How To looking for some advice on milling grade 2 titanium on a mini mill

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alex42

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Jan 8, 2020
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i am a relatively new to milling i have done some manually milled channel(brass and Aluminum) balisong handles and stuff and i'm looking to do some ti channel handles out of half inch round rod grade 2 titanium as i don't think i could mill much more than grade 2 on my mini mill

mechanically speaking what i need to do is mill a 3/16 slot down the middle of the rod then face mill the side of the rod so that the back is rounded and the side have a flat portion



iam looking for some advice on the following questions

-is my mill capable enough? as i have heard lots of other forums say it is
its a craftex cx605 from busy bee. same model as the more common x2


-what rpm should i use? it can go up to 2500 rpm by itself or would i need the belt conversion that lets it achieve up to 4300 rpm

-how fast should i go(feed)? is there a comparison to like (up the rpm but mill the same speed as aluminum) that type of idea as i will be milling manually


-will a hss end mill work as long as i use lots of coolant or will i need to get a 3/16 carbide end mill and will just a cheap carbide be sufficient as i will only be milling x2 at most x4 3/16 slots and will a hss be sufficient for milling the side flat and the previous question of will a cheap carbide be sufficient for making x2 sides for each piece flat(x2 pieces of .5 inch x 5.5 inch maybe 4 pieces )


-what type for drill bits will i need? will cobalt do or will i need carbide? i need to drill x2 3/16 holes all the way through for the pivots


any help or other advice would help tremendously and would be much appreciated thank you for any help and tips you might be able to give me
 
I made some similar work with a mini mill, you can safely use HSS but I prefer carbide tips that will be more durable. With these milling machines, if you want acceptable precision you have to work very patiently and remove a few tenths at a time.
 
6AL4V would be a better much better choice than Grade 2, FWIW.

Get yourself one of these: https://www.whitneytool.com/Product.aspx?ID=7668

You can do the slot and facing with the same tool, you just need to clamp the rod sideways. An end mill will smear the slot, especially with Grade 2 Ti.

Titanium work hardens. Bad. Most tool failures are caused from too light of a cut, or stopping and attempting to restart the cut. Cut full depth in 1 pass & don't stop. As the Count mentioned, look out for edge buildup as well. Use coolant, even if it's just a mist from a spray bottle.

For the tool linked above, on Grade 2, use the following feeds & speeds:

130 SFPM (500 RPM)
0.002'' chip load per tooth
6 inches per minute
Climb mill, don't conventional mill.

If you still want to use an endmill, use a 4.5mm diameter and finish the slot in 2 passes. If you don't, the surface finish is going to be crap. To keep the same surface footage (130), you need 2,800 RPM, take the chip load to 0.001'' and feed at 5.61 inches per minute.
 
Sam Dean said:
6AL4V would be a better much better choice than Grade 2, FWIW.

Get yourself one of these: https://www.whitneytool.com/Product.aspx?ID=7668

You can do the slot and facing with the same tool, you just need to clamp the rod sideways. An end mill will smear the slot, especially with Grade 2 Ti.

Titanium work hardens. Bad. Most tool failures are caused from too light of a cut, or stopping and attempting to restart the cut. Cut full depth in 1 pass & don't stop. As the Count mentioned, look out for edge buildup as well. Use coolant, even if it's just a mist from a spray bottle.

For the tool linked above, on Grade 2, use the following feeds & speeds:

130 SFPM (500 RPM)
0.002'' chip load per tooth
6 inches per minute
Climb mill, don't conventional mill.

If you still want to use an endmill, use a 4.5mm diameter and finish the slot in 2 passes. If you don't, the surface finish is going to be crap. To keep the same surface footage (130), you need 2,800 RPM, take the chip load to 0.001'' and feed at 5.61 inches per minute.
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Thanks so much for the info do you think the mini mill can handle grade 5? i heard its a very difficult to mill thats the only reason i was going to use grade 2
 
alex42 said:
Thanks so much for the info do you think the mini mill can handle grade 5? i heard its a very difficult to mill thats the only reason i was going to use grade 2
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I don't have any experience with that machine, so I can't give you a firm answer on that. If it was mine, I'd try it. Titanium is difficult to machine because it work hardens when you look at it funny, it has extremely low thermal conductivity which creates super high temperatures at the cutting edge....which then leads to plastic deformation and sticking (welding) to the cutting edges. To avoid those issues, climb mill, pull the heaviest chip you can, use coolant and don't stop. Climb milling is #1 priority. All bets are off if you conventional mill.

Also, avoid PVD coated tools. Plain HSS is better for your application than HSS/Co (like M42 Cobalt) or solid carbide. Titanium actively bonds to cobalt and aluminum (and titanium). Tools coated in TiN, AlTiN, TiAlN, etc... will just make the chips stick more. Tungsten carbide uses cobalt for a binder, which also makes the chips stick more. CrN and ZrN are the only PVD coatings I recommend for machining titanium. The cost of those coatings isn't worth it to you.

This is a good horsepower calculator: https://www.kennametal.com/en/resou...lling-calculators/force-torque-and-power.html

I'm coming up with about 1/2 horsepower to machine a slot 3/16'' wide X 3/8'' deep, with a 1'' diameter X 6 tooth cutter in 6Al4V, at the feed rates I gave above. (Grade 2 is going to take less power)

If it's a DC motor, it may not have enough torque at slow speeds. In that case, cut the feed rate down a touch.

If you don't want to mess with it, just go with a 4.5mm endmill. The surface finish will be much better with the slot cutter, but everything in life is a trade off.
 
It is a 1/2hp so its worth giving it a try with the slot cutter but i will put it on the low speed gearing to make sure there enough torque


Thank you so much for all your help and tips i cant wait to give it a try i will give a update once i get the cutter and try it.
Once again thanks and have a great day
 
alex42 said:
It is a 1/2hp so its worth giving it a try with the slot cutter but i will put it on the low speed gearing to make sure there enough torque


Thank you so much for all your help and tips i cant wait to give it a try i will give a update once i get the cutter and try it.
Once again thanks and have a great day
Click to expand...
After taking a look at the cost of the slot cutters i wont be able to afford one right now so a end mill will have to do for the time being but still thanks for your help
 
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