Landracing Forum
Misc Forums => How To Section => Topic started by: wobblywalrus on July 12, 2015, 03:53:58 PM
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Titanium is sometimes referred to as "the titan of metals." It is also called a number of other unprintable names. The stuff can be difficult to impossible to work with. Some methods follow. They are done using small and old tooling like most of us have. Suppliers are named so a person will know about a source. ASTM Grade 5 annealed titanium alloy with 6 percent aluminum and 4 percent vanadium is used. This is often called "structural ti." References to "Bradley" are in Volume 2 of John Bradley's "The Racing Motorcycle." He has a chapter on titanium alloys.
The metal can be machined using conventional high speed steel or carbide bits and drills. Occasionally there will be a tool that wears quickly. The carbide boring bar bit shown wore down almost instantly. There was never a problem when it was used on other metals. Carbide insert tooling is what I use now for these reasons. The bits are available with a variety of coatings and some resist wear very well. This saves a lot of sharpening. A variety of chip breakers can be had that result in good finish quality and I cannot duplicate them on HSS bits. Bradley recommends using tools for titanium that are not used to machine other metals. It is easier to have a supply of bits used for ti rather than a special set of cutting tools.
My little lathe uses 1/4 inch by 1/4 inch tool bits. It would be very expensive to adapt it to modern tool holders for carbide insert bits. Instead, an intermediate solution is used. It is the tool bits shown. They have carbide inserts and fit in old style tool holders. A page listing the bits is shown from the 2011 Sam A. Mesher Tool catalog. They are in Portland ad they specialize in being able to find weird machine tooling. www.meshertool.com (http://www.meshertool.com)
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WW;
I don't do any titanium machining (6Al4V usually) other than drilling & cutting sheet metal. If you treat titanium like stainless steel, you'll be on the right track-- heavy pressure & low rpm with cutting fluid works well with high-speed steel drills.
Cutting 6Al4V sheet metal is problematic. I've tried hacksaws, abrasive cut-off wheels, and anything else I could think of but the only method that works for me is a plasma cutter. To dress up the cut edges, I use an angle grinder with a 3M Cubitron II oriented ceramic abrasive disc.
One more point to add to your excellent post-- even 6Al4V titanium is not necessarily stronger than many good alloy steels; it is its strength to weight ratio that is outstanding.
Regards, Neil Tucson, AZ
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Ti is sexy and light, but often not necessary. Check out the retainers on MM's BMC.
:cheers:
Fordboy
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A post coming up will address this. Ti is real good for a limited range of applications, like you say.
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Be mindful of your titanium dust when grinding. I ignited my Tshirt once when a spark lit all the dust on my shirt. There was a bright flash, a wave of heat crossed my face, and I suddenly had an 8 inch diameter glowing ring on my stomach with exposed skin showing. It quickly went in the sink while I secured another shirt.
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Be very aware when machining titanium alloys that it will burn, and can be ignited even in a solid state. It is the only material that will burn in a pure nitrogen atmosphere. In the airplane plants, they keep buckets of a black sand close at hand anywhere that TI is being worked, just in case it ignites. I forget exactly what this substance is, but it is the only thing that will smother and extinguish at titanium fire. Water, dry chemical, Halon, etc will not put it out.
I only saw it happen once. A new guy was trying to drill a hole, not knowing what he was doing. He was almost through when the bit dulled. Instead of getting a new bit, he spun up the drill motor and pushed harder. Before he could be stopped, sparks and then a blinding white glare. The guy next to him covered the area with black sand and put it out. Almost cost several million dollars. New guy got some extra training.
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https://www.youtube.com/watch?v=NDhnwLheoU4
Ti can be a real danger:-o
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I had similar self ignition issues when machining zirconium years ago, (making nozzles for an acid spray cleaner which needed the high corrosion resistance of the zirconium), but I was unaware that Ti could do the same thing, and even in a pure nitrogen atmosphere.
