[Azalin]

The square fingers.

[RustedOut]

Looks and sounds like you're off to a good start. You'll find lots of uses for a 4 jaw chuck in the future, so it was a good investment. One suggestion on the new gripper, I found that the small springs used in oil seals a good candidate for the springs on the top end of the grippers. They are almost continuously wound. I tried making my own, but for a few bucks a guy can get the seals and remove the springs. And one other suggestion, make a couple sets of the fingers while you got things set up. They wear out I've read.

Bob

[Azalin]

Thanks Bob.

I know I'm a horrible welder. But It's going well for now.

[RotarySMP]

Good start Azalin,

7007 defines the bearing size, the rest define everything like cage material, pressure angle, accuracy, tolerances etc.

For example:

FAG B7007-C-T-P4S-DUL
C Pressure angle 15°
T Phenolic cage
P4S Tolerance P4S
DUL Provided as pair (2 Bearings), Ground for light preload.

[Azalin]

Thanks Mark. Lots to learn for me.

[RustedOut]

Yep, you're off to a good start. Must have a mig welder, I tig weld nearly everything and gas weld what isn't tigged. My mig collects dust, but it used to be the only welder I had, so I remember those days. Just not fondly.

On bearings, I'm considering using a 5207ZZ on the lower end of my spindle, which is a double row angular contact double shielded bearing. But it's good for only up to 7000 rpm and I read that you want to run faster than that. I'm considering it due to the fact that I can then just install a spacer between the lower bearing and top bearing and not worry that much about preload. And since I'm not that smart about that science, it takes the gamble away for me...I think.

But that requires me to make a new spindle housing. I have the cast iron for that now and am working on the model/drawing for it as well as the changes I need to make to the spindle for the gripper. Also designing a new lower bearing retainer that screws in like on a Bridgeport mill. The top bearing will float in it's bore to account for expansion from heat in the spindle.

Bob

[Azalin]

Thanks Bob.

Very interesting that everyone who builds a BT30 spindle prefer 35mm ID bearings for the lower end. Only one person (a cnczone member) used 50mm ID bearings.I am considering 7008 A or B bearings. 40x68x15mm. 40mm ID to move the spindle shaft little more upward for better rigidity and 68mm for a smaller cage (no need for a huge spindle). Of course my opinion is just in theory and I may be wrong about the rigidity.

I see you read my other thread about bearings. Forget about what I've said. I've never used a spindle that fast and probably never will. So 6-8k RPM is fine

[RotarySMP]

I am also working on making a BT30 spindle. I bought a pair of FAG B7210/E/T/P4S/UL (cheaply) for the lower, which I am using with a NU208 at the top.

If you are still flexible with the design, Christian Knapp was selling some really nice bearings... That is where I got mine.

Peters CNCECKE

MArk

[RustedOut]

I'm in a different position than you, I'm retro fitting an existing mill that now has an R8 spindle with a soon to be modified NMTB30 into a BT30 spindle. So the I.D. of the bearings has been dictated to me already. My target has been to run up to 6000 rpm, so choices have been made based on that number. That keeps my choice of tool holders real simple as I won't required balanced holders.

This has been a long journey for me on the conversion, but I fell into milling a lot of steel and tool steel for a few years with an occasional piece of aluminum or brass/bronze. Throw in some acetal once in a while and the need for speed really was't there. But the desire for a different type of tool holder was. I wanted out of the R8 setup. So it became BT30 spindle first and faster second. I have a very nice tool pre setter set up for BT30 tooling now and a host of BT30 tool holders, but not all I want to have. Once I have all the tool holders, I'll be ready to swap spindles.

I work pretty slow, especially when I don't know exactly what I'm doing or making. And I hate starting something when I don't know what I'm doing or making. So I spend lots of time designing, but not everything I design sees the light of day. Like you, it's all theory until it's built and tested. I worked part of this last spring and the whole summer on a new metal shaping machine design and build, then tested a pair of them for quite a while. Hopefully that all is going to wrap up around the first of the year and I can go back to work on the mill spindle upgrade. And follow that with new electronics, then the new 3hp motor and vfd for the mill. But I got some hard decisions to make before the new motor goes on it.

Bob

[Azalin]

@RotarySMP
I registered to the forum to see the items but unfortunately they don't have 35-40 ID range bearings.

