What's new
What's new

Pull stud conversion - possible?

Zahnrad Kopf

Diamond
Joined
Apr 5, 2010
Location
Tropic of Milwaukee
I'm curious - Would there be enough room inside a Bridgeport type 30 taper spindle to put some sort of pull stud system inside it? Anyone got a link to a drawing of Bridgeport's QC30 spindle internals?
 
the quick change spindles i've seen are solid and not bored for a drawbar......

i think it would be pretty easy to grind an R8 spindle for the 30 size tool holders, add the drive dogs to the nose and adapt some kind of pull stud mechanism.
 
The gripper that grips the pull stud is either one where there are steel balls that are held in a cage and pulled into a taper socket to engage on the pull stud or a multi finger gripper that grips on the pull stud. See pics.

Look up patent 4,915,553 for more detail or there's a nicely documented project here:
New_Machine

or another patent here:

Clamping apparatus for a spindle of a machine tool

No major engineering hurdles, but a fair amount of work.

Chris
 

Attachments

  • mac_p.jpg
    mac_p.jpg
    18.7 KB · Views: 14,448
  • 04915553-002.jpg
    04915553-002.jpg
    99.8 KB · Views: 6,964
the quick change spindles i've seen are solid and not bored for a drawbar...... i think it would be pretty easy to grind an R8 spindle for the 30 size tool holders, add the drive dogs to the nose and adapt some kind of pull stud mechanism.

I might not have been clear... I already have an Erickson QC30 spindle... And it is bored. I already use a drawbar with NMTB30 and QC30 holders. What I'm curious about is if the QC30 spindle might be adapted to a pull stud type system or retention, with my long view relating to making a tool changer for the machine.
 
The gripper that grips the pull stud is either one where there are steel balls that are held in a cage and pulled into a taper socket to engage on the pull stud or a multi finger gripper that grips on the pull stud. See pics. <snippage> No major engineering hurdles, but a fair amount of work. Chris

Thanks, Chris. Good stuff there. The one with the balls if very similar to what I have in mind. It all looks very easily able to be done. At this point, I just need to find out what the inside of a Bridgeport QC30 spindle's geometry looks like, to see if there's a shoulder in a suitable area for me to utilize for the gripper.

Thanks.
 
Just went and shined a light on a mirror and looked up inside the spindle. Looks like it continues the straight section of the holders for another .4" - .5". So, sadly, it doesn't look like there's room for a gripper. The good news is that ( if I'm correct ) it appears to be a fairly trivial thing to put one in there. What I'm thinking is to drop the spindle cartridge, put it in a lathe, and put a larger diameter just behind the holder's profile that would accommodate a gripper and pull stud.

Thoughts? Experiences? Warnings? Finger pointing and giggling?
 
nice to know that there are hollow quick change spindles:)

i say just hold an R8 collet next to your 30 taper holders and you'll see that there is a lot of metal you can remove inside the spindle to make room for the ball stud and everything else.

i would like to do this with a long stroke air cylinder to actuate the drawbar no matter where the quill is set.... but then how much force can you put on it before overriding the quill lock? as goofy as the mach-1 system of bumping the quill up to change tools looks it might just be as good as it gets for a bridgeport.

Quick change tooling system for Bridgeport style milling machines, R8 kneemills, bed mills
 
Why are you using a draw bar on the qc 30 holders not the spindles special qc 30 nut?

How are you going to make the release mechanism ride the quill strokes travel?

As to qc 30 spindles being solid. From what i have read that only applies to some of the cnc fixed head bridgeports. Most normall manual bridgeports i have encountered - read about with a qc 30 spindle are indeed hollow for a draw bar.
 
Why are you using a draw bar on the qc 30 holders not the spindles special qc 30 nut?
Because I'm also using NTMB holders for their better availability and price point.

How are you going to make the release mechanism ride the quill strokes travel?
My thinking is to simply make it work only at the home position.

As to qc 30 spindles being solid. From what i have read that only applies to some of the cnc fixed head bridgeports. Most normall manual bridgeports i have encountered - read about with a qc 30 spindle are indeed hollow for a draw bar.
Yes, it's amazing how people simply won't believe you even after you tell them. It's more probable that you're mistaken because they never made any with a through hole. :rolleyes5:
 
Sounds good. Normally i just buy NMTB holders, run a ring of weld around the grove and machine them back to qc 30 nut flange spec. Should realy run anouther bead around the back so they eject, but nomaly i just give them a tap with my c spanner :-)

First one i did i was concened the weld heat would distort the holder, but a nice short hot pulse on the tig and plenty of filler and i have yet to get any measurable change in run out, done 3 to date all er 32 collet chucks. There from a certain Hong Kong ebayer. Quality is fair but price is brilliant :-) Originally i was planning on regrinding the collet taper after welding - machining, but its proved unnecessary to date.
 
Hi Zahnrad
Did you ever try this yourself? I just completed one myself a couple of weeks ago. Seems to work quite well. I may finesse the spring rate but apart from that it came out as I expected. Short answer is - it seems to be doable.
There's a short thread I posted here: Quick change NMTB system for milling machine | Model Engineer
Muzzer

Muzzer - No. I had draw some rough sketches of a split collet type of puller, but I never did actually get to the point of making parts. Machine and I were never really idle enough at the same times. You, on the other hand have done quite a wonderful job of it. Well done. Very nice execution of it. Thank you for posting it. You should post it here, too so the pics will be here for others in case they can't see them at the other site for whatever reason. Well done, Sir.
 








 
Back
Top