[miljnor]

he says commercial spindle producers have had a lot of problems with them, especially the ball bearing type. They nearly all use the finger type grippers now.

Every machine I have worked with in the past 10 years has used the ball style grippers and they have been around much longer than that. Now they might not be the best method to use (not an engineer so would hazard a guess) but they certainly work just fine. The main negatives for this style gripper that I see is that the pull stud better be made of some sturdy stuff because with only tangent contact on the balls you will develop dents fairly quickly with cheap Non-hardened material.

[pstockley]

Like you say I am sure they work once setup correctly but I think he was referring to that fact they are a bit tricky to design to work 100% reliably and not wear out prematurely.

[CNCfun&games]

pstockley,
You have done a lot of nice work here!
W. Smith

[pstockley]

If I didn't want to make an automatic tool changer I would definitely consider the ER collet route. At the moment I don't really have much at risk financially so I will go this route as a learning exercise. The TTS style setup seems to work OK so I am not worried about that.

If the design works out OK I could easily adapt it for bigger bearings and maybe a R8 or a 30 taper once I have some more experience. If someone wanted just a high-speed spindle with manual draw bar even this current design could easily be changed to fit ER25 collets.

[unterhaus]

I just got a workholding catalog from Schunk, and all of their devices use ball retention. Not quite the same thing, since they are holding chucks, but it's a data point.

[ger21]

I will use a pneumatic actuator similar to the following to press on the drawbar to release the collet and holder.

http://www.automation4less.com/store...CDQ8A250%2D050

You might want to check out Surplus Center for those.

[andy55]

Hi Group,

Does anyone have experience with the Littlemachineshop MT3 spindle ?

I'm considering buying their spindle box assembly and taking out all the gears and putting a timing belt on top.

the spindle box is at
http://www.littlemachineshop.com/pro...ProductID=1906
and is only $85

specifically, if anyone has measured runout on this spindle I'd be very interested in hearing about the results.

[Salty72]

Has there been any updates? I have just re-read this post from start to finish and all is looking REALLY PROMISING !!

[pstockley]

I am tied up on my Hardinge lathe conversion at the moment. Generally I go into the workshop a lot less during summer so I don't expect to finish this until next year.

Some things have progressed regarding my spindle design. Firstly, I picked up some 40mm ID Fafnir super precision bearings off eBay for $54. So I plan on going back to a BT30 taper design. However, I first plan on building a ER25 spindle using my 30mm bearings. This will be easier to build especially since I already have an ER25 closer nut. I plan on using this smaller spindle as an auxiliary unit on my Tormach. The aim is to learn from this design and then process to the more complicated automatic toolchange version.

[ViperTX]

andy55...stick with the R8 spindle from the same company.....yes you can strip out all the speed change gears...

[Salty72]

does anyone have any idea how the AIR Spindles work ? why are they (if infact they are) self centering friction free????

[andy55]

andy55...stick with the R8 spindle from the same company.....yes you can strip out all the speed change gears...

Hi, do you have any info/experience on the R8 compared to the MT3 ?
I am in Europe and seems that MT3 tooling has much better availability.

[bprzybyl]

In regards to pstockley's spindle,
have any decisions been made as to the top bearing? As far as bearings go, I'm using quad NSK angular bearings, but haven't found any good info on what to use for the bearing nearest the pulleys. I remember seeing in an NSK brochure the use of cylindrical bearings, but I've also seen ball bearings somewhere else. What things are important in the choice of this bearing? The angular bearings I have are ABEC 7, so does that mean they would require an ABEC 7 radial bearing? I would also assume that I would want the radial bearing to be able to acheive the same speeds as the angular ones, if not greater. I looked through this thread, and this seems to be the one part not covered.

Thanks,
Brooks

[NC Cams]

Top bearing to be used is a function of who designed and supplied it.

If NSK did the design, they'd probably spec out a PA( ) where ( ) would involve a non-published semi standard version of a ABEC 3, 5 or 7 to make it suitable with the lower ultra stiff QUAD. How they did this was a trade secret of the machine tool dept and they didn't explain it too much.

To use off the shelf, get ABEC 7 and hold end to end mounting surface concentricity as close as possible to dead nuts 0.0000 TIR.

The top will have to "float" a bit as the bottom will tend to establish axial and radial postioning under thermal growth. Probably the easiest way to do this would be an ABEC 7 (ISO P4) cylindrical - pricey but high capacity and accuracy.

