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Pull stud installation question

Chris Hall

Cast Iron
Joined
Feb 28, 2013
Location
Greenfield, MA
I purchased an iCarbide CAT40 tool holder. It has ⅝"-11" thread on top (female) so I needed a pull stud to fit my Riken mill. I bought a pull stud from F. Singer, which has the Deckel buttress thread on top. When the pull stud arrived, I went to fit the 2 parts together and while the ⅝"-11" male thread on the pull stud will go in cleanly, the machined shoulder above the thread does not enter - it seems to be an interference fit. I emailed F. Singer about this, but they are slow to respond and so far I haven't received an answer. Does anyone know how these 2 parts are supposed to fit together? Should I crank the pull stud in and force the interference fit together? Or should I have some machining done to make the fit a slip fit? Either solution makes sense to me, but I figured that someone here would know the actual answer. Hopefully Singer will reply definitively within the next 24 hours.
 
It sounds like a bad idea to have an interference fit, because it will expand the upper end of the taper and cause a bad fit with the machine's spindle taper.
 
shouldn't be an interference fit, slip is enough

I'm not sure about the spindle taper in Riken mill, but usually the very top (narrow) end of the taper is relieved in the spindle taper, so even if there is small amount of expansion in that area on the tool taper, it might not cause any problems, and you can always blue it up and check for proper contact
 
Matt, what feature determines the final depth of the pull stud? Is it the end of the 11tpi thread on the stud, or the stud bottoming in the threaded hole or something else? In metric pull studs I am pretty sure there is a shoulder that seats. Cheers, Bruce


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shouldn't be an interference fit, slip is enough

I'm not sure about the spindle taper in Riken mill, but usually the very top (narrow) end of the taper is relieved in the spindle taper, so even if there is small amount of expansion in that area on the tool taper, it might not cause any problems, and you can always blue it up and check for proper contact

Riken takes standard Deckel 40 taper
 
Does not enter at all or does not fully enter? Adapters that I've installed look like the image below.

View attachment 281497

Does not appear to enter at all, though I have not measured anything yet. According to Glacern's site the machined shoulder above the machined/ground shoulder above the pull stud's ⅝"-11 threaded portion is supposed to measure 0.636" in diameter and that's the only solid info I can find so far. I'll measure Singer's part later today Would like to find out what the entry hole size in the tool holder is supposed to be but I don't have a bore gauge or to/gage pin or similar to check mine directly
 
Matt, what feature determines the final depth of the pull stud? Is it the end of the 11tpi thread on the stud, or the stud bottoming in the threaded hole or something else? In metric pull studs I am pretty sure there is a shoulder that seats. Cheers, Bruce

The diameter/ shoulder between the two threads on the adapter bottoms out in the bore. The adapter (shoulder) does enter the bore but the bore (counterbore really) is not very deep.
 
Some points to consider:
First a point of clarification.
In the machine community at large, a pull stud is understood to be an adapter that is made to accept the gripper fingers from a power draw bar...ie CNC machine.
Threaded at one end where it threads into the tool holder and with a formed end opposite that conforms to the gripper requirements for shape and length...these "studs" are machine specific.

What is being discussed here is a threaded adapter to convert a CAT or BT style tool holder to accept female Deckel style threaded draw bar...threaded one end to fit the holder and
threaded opposite with the Deckel draw bar thread (20x2.0 buttress)

If you compare the gauge length of a CAT 40 tool holder to the gauge length of a factory Deckel direct mounting collet what you get is a difference of .950" (+- 24mm)

That should be the length of the threaded adapter when installed on a CAT 40 holder as measured from the end of the taper (small end) to the end of the thread, give or take.

Further the Deckel collet has a bit under 24mm of thread, so would surmise that you need to be able to thread the draw bar the full length (24mm) to be sure that things will not bottom on the adapter stud.
Of course the above info assumes that the machine was built to the Deckel standard .
Cheers Ross
 
Okay I, measured theSinger Pull stud shoulder and at the ICarbideCAT40 tool holder's insertion hole diameter's: the pull stud shoulder diameter is 0.6715", and the toolholder insertion hole diameter is 0.6065"Too much interference obviously, but how much would be ideal if any?
 
