treat them to hold an edges and be flexible enough to not chip the edge, and if someone wants to snap one by using it to pry out a nail, thats not a use case im particularly interested in.

Again, im not looking to upend the entire process i have by selectively drawing back the temper on every blade, because the advantages arent there. In addition to the advantages not being there, as i already mentioned at least once, several of the alloys i use just dont lend themselves to spot annealing or differential hardening. Its not that im incapable od doing it, not by a long shot, its something that ive done before on other knives.

The question at hand isnt "should i make my knives to serve double-duty as a crowbar", the question is "can i expect a carbide tool to cut through hrc60-61 steel". Demanding justifications to my design or insulting my mental capabilities do nothing to answer that question.

And again, sorry if it seems ive singled you out mattthemuppet, this entire thread has just been an exercise in frustration. I figured itd be a relatively simple question, but 4 pages in and theres about 4 responses that actually address the question, or at least focus on the "i need to put a hole in hardened metal" part, and not "oh, just soften the metal". Had i said "i need to put a hole for a dowel pin in an injection mold thats got a mandated hardness of 60rhc", i bet the answers wouldve been a lot different


um, ok. No insult intended, simply an honest question asked out of curiosity.

Rich V
07-03-2019, 10:39 AM
@epicfail48

Your best bet is to start with an undersized hole and enlarge after heat treatment as you originally asked.
A carbide reamer/drill might work but there is a better & cheaper tool, a 3/16 carbide ball end mill.
These are cheap, self centering and cut accurate holes in hard steel. Use a 4 flute for better centering in those oblong holes and as short a length as will comfortably allow for your work setup.
Run it dry at ~200rpm and use steady feed pressure for the cut. Adjust feed & rpm to avoid any chatter.

Buy an end mill for <$20 and give it a try, cheap experiment and I'm sure it will work out well.

BCRider
07-03-2019, 12:05 PM
Thats a good suggestion on the carbide drills, and i know that some bladesmiths use them to drill holes after hardening already. The one worry that i have there is ive always heard that you dont grab a drill when you need a hole with a critical tolerance, because its likely to be out of round or off-size. If the carbide drills can be expected to drill a hole with good tolerances theyd be something to look into though. Then again, given that carbide drills work fine in hardened steel, it occurs to me that there shouldnt be any issue with a carbide reamer, so i may have answered my own question.
......

My thinking on the carbide drills being accurate and round in hard steel is due to how intolerant they are at flexing. So they had better not wobble around and cut an oversize or tri-lobe shaped hole. And that's something regular drills do in steel and aluminium more because those materials are soft. I've always found that I got worse performance in this area the softer the material was. On the other hand the times I've drilled harder alloys with smaller drills provided I get a clean start to the hole they do tend to come out rounder and truer to size.

And the one time I actually did grind and diamond hone a masonry drill to go through a hard file the hole was very round and clean looking.... Hardly a valid test for what you are trying to do but it was an eye opener for myself.

And just to re-confirm something. I suspect that Yondering and I were thinking the same thing in suggesting drilling after hardening. Namely that any distortion is going to shift the spacing and put side pressure on the reamer. And as noted solid carbide doesn't like side pressure. And also that if there is any distortion doing all of the drilling after hardening ensures you get the same center to center hole spacing. And if using the right setup (jigs and/or DRO) that you can get the drilling and reaming done with essentially zero difference from center to center for the holes. That is, if you need or just just want that sort of precision. Otherwise you'd need to let the blade float a little so the reamer can seek out it's own cutting center of any out of round holes.

Norman Bain
07-03-2019, 05:23 PM
Think I would be trying a carbide end mill ... one of the blue ones. They are super hard and cheap enough to give one a spin.

Link here (https://www.ebay.com.au/itm/264146175879/) is an example. Some sellers define use thru to 50HrC as a full on milling cutter ... so they should be good for a few cuts at the 61HrC.

The end mills are also short and stiff which should aid making a clean hole where an existing hole exists.

rcaffin
07-05-2019, 06:13 AM
Really good carbide should work.
A ball-end mill might be better than a square end mill.
Short tooling and hard clamping would be essential.

But have you considered using a 4.0 mm diamond point in a CNC machine? You would have to calibrate the point of course, but that should take no more than 2 or 3 holes.
I have been using diamond on Basalt, which is Mohr 9 and a lot harder than the steel. Works fine, but you MUST (absolutely) do this under water.
You can get diamond points very cheaply from eBay. I have used HKTreasure (or something like that).

Cheers
Roger

oxford
07-05-2019, 09:49 AM
I’m not sure if it would work in this situation or worth the time to set up but I seem to remember a thread where a member converted some sort of boring head to hold an air powered die grinder and was grinding out a hardened gear or bearing.

BCRider
07-05-2019, 11:56 AM
I’m not sure if it would work in this situation or worth the time to set up but I seem to remember a thread where a member converted some sort of boring head to hold an air powered die grinder and was grinding out a hardened gear or bearing.

That's a nice trick to keep in mind.

In this case though he's looking at a bunch of 3/16" holes. I'm not sure that small a stone point size would stay consistent enough over the course of a number of holes.

Corbettprime
07-05-2019, 12:42 PM
That's a nice trick to keep in mind.

In this case though he's looking at a bunch of 3/16" holes. I'm not sure that small a stone point size would stay consistent enough over the course of a number of holes.