Gets interesting when your mill catches fire and the spray mist accelerates the fire in the chips because zirconium strips the water just like magnesium does.
The black sand was probably magnetite (black iron oxide).
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We work with titanium all the time on a daily basis.
If you keep in mind certain basic safety guidelines, it is as safe to work with as any of the reactive metals.
Titanium is very reactive to oxygen and will start oxidizing in short order at room temperature, if heat is added that oxidation may rapidly escalate into a fire. So keep your work area and machines clean and free of chip buildup. A chip pan fire will do in a a machine in a matter of minutes.
When machining feed rate and surface footage is the key to success. When that combination is just right chips will come off the part as easy as machining aluminum, whoever, if your surface footage is to high you will eat up a lot of tooling in short order. Keep coolant on your part at all times while machining, flood coolant is best, dry machining will get you in trouble if your not very careful.
High speed tooling works fine if you watch you surface footage, all in all a little slower than carbide, but it works fine.
Keep your chip pan clean. Have fun.
Rouse
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It looks like I need to do some research. Geez. I was using a torch to heat up the stuff to bend it on Sunday. Maybe fool's luck saved my butt.
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I've cut it with a cutting torch. It cuts beautifully. I'm now realizing I may have been playing with fire so to speak. I'll look for further advice before I try that again. The material was fairly heavy titanium pipe. the customer wanted it for an inert liner. We never did solve the cracking problem then, but I think I could do it now knowing what I know now about welding the material.
This is an interesting thread because I also weld magnesium with great success on a fairly regular basis.
Pete
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I, personally, love the way magnesium welds. I have done it a lot on Vw and Hewland gearboxes, and side plates. Most guys are sh** scared to do it. Have not done any for a number of years now though.
Like everything else tricky, you need to make the proper preparations of the material, use the correct filler rod, and take the proper precautions for fire.
:cheers:
Fordboy
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One key to machining Ti is the basic machines rigidity.
CNC mills/lathes with ball guides have high speed capability, box way machines are very rigid.
Never had an issue with Ti, cut and weld very nicely.
I used to weld Mag parts all the time, injected Hydrogen with Argon to get better heat and penetration.
Keep making chips to get to the hidden parts within, J
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If you heat Ti up with a torch you probably just destroyed it. Ti will start oxidizing at temps over 600 F and even faster as the temp goes up from there. Chances are good that the part you heat is now brittle as glass, especially if the part had white powder on the surface once you were finished heating it.
Ti does indeed cut very good with a cutting torch, when working with large sections such as plate. You would use a very undersized tip for the plate thickness you're working with, because you need as little preheat as possible. Once you get the initial cut stared, the reaction to the oxygen keeps the cut going. You will need to cut at 3 or 4 times the speed of steel plate. Lots of white smoke, so do it outside.
Rouse
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The part was chucked up in a vise with an piece of strap aluminum alongside it. This keeps the vise jaw from dimpling the part when it is bent. The aluminum tube protects the part that will be hit with the hammer.
I started out by heating the part with a propane torch and wacking it with a ball peen. No bending at all. I was going to put the propane away and get out the torch and give the part some serious heat. Then I decided to get out Bradley's book and read the Ti chapter. My testosterone level is dropping, I guess. The brain engaged itself. This would never happen in my younger days. Bradley says that major heat with a non-oxygenating source, like a vacuum furnace, is needed for structural Ti. He said lesser applications of flame are a waste of time. I decided to do a cold bend.
It was time for the mini sledge. Some big banging barely bent the part. This is a piddly little 0.410 inch diameter rod. Then I got out the big mama sledge. Ones like this are used on the railroad to spike tracks. It must have taken over 30 blows and some major cussing to bend the rascal. Dishes were rattling upstairs.
Steel with this much strength would have had a brittle fracture during the bend. The annealed 6V4Al Ti part has the needed ductility with enormous strength. The picture shows the thick steel shaft I am replacing with the slimmer and much lighter Ti one. Both have identical resistance to bending according to calculation.
