My experience with Titanium - a conrod made with no problems at all.

[edholly]

After much research about machining titanium, I thought the only way to find out about machining this metal was to try it myself.

I bought some 9.5 and 12.7 mm rod from a WA supplier with the idea that I would use it to make the conrods for the small diesels I am interested in.

I was very pleasantly surprised to find it to be one of the nicest machining metals I have ever used. I did many cuts including some heavy and some of just one thou (.001") and the swarf came off like fairy floss. No hint of catching alight and the workpiece maintained a shine like polished aluminum.

I was using a Valenite DNMP-432-1W VC2 tip with about a 1mm radius, and I have found these to be terrific for any metal, including 41/40 and spring steel. They never seem to blunt, and the one I actually used has done well over 2 hours of work on all sorts of hard and soft metals.

The tiny centre drill used to spot the bigend and gudgeon pin holes went into the titanium quite nicely, maybe a little less easy than mild steel, and the cobalt drill had no problem drilling through it. I then used a reamer and hand turned the mill and it went into the Ti again about the same as steel.

I then tried the time honoured way of reducing the diameter around the gudgeon pin with a HSS slotting mill and again found the Ti just a little heavier than aluminum but not overly so.

To sum up, I would thoroughly recommend Ti for this type of application, it doesn't seem to have the inherent problems that I have read about in the way I have used it.

The bonus is the conrod weighs 4 grams !

I have prepared a .pdf file of the photos I took whilst machining it and it is attached just below the text here.

The conrod will go into the 5th model diesel engine thread - in the Plans forum on HMEM.

Ed

>pdf below ....

View attachment 25mm conrod in Ti.pdf

 

[johnny1320]

I have machined titanium valves for my race bike and had the swarf spontaneously combust to my surprise, went up like a flash bulb. LOL

 

[Mainer]

I'm glad it worked so well for you.

When I tried machining titanium, the main thing I noticed was that the machining process generated a LOT of heat. Coolant seemed to be a requirement. That may have saved me from johnny1320's experience.

It did machine pretty well otherwise though, but personally I don't have any situations where its special properties would be important. A friend of mine gave me a piece -- he couldn't figure out any reason to use it. Somebody had given the stuff to him in the form of stakes that the guy had used to hold up tomato plants in his garden. He couldn't figure out any other use for it. This year I used my piece for its original purpose -- a tomato stake.

 

[bazmak]

I didnt realize that titanium combusted.Thought it was only Magnesium alloys.More comments please
Only thing i know about titanium is that it has the strenght and machining qualities of stainless steel
and the weight of Aluminium.

 

[dman]

its more like twice the weight of aluminum. around 60% the weight of steel. it's pretty easy to cut if you have a continuous chip like lathe work or drilling.

the problems come when you mill it. it prefers climb milling with high chip loads, conventional milling will make it difficult to create a proper chip because it is odly spongy and work hardens easily. when you climb mill the cutting edge sinks into fresh material first and at a steeper angle and the chip starts thick and gets thinner at the end of the cut. conventional cutting causes the edge to try to dig in to the hardened surface left from the last flute of the end mill and thing tend to deflect instead of cut. the ideal way to mill it is on a cnc with ball screws since backlash can cause problems when climb milling, and ti is also sensitive to changes in feeds. tool sharpness is key to machining titanium. if there is anything that will combat the problems conventional milling titanium it's having sharp tools.