# Making Square Broach



## aqualibguitars (Nov 29, 2016)

Hello friends
after long time im on this forum again.
before i have posted regarding making guitar tuning keys.
im getting the gears done. but want to broach square hole in it.
can anyone guide me how to make 4mm square broach or can make for me?
drawings or videos will help more.
waiting for ur reply..


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## intjonmiller (Nov 29, 2016)

There are excellent videos on the subject by Clickspring and This Old Tony (two of the best channels on all of YouTube). I think Tony's was part of another project, so it might not be titled that. I'll see if I can find it.


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## intjonmiller (Nov 29, 2016)




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## wawoodman (Nov 29, 2016)

They aren't really cheap, but they can be purchased. I guess it all depends on your time, tooling, and skill level.


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## johnreese (Nov 29, 2016)

Will a rotary broach work?  There are a lot of drawings available on hobby/home workshop forums.  Can be used in a lathe or a mill.


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## Christian Poulsen (Nov 29, 2016)

intjonmiller said:


>


This is a top notch, step by step (excuse the puns!) video to making a broach....
...I have a variation (though not quite as fast or nice) of 2 broach's I made a few years ago due to stock and equipment at hand (Plus I am a lover of air hardening A2 and D2 tool steel):
All basically the same machining but milling D2 rounds to the square sizes needed then to the lathe using the compound for the gradual lead in...
But my home HT (no oven or wrap) just requires a torch (Oxy/Acty) with a "rosebud tip (or the biggest welding tip for "smalls")  and air (compressor)...
...although there will be some scale and blistering....
I have some ceramic setters and half round lengths (for rounds) I dug out of the reclaim of my employer (before I retired) but some flat bricks work to make a Heat Treat "roofless house"
...Laying the finished broach (or whatever part) flat on a setter(s), I just torch (flame HT) the part evenly to critical temp. which for A2 and D2 is past a bright cherry red until you see a "flashing" in the steel (you can almost see the carbon globules "melting", and  "shooting thru" the steel)...
...then, at that point of course, you have to freeze the part as fast as possible by blasting with the air nozzle evenly from all angles until it's completely cooled....
...but then, if there is no bead blaster** available, its all hand and flat steel table abraisive paper work, (to remove the "black" and any blistering) before using the torch to draw and temper the part back a little ("straw" color).... and your part will end at rc55-60
**= easy does it if with a bead blaster and hold (covering) the finishing square ends of the broach with the gloves where you should remove the scale by hand as the bead blaster will do some rounding of your sharp edges (the more you bead blast for looks, the more tiny edge radius on your sharp cutting edges)
...anyway, yoose' save over 120 bones' to make one yourself and I couldn't or/but could anyone here make one for less than this?:
http://www.mscdirect.com/product/details/00294264


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## T Bredehoft (Nov 29, 2016)

Interesting Video.   Wish I knew more about his heat treating. I'm used to a tiny oven and a torch, but what was that about Borax? and where do you get it? And what was his "container?"


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## Christian Poulsen (Nov 29, 2016)

johnfreese said:


> Will a rotary broach work?  There are a lot of drawings available on hobby/home workshop forums.  Can be used in a lathe or a mill.


Good question for him to check out (I've never used or even held a rotary broach myself)

To also add, depending on the toughness and length (depth) of the stock being broached; An over size hole works better if its OK to not have a "full square holes" (less pressure because not a full cut of 4 sides at the final 
http://dumont.com/our-broaches/square-broaches/


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## Christian Poulsen (Nov 29, 2016)

T Bredehoft said:


> Interesting Video.   Wish I knew more about his heat treating. I'm used to a tiny oven and a torch, but what was that about Borax? and where do you get it? And what was his "container?"


On the job, we had an old container in our welding and HT area along with other anti scale, chemicals, fluxs that you can still get online (Google: Heat treat supplies/chemicals)
...after we got 2 new nice HT ovens (Dro's, timers, "set it and forget it" until the buzzer sounds), 95% we used was wrap (it came in rolls like thick aluminum foil and you cut and wrapped a tight package (with as much air squeezed out as possible)
....we did a little (about 5%) 01 and Starrett stock oil hardening
...we also farmed out some work to "Temperature Processing" here in my area (A specialized, certified, all HT Company) 
I gotta' drop their name here and give them props because you could give them a 3 foot long skinny tool steel rod and tell them you needed it RC58-60 and to come back less than .002 out of "straight" (no bow)....and it did!