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Some of the newer Triumph use titanium valves. There must be a way to get Ti to resist ignition. The combustion chamber is a very hot place.
Looking down on the lathe from a bird's eye view, the bit holder centerline axis should be 90 degrees to the rotational centerline of the part with insert tooling, as shown in the first photo. It should not be at an angle like in the second photo.
Looking down the rotational axis of the part, the top of the bit holder should be horizontal and at the same elevation as the rotational centerline as shown in the third photo. The typical tool holder used for HSS steel tools, as shown in the fourth photo, is not suitable for insert tooling.
These are general rules and there are exceptions, like cutting tapers.
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Corrosion is a big issue with salt flat racing. The corrosion resistance of non-ferrous alloys appeals, and metals of choice become titanium, stainless steels, the aluminums, brass, etc. Positive results with initial efforts convince me of the value of the carbide insert. A moderate investment in specialized tooling is justified.
Holders that position the tool level are hard to find for old lathes. The 1/4 by 1/4 size holders for mine are especially scarce. The straight one pictured is hand made and it came with the lathe. The offset holders are also hand made and they are new and from India. They are available from Sam A. Mesher and the catalog entry is shown.
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I'll tell you Bo, the best investment I made for my lathe (1936 vintage 10 inch Craftsman, flat ways and plain bearing headstock) was a quick change tool post with several holders. Worth it's weight in gold as far as I'm concerned. I held onto my lantern tool post for a while, but after not using it for almost 10 years I gave it away to a friend who got a lathe with no tool holder at all.
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Ed, cost was the only issue. The modern tool post setup is better than the lantern.
The world of carbide inserts is intimidatingly complex. I drove up to Mesher's in Portland and asked them all sorts of questions. They gave me a handful of year old catalogs and said the Dorian ones explain what I need to know in an understandable format. This is the one I will be referring to. It is worth it to download it and to print it out. www.doriantool.com/wp-content/uploads/dorian_tool_TurningTools_CarbideInserts.pdf (http://www.doriantool.com/wp-content/uploads/dorian_tool_TurningTools_CarbideInserts.pdf)
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I forgot the underscore after inserts. www.doriantool.com/wp-content/uploads/dorian_tool_TurningTools_CarbideInserts_.pdf (http://www.doriantool.com/wp-content/uploads/dorian_tool_TurningTools_CarbideInserts_.pdf)
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The American National Standards Institute (ANSI) designations will be used here. The tool holders shown earlier on this thread use CCMT 21.51 inserts. Refer to Pages 54 and 55 of the Dorian catalog.
The first "C" is the bit shape. It is an 80 degree diamond. This cannot be changed without using a different tool holder.
The second "C" is a 7 degree positive rake. The tool holder is made for this bit rake.
The "M" is the tolerance. It is plus or minus 0.005 inches for bit thickness. Bits with different tolerances can be used in the holder.
The "T" is the bit type. This means: Hole. 1 sided chip breaker, 40 degree-60 degree ISO countersink. A "W" insert can also be used in the tool holder. It is similar to the "T" except it has no chip breaker.
The "2" is the bit size. It is 1/4 inch. This cannot be changed without switching to a different tool holder.
The 1.5 is the bit thickness. It is 3/16 of an inch. This is the size that fits the tool holder.
The "1" is the radius of the insert tips. it is 1/64 inch. This can be varied with use of the same tool holder.
An insert with a chip breaker has this designation where the underscored can be changed. CC_T21.5_
An insert without a chip breaker has this designation. CC_W21.5_
This insert geometry, clearance angle, size, type, and thickness is well suited for small belt driven lathes.
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The catalog has a section on various metals with troubles and cures. A fuzzy copy of the Titanium section is shown. There is a lot of info in this publication. It is much more than just a listing of what they sell.