Idle thought: Diamond burrs with a 1/8" shank for Dremels are quite inexpensive. I have one I've been using for about four years to sharpen several chain saws and it doesn't show any wear.

nickel-city-fab
07-05-2019, 09:59 PM
I hate jobs like that. In my case it only happens once or twice a year thank goodness. A carbide end mill with radius corners (1/64) works OK if the rest of the setup is sufficiently rigid. Full dia endmill, plunge right in with the knee, don't even think about using the quill. Make sure everything is locked if it doesn't have to move. Gotta pay attention to things.

JRouche
07-05-2019, 11:05 PM
I hate jobs like that. In my case it only happens once or twice a year thank goodness. A carbide end mill with radius corners (1/64) works OK if the rest of the setup is sufficiently rigid. Full dia endmill, plunge right in with the knee, don't even think about using the quill. Make sure everything is locked if it doesn't have to move. Gotta pay attention to things.


I agree 100

Now my questions. I like a very sharp tip on center cutting carbide end mills. I do run them full out on my old BP, but with a conservative feed. You cant hurt the carbide by feeding too slow has been my notice.

And like you said. If you can lock down any axis you are not using that helps big time. JR

JRouche
07-06-2019, 01:32 AM
Have you thought about punching it. I have worked with many die sets. That sounds like a punch job. Small 250-350 ton press and a double sided die block. Easy peasy. JR

rcaffin
07-06-2019, 02:29 AM
Yeah, a Dremel diamond point should be fine. Same thing.
Yes, AlOx will wear away, but a diamond point will show very little wear.
Punching???? Into 61 Rockwell steel? With what???? (Not carbide: too brittle.)

Cheers
Roger

Arcane
07-06-2019, 03:27 AM
If all else fails, what about EDM? (http://www.northwestwireedm.com/wire_edm_faqs.php)

nickel-city-fab
07-06-2019, 06:17 AM
I agree 100

Now my questions. I like a very sharp tip on center cutting carbide end mills. I do run them full out on my old BP, but with a conservative feed. You cant hurt the carbide by feeding too slow has been my notice.

And like you said. If you can lock down any axis you are not using that helps big time. JR

Yeah sharp tips probably work just fine, but I kept breaking them, so I switched to a radiused end mill. Most likely the machine wasn't solid enough, or I was too hyper to go slow -- guy was standing right there waiting for the part, holding up production in his dept. Side note, the machines I had to use at work were total junk anyway -- I measured 30 thou of runout with the quill fully extended once. Showed the boss, he said if the motor still turns then its good enough for us. A couple weeks ago the TIG caught on fire, but by then I had already gave notice.

Doozer
07-06-2019, 11:36 AM
.... the machines I had to use at work were total junk anyway -- I measured 30 thou of runout with the quill fully extended once. Showed the boss, he said if the motor still turns then its good enough for us. A couple weeks ago the TIG caught on fire, but by then I had already gave notice.

Glad you got out of there.
I once worked at a shop on Gunville Rd in W Seneca where they had a Sunnen hone.
I had to hone some parts one day. The oil was filthy black. The sawyer told me
that the oil was from when they changed the oil on the forklift !?!?!?????
Used black motor oil is very carcinogenic. Well whatever. So the belt came off
the oil pump and I had to go fishing down in the sump to put it back on. Well in
there I found a whole bunch of scrap ?!? parts. I was told they were put in there
to displace the oil so they did not have to add so much to get the pump to pick
it up! Cheap bastards does not begin to describe. Every machinist HATED the
owner and his son. I quit soon after, as it was only a temp job for my, as I was
moving out of state.
The bathrooms had shlt on the walls and the toilette seat. All the machinists had
a shlt chair like they sell for elderly people who can't get up from a seated postition
very well. Everyone's shlt chair they kept near their work area, and they took it to
the bathroom so they would not have to sit on the toilette to take a dump. There
was actually poop everywhere in that bathroom. Of course the owner's daughter
had her own clean bathroom to use up front. I held my poop until lunch and used
the Burger king at the corner.
This was also a shop where you were not allowed to speak to anyone but the owner
or the owner's son. Not a word except maybe Hello to the other machinists would
be tolerated. It was like working in a Russian prison. I held my tongue and played
their sick sadistic game for a few months, and I was outta there.
Funny thing was, I got a phone call about 4 years later about a company in Buffalo
who was looking for a mechanical engineer. They said that this machine shop had
given them my name as good employee that they might want to hire. I was mystified
and flattered at the same time!?!? Just shows you never know in this world.
Never burn bridges.

-Doozer

nickel-city-fab
07-06-2019, 11:44 AM
Glad you got out of there.
..........................
I was mystified
and flattered at the same time!?!? Just shows you never know in this world.
Never burn bridges.

-Doozer

Yeah yer probably right. I burned that bridge so hard you wouldn't believe it. My thinking was, why do I want a ref from a $#thole since it'll only get me into another $#thole. Same thing, the boss would only let me talk to him... now that I'm gone, he is looking like the piece of crap that he is. The owners are not happy, last I heard. Oh well.

Doozer
07-06-2019, 01:14 PM
...Same thing, the boss would only let me talk to him.....

What is it with people like that?
Tyrants ?
Hard to believe the level of asshole that exists in this world.

--Doozer