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## intjonmiller (Nov 29, 2016)

T Bredehoft said:


> Interesting Video.   Wish I knew more about his heat treating. I'm used to a tiny oven and a torch, but what was that about Borax? and where do you get it? And what was his "container?"


He has a number of videos on that subject. He packs items to be heat treated in a borax and denatured alcohol mixture, after wrapping it in cheap wire. The wire helps hold the cover in place and distributes heat. It prevents the nasty scaling you normally get in heat treating, minimizing the work that needs to be done to clean it up after. 

It sounds like you aren't familiar with his work. Just open up his channel and watch every video from the first to the last. I doubt there's a single video where you won't learn something, no matter how experienced you may be. And with the best production values of any machining/making channel you'll also be thoroughly engaged. Best thing on YouTube.


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## intjonmiller (Nov 29, 2016)

My mistake. I just re-watched that one. He doesn't wrap it in wire here, but he often does.


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## Dan_S (Nov 29, 2016)

aqualibguitars said:


> can anyone guide me how to make 4mm square broach or can make for me?



Honestly, for something that small, unless you have all the tools and materials on hand, and don't value your time, its probably just better to buy one. 

http://www.mscdirect.com/product/details/00294264 ($121.80, $112.91 if you are a member). I've seen them go on eBay for half this.


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## chips&more (Nov 29, 2016)

If the hole is not too deep. Then, my vote is also using a rotary broach.  I found mine on fleabay. And make the cutters as I need them. It is a well-used toy in my shop! I don’t know how I got along without it!...Dave.

Also, 4mm is not that big. A broach that size sounds like you could break it just looking at it. Another reason to use a rotary broach.

I have rotary broached 1/16” hex in 1144 with no problems.


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## David S (Nov 29, 2016)

I will offer an alternative that doesn't cost much.

I repair old clocks.  Often people use the wrong size key for years and it eventually rounds over the square winding arbor.  When I finally dress the winding square back to square it can be too small for a standard key.  So here is how I make a square winding key.

I have a selection of square brass tubing that is sold in hobby stores.. it comes in telescoping sections.  I will select one that is close..usually too small.  Then we make a square punch the size of the winding arbour square.  Place some anti seize on the punch and drive it through the square tubing to size it.

Next make a round arbor on the lathe and drill a hole in it to accept the diagonal dimensions of the resized square tube..Solder it in with 100% tin solder. Trim and face and all done.

Not know exactly what the OP's part looks like, I am not sure if this would work or not.

David


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## Tersti (Nov 30, 2016)

I can vouch for clickspring's approach to using boric acid to protect parts during heat treating.

This 4mm broach sounds fragile, how will you be pressing that through the workpiece may I ask? I've thought about making broaches before but always get stuck when I realise I don't have a press and am never going to buy one for that experiment.


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## Subwayrocket (Nov 30, 2016)

intjonmiller said:


> excellent videos by This Old Tony (two of the best channels on all of YouTube). I think Tony's was part of another project, so it might not be titled that. I'll see if I can find it.


ThisOldTony is a great channel . His dry sense of humor is hilarious too . You know anything about the guy ? I don't think he's located in the US .


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## intjonmiller (Nov 30, 2016)

Seems like he said he's Australian living in Norway?? But he sure sounds American to me. I'll have to see if I can find which video that was in. 

Edited: He bought a Valex drill press for one video. That appears to be exclusive to Italy. 

Clickspring has the highest production values, and I love the long-format project he's been doing. I have been watching since like the 4th video of his clock, reading his blog, etc. I have been anxious to see it complete. But now that it's nearing the end I'm almost sad and I don't want it to end, except that he will surely do more great things in the future. In the video where he first assembled the whole clock, but not yet all polished, and tested the movement, I commented that I was really surprised by the level of emotion I felt seeing it work, after all these videos, so I can't even imagine what that's like for him. Last I checked it had like 200 upvotes, which is seriously a lot for a comment on a metalworking video. He has succeeded in a very interesting way, and I'm starting to see others picking up on his style (and as I prepare to put up a few videos myself I'm taking cues from him as well). Most recently I noticed a new one called Centurial that was clearly inspired by him. 

