Finally, BT-30 Headstocks For Taig & Sherline!
Are you looking for the ultimate in precision and rigidity for a small headstock? Do you like the idea of quickly changing out tools? Then this is for you… You can now be among the first to get the GlockCNC BT-30 ATC Ready headstocks for Taig, Sherline, Chinese Mini Mill or custom mills. Until now, there were no bolt on headstocks that allowed for commercial grade 30 taper tooling. One of the great parts about owning a BT-30 headstock is the tooling availability. BT-30 tooling is very inexpensive for extremely high precision, tons of tooling types available and even lots of great quality used BT-30 tools available, if you want to go that route.
Is a BT-30 Taper Headstock Overkill For a Small Machine?
Initially, I wondered the same thing. Then I came up with the simple (if not obvious) solution…use bigger bearings that allow the tooling to fit deep up into the spindle bearings. By the time we finished engineering the whole thing, the headstock casing ended up being just 95mm (less than 4” tall) with minimal tool “stick-out” to conserve Z axis space. Yes, this is bigger than the stock Taig or Sherline headstock, but the payoff is huge by comparison.
Is There Any Advantage to the BT-30 System Over the R8 System?
We’ve done plenty of testing to answer that very question. As it turns out, there’s better vibration dampening, better finish quality and more precision…and here’s why;
Long Tool Taper – By using two good size Internal Dimension stacked bearings, we were able to fit almost the entire BT-30 tool taper up inside the bearings (a 3rd bearing holds the tail section of the spindle arbor). This my friend, puts the tooling load inside of the bearings, where all the work is being done…and frankly, that’s where the taper should be, high up into the bearings. (Take a look at the first image up to the right side on this page. See how far the tooling taper goes into the bearings? It actually goes a little further than what is shown, the 3D printed plastic spindle arbor shrank a little and didn’t allow the tool to seat as far up as possible.) This is a significant advantage over an R8 spindle arbors. Most R8 spindles arbors hold the collet or tooling below the bearings…which is exactly where you don’t want it…especially on a smaller mill. Because most R8 spindle arbors hang well below the bearings, it acts like a lever putting a heavy angular load on the bearing for sideways cutting.
Tooling & Spindle Mass – BT-30 tooling is simply more robust than R8 tooling. Some may argue that the taper on both the BT-30 and R8, at the widest point, is close to the same and may not make a difference. However, there’s more to the story than taper width. Testing shows the larger tooling mass, far longer taper, and larger spindle arbor for the BT-30 results in far better rigidity and vibration damping. Once the BT-30 tool is seated in the spindle, the entire spindle now becomes one nice solid chunk of metal ready to do some real precision work.
Tooling Precision – Nowadays, anybody can find inexpensive BT-30 tooling good from 0.0001” to 0.0002” TIR (.0025mm to .004mm)…by comparison, most good R8 collets are .0005” to .0006” TIR. That means R8 tooling is 3 to 6 times less accurate than good BT-30 tooling! Simply put, you can find much more accurate tooling for BT-30 systems.
Tooling Variety – True, there is a lot of tooling for R8 spindles. However, your new BT-30 headstock will open you up to even more tooling options..including modular cutters. Plus, as mentioned before, the tooling offers much more precision than comparable R8 tooling.
Made From Solid 6061 Aluminum Billet – Of course, the images and video show the 3D printed version. You’ll be getting a nice chuck of precision milled 6061 aluminum anodized in black. There’s enough “meat” on this headstock to dampen vibration and if you need to do some custom drilling and tapping into the headstock, you can do that too.
How Does BT-30 Compare to Tormach Tooling System (TTS)
I really like the TTS for those who already have an R8 spindle. It’s a good compromise if that’s your only choice. Tormach now has a nice selection of reasonably priced tooling too. I also like the idea of dual contact. They made a nice business centered around the TTS. That being said, many have experienced some real downfalls to the TTS.
