Small spindle head

[bambuko]

I have been lurking here long enough :tongue: , so here is my project.
Small spindle head, un-ashamedly inspired by sherline spindles (http://www.sherlineipd.com/spindles.htm).
It probably would be cheaper, quicker and likely better to buy one, but ...
- it's not all about money
- here, in our Rip Off Britain they are slightly more expensive (http://www.millhillsupplies.co.uk/chuck_&accessory.htm) than in US
- I wanted to try an idea I had for bearings, different to those used in Sherline
- and of course for me, it's about making things rather than just buying lol

The rough plan (not fully detailed) is as follows:

http://lh3.ggpht.com/_ozT1G3WqXg4/SxUf0CGtraI/AAAAAAAAI-Y/OHUKuIXHS2Q/s800/002-cad_layout.jpg

The idea is to use for the main/front bearing double-row, angular contact ball bearing. The one I had laying around was 5204-2RS (OD 47.0 ID 20.0).
They are supposed to be good enough for 8000rpm (10000rpm with oil ?) and in design correspond to two single row angular contact ball bearings.
They can also accommodate axial loads acting in both directions.
They are supposedly C3 axial internal clearance... ?

That's theory and we shall see ... :rolleyes:

The plan is to use this head with ER16 collets and various grinding, polishing, cut-off wheels on mandrels of various diameters, and if turns out any good maybe in future for other things as well.

I made the housing out of lump of alu I had laying around (again if it turns out OK, next one might be made in steel).

http://lh6.ggpht.com/_ozT1G3WqXg4/SxUewevHgNI/AAAAAAAAI-U/YnUis-5anY8/s800/001-hsg.jpg

Both front and rear bearing housing have been turned in one operation, so whatever the accuracy of my lathe, they should be concentric.
And I have clocked side and bottom of the housing to make the spindle parallel to both (not needed for the particular application I have in mind for this head, but good exercise nevertheless).
I have turned the front at 46.98 and fitted the bearing by warming the housing in the oven and freezing the bearing (in plastic back) in our freezer.
It dropped in perfect and now is fixed solid and for life (I do not envisage ever having to take it out - it is sealed for life)

Rear bearing is simple 6203-2RS (OD 40.0 ID 17.0) radial deep grove ball bearing. I made the housing for it sliding fit and intend to secure it once assembled with Loctite.

Well, this is my cunning plan, and if it doesn't work, the loss will be minimal. In the meantime it is all good turning/milling exercise :whistling:

Chris

later edit:
References to Loctiting rear bearing (highlighted in red in my original message) are clearly wrong and a result of my running in circles when thinking how to do the job. As rightly pointed out in the later message they rear bearing should be "floating".
Please disregard

[ptjw7uk]

Wish you luck with the spindle.
Keep us informed on your and its progress
Peter

[Robin Hewitt]

The idea is to use for the main/front bearing double-row, angular contact ball bearing. The one I had laying around was 5204-2RS


Hi Chris

Unless you're planning to loctite this beastie together, you're only loading the double bearing on one side.

Try again :heehee:

Robin

[bambuko]

thanks for paying attention :tongue:
As usual it doesn't pay to cut corners when explaining things :dance:
a) I said about my sketch "... (not fully detailed)..." - I definitely plan to close it from the front (just didn't bother drawing it because I am not sure about details yet). Sorry :redface: if it has caused any confusion.
b) I also said "...It dropped in perfect and now is fixed solid and for life..."
This bearing has the housing heat shrunk on it - it is not going anywhere easily. And whilst I am planning to loctite rear bearing, I don't think I will need it for the front one.
And as for pre-loading the bearing - it is internal in the double row bearing so I don't need to (and couldn't) do anything about it. Ijust need to secure the bearing in place.
This is the experiment part of it - ie will the pre-loading inherent in the design double-row, angular contact ball bearing be good enough for this spindle?
Chris

[Robin Hewitt]

And as for pre-loading the bearing - it is internal in the double row bearing so I don't need to (and couldn't) do anything about it. Ijust need to secure the bearing in place.

Not pre-loading, just loading. As drawn it resists a push but not a pull.

If the double race is tight in the housing you could put a sleeve down inside so when you nutted the pulley on the top you pinched the double angular inner ring.

That'd do it.

