This Miserable Titanium

Erin Burke

Erin Burke

Well-Known Member
{Cross-posted w/ BF}

Hey all,
I am attempting to make my first non-fixed blade knife (Knife #13), a sweet little balisong based on a design I did earlier. Below is a rough CAD sketch.

5011405905_8d12b0bdbd_o.jpg



This will be my first time working with titanium. I have a plate of 0.13" 6AL-4V and have already had a bunch of fun drilling 1/8" & 3/16" holes to screw it tight to my "fixture plate". Base on this initial experience I now have a number of questions:

  1. Do I have to use a "very hard" material for the fixture/backing plate to avoid binding the bit as it comes out the back side of the Ti? Currently I have a scrap of African Padouk (hardwood) that I milled flat. I have broken a couple of 1/8" bits as they exited the Ti. I'm not sure if this is the fault of my backer material or the crappy bulk HF bits that I was using. Also, the Ti plate may have been less than perfectly RIGID since I was in the process of drilling holes to mount it to the fixture plate. I can post photos later.
  2. What type of bits do you use for drilling Ti? Like I said, I tried some cheap HF 1/8" bits and they chattered and broke... maybe crappy bits, maybe crappy speed/pressure/rigidity. I have heard many folks recommend cobalt bits. Seems like this may be something to buy in bulk... what bits do you buy and where do you buy them? Any recommendations on point angle?
  3. What speeds do you use for drilling 6AL-4V? Based on the link that I found HERE, I should be using 20-30SFPM or 611-916rpm with an 1/8" HSS bit. Does this seem about right? This gives me 407-611rpm for a 3/16" bit. I have a VS small mill, so I should be able to play with the speeds a bit.
  4. I have heard that you need to keep pressure on the bit when drilling Ti. If my bits are "chattering", is this a sign that I may be putting TOO MUCH pressure on the 1/8" bit?
  5. How many of y'all are using flood coolant when drilling your Ti? This is not something that I have set up on my mill... do I need to come up with something?
  6. How about reaming holes in Ti? I've been told a good rule of thumb for reaming is "half-the-speed, twice-the-feed" used when drilling the hole. However, THIS TABLE that I found on the internet seems to indicate that the speed should be faster for reaming Ti than for drilling (as seen in the previous table). Any recommendations for SFPM for reaming?
  7. Lastly - and this is just a general milling question - if I am drilling/reaming a screw hole that will also have a counter-bored area for the screw head should I:
    1. Drill the hole first then create the counterbore with an end-mill or
    2. Use the end-mill first, then drill the center thru-hole for the screw.
    This assumes that I have to use an end-mill because I do not have a piloted counterbore that fits.
What I'm really trying to do is get the most life out of my drills while producing a clean hole. I am not in a hurry, and want to do things right. I'm sure I'll have more questions as the project progresses. Thanks in advance.
Erin
 
treat 6/4 Ti like 304 ss same speed and feeds it work hardens just like the ss I have never had an issue with good quality bits ( screw length)
 
I can't answer all of the questions, but I'll answer what I can:

2. Cobalt bits probably would be better.
4. Chattering could be caused by too high of a speed,or not enough ridigity. I'm not sure about too much pressure, but I imagine it could cause it as well.
5. You defiantly should use some kind of coolant. I'm not sure if flooding is necessary, but you at least should use a spray bottle or something.
7. You should drill the hole first, then counterbore as it'll be harder to get the hole aligned how you want it if you counterbore first. Not to mention it'll be harder on the end mill as well since it'll have to cut through more steel since the through hole wouldn't be there.
 
Go to hardware store and get some Carbide tip drills. They run about $6.00. They like High Speeds, I used the highest Speed my drill press has. I use them to drill holes in Harden Knife blades. They use them in hammer drills.
That is one hell of a design. I want one. I would send the drawing to David at GLWJ and have him cuts your parts. It much cheaper than Drill bits, Saw blades and Time. I can't afford to cut Titanium. It cost me too much in blades. It takes the grief out of it.
 
Thanks to all the folks who offered advice... I'm now drilling Ti like a dream. This is what I did:

  1. Finished securing the 0.13" Ti plate down to the backing plate. I believe the rigidity helped a lot.
  2. I bought a TON of made in USA cobalt bits from MSC. They were having a 35% off sale. I figured that I might chew through a few bits on this project so I bought a dozen or so bits in 3/32", #31, 1/8", #14 and even a few #29 bits.
  3. I adjusted my cutting speed to 20sfpm... which is the low end of what was given in the table linked in the OP.
  4. I peck at the holes... three pecks (with firm pressure) and I'm through... no fuss. I use a brush on the spinning bit to remove chip coils between pecks.
  5. No cutting fluid. I do not have a flood coolant system, but alot of times I'll use a little Kobalt cutting fluid in the holes as I'm drilling steel. This Ti does NOT like this. Likely I have much to learn concerning the differences between "cutting fluid", "cutting lubricant" and "coolant"... but for this project I'm drilling them dry.
Results?... I've drilled all of my 3/32" holes and most of my #31 holes (close to 40 holes so far) with no sign of wear on the first set of bits. The difference is night-and-day better than I was having with the HF bits. :thumbup:

I still have a bit more drilling, some countersinking/reaming and counterboring left to do, but things are looking up. :D Thanks again for the help.

Erin
 
joe levy said:
If you use a center drill first it will help drilling the holes.

Joe
Click to expand...

Thanks Joe... I forgot to mention above that I did spot the holes first with a center drill. Though I think the "technically correct" way to do it is to use a spotting drill. I didn't think it was worth the extra $20 for a 140-deg spotting bit, so I used one of the cheap center drills (maybe more accurately called "combination drill/countersink" bit) that I already have laying around. Worked fine.

I also would like to add that this project would be nearly impossible without the DROs on my mill. It's nice to be able to hit the exact same location (within 0.00005") with each tool. I love it. :)
 
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