Accuracy – As most machinists know, anything added between the bearings and the cutter create error or inaccuracy. TTS uses a flat nose ¾” collet, which adds runout and that holds on to the TTS tooling, which adds more runout. This is called “stacking error”. It’s when you stack runout error on top of runout error. This reduces accuracy, reduces cutter life and can create chatter. BT-30 tooling can easily be found with .0001″ or .0002″ runout and it doesn’t require an extra part in between the tooling and the spindle arbor. This radically reduces the chance for runout issues.
Slip Pullout – If you imagine what an end mill looks like, it looks like a screw. As you know, when a screw grabs into material, the screws helix pulls itself into the material as it’s twisted. The same happens with end mills. End mills want to pull out of whatever is holding it. Normally, this isn’t a problem. But if the machine starts to chatter, then the grip on the TTS shaft can break and the tool holder is pulled out. Even a small amount of pullout can damage your part, ruin precision, break cutters and so on. Plus, if it creates a gap between the TTS dual contact face and the spindle arbor, you’ll loose the benefits of dual contact and create more angular stress on the hollow pull tube on the TTS tool.
Short Taper and Bearing Overhang – Unfortunately, in most R8 systems, the TTS collet taper is well below the bearings. This is not the optimal design and its especially problematic for smaller mills. All the work really happens in the bearings, so you want the tooling taper to be up inside the bearings if possible. This is solved with your GlockCNC BT-30 spindle. It’s low profile means the tooling taper fits up into the bearings.
What About Dual-Contact With TTS? – I really like the idea of dual contact and it’s a great improvement for R8 users. What we ended up discovering is this; compared to the benefits of TTS dual contact, small mill users are far better off using tooling that has a longer taper that fits well into the ID of the spindle bearings. As previously mentioned, it puts the workload inside the bearings where it should be and provides better damping than the TTS. What testing has also showed, is that, the solid mass of 30 taper tooling more than outweighs the benefits of the TTS dual contact. Don’t get me wrong, I like the TTS idea and we use it in our R8 products. However, for the small mill user, many hands down prefer the BT-30 tools. You find BT-30 spindles in commercial machines for a reason…
Gazillions of Tooling Options – From shrink fit end mill holders to larger indexable cutters to modular cutters to ER holders to basic end mill holders…you now have virtually unlimited choices.
Precision – Your new headstock will have .0005” TIR or less. You can upgrade to ABEC-7 bearings and dial the runout down to .0003″ or less. Pick up some super accurate tooling and you now have the ultimate mill!
Options
Ribbed Pulley – You can get our 2 step 5 rib pulley (60mm & 40mm steps) or come up with your own. The ribbed pulley gives you lots of belt brand choices if you need to replace the belt. The belt we supply is good for up to 3,000 watt motors and 10,000RPM.
Petal Clamp – Our petal clamp is steel with hard brass petals for use with 45 degree pullstuds. However, we’re still sourcing the belleville disc spring washers and best pneumatic cylinder. Those aren’t included. When we narrow down the best supplier, we’ll add disc spring parts and pneumatic cylinder as an option or you can get your own. You want to add your own M12 pull stud to match your disc spring choice.
ABEC-7 Deep Groove Bearings – Do you want to add a new level of precision? Upgrade your bearings to ABEC-7 for .0003” or better runout.
Angular Contact Bearings – For the ultimate in precision, speed and long life…angular contact bearings are the way to go. We stock ABEC-7 steel angular contact bearings. Hybrid ceramic/steel and ABEC-9 bearings are available, but will add some time and definitely more cost to the order. We don’t stock the ABEC-9 or hybrid bearings.
Taig Mill Adapter – You’ll really like our new Taig mill adapter. It’s a nice thick chunk of 6061 anodized aluminum that has 4 points of contact with the Z axis carriage…the face, top and both sides (images will be coming soon). This allows for a more dampening and rigid fit for plunging and lateral moves!
High Speed Balancing – You can opt for the 20,000 RPM balanced spindle arbor if you want to ramp-up your cutting. We recommend angular contact bearings for anything over 8,000RPM.