[RotarySMP]

He has 45mm ID 7009/ACDGB/P4A. Too big? I choose the 50mm 7210, because I wanted the bearings as Close to the nose as possible for stiffness.

Bob, Azalin, I think the three off us Need to post some drawings and or Pictures so we can see where we are at.

Mark

[RustedOut]

Mark,

Drawings of which part of it? I'm currently working on the internal shape of the spindle in my 3D model to agree with the BT30 drawing I got off of the finger gripper Chinese sellers ad. There are a couple different version, one is called an external thread gripper and one is an internal thread gripper, and they are slightly different. I'm working off of the external thread gripper drawing. It leaves me with a thicker wall on the spindle. Like I mentioned before, I'm still leaning toward just buying the gripper from the Chinese seller. But either way, I have to modify my spindle.

Bob

[Azalin]

Bob do you have a cad model of the gripper?

[mactec54]

Yep, you're off to a good start. Must have a mig welder, I tig weld nearly everything and gas weld what isn't tigged. My mig collects dust, but it used to be the only welder I had, so I remember those days. Just not fondly.

On bearings, I'm considering using a 5207ZZ on the lower end of my spindle, which is a double row angular contact double shielded bearing. But it's good for only up to 7000 rpm and I read that you want to run faster than that. I'm considering it due to the fact that I can then just install a spacer between the lower bearing and top bearing and not worry that much about preload. And since I'm not that smart about that science, it takes the gamble away for me...I think.

But that requires me to make a new spindle housing. I have the cast iron for that now and am working on the model/drawing for it as well as the changes I need to make to the spindle for the gripper. Also designing a new lower bearing retainer that screws in like on a Bridgeport mill. The top bearing will float in it's bore to account for expansion from heat in the spindle.

Bob

You would only use these Bearing for a low quality inexpensive spindle,if that's your goal, then get a quality Bearing as they will have less running clearance inside the Bearing, if you put a belleville washer under the top bearing this will keep some tension/load on the Bearing, no more than 4 lbs, may need less

[RustedOut]

Not yet, just the drawing from the Chinese vendor. I just finished the assembly of the housing, spindle and bearings and a drawing with a section view, so I added that to the spindle and housing detail drawings so I can look for problems. The BT30 gauge line is a moving target for me right now and I need to determine where it's at relative to the end of my spindle so I can finish the internals of the spindle in the gripper area. At that point, I intend to start on the actual gripper from this drawing along with the bearing spacer and the bearing retainer.

But here's the drawing from the Chinese.

Bob

Attachment 300980

[RustedOut]

You would only use these Bearing for a low quality inexpensive spindle,

I guess I'm not that clear on what makes this bearing a lower quality than a pair of standard angular contact bearings other than maybe less balls in it than in two bearings. But understand I'm a rank novice at specing out bearings for a mill, so things not being clear to me is justifiable.

What's in the mill right now is two tapered roller bearings, one at the top and one at the bottom of the spindle. And I understand those will handle way more loading than the double row bearing will in each direction. But they aren't rated for the higher rpm I'm looking for and they don't handle thermal expansion of the spindle much at all as they are currently installed. And I run the mill long enough in sessions that thermal expansion is an issue.

I've looked at a matched pair of angular contact bearings and the cost is up there. Cost isn't driving this project, but it is something I pay attention to. The bigger thing for me is the preload. Did I mention I'm stupid on that subject? And extended reading on the subject isn't clearing the air much on it. I have used belleville washers on the angular contact bearings on my X, Y and Z ballscrews and that worked out, but I'm not that sure how I'd approach that in my spindle. If I could get my arms around the preload issue in deciding which pair of bearings to buy and how to measure it at installation, I think I'd be fine with that direction. As is currently, I'm not sure on either of those.

But my goal has been to use either a pair of angular contact bearings on the bottom of the spindle or the double row angular contact bearing in lieu of them. Then a spacer up to the top single ball bearing that will float in the housing. The lower bearing(s) will be held in with a flat retainer screwing into the lower end of the housing pressing them against a shoulder in the housing. If the preload on the two bearings is easy to accomplish, I'm all in, but about all I would be able to measure at the point of final installations would be torque on the spindle nut.