Allow some clearance. Threads may not be exactly concentric with the counter bore...It does not matter if it is slightly loose here.
On a long taper like a CAT or BT the taper does all the alignment, unlike the R8 collet where the end of the collet has a straight section that is part of the collet
alignment mechanism.
Funny that your counterbore is not sized at least to the major diameter of the internal thread......
My "Lyndex" CAT40 holders measure .640" on the counter bore.
Cheers Ross
 
This got me curious so I went back and looked at different holders and the adapters. I have made adapters and I have bought some from Singer. I've never paid that much attention to them- when I installed them they seemed to work so why investigate?

I believe Singer's Cat40 (5/8-11) adapters are actually made incorrectly. The shoulder that Chris notes (0.671" diameter) is close to the measurement on the shoulders on the adapters I have purchased from Singer (mine measure ~0.667"). This measurement corresponds to the counterbore on BT40 holders not Cat40 holders. This makes some sense as Singer would be more familiar with the BT40 tooling and would more likely have this readily available. Assuming Ross' measurements are correct the Singer adapter sits about 0.2" or more high. They still seem to work fine.

Ross' comments about threads not being concentric to the counterbore/ taper and still allowing the holder to seat correctly I have not found to be true. One of the adapters I made was off and this showed up in excessive runout of the holder. I never got around to measuring how far out the threaded portions were in relation to each other so I do not have any useful numbers to quote.
 
Wondering how you verified that it was the thread that caused the run out issues, and not just a poorly made holder?
Hard for me to believe that with the full contact of the taper and the distance the actual "pull" comes from (length of the draw bar) and the clearance that exists between the draw bar and the holder threads that you could appreciably affect the accuracy of the holder/tool unless the thread was way off center, and the draw bar fit the thread quite well.
Was this a direct mounting split collet or a solid tool holder?

Cheers Ross
 
Wondering how you verified that it was the thread that caused the run out issues, and not just a poorly made holder?
Hard for me to believe that with the full contact of the taper and the distance the actual "pull" comes from (length of the draw bar) and the clearance that exists between the draw bar and the holder threads that you could appreciably affect the accuracy of the holder/tool unless the thread was way off center, and the draw bar fit the thread quite well.
Was this a direct mounting split collet or a solid tool holder?

Cheers Ross

Hopefully these 5 pictures will provide clarity:

P3120071.jpg
Not a poorly made holder by any stretch:
P3120072.jpg

Pull stud shoulder diameter above the 5/8"x 11 threaded portion:

P3120068 2.jpg

The zone of interference:
P3120067 2.jpg
 
Wondering how you verified that it was the thread that caused the run out issues, and not just a poorly made holder?
Hard for me to believe that with the full contact of the taper and the distance the actual "pull" comes from (length of the draw bar) and the clearance that exists between the draw bar and the holder threads that you could appreciably affect the accuracy of the holder/tool unless the thread was way off center, and the draw bar fit the thread quite well.
Was this a direct mounting split collet or a solid tool holder?

Cheers Ross

Ross,
This was some years back...
It was not a split collet but a solid holder or drill chuck. From what I remember I noticed a problem, swapped one of the adapters I had made with a Singer adapter and the problem went away. I freely admit that I did not fully investigate.
 
Hey guys,

this topic is directly related to what I am planning to do on my scope, but also interests me both as general topic of interest and, more directly, since I've always made S20x2 adapters for any tool that needed it, without too much thought.

I am, by no means, an experienced machinist, nor to I work at tolerances like many of the guys here.
Given this, I think the drawbar stud is a low precision part. I think the dimensions of the 40 taper (or even MT4) are hefty enough to provide centering without being too vulnerable to drawbar stud runout.
Also, as I have learned here, one of the advantages of the Buttress thread is that, at tightening, radial forces are minimal (compared to a triangular thread) for runout reasons exactly (much more important for 355E collets than 40 taper, but still).
And then, there is the drawbar length. It's long and slim, can't think it can bend something out of running true.

All these might be applicable to the degree of precision I am involved with and completely useless for real accurate work, which is something I would really be interested in learning!

BR,
Thanos
 
Seems we have some empirical evidence to suggest that having a "true" draw bar connection is important and that a poorly made adapter stud can lead to issues with
tool run out.
Suggest that here being its a "centering" scope one would strive to make the draw bar connection accurate and true.

On that pull stud, i would internally thread an emergency collet by single pointing on the lathe to hold the original thread.
Having previously made the new thread blank (unfinished on the OD, but internally threaded and made to length).