Edit: I do have experience, here is a double angular bearing loctited on a spindle from my junk box :eek:

[bambuko]

Sorry, I understand you now :redface:
The spindle is meant to be interference fit in the bearing as well, so this is as good as loctiting it, but I was also thinking about either a sleeve or a nut behind front bearing.
Most likely something like this:

http://lh4.ggpht.com/_ozT1G3WqXg4/SxV19frha-I/AAAAAAAAJAE/2NLAXAVxtaQ/s800/spindle%20head2.jpg

Chris

[bambuko]

Edit: I do have experience, here is a double angular bearing loctited on a spindle from my junk box :eek:
And what was your experience of them like?
Am I wasting my time?

[Ross77]

Nice work, it will be interesing to see how you get on.
Have you seen the "Diy spindle design" thread? It might be worth a read as I seem to remember he had an initial issue with putting to much preload on it and it got very hot. If you have it adjustable then you can get the balance between removing play and to much friction.....

I'm interested to see what you are going to drive it with? I have the Er11 spindle but not tried to power it yet. I've got a 100amp esc and Rc motor but not sure wether to belt or direct drive it?

[bambuko]

thanks Ross,
DIY Spindle design (http://www.mycncuk.com/forums/showthread.php?t=445&highlight=spindle+design) is one of my favourite threads.
Main difference is that he wanted high speed router at 20k rpm, my target is 5k rpm - my application is different.
My pre-load is not adjustable. It is set by the manufacturer of double-row, angular contact ball bearing that is used in the front.
If I was doing high speed spindle I would use the usual design of matched pair with adjustable pre-load, but I am hoping that at lower rpm I will get away with what I am proposing.

[Robin Hewitt]

And what was your experience of them like?
Am I wasting my time?

The nice thing about the double angular bearing, unlike your average single angular bearing, is that it comes with rubber seals. Pop the top one out and add oil, something like Castrol GTX would do nicely, and I don't think you will have a moments worry with it.

I eventually went for stretching the shaft between two singles with Belleville washers. I have become a big fan of Bellevilles since I started aiming for truly zero backlash on everything. A thrower ring on the base to keep the crut out and not overly generous with the oil.

I ran it up to 6000rpm then started winding the speed up on the digi phase controller. I was heading for 12,000 but started worrying about the belt driving it, felt pity in my heart. Probably be okay, but you do need a noise level that everyone in the shop can live with for those long cuts :whistling:

[BillTodd]

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

[edit]

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

[bambuko]

The rear bearing should float ...
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.


...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...
Yes, this is in my favourites,


...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 (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 (http://www.practicalmachinist.com/vb/showpost.php?p=1065158&postcount=10)

Thanks for the links!

[Ross77]

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:

[bambuko]

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

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

[Ross77]

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:

[bambuko]

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/Sxv1A7KOQjI/AAAAAAAAJBU/o2zsI4VTlQ0/s800/002.jpg

While at it, I have also checked my lathe (Prazimat from the old DDR (http://www.lathes.co.uk/hobbymat/page3.html))

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/Sxv1CC2HowI/AAAAAAAAJBY/XHuFCqC0jHI/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/Sxv1Dypte2I/AAAAAAAAJBc/uyNnWVXLczU/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

[ptjw7uk]

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

[bambuko]

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 (http://www.lathes.co.uk/latheparts/page8.html) at lathes.co.uk (http://www.lathes.co.uk)
Chris

later edit:
It would appear (from this web page (http://www.mini-lathe.com/C6_lathe/Back_plate/backplate.htm)) 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?

[bambuko]

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

http://lh4.ggpht.com/_ozT1G3WqXg4/SyOsBnLiLII/AAAAAAAAJHg/-1Svde0EuOM/s144/005a.jpg (http://lh4.ggpht.com/_ozT1G3WqXg4/SyOsBnLiLII/AAAAAAAAJHg/-1Svde0EuOM/s800/005a.jpg)

Almost ready to start turning the spindle ...

[bambuko]

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/SyqDpdd9sGI/AAAAAAAAJMI/u62YbTT0s2M/s144/006.jpg (http://lh5.ggpht.com/_ozT1G3WqXg4/SyqDpdd9sGI/AAAAAAAAJMI/u62YbTT0s2M/s800/006.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

[bambuko]

I have turned test piece, using topslide set as described and ...
It would have probably been good enough for most other jobs,
but I wasn't happy - I am blue all over :heehee: but the fit of the collets in the spindle is not up to my expectations :thumbdown:.
Mostly to do with the boring tool (stiff one was too big, and the next one I had, was too flexy). So need to make better one, just right for the job.
Also will try another/better method of setting the angle.

[BillTodd]

Also will try another/better method of setting the angle.

Try chucking a test bar* - to give you an edge parallel to the centre line, then use a sine bar against the edge of your compound slide. If your compound slide has no reliable straight edges expose as much of the dovetail as you can (remove the slide if necessary) then use