Expanding Ti with heat to fit things inside

[mikemetal]

Hi I'm coming from the machining/wrenching/heavy industrial area. Really I'm a machinist with some knowledge of heat treating mainly martensitic steels (I have read a few books).

Anyway my situatiuon is this: My father is into rc helicopters. He crashes these a lot. Most of the fasteners on these are where a hex-wrench of 1.5-3.0mm fits. And when I last saw him he was complaining about how bad the quality of the tools you can buy was (getting rounded off fast).

I have decieded to build him new hex wrenches. These will be like screwdrivers but hex/allen format, with 6al-4v ti handles instead.

So basically what I want to know is this: how much will a 2.00/3.00mm circular hole drilled in 6al-4v ti (round stock outer diameter 15.00mm) expand at 1000deg C (in millimeters)? I'll heat the handles and cool the steel hex material (bondhus chopped L-wrenches).

I'm building hex screwdrivers out of ti (handles) and steel (tool tips) and I want to shrink the steel inside the heated ti and end up with a rock solid fit that will never ever turn/slip in the handle.

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(off topic) well there are many ways to do this. I tried calculating this myself with knowledge about thermal expansions found online, and even calculators too. I figured a 2mm hex wrench with a maximum outer dimension of maybe 2.25 or so could be shrinked into a 1.9mm hole if the ti was heated enough, but the online calculators told me this was not gonna fukn happen, ever.

So now I want to know for real. And to be honest I don't really want to glue these things in. Its just not gonna happen.

 

[btrueblood]

1. Why not carve the handle to fit the normal L-bent allen wrench, maybe as a 2-piece shell that clamps on?
2. The "beauty" of cheap allen wrenches is that you can correct the rounded corners fairly quickly by grinding the end down to expose fresh, undamaged hex section.
3. The ugly of allen wrenchs is that cheap stainless socket head screws round out so readily. Try getting decent strain-hardened versions of the fasteners, in the sizes his choppers use, so that he can replace them all.

 

[EdStainless]

Why Ti?
Make both from steel and braze them.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[mikemetal]

Well i'm trying to go even more basic than that. I'll just turn the handle to spec (od) then make serrations of half of it then turn it around and make the hole. and then shrink the steel in there / heat the ti so it fits. what could be more simple than that??

I just want to know my drilling diameter considering the heating of the ti (I use acetyle so at least 1000C). I also have access to liquid N and dry ice for cooling of the actual tool tips. And I usually work with these chemicals. I replace liners on hydraulic breakers a lot. and to make that work you need both heat and cold. I do this several times a week. there are no safety issues here.

but yeah I'll try making him get better fasteners. A regular helicopter seems to have at least 40-100 of them. They are mostly the same size of hex for a given helicopter it seems.

I just want to build him 4 ultimate tools for this (both feel and function) and for function i go bondhus since these are the best hex wrench makers, and forf feel I go 6al4v since this is the most luch feeling material on earth, feels like heaven no matter if its 100C or -100C somehow.

 

[mikemetal]

e4d stainless. steel fells a whole lot different if you actually have it in your hand, compared to 6al4v. its both heavier and there are other mechanisms at work too. I was expecting to get flak from thbis selection though.

All I can say is this: i haver table wear made of 6al4v and sometime i run it in the ove with food, and its never burned me. equally but really not totally equally when you put it in the freezeer it never FEELS really cold. it feel like you kinda. its a strange material. you should try it out. I'll also say that CP ti and 3al-4.5v is no the same, but you will very soon find this out just by looking at the specs.

so what drill diameter??

 

[ornerynorsk]

Well here's a newsflash, you can buy extremely high quality tools that will not round or strip after a few uses, but you're not going to find them at Walmart or your local DIY. I don't mean to sound like a jerk, but unless you want to build your own set just for the exercise of it, you're going to have more time and money invested than in a really good commercially manufactured set.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[btrueblood]

Not sure you will ever get a shrink fit to work very well with that combination.

You might look at roller swaging the handle.

 

[tbuelna]

mikemetal-

Don't know why you think this is a better idea than a wrench like this, but here you go: Below is the CTE (alpha) curve for 6Al-4V wrought titanium. At 1832degF (1000degC) the CTE is 9.6ppm/degF. So heating your titanium handle from RT (70degF) to 1832degF would grow the .1181" (3.0mm) diameter hole by .0020".

I don't know how you plan to heat the titanium handle to 1000degC, but it would be best to use an electric furnace. Using a torch to heat the handle in open air would be dangerous since titanium burns very energetically and is a very difficult type of fire to extinguish.

I guess you must really want to impress your dad.

 

[mikemetal]

Hello again guys. yes obviously you are all right about just buying better tools, like WERA, WIHA, FELO, GEDORE and so on, and I actually have done that now

the thing with these small tools is first the heat treatment, (and steel selection) of the actual tool tips (and I assume this the cheapest crap known to work, even with these high dollar brands) and then IMO just as important or even more important is the ergonomics. So I invested in FELO. they simply have the best ergo of all the good brands.

the wihas seems to be just bad designs.
the weras (that my father already has, but not in hex) seems really shitty when you actually have them in your hand.
the felos seems better, so i got those. but the regular precision series and the esd specific series (that one seems to be the best one ever, ergonomically speaking).

Yeah, regarding the heating of ti. if I drill a hole that would be 3.00mm it would expand to 3.05mm at 1000C. and its highly uncertain the actual 3.00 hole would actually come out at 3.00. most likely it would come at at between 3.00 and like 3.05. and that is the exact same tolerance that the actual ti would expand to. so in reality this would probably never work.

Unless...

I do a 3 piece approach. first steel hex tool tip. Then either brass or bronze middle part (it has 3x the thermal expansion of 6al4v ti) and then outer part ti (the part you hold in your hand).

I was thinking the middle part could be bronze with a drilled hole of 3.10mm nominal. and that would expand to like 3.25mm (3x more than ti would) and then I can fit the hex 3mm in there.

And then when step 1 is done I move to step 2, and that is fitting the brass to the 6al4v. But now the brass outer diameter is like 10.00mm instead. And obviously I could do more things now with low precision machines since i have a material that is 3 times as "thermally expansive" and its 3x the diameter to begin with. win-win imho.

so yeah thats pretty much what I'm going to do here. use a middle bronze piece. pretty much.

also its elastic behaviour is better than ti.

I'm guessing I could just as well just bang all these pieces together cold and hope elasticity saves me (and it probably will), but i still have some kind of pride.

I will post pics of the finished tools

 

[ornerynorsk]

You might also want to consider Bondhus. Lifetime, no hassle warranty. A tool does not need to have "Made in Germany" to be of superior quality, even though the German brands have very nice ergonomics that outclass the Bondhus offerings.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[mikemetal]

Yeah I like bondhus tools. I'd say they make the best quality hex wrenches period. I guess the german brands make just as nice/good hex wrenches (now).

I ordered bondhus ball-end hex "screwdrivers", since i knew they are the top quality brand for hex shaped tools. Also pretty much the only thing they make are hex wrenches so I'd guess they are good at it now after all these years

I also ordered lots of other precision tools, torx from t5 to t10 (felo), philips from ph00 to ph1 (felo esd), hex from 1.5 to 3.0mm (felo), and ball hexes (bondhus), some flat ones (felo esd) and also a set of miniature socket drivers (felo).
My father has wera mini socket drivers but imo these suck ass, since they are highly unergonomic, its just a flawed design imo.

and this is what lead me down making my own tools. I make lots of stuff for myself, specialised stuff like kitchen knives, tables, stands. pretty much everything i cant go out and buy but that I still want.

trevlig helg!