Small spindle head

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And whilst I am planning to loctite rear bearing, I don't think I will need it for the front one.

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The rear bearing should float (or at least not be too tight) to avoid stress from thermal expansion differences between spindle and casing.

BTW interesting article on Bob Warfield's site about using standard deep groove bearing in a spindle:(scroll down a bit)
http://www.cnccookbook.com/CCMillBeltDrive.html

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And this is from a bearing expert:
[ame="http://www.practicalmachinist.com/vb/showpost.php?p=1065036&postcount=4"]Practical Machinist - Largest Manufacturing Technology Forum on the Web - View Single Post - Tapered roller vs angular contact ball bearings[/ame]

[ame="http://www.practicalmachinist.com/vb/showpost.php?p=1065158&postcount=10"]Practical Machinist - Largest Manufacturing Technology Forum on the Web - View Single Post - Tapered roller vs angular contact ball bearings[/ame]

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Originally Posted by BillTodd

The rear bearing should float ...

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That was my original plan and I have turned the housing with sliding fit for the rear bearing (as opposed to front one, which is interference fit).
I was considering using Loctite on rear bearing after assy to keep things "solid" as I didn't expect the spindle to heat appreciably at my target max 5k rpm. But I am probably running in circles, changing my ideas every five minutes :wink: - so I will stick with original idea (rear bearing floating) and see how it works.

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Originally Posted by BillTodd

...BTW interesting article on Bob Warfield's site about using standard deep groove bearing in a spindle:(scroll down a bit)
http://www.cnccookbook.com/CCMillBeltDrive.html...

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Yes, this is in my favourites,

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Originally Posted by BillTodd

...And this is from a bearing expert:
Practical Machinist - Largest Manufacturing Technology Forum on the Web - View Single Post - Tapered roller vs angular contact ball bearings

Practical Machinist - Largest Manufacturing Technology Forum on the Web - View Single Post - Tapered roller vs angular contact ball bearings

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Thanks for the links!

Ah. so you dont need such tight tolerances at low rpm then?

That would also explain how the other spindles I have work. Couldnt work out where the tensioning nut was :smile:

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Originally Posted by Ross77

Ah. so you dont need such tight tolerances at low rpm then?...:smile:

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Didn't quite say this :tongue:
It's a combination of target (comparatively low) rpm and light duty, that makes me think I can get away with a simplified design.

BTW, you have also asked:

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...I'm interested to see what you are going to drive it with?...

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Didn't give much thought yet. Definitely nothing fancy until I am convinced that I can make it work OK.
For the moment I have (don't laugh) sewing m/c motor and that will do for the testing.

Sorry it was more of a question than a statement, Im still learning.

dont think I can laugh at the sewing machine motor, I'm one of those fools converting a pillar drill to a cnc mill :heehee:

Before continuing with the spindle I needed to take care of my DTI.
Up until now it was all a bit Heath-Robinson and this was reflected in "variable" :heehee: results when it came to taper turning.
So first thing was to make a bracket for DTI, which would allow fixing of the clock directly to QCTP:

http://lh5.ggpht.com/_ozT1G3WqXg4/Sx...0/s800/002.jpg

While at it, I have also checked my lathe (Prazimat from the old DDR)

My usual clock (with 0.01mm resolution) detected hardly any movement, so I used my new clock from Draper (0.001mm resolution):

http://lh3.ggpht.com/_ozT1G3WqXg4/Sx...I/s800/003.jpg

Prazimat uses DIN55027 spindle head, size No3 and one can get chucks with this fitting on the back,
but they are rather expensive :redface:, so mine are all with usual backplate arrangement.

The reading on my Draper DTI was +/- 0.0015mm (total movement of 0.003mm) and just to check it I have tried my best DTI (with 0.0001" resolution):

http://lh4.ggpht.com/_ozT1G3WqXg4/Sx...U/s800/004.jpg

The reading was below one division, roughly about +/- 0.00005" - 0.00008", with the total movement of about 0.00015

Now, the only thing I still need before setting the topslide with the DTI, is the straight probe for the front (instead of the usual ball-nose)
to overcome my usual difficulty of setting the clock exactly at the centre (usually ending with the taper not exactly replicating the original :naughty:)
Chris

Hi Bambuko
Thanks for your post it appears to anser one of my long running questions as to what type fixing my lathe has, it looks very similar to the one you have although my one is chinese as the Sieg C6.
I obtained a back plate for a C6 which fits but have had no luck in sourcing another.
I will check the measurements for the Din 55027 fitting now that I have them.
Peter

You are welcome Peter,
but I doubt that your Chinese lathe is using German spindle.
It's more likely American spindle?
Have a look at Lathe Spindle Nose & Backplate Fittings at lathes.co.uk
Chris

later edit:
It would appear (from this web page) that C6 has copied some aspects of DIN short taper spindle, but missed the most important ie "taper".
In which case it looks like it is "Sieg special" and it does not conform to any norms?

latest update:
Finished tip for DTI to be used in clocking the tapers.
Here being set up vertically:

http://lh4.ggpht.com/_ozT1G3WqXg4/Sy.../s144/005a.jpg

Almost ready to start turning the spindle ...

Today got a chance to try clocking the taper.
My idea was to use actual collets to set the angle - clearly an iffy idea because they are not solid, but worth a try before using something more complicated.

When preparing the spigot I made sure it's diameter was the top of the collet range - ie when using 9mm/8mm collet, the spigot was 9mm.

Also having clocked the largest collet, I than turned the spigot down and clocked smaller collet and checked whether the readings were the same for both:

http://lh5.ggpht.com/_ozT1G3WqXg4/Sy...M/s144/006.jpg

I have managed to clock the taper to within +/-.0008 for both collets.
I don't know if this is good enough ... but I will try to go with it