The preceding post listed two bit sizes. There are only two entries in the catalog for them. One is for bits without a chip breaker groove CCGW-21.51-KEU. These are best for cast iron and I will use them to skim the brake disks on my truck. Uncoated DKU10HT is best in the wet condition. My lathe has no coolant and I work with dry conditions. This coating is not optimal. DUP35RT coating works with wet/dry conditions. It is best for roughing with cuts .008 to .157 deep. The belt on my lathe will slip when I try these deep cuts. This is not the best choice. DUP15VT is best in dry conditions with .002 to .098 inch deep cuts. This matches the lathe capability and it is the best choice. I will order a few.
The third posted page shows bit CCGT-21.51 with UEU chip breaker groove. It works best for almost all materials. The DUP15VT coating is best for shallow cuts in the dry condition. This is what I am using now.
These posts show a method to use these tools. It can be adapted to use on many metals with other brands of inserts.
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Titanium is hard to almost impossible to thread with a die using normal methods. The die seizes in place and is very hard to turn. Sometimes the threaded end twists off of the part and it is stuck in the die. Special methods are needed to make male threads.
The shaft is turned to the diameter shown in the first photo. A die is used to cut threads. Note how the outside diameter increases when it is threaded as shown in the second pix. The die cuts and extrudes threads. This jams up the die if the rod to be threaded is turned to the major diameter. Jamming is less of a problem if the shaft is turned undersize before it is threaded.
My formula is shaft diameter = major diameter - (2 x 20% of thread depth) where thread depth (metric threads) = (0.5 x thread pitch) / tan 30 degrees
For example, the major diameter is 10 mm for this rod with 10 mm x 1.25 mm threads. Thread depth is (0.5 x 1.25 / 0.57753 = 1.083 mm. Undersize shaft diameter is 10 - (2 x .2 x 1.083) = 9.566 mm = 0.377 inches. The shaft is turned to this diameter before threading with the die.
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Your best bet for threading Ti would be to single point thread it on the lathe.
Your right that die threading is not an easy thing to do, almost not possible to do right with good results, as you material will twist with the torque of the die and the rebound will lockup on the die, and there your are, stuck.
Set the parts up in the lathe and single point your threads.
By the way; if you use a Ti nut or any Ti female thread with these parts you will need to coat these threads with something to prevent galling, or they well "weld together" as soon as they are torqued.
Rouse
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The lathe works great for making American threads. The bike is metric.
An adjustable die is used to make the first pass. The die is loosely clamped in the holder so it can expand as needed. Anti-seize is used as a cutting lubricant. The first pass partially cuts the threads. More lubricant is applied and a non-adjustable die is used for the second pass. Most of the time this is the finish pass. The titanium compresses in the die when it is cut. Sometimes a third pass with a very sharp die is needed to cut the threads to the proper size.
Rouse give good advice about using unlubricated titanium to titanium connections. They can friction weld together.
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When I was working at Standard Tool and Die in LA we did quite a lot of Ti machining and as previously stated machine rigidity is a big requirement. One of the things that we did for doing the rough cuts when milling Ti was to use liquid nitrogen for the cutting fluid. Makes Ti cut like aluminum. Fun to watch the end mill snap the micro second that the liquid nitrogen stopped!
Rex
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That is amazing. I wonder how they figured out that it would work?
The formula I use for metric tap drill size is: tap drill diameter in mm = thread outside diameter in mm - (1.08254 x TE x thread pitch in mm) where TE = 0.65 for 65% thread engagement or 0.75 for 75% thread engagement
Usually I start with a tap drill for 75% engagement, and if it is hard to turn, the hole is enlarged to the size for 65% thread engagement. Anti-seize is used as a thread lubricant.
Taps made for ti are essential. Two entries in the Sam Mesher catalog are shown. The taps I use are selected from these lists. They are used for ti only, and nothing else. They are easy to turn and cut nice threads.
