[Beowulfenator]

Hi!

Let's say I have a ER20 collet with shank (shown in green). Let's say I put it into some housing (black) along with two tapered roller bearings (dark and light blue). The lower bearing rides on the shoulder of the shank.

Would it be plausible to machine a fine thread onto the shank and use some kind of nut (red) to hold the construction in place and also manage preload?

I've seen a design where there instead of a nut there is some element that is held in place with a set screw. I don't think that's a good way to regulare preload, but maybe there's some problem with machining the shank?

Thank you for your time!

[Dragonfly]

This is quite popular solution but you will need a counter nut or another way of securing the nut from loosening.
Depends on what speeds the spindle is intended to work at because roller bearings, while able to carry high axial and radial loads, are not able to run at high speeds and will heat.
Usually radial-axial ball bearing pairs are used. And if the speed is going to be high there are such bearings with pre-manufactured looseness (not sure how it's called in English). Those bearings are usually manufactured in such a manner (their inner rings) that when placed face to face and tightened together the nominal preload is achieved automatically.

[Beowulfenator]

need a counter nut or another way of securing the nut from loosening.

...

And if the speed is going to be high there are such bearings with pre-manufactured looseness

That's a great idea! Now, do you think it's possible to machine the shank? Perhaps they make it out of some super-hard stuff?

These bearings you mention... Can you point them out here?
Bearings, units and housings - SKF.com / Products / Interactive Engineering Catalogue

Thanks!

[mactec54]

Beowulfenator

Take a look at my spindle build, a different design than your one, but your bearings can be preloaded, the same way, You want to have a spacer between your bearings, & you ajust the length of this main spacer to get your preload, Make sure the ER25 has a thread on the inside you use this to lock everthing up, If you wanted to thread the shank it could be done, But the shank is around 62/65RC so quite hard to machine, but can be ground

http://www.cnczone.com/forums/cnc_wo...dle_build.html

[Beowulfenator]

Beowulfenator
Make sure the ER25 has a thread on the inside you use this to lock everthing up, If you wanted to thread the shank it could be done, But the shank is around 62/65RC so quite hard to machine, but can be ground

Thank you! I'm looking at your design, but I can't understand how it is all held in place. Perhaps you can show a drawing or an exploded view?

It seems that I will not be able to thread the shank, right?

[grg12]

You may consider using taperlock bushings to avoid threading of shank. Here: http://members.chello.at/~grzegorz12/wtf/calosc.stp is my spindle that uses DIY taperlock.

[mactec54]

grg12

A taper-lock bushing can not put the preload on the bearings

[mactec54]

Beowulfenator

The cap-screw that goes in the End of the shank,(the pulley end) pulls everything together, putting the preload on the 2 front bearings, The front 2 Bearings (Back to Back) are held into the housing by the front threaded nut, which locks the outer edges of the bearing into the housing

The shank in most cases is to hard to cut a thread on with normal tooling, but can be done, That is why I use the centre threaded hole to put the preload on the bearings,

If the threaded hole in the shank is to big, I locktite a threaded plug in there, & then rethread the plug for a smaller size cap-screw

[mactec54]

Beowulfenator

I don't make them like this now, but your design using 2 Bearings could do the same for preloading your bearings, you just need to make the spacers to suit your Bearings

[RICHARD ZASTROW]

mactech54's spindle drawing shows a typical spindle assembly.

I offer a small caution. The end surfaces MUST be perpendicular to the I.D. of the spacer and parallel to each other. If not, the bearings will try to conform with the spacer and bind. We keep ours parallel within .000050". .0001" or more caused premature bearing failure.

The rear bearing must "float" to compensate for linear heat expansion, especially in high speed applications. mactech54's drawing appears to accomplish this also?

Dick Z

[Beowulfenator]

Beowulfenator
The shank in most cases is to hard to cut a thread on with normal tooling, but can be done, That is why I use the centre threaded hole to put the preload on the bearings

Oh, so your shank actually comes with a threaded hole in the center!

[mactec54]

Beowulfenator

Yes most have the thread inside, so just make sure when you buy them, look at the specs,to make sure they have the thread, or you will have to thread the outside, which is not easy on these hardened shafts

[Beowulfenator]

Beowulfenator
Yes most have the thread inside, so just make sure when you buy them, look at the specs,to make sure they have the thread, or you will have to thread the outside, which is not easy on these hardened shafts

Darn. I already ordered this one:
ER20 20MM 150MM LONG SHANK COLLET CHUCK CNC MILLING LATHE TOOL & WORKHOLDING F67 | eBay

Doesn't say it has a hole.

[mactec54]

RICHARD ZASTROW

All my spindle parts are Ground 0.0 face to face, This is one of my older spindle builds, I do them different from what is shown in the drawing, there are also some parts not shown in the drawing to do with the floating top bearing, but I don't use this type of top floating bearing setup anymore

This was just to show Beowulfenator how the Bearings can be Preloaded, with a central cap-screw

[mactec54]

Beowulfenator

Just email CTC tools & ask which one has the thread inside, they have both I have used there's before, They used to show it in there spec's

[Beowulfenator]

Beowulfenator

Just email CTC tools & ask which one has the thread inside, they have both I have used there's before, They used to show it in there spec's

You're right! They haven't shipped it yet so maybe there's still a chance. Thank you!

[mactec54]

Beowulfenator

Here is another one to look at, but email to ask about the inside thread

New C20 ER20 150L Extension Milling collet chuck holder | eBay

[Beowulfenator]

Beowulfenator

Here is another one to look at, but email to ask about the inside thread

New C20 ER20 150L Extension Milling collet chuck holder | eBay

Great success!

The one that I originally ordered has an M10 threaded hole on its end!

[Dragonfly]

That's a great idea! Now, do you think it's possible to machine the shank? Perhaps they make it out of some super-hard stuff?

These bearings you mention... Can you point them out here?
Bearings, units and housings - SKF.com / Products / Interactive Engineering Catalogue

Thanks!

I see a lot of people have given their advice but about the bearings I think these are the type I had in view
Single row angular contact ball bearings - SKF.com / Products / Interactive Engineering Catalogue/Bearings, units and housings

As for the shank I think the best approach is to buy one with suitable diameter and desired collet holder ready made.

[RICHARD ZASTROW]

machtech54, my cautions were for Beowolfenator's benefit. You already are aware of the things I cautioned about. Just trying to be helpful.LOL

Dick Z