Meanwhile Tony is absolutely, side-splittingly hilarious, to me. My wife enjoys maybe 1/3 of his jokes, and can't sit through a whole video with me because she has no interest. But I find them overwhelmingly funny. The way he references other video creators in ways that only their own fans will recognize (what a BRILLIANT way to get people to notice your channel!!), the way he's subtly self-deprecating (when he's not overtly so), the way he emulates other video and even cinematic styles, and even throws in pop culture references. I enjoy every minute of it. When my phone notifies me that one of his videos (or Clickspring's) has been published it's all I can do to finish working before watching it.


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## intjonmiller (Nov 30, 2016)

Tersti said:


> I can vouch for clickspring's approach to using boric acid to protect parts during heat treating.


It makes perfect sense, as boric acid is an excellent flux for nearly all metals (but, while it does flux aluminum effectively, it shouldn't be used there as it weakens the aluminum considerably). He learned all his stuff the same way I am, reading books and forums and watching YouTube. He's only been machining for a few years, and his shop makes my single car garage shop look palatial.


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## intjonmiller (Dec 4, 2016)

Chris at Clickspring just uploaded the final video of his clock series, and it features the square broach making the drive section of the winding key. He also polishes up the entire clock to an unbelievable shine and shows it complete and working. I was a little disappointed that we didn't get a time lapse of the hands moving around the chapter ring as the camera circles the clock, but I've learned so much and enjoyed the series tremendously, so I really can't complain.


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## Mutt (Dec 6, 2016)

Tersti said:


> I can vouch for clickspring's approach to using boric acid to protect parts during heat treating.
> 
> This 4mm broach sounds fragile, how will you be pressing that through the workpiece may I ask? I've thought about making broaches before but always get stuck when I realise I don't have a press and am never going to buy one for that experiment.




Can I get some details on the use of boric acid to eliminate scale during HT? I scored a NICE  Paragon heat treating oven and use it often pn O-1, A-2 and D-2, but would like to not have to deal with the scale as much as possible.


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## Tersti (Dec 6, 2016)

Mutt said:


> Can I get some details on the use of boric acid to eliminate scale during HT? I scored a NICE  Paragon heat treating oven and use it often pn O-1, A-2 and D-2, but would like to not have to deal with the scale as much as possible.


Clickspring's videos are a much better source of that information than I am, he uses methylated spirits to form a paste which he can pack into wire baskets or specially made trays. The methylated spirits evaporate/burn off cleanly as the boric acid melts. I've also experimented with oil which is a bit stickier and adheres well enough to not need the basket/tray but the coverage isn't quite as good and the flames are a bit alarming if you're not expecting them (although they don't seem to cause a problem, just make sure you're doing this somewhere well ventilated).


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## Mutt (Dec 6, 2016)

Also,, I don't value my time, I value my cash. I would lihe to make my own 9mm square broach


Christian Poulsen said:


> This is a top notch, step by step (excuse the puns!) video to making a broach....
> ...I have a variation (though not quite as fast or nice) of 2 broach's I made a few years ago due to stock and equipment at hand (Plus I am a lover of air hardening A2 and D2 tool steel):
> All basically the same machining but milling D2 rounds to the square sizes needed then to the lathe using the compound for the gradual lead in...
> But my home HT (no oven or wrap) just requires a torch (Oxy/Acty) with a "rosebud tip (or the biggest welding tip for "smalls")  and air (compressor)...
> ...






where can I find O-1, A-2 or W-1  square stock in 9mm? I need to make a square broach


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## intjonmiller (Dec 6, 2016)

I haven't checked specifically, but onlinemetals.com is a great resource for tool steel when you don't need a ton. (If you need a lot they're probably not as economical as buying more locally.)


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## Mutt (Dec 6, 2016)

onlinemetals.com has nothing in metric. Any one else?


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## RJSakowski (Dec 6, 2016)

T Bredehoft said:


> Interesting Video.   Wish I knew more about his heat treating. I'm used to a tiny oven and a torch, but what was that about Borax? and where do you get it? And what was his "container?"


Borax is available in supermarkets as a washing aid.  Borax is sodium tetraborate or the the sodium salt of boric acid and is not the same as boric acid.  Boric acid used to be available in drugstores.


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## benmychree (Dec 6, 2016)

Another consideration that I have not seen in this discussion is how thick is the part to be broached?  A broach should have several teeth engaged in the cut to keep it stable in the part being cut; if this cannot be accomplished with a broach, another method might be considered.  I suspect that these gears used on musical instruments are fairly thin and MAY have punched holes.  The punch could be piloted to insure concentricity.