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There is an easier formula for cutting metric threads:
outer diameter minus thread pitch is the diameter of the bore to drill:
Metric 8mm has 1,25mm pitch so its: 8 - 1,25 = 6,75mm (6,8mm) Drill
Metric 8mm FINE has 1mm pitch so its: 8 - 1 = 7mm Drill
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You're spot on Weal. :cheers:
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The thing I am trying to show is that the titanium piece is turned to a slightly smaller diameter than is customary before the die is used to cut male threads, and the hole is drilled slightly bigger than normal before it is tapped. This makes the ti easier to thread with normal taps and dies. Otherwise, the metal is very difficult to work with and it is easy to break the tap or have other big problems. Quite often I do not need to do this if special taps and dies are used that are made to cut titanium.
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I'm curious (and maybe this was answered and I missed it?)- can thread-forming taps and dies be used with titanium? A local aerospace machine shop has switched almost totally over to thread-forming (as opposed to thread-cutting) of tool steels and chrome-moly alloys. Personally, I've never tried them.
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Thread forming makes a stronger fastener. It is the best method.
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jack;
I agree with WW- roll-forming produces a grain structure that follows the thread profile rather than cutting through it. Roll-forming takes a lot of torque, though, to roll the threads on. Since the forming causes the tip of the thread to rise as the root is formed, you have to start with a smaller diameter material.
Regards, Neil Tucson, AZ
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I agree about the advantages of thread-forming; but I don't know whether it can be employed with titanium? :?
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Yes you can thread form Ti. But, careful consideration needs to be paid to a whole host of factors that may come into play.
Ti has very different properties than other materials like Aluminum or Stainless Steel. For that reason, for short runs or one off threading, most folks just cut threads as opposed to thread forming. If you are going to thread form Ti for the first time, do yourself a big favor and start with test pieces in order to perfect the process on your part.
Rouse
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High speed steel tool bits seem to work OK with 6AL4V titanium alloy. Bits with carbide cutting edges fused to steel give mixed and mostly poor results. The ti erodes them quickly. The setup I use most of the time is this washer supporting a tool bit holder. The holder positions the bit level with the bit tip at the level of the part's axis of rotation. In bird's eye view the bit is at 90 degrees to axis of rotation. Exceptions are mad like this where I am cutting at an angle. The bits are carbide with a geometry and coating to be suitable for all sorts of metals without coolant.
The total tooling investment for the carbide bits was real reasonable. It is shown, and it is a box of bit holders with bits and a boring bar, some holders that position the bits level, a parting blade, and a few bits for it. The different tool holders hold the bits in varying orientations to the part and the bits can be shifted around so all for corners get used. It takes awhile to completely wear out a bit.
A lot of this stuff was shown in earlier posts on this thread. Not many folks know how little it costs to adopt this carbide bit technology. Most of the items shown are hidden deep in obscure catalogs and learning what low budget tools are available is the hardest part.
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Concerns about me taking a perfectly good carbon steel bolt off my bike and installing a titanium bolt I made are valid. Does anyone have a good reference for titanium fastener design? It is easy to figure out the clamping force provided by the carbon steel bolt. Now I need to check the titanium bolt I made and to verify it provides equal or greater clamping force. Also, I want to design titanium fasteners. Everything I have is for carbon or stainless steel and it does not apply to ti.
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Bo,
I seem to recall some very basic information buried deep somewhere on the ARP website. You might also try the websites of the Ti material suppliers or check the Government's aerospace suppliers. Some manufacturers are going to consider what you are looking for proprietary/trade secret info.
:cheers:
Fordboy
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Shouldn't be any secret about the strength of the materials. High strength CS bolts are going to have better clamping capacity than TI, they just weigh more.
Rouse
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WW;
This has some useful info and it also references other documents that may be of interest.
Regards, Neil Tucson, AZ
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Thanks for all of the advice. My son, Johann, who works at the nuke plant, told me what they do. Three factors influenced my decision which pertains to clamping force. This is critical in this application. The frame is held together with bolts.
