[J S Machine]

Looking for help on Ti SFM. What are you guys running? I have found anywhere from 20-150 SFM in research, and kind of been experimenting with 100.

I do a lot of small hole work and use a lot of small diameter tools. I am running the 770, so i do have the high rpm capability.

Also curious on something I had never really thought about - when figuring speeds for a center drill, do you use the small pilot diameter or the whole tool shank diameter (max dia. of the bell) ? It has always seemed to me like using the shank dia. puts undo stress on the pilot tip area.

I use mostly high speed tools and can use coolant or not, but I do have a few carbide tools.

[SCzEngrgGroup]

For center drills, go by the smaller diameter. You should also consider, instead of using center drills, buy a few 90 degree carbide spot drills. They'll do the same job, they'll last a lifetime if not abused, and can also be used as chamfers to finish edges. They can also provide longer reach (to get to holes on lower features of parts), while still remaining very stiff.

Regards,
Ray L.

[J S Machine]

Many thanks. I have never used a spot drill much, but after reading about them I see the advantages. Do they have a web similar to a drill? If so, does this web get smaller with smaller dia. tools? Reason I ask is because I'm not sure if I'd be able to use something like a 1/2" spot drill to spot holes for say a 3/32 drill.

[SCzEngrgGroup]

Many thanks. I have never used a spot drill much, but after reading about them I see the advantages. Do they have a web similar to a drill? If so, does this web get smaller with smaller dia. tools? Reason I ask is because I'm not sure if I'd be able to use something like a 1/2" spot drill to spot holes for say a 3/32 drill.

Just like with center drills, you'll want several sizes of spot drills - I use sizes from 1/8 - 1/2". The "point" does get larger with larger sizes, but a moderate size, like 1/4" or 5/16" is quite adequate to spot-drill for anything from 1/8" to perhaps 1/2".

Regards,
Ray L.

[J S Machine]

Sounds good. I'll get some ordered.

I did some work last night with what I thought were pretty decent feeds and speeds, but they still seem too high.

This is 6AL-4V Ti, and I found 50 SFM for machining, and 30 SFM for drilling. Doing calculations, I got the following:

#1 center drill - @ 30 SFM (for the .047" tip), 2438.3 RPM, .002 feed/tooth, feed rate 9.8 (still seemed way too fast on feed, I backed off somewhere around 1.5 - 2 on feed.)

#43 .089" drill speeds and feeds- @ 30 SFM, 1287.6 RPM, .002 feed/tooth, feed rate 5.2 (I backed off on feed to around 2.5 to 3)

#14 .182" drill speeds and feeds- @ 30 SFM, 629.7 RPM, .002 feed/tooth, feed rate 2.5 (I think I slowed the spindle a little bit and backed off to about 1.5 on feed)

5/32 .15625" HSS TiN coated 4 flute endmill @ 50 SFM, 1224 RPM, .002 feed/tooth, feed rate 9.8 (This was a full face cut, profiling around something, at .050" depth of cut. I had to back off to about 1.5-2 on feed).

All these ops had flood coolant. Calculated speeds / feeds were producing a blue / purple chip and causing the machine to shake and vibrate. It seems that everything had to be slowed down to around 1/3 of the feed my calculations gave me, before I was able to stop the machine vibration and produce a normal colored chip and keep tools sharp.

I know carbide would be better, but i don;t have any at the moment.

[BAMCNC.COM]

FSWizard - Free Advanced CNC Speed and Feed Calculator