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## 4GSR (Dec 6, 2016)

Mutt said:


> onlinemetals.com has nothing in metric. Any one else?



Most tool steels are hot finish and usually a few thousands oversized.  You want to buy it bigger than what you need, and machine it down to size you need before heat treat.  I highly doubt you will find any sizes in metric in the USA.  And be sure to allow material for cleanup after heat treat and grinding, if intend to grind it afterwards.


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## Mutt (Dec 6, 2016)

Buying something slightly oversize, I sorta figured that out after searching all the venues I knew about and found nothing in 9mm. I can get 3/8"square in any type I want and pretty cheap to.  So I have a question  about actually machining  the  broach.

In the video above,  the guy takes the headstock of off that little lathe  removed the bar that keeps the headstock indexed and turns it 3º.

 I have a Grizzly 4003 lathe. Mine won't do that . So the question is: with my lathe, is it still possible to cut the 3ºcuts I will need to make?


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## T Bredehoft (Dec 6, 2016)

Sure, pivot the compound to 3º, or would that be 1 1/2º? And hand crank each cut.


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## Mutt (Dec 7, 2016)

what cutting tool ?  A left hand turning tool?


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## Billh50 (Dec 7, 2016)

I remember another way to ht A2 without scaling in an oven. I did not have any wrap left and needed to HT a piece. An old timer told me to go over to the large vertical miller and pick up enough cast iron chips to cover the part in a small stainless pan that was under the oven. By packing the part in the chips it keeps most of the air from getting to the part and thus no scaling. Worked like a charm. Part came out the right ht and no scaling what so ever.


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## TacticalAnt (Dec 7, 2020)

These guys use a square file as the broach with an arbor press:


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## benmychree (Dec 7, 2020)

In 


Billh50 said:


> I remember another way to ht A2 without scaling in an oven. I did not have any wrap left and needed to HT a piece. An old timer told me to go over to the large vertical miller and pick up enough cast iron chips to cover the part in a small stainless pan that was under the oven. By packing the part in the chips it keeps most of the air from getting to the part and thus no scaling. Worked like a charm. Part came out the right ht and no scaling what so ever.


the shop where I apprenticed, we packed all the work in a covered stainless box filled with crushed peach pit charcoal, it worked well; after I left they could no longer find peach pit charcoal, and went to using crushed coke.  I suspect that crushed mesquite charcoal would work as well.  I always wondered if the carbon penetrated the steel and gave a case hardening effect, but I think that the limited time at heat, usually one hour, and at a temperature below case hardening temperatures, that there would be any significant effect, and besides most all that treated work would be finish ground after HT, removing any superficial effected zone.


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## RJSakowski (Dec 7, 2020)

Making steel from iron by heating in a closed container packed with carbon bearing material was a common practice before the advent of modern smelting practices.  The ingredients were closely guarded secretes and some  carbon bearing materials used were manure, straw, virgin's blood.  Swordsmiths staked their reputations and sometimes their lives on their ability to make a superior steel.  Japanese swordsmiths are one example. 

This was essentially the process used to make blister steel.  The biggest problem with steel made in this way was the inability to make steel with a uniform composition. 

I have used a process like this to convert mild steel to a spring steel.  I embedded the steel in a bed of hot coke  in the forge for a working day.  I wouldn't claim to have sword quality steel but it made fairly decent spring steel.


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## MrWhoopee (Dec 8, 2020)

These are guitar tuning gears, so not very thick and possibly brass. This is a small hole requiring very little material removal.  I have literally broached (punched?) a 5mm blind hex in steel using an Allen wrench. The wrench was cut to about 1-1/2 long, hand ground on the end to create sharp edges, held in a chuck in the tailstock of the lathe and forced into a 5mm dia. hole. The cutting forces caused it to self center. For a hole as small as 4mm, I would make a 4mm square broach/punch from some O-1 drill rod, flame harden it and sharpen the end. At least that's where I'd start.


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## Illinoyance (Dec 9, 2020)

johnreese said:


> Will a rotary broach work?  There are a lot of drawings available on hobby/home workshop forums.  Can be used in a lathe or a mill.


Yes but the pilot hole needs to be pretty big.  Check a broach mfg. for appropriate relief hole sizes.


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