1) I have good data about the grade 10.9 carbon steel bolts that originally came in the bike. I do not know the grade of the stainless steel fasteners I am replacing them with.
2) The data I have on the carbon steel bolts and nuts indicates they should be used only once in critical applications. The ones I am using are 12 years old and have been reused a bunch of times.
3) The carbon steel bolts are reasonably priced.
The decision is to install all new carbon steel bolts and nuts in the critical locations on the frame and forks.
I do not have much data about the have a lot of daThey are OEM fasteners, stainless steel bolts I am and this bike will be moving well above the operational envelope it was pey need to provide adequate
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I had similar self ignition issues when machining zirconium years ago, (making nozzles for an acid spray cleaner which needed the high corrosion resistance of the zirconium), but I was unaware that Ti could do the same thing, and even in a pure nitrogen atmosphere.
Gets interesting when your mill catches fire and the spray mist accelerates the fire in the chips because zirconium strips the water just like magnesium does.
The black sand was probably magnetite (black iron oxide).
Aluminum dust will ignite pretty damn good too. Ask the poor sap that was welding on the dust collection system at one of the local foundaries here in Portland. There was a loud woosh noise, and a slight pressure wave we felt in the shop. Then a guy walking around screaming with the skin falling off his arms. Then the sprinkler system going off in the building. Rough day at the shop that one. Anyway, Don't keep piles of either of those metals in dust form inside your shop. All it would take is one little piece of welding slag to land inside of it and boom, now you got yourself one hell of a fire.
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Titanium is expensive to machine. It is hard to make fast or deep cuts, it eats up tooling, and the cutting tools are often expensive and specialized. It pays to plan out the part so it can be made with as little machine work as possible. This often requires the purchase of a small bit of ti that is close to the right size. One source is www.titaniumjoe.com (http://www.titaniumjoe.com) in Ontario, Canada. They have little pieces and they list the alloys. The picture shows a little bar I got to make a pair of footpegs.
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Shouldn't be any secret about the strength of the materials. High strength CS bolts are going to have better clamping capacity than TI, they just weigh more.
Rouse
Ti may well have longer fatigue life than carbon steel fastners however.
The real thing I would worry about with Ti fastners is corrosion. Titanium and vanadium don't get along very well. Vanadium steel tools can cause titanium fastners to start to corrode. The air force learned this the hard way the first go around.
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Shouldn't be any secret about the strength of the materials. High strength CS bolts are going to have better clamping capacity than TI, they just weigh more.
Rouse
Ti may well have longer fatigue life than carbon steel fastners however.
The real thing I would worry about with Ti fastners is corrosion. Titanium and vanadium don't get along very well. Vanadium steel tools can cause titanium fastners to start to corrode. The air force learned this the hard way the first go around.
That hasn't been my experience.
Rouse
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Thank y'all for all the useful, informative postings. It's a sad (I suppose) bit of irony that materials that are so wonderful in some respects are difficult to deal with in other respects.
I've done a bit of titanium (TIG) welding with great results, but no machining of it. I did a little sanding on some once, using
a belt sander, and did notice the bright white sparks. Kinda scary looking. I urge an abundance of caution, and always try to
practice what I preach. This helped me become quite an old guy (well, maybe not so old in land speed racing circles).
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"It is the only material that will burn in a pure nitrogen atmosphere"
Apparently there are no chemists or firemen here?
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https://www.sciencemadness.org/talk/viewthread.php?tid=23529 :cheers:
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I didn't realize that weight-saving was such an important thing in land speed racing. I realize that salt is relatively corrosive,
and I also realize that there are some pretty strong types of stainless steel available (that are also relatively corrosion-resistant).
Many fasteners are available in some pretty strong stainless alloys. Instead of being on a major crusade to save weight in
a land-speed vehicle, I'd probably lean more toward minimizing friction (including wind resistance) -- except where traction is
desired -- , and improving aerodynamics.