Hold the stud in the collet gripping on the thread form (not just the OD) Turn and thread to match the Iinternal thread of your blank..then while the part is still in the collet, thread the blank on to the
modified pull stud, using Loctite .
Finish the OD of the blank and thread to fit the draw bar (20x2.0).......

Return the modified pull stud/threaded adapter to the centering scope using a spot of Loctite....

Cheers Ross
 
Seems we have some empirical evidence to suggest that having a "true" draw bar connection is important and that a poorly made adapter stud can lead to issues with
tool run out.
Suggest that here being its a "centering" scope one would strive to make the draw bar connection accurate and true.

On that pull stud, i would internally thread an emergency collet by single pointing on the lathe to hold the original thread.
Having previously made the new thread blank (unfinished on the OD, but internally threaded and made to length).

Hold the stud in the collet gripping on the thread form (not just the OD) Turn and thread to match the Iinternal thread of your blank..then while the part is still in the collet, thread the blank on to the
modified pull stud, using Loctite .
Finish the OD of the blank and thread to fit the draw bar (20x2.0).......

Return the modified pull stud/threaded adapter to the centering scope using a spot of Loctite....

Cheers Ross

Hey Ross,

copying this to the other thread (https://www.practicalmachinist.com/...ing-microscope-308892/index2.html#post3506237) and replying there so as not to hi-jack this one.

BR,
Thanos
 
Some points to consider:
First a point of clarification.
In the machine community at large, a pull stud is understood to be an adapter that is made to accept the gripper fingers from a power draw bar...ie CNC machine.
Threaded at one end where it threads into the tool holder and with a formed end opposite that conforms to the gripper requirements for shape and length...these "studs" are machine specific.

What is being discussed here is a threaded adapter to convert a CAT or BT style tool holder to accept female Deckel style threaded draw bar...threaded one end to fit the holder and
threaded opposite with the Deckel draw bar thread (20x2.0 buttress)

If you compare the gauge length of a CAT 40 tool holder to the gauge length of a factory Deckel direct mounting collet what you get is a difference of .950" (+- 24mm)That should be the length of the threaded adapter when installed on a CAT 40 holder as measured from the end of the taper (small end) to the end of the thread, give or take.

Helpful info-thanks!I have a couple of Deckel close collets on hand, so I can check these numbers out for myself and confirm, then get a machinist friend with a lathe to have at it with the components I have to work with

That should be the length of the threaded adapter when installed on a CAT 40 holder as measured from the end of the taper (small end) to the end of the thread, give or take.

Further the Deckel collet has a bit under 24mm of thread, so would surmise that you need to be able to thread the draw bar the full length (24mm) to be sure that things will not bottom on the adapter stud.
Of course the above info assumes that the machine was built to the Deckel standard.

Cheers Ross

Thanks! My Riken comes with a selection of Riken-made toolholders, along with a Kuroda boring head, centering microscope, Nikken milling chuck, etc., all of which which appear to have the same Deckel standard S20x2 pull stud incorporated. Call me crazy, but if I expect that if Riken copied that unique Deckel toolholder standard, which many clones of FP1/FP2 did not bother with, then it is going to conform precisely to the Deckel standard, Similarly, for Kuroda or Nikken to make the boring head and milling chuck different in some way from the Deckel standard would make no sense

A question remains though about the fit of the parts I have acquired: How would you specify the fit in this case between the ICarbide CAT40 holder and the Singer pull stud? What degree of slip/ slop/ interference is ideal do y'all think?? I've got some meat to play with at this stage, so I have some options. A few here have already expressed reservations about an interference fit - but what if it was only a slight interference, on the order of 0.001" or so? What about the idea of making the interface slightly conical so the stud and holder would tighten together as they were assembled? Would you use some type of thread locking compound between the parts if a slip fit was called for?
 
Any CAT40 pull stud I ever dealt with locates axially against a shoulder at the top end of the toolholder and radially via the threads. If anything, the neck at the top of the pullstud threads is undercut to reduce stress concentration, and there is no cylindrical locating feature. The 7:24 taper takes care of locating the toolholder axially and radially with respect to the machine spindle no matter any small lateral offsets of the pullstud. It is important to torque the pullstud correctly (see MariTool's site for recommendations). If it is under-torqued, there is risk that the pullstud threads will fail due to cyclic loading (fatigue), and if over-torqued, there is risk of expanding the top of the taper so that it no longer fits the spindle taper correctly.
 








 
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