BTA deep hole drilling on Titanium

celhz · May 14, 2018

Hello to all,

I want to know if there is any with deep hole drilling experience especially with solid bars turned into tubes.

I have a BTA drilling machine working on stainless steel with a cobalt insert, 360 rpm and 1.8 in/min feed rate and the machine was working quite fine on a 1.8in OD and 1.702in in ID ( the one drilled ). But when I switched the material to titanium couldn't seem to find the right parameters because inserts degrade too fast (almost 1 per bar) and the chips are long and thick.

Anyone here have experience in this subject, maybe how many rpm and feed rate to start with?

Thanks in advance,

mkd · May 14, 2018

So you're attempting what alloy of Ti at those same quoted speeds, correct?
for cobalt inserts, I'd say 40-50 sfpm which starts @ 90rpm

DMF_TomB · May 14, 2018

recommended speeds and feeds are normally max, quite often they need to be reduced cause of hole depth and coolant issues reaching drill tip

celhz · May 14, 2018

Yes, titanium is Ti-10V-2Fe-3Al so is quite difficult to work with. For BTA isnt 60 RPM a little slow? Just asking.

Tom, what do you mean by max? max of the machine?

DMF_TomB · May 14, 2018

celhz said:
Yes, titanium is Ti-10V-2Fe-3Al so is quite difficult to work with. For BTA isnt 60 RPM a little slow? Just asking.

Tom, what do you mean by max? max of the machine?

.,
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obviously the drill bit maker has no ideal what machine you have. you have to take the tool recommendations and modify them for your job. often you need to reduce sfpm and ipt feed cause of tool length and hole depth and if you are using through the tool coolant blasting chips out of the hole or using external coolant which often does not reach the bottom of deep holes.
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then theirs hp requirements a big drill can easily require well over 10 hp and push over 1000 lbs when drilling which many machines cannot do

Milland · May 14, 2018

Tom, you need to read up on what BTA drilling is: What is BTA Drilling - UNISIG Deep Hole Drilling Machines

For celhz, you might want to try carbide inserts rather than cobalt. It'll be more expensive, but you should get many more holes per insert, along with a more stable process once you dial it in. Coming up with a schedule of insert pull and regrind before failure will help.

mkd · May 14, 2018

Milland said:
Tom, you need to read up on what BTA drilling is: What is BTA Drilling - UNISIG Deep Hole Drilling Machines

For celhz, you might want to try carbide inserts rather than cobalt. It'll be more expensive, but you should get many more holes per insert, along with a more stable process once you dial it in. Coming up with a schedule of insert pull and regrind before failure will help.

IMHO, cobalt will have a more predictable failure rate than carbide. Gotta balance tooling cost and labor rates. Cobalt works very very well in Ti.
I said 90RPM to start assuming 1.7" dia drill!

E189552 · May 14, 2018

Have you tried grinding a chip breaker on to the cutting edge?
We always used carbide for our BTA tooling, mostly inserted.
The cemented carbide tools for TI had a positive rake chipbreaker ground in the first .06-.09 of the cutting edge.
TI is really tough to get chips to break on flow properly.
We would usually run slower spindle speeds and heavier feeds.

E189552 · May 14, 2018

Couple of questions.
Are you drilling from solid to 1.702” dia.?
The wall thickness is only .05” & that may add to your problems.
What is the length of hole and part?

celhz · May 15, 2018

E189552, yes our insert have chip breaker as you said in the cutting edge.
This one is the same type http://www.gnuttibortolo.com/media/products/standard/11780_a.jpg

For wall thickness that is correct is a small wall thickness. The length of the bar is 12 inches and the hole goes trough all. And yes we are drilling from solid to 1.702. We do a preparation of the bar before the drilling process that consist in doing 2 guide holes with a lathe, the holes are of the same diameter (1.702) in each side of the bar. Each guide hole depth is 2in.

DMF_TomB · May 16, 2018

a regular spade drill would do it. just saying feeds and speeds recommended are max. in the fine print at the bottom of recommendations you see the reduce for longer tool lengths and deeper hole depths and if you do not have through the spindle and tool coolant.
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i have often seen drilling problems go away when using 50% of the maximum recommendations. sure salesman selling you tooling going to recommend more that how they make money with short tool life and sudden tool failures

E189552 · May 16, 2018

What type of cutting fluid are you using?
We always used a high sulphur content cutting oil.
Cutting fluid flow rate was about 50 gal/min.

May I ask why on such a short hole are you pre-boring both ends?

E189552 · May 16, 2018

Drilling head similar to what we used.

celhz · May 16, 2018

The oil is ecocut 7505 with no active sulfur. Rate is 60 gal/min, the pre boring is just company process.

E189552 · May 16, 2018

Here is a typical chipbreaker grind.

gwbolton · May 17, 2018

Milland said:
Tom, you need to read up on what BTA drilling is: What is BTA Drilling - UNISIG Deep Hole Drilling Machines

40+ years as a die maker and never heard of this. Still learning every day!

DMF_TomB · May 17, 2018

depends on how many holes you drilling. spade drill works good enough if only making less than 10 holes a day.
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if drilling 100 or more holes per day sure look for better drill. many bigger drills are over $1000. as long as it saves enough to pay for the drill

celhz · Jun 8, 2018

Hello to all,

Just to let you know that I finished my set up and I want to thank you guys for all your help.

I ended up using BTA DRILL spade style. With 220 rpm and 0.005 in/rpm. Drilling on titanium bar of 12 in 17 in diameter.

And with that, chip is fine and the drilling process is soundless. Surface texture is a little bit high around the 63 -90 microinches but overall the part is good.

Thanks again I wanted to post results if anyone in the future has the same issues.

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