[Azalin]

I am willing to make an ATC spindle but the petal camps are quite expensive so I think someone have tried to make it at home or shop.

After the lathe work I think the tricky part is to split the one piece into 4 (the jaws). They must be perfectly cut to get 4 equal pieces. But how?

[RustedOut]

How about starting with 4 pieces of square stock? Possibly tack weld the held ends together, then hold them in a 4 jaw chuck or in a square collet.

Bob

[Azalin]

That seems like a good idea Bob.

[RustedOut]

If you have to flip the parts end for end, make a collar to lightly press them into and hold them in that. I'd do the inside work first, then the outside.

Bob

[Azalin]

Too bad I don't have a 4 jaw chuck. Maybe it's time to get one.

[RotarySMP]

You can also split then with a dremel and cut off disks mounted on a mill, and a Rotary table Holding the gripper. This leaves nicely finished 1mm gaps.

[bhurts]

You could also mount a cutoff disk to your toolpost and split it on the lathe before parting it off. I don't think 4 square pieces in a 4 jaw will work. Draw it up on a piece of paper. The orientation of the four pieces would be off and they couldn't be held by the Chuck anyway. Sounds like a good idea but I'm fairly certain it's a non starter.

Ben

[RustedOut]

I don't think 4 square pieces in a 4 jaw will work. Draw it up on a piece of paper. The orientation of the four pieces would be off and they couldn't be held by the Chuck anyway. Sounds like a good idea but I'm fairly certain it's a non starter.

Ben

If you go back and read my original post you'll see that I recommended tack welding the 4 pieces together. They become one at that point. The welded area is held in the 4 jaw chuck, but I prefer square collets for this project.

Bob

[Azalin]

Bob

As I only have a 3 jaw chuck, what about using 3 hexagonal rods? I really don't like this idea because clamping points will be very small. That's all I got though.

[bhurts]

You could throw them on a mill and cut that point off giving you flats to clamp on. You would only need to flat the part gripped by the chuck.

Ben

[Azalin]

Exactly my thoughts. I don't have a mill anymore but I could let the job to my cnc router.

[RustedOut]

What about a set of soft jaws for your lathe. That may require a mill to make them though although with some thought you may be able to do it on your router. Are the ends of your jaws rounded like in your picture? If so, that's a scary proposition. But if not, maybe do that and lightly turn the points off and regrip on that turned section. It won't take much to give yourself more gripping area. But make them cuts shallow and use a small nose radius on your cutter, or no radius at all to reduce the cutting pressure.

Please be aware of concentricity on these things, you don't want to be throwing things off center at the pull stud. And be aware too, a failure on the gripper can lead to devastating results.

Me, I was set up to make a set using the method I described originally, holding the pieces in my square collet. I've got the 3/8" tool steel, the collet, the 3d model and a special cutter for the inside angles, so I actually started down that road. I have heat treat ovens to deal with that after the parts are made. But all of a sudden these things started showing up on eBay and I got to thinking why go to the effort of making them when they are available to purchase. So I put that project on hold and turned my attention to the BT30 spindle. Bought a NMTB30 spindle and am now working on a new cast iron housing (quill) to hold it with more bearings that will allow higher rpm than the old R8 spindle. That new spindle will need to be modified to accept the BT30 petal gripper and that's when I'll need to purchase one (or two, one for a spare). I've been talking to the fellow in China who is putting some of these grippers up on eBay asking to consolidate the shipping and I have a price for a pair of them from him. So I'm slowly following my revised plan to get this done. You might take a look and see if there's any you can make a deal on, I seen one this morning with free shipping to most areas in the world and with little time left on it, it was at a give away price.

Bob

[Azalin]

Yup I know the grippers on ebay but prices are little high. Asking myself, does a gripper worth $150+ when a complete spindle can be purchased for $500-600? But that's just me. On the other hand, I know the gripper is the most important part of the spindle. So maybe it does worth.

Speaking of bearings, which ones would you recommend? Especially if the target speed is more than 6000. I didn't start to the solidworks design yet but the bore for the main bearings will be like 40-45mm.

Thanks Bob.

[RustedOut]

You gotta look at the complexity of the gripper petals, those aren't a cake walk to make. And a poorly made set can cause so many problems with the tooling they're holding. I got a quote for a pair for $220.00 shipped to me, so in my mind that's not bad. But you're right on the spindle, mine was $150.00 but is a bare spindle. I've looked long and hard at the skyfire BT30 spindle, but my mill's head won't accept it without a lot of work or making a new head.

My spindle requires 35mm bearings at the bottom and a single 30mm at the top, so the O.D.'s will be 72mm for the lower and 62mm for the upper. I'm going with a matched pair or twin deep ball bearings on the bottom and a deep ball on the top with a spacer between the top and bottom bearings. But I'm considering sealed bearings for the three bearings. I have some time to consider that as work is just starting on the spindle housing. I have to find someone to do the bearing bores for me as my lathe is too short in Z travel to do that, it's a 10ee with only 20" of z and the housing takes up 12" of that. Talked to a guy yesterday about doing it and he's agreeable to look at it. So next step is to get him a drawing to see if he's willing. He does quality work, but it may be too big of a job for his lathe.

Bob

[RotarySMP]

Another Option, rather than welding the Ends of bar stock together, would be to solder the bar stock completely. The solder will release durnig heat Treatment.

[Azalin]

The bearing codes are very confusing. I picked 7007 bearings but some are very high speed and some are slow. I have no idea what the letters really mean. Anyways. I'm starting to design the spindle.

[Azalin]

You can also split then with a dremel and cut off disks mounted on a mill, and a Rotary table Holding the gripper. This leaves nicely finished 1mm gaps.

Thinking about this, do you think the 1mm gaps between fingers can affect the balance at high speed?

[bhurts]

Have you seen the ball bearing gripper? There much easier to make. Not my favorite design but it's diy friendly. The haas at work uses this design and no problems after 10 years.

Ben

[Azalin]

Have you seen the ball bearing gripper? There much easier to make. Not my favorite design but it's diy friendly. The haas at work uses this design and no problems after 10 years.

Ben

Yup, that's my plan B.

[Azalin]

OK I got the new 4 jaw chuck, cut the back plate, installed the chuck. Then I get a stock of 10x10 C45 steel for the fingers. Now it's the time to open a new build thread. Thanks for all your help.

Bob I'll take your suggestion and tack weld the ends together but considering copper solder all parts together but this will mess the flat surfaces and make it hard to chuck.



Unfinished photos of the backing plate.