An ABEC 7 ball would work but you'd have to set it up to slip in the housing and light thermal shrink on the shaft - probably w/C3 clearance. You'll get better runout with open bearing over sealed or shielded. I'd run external seal because bearing seals are not "sealed" - they have vents to relieve pressure, hence they can let liquid stuff in when they cool.

Hope this answers the question...

[Salty72]

most guys are saying that they are using ABEC 7 bearings but as this is the class of bearing can anyone give part Numbers??

[bprzybyl]

NSK 7205CTDULPA7
And thanks to NC Cams, I know what they all mean-
05- bore(25mm)
C- 15 degree contact angle
T- Retainer
DU- Duplex (2 matched bearings)
L- Light preload
PA7- Special machine tool version of Abec-7

I'll be using 4 of them in my spindle design, which will be very similar to pstockley's. Mine will have an ER20 collet as opposed to his. Aside from that, I don't think there will be many other differences. As to what orientation for the quad bearings, I still don't know enough to write down which I will do. Research, research, research...FUN!

-Brooks

[Salty72]

Well it's official.. I have just been to the boys in the machine shop and they are only to happy to machine what ever it is I want :banana: there is only one draw back....they all drink scotch!!! so it looks like 2x 1125ml bottles is what I need to buy

Oh did I say one draw back ... well its more like two they need specs and with spec come drawing I'm guessing

:withstupi unfortunateley unlike the reference [left ] Rather than being with stupid -I'm stupid, when it comes to drawings etc... so has any one done anything that allows for tool change?

I did like the graphics post early on in the tread but I have not seen anything with TOL.s and diamentions are there any out there....

ALso has anyone given any thought to extending the spindle up several inches past what would normally be considered the top, and fixing the motor so that when the z-axis moves up and down the stepper/servo does not need to lift the motor weight.
The spindle could have splines so the pulley was free to ride up and down (much like a drill press)

please all flames welcome

[Chivo]

Hi.. First, I'm sorry about my english.

I'm attaching some drawings and one assembly SAT file.

I took some ideas from the first draws of this tread and I searched some.

To make this POWER DRAWBAR, I'm trying to use the cat 40 tool holder, I read that it is the most comun and cheaper tool holder.

I want to make an Autmatic Tool Changer, spindle speed of 18.000 rpm for a (strong & fast) Wood Router.

For what I read, the easy way to clamp the tool holder is using a Drawbar preloaded. I'm using a Coil Spring "Extra Heavy Load (green one on the draw )" It has 2167 Newtons (221 kgf - 487 lbs), But it isn't enough power clanmp, no even closer. But Maybe It is enough for wood.

Also I'm using 2 angular Ball berings (couple) - precission ABEC 7.


I found a Drawbar, Model: BERG SEK 2-48 , from (http://www.transconn.com/ ) It has a Tool Clamping Force: 18,000 N (4030 lbs), Spindle Speed: 20,000 RPM but it isn't for cat 40, It is for a Tool Size: HSK A 63.

I read that Cat 40 / 50 + , They aren't good for fast spindle speeds 8k and up
, so you have to use HSK tool holder's model.
Or you can use the same Drawbar for cat 40, but using a new model of tool holder, which is call BIG-PLUS (http://www.bigkaiser.com/).

Well, I'm really an amateur, bigginer about this, so I will appreciate very much some ideas, before I can hurt my self.

V flange Female Drawbar Dimentions aren't ok. I can't find the real dimentions.
Some help with the V flange dimentions

[NC Cams]

Re: bearing sizes in ABEC 7.

Sure can.

What is the generic size you chose for the application???

What type, ball or roller???

No guarantees about capacity or viability - that's the responsibility of the spindle designer to figure out proper size based upon load/speed requirements.

[miljnor]

For what I read, the easy way to clamp the tool holder is using a Drawbar preloaded. I'm using a Coil Spring "Extra Heavy Load (green one on the draw )" It has 2167 Newtons (221 kgf - 487 lbs), But it isn't enough power clanmp, no even closer. But Maybe It is enough for wood.

I hear stuff like this allot!

Power used is a function of programing and fixturing, not of what material your cutting! If you have an easier to cut material (like wood) then you tend to feed faster so the load on the machines CAN be the same as cutting steel. Atlhough the load may be smoother with less hammering from the cutter the side loads are the same.

Personaly I run aluminum harder than steel just because my tooling is more geared for aluminum. And I don't do enough steel products to warrent buying the bling type steel tooling. And thus the loads cant be as high do to cutter strength.

So don't make the mistake of saying it will work for wood becuase its weaker. It would be better to say it will work because you are nursing/babying the machine to make it work.