[setlab]

I think I remember 5 ball bearings. Here a schematic of what the internal spindle looks like for anyone thinking about building a new draw bar. It probably wouldn't be too difficult to do.

[MrMetric]

Yeah, actually, I think you are correct there. I wasn't sure if it was 4 or 5, but it is still academic. You cannot just extend the drawbar, or make a new bearing holder. Both would achieve the same objective of lowering the bearings. But this likely mess up the timing. Either the cross holes will fall too low, allowing the bearings to escape, or the bearings will not be forced inwards, thereby capturing and securing the holder. The idea is sound, but I am pretty sure that you will need to modify the spindle too, and that gets to be quite a bit more work.

The pivotal thing here, though, is what is the LONGEST knob you can find that is widely available. If it is fractionally smaller than the Dyna one, you might be able to get away with manufacturing a new rod or holder, thereby changing the required retention knob. But the Haas ones, as I recall, are quite a bit smaller.

[MrMetric]

I just took a 2 second gander at the drawing from Timothy against a common BT30 knob. There is about a 4.5mm difference in height between the mounting face and the top of the 45 degree bevel which acts as the ball bearing face. That means to get that particular sample knob to work in our spindle, we need to lower to location of the ball bearings about 4.5mm. Frankly, my gut feeling is that this is quite a bit. I suspect that we'd drop the bearing out the backside of the nut. But.... It *is* an idea worth investigating....

alan

[funford]

Has anyone considered using the 2800 or 1007 itself with lathe tooling to make the studs?

[MrMetric]

Absolutely.... I referenced doing just that in one of my previous comments. This is what MariTool (think it was Mari) suggested I do. He said it wasn't all that hard and that it wasn't necessary to harden the part. The hardening only really helps alleviate all bearing indentation into the bevel area. The key here, however, is more fear, whether rational or not. I don't want a stud breaking, so I've been opting to go down the purchase route. However, at some point that will no longer be an option and some other approach will have to be taken. To me, making the part is probably more feasible than trying to adapt the spindle, but I think setlab's thoughts are worth investigating further. if the spindle doesn't have to be modified, then I'll probably go that route. However, 4.5mm is an awful lot to top the bearings. I have *very* strong suspicion that the bearings will no longer be captive if their location is dropped that much (remember, we are talking 4.5mm drop of the unclamp position too) and the ball bearings will just escape out of the back side of the holder. That would be a fatal flaw, and the only way to prevent this would be to somehow shim the ID of the spindle. At some point that gets to be so much work that you might as well just make the retention knobs.

[funford]

Geesh, I need to do a better job of reading looks like setlab already suggested changing the draw bar. Its a shame I have about 12studs but 50 holders I would be happy with 20 more but damn they are pricey. Seams to me there would be very little chance of breaking the non hardened studs. I would imagine that they are hardened to protect from outside wear. Stuff harden breaks way before tuff. They wouldn't be to difficult to case harden them.

[setlab]

Geesh, I need to do a better job of reading looks like setlab already suggested changing the draw bar. Its a shame I have about 12studs but 50 holders I would be happy with 20 more but damn they are pricey. Seams to me there would be very little chance of breaking the non hardened studs. I would imagine that they are hardened to protect from outside wear. Stuff harden breaks way before tuff. They wouldn't be to difficult to case harden them.

Not something I feel like tinkering with but turning a slightly longer copy of the drawbar on a lathe and adding a small sleeve in the spindle to engage the ball bearings sooner for a shorter pull stud may work.

[MrMetric]

LOL. Don't worry about it funford. I'm guilty of the same thing on a regular basis.

They are, indeed, pricey, but not as bad as you might think. We have gotten used to $4 items from China. Well... everything is made in China now, but I guess I'm talking about the $4 items that were probably rejected from the manufacturer charging $30. The point is, it isn't hard to find retention knobs in the $30 range. Just look at MariTool or any of the other quality manufacturers of knobs (although, those *are* made in the US). I am sure that the ones that I was talking about bulk buying were probably made in Taiwan, likely in the same factory that produced them for Dyna when they were in business.

Long term, I think that making our own is likely going to be the solution. I actually have that on my todo list as an experiment. And, yes, hardening them isn't going to make them less prone to break. Even the US manufacturer that told me I should make my own said that. It is about wear and that is all. But I'm a hobbyist. I don't use my machine that much. If I make 30 studs, they will last me a lifetime, even if I put a time limit on them of 100 hours (or whatever... literally just pulled that out of, well, you get the idea). The material just isn't that expensive either... So just replace them. And, let's face it, for those of us doing this as a hobby... It is just another thing to make!

The ONLY thing that keeps me away from this is a concern that what I make might be somehow inferior to a commercial product. I do *not* want a stud to break on me.