Bob

[mactec54]

I guess I'm not that clear on what makes this bearing a lower quality than a pair of standard angular contact bearings other than maybe less balls in it than in two bearings. But understand I'm a rank novice at spec’ing out bearings for a mill, so things not being clear to me is justifiable.

They have clearance and are nonadjustable, so you can't add a Preload to them, so the clearance of up to .002” is normal for the poor quality Bearings in this style, a good quality one they can be if you are lucky have from .0005” to .0009” clearance

What's in the mill right now is two tapered roller bearings, one at the top and one at the bottom of the spindle. And I understand those will handle way more loading than the double row bearing will in each direction. But they aren't rated for the higher rpm I'm looking for and they don't handle thermal expansion of the spindle much at all as they are currently installed. And I run the mill long enough in sessions that thermal expansion is an issue.

Yes these spindles with the design the way they are, is a very poor design, but they get the job done for a lot of users

But my goal has been to use either a pair of angular contact bearings on the bottom of the spindle or the double row angular contact bearing in lieu of them. Then a spacer up to the top single ball bearing that will float in the housing. The lower bearing(s) will be held in with a flat retainer screwing into the lower end of the housing pressing them against a shoulder in the housing. If the preload on the two bearings is easy to accomplish, I'm all in, but about all I would be able to measure at the point of final installations would be torque on the spindle nut.

If you use 2 AC Bearings in the front they would be installed Back to Back and you could have 2 spacers between for the preload, if these Bearings are not a matched pair, then you can adjust one of the spacers to get your preload

Yes your locking ring in the front will do for the outside of the bearings, then you need a nut behind the Bearings, or another spacer top Bearing and a preload nut behind it, see attached, this is a smaller spindle build but the same principals apply

http://www.cnczone.com/forums/cnc-wo...dle-build.html

[RustedOut]

My original plan, sometime back, was two duplex 15º AC bearings in a back to back configuration with no spacers between them. So they would be purchased in a matched set. Spindle presses tight to the bottom AC bearing and the two AC bearings are pressed into my housing tight to a shoulder in the lower end of the housing. Then the screw in retainer is installed to hold them in a fixed location. At the top of the spindle, 8" up, there will be a deep groove ball bearing with the inner race sitting on top of a spacer that sits on the inner race of the top AC bearing. On top of that single bearing I have a tabbed lock washer and a spindle nut. The outer race of the top bearing is free to float in the housing.

But as I mentioned, I read a couple days ago that a double row AC bearing could replace both the single AC bearings and give me results similar to the two singles. About the best I've found is ABEC-3 bearings in a double row, where as the singles in matched sets are ABEC-7's. Hence the large price difference. That's what got me to thinking and reading a bit more on the double row bearing. But like I said, that was a couple days ago that my thinking started on that choice and why I mentioned it. But to be honest, I couldn't recite the difference between the two classes of bearings, only knowing the -7 is a higher precision than the -3. And so far I've not found much info on comparing the two choices, single row vs double row, other than it could be considered. So not much to go on. On the other side of that is choosing the outer diameter of the AC bearings, with my choices being 72mm, 62mm and 55mm. So there's lots of things to study on and come up with answers for. I'm leaning to the 72mm in a matched set if the double row isn't up to the job.

Didn't have much chance to browse your build on the router spindle, but what I glanced at it looks like you did an admirable job on it. I'll try to take a closer look at it tomorrow.

Thanks for the advise
Bob

[G59]

I know this will prolly stir up some s***, but why are you even bothering making 4 individual petals????
Use a piece of round stock, detempered spring steel, drill and shape the inside bore, then do the outside profile, then cut slots with dremel mounted in toolpost, then sand and polish.
Then heat treat back to spring, and you'll see why they were originally called petals as they will slightly expand/grow just like a flower, slightly outwards.
Of course before all this you would of already turned and threaded the opposite end so you could thread a pull rod on it( you know, the one the Belleville washers slip on).
This is how I've done it and kind of wish I was home to show you.
The advantage is it keeps good balance, is one piece with no springs or other loose parts, and is relatively easy to make.
Just my thoughts, so go easy experts.

[RotarySMP]

Here is a drawing of my spindle plan.The Bore is not finished, as I have not yet decided between petal or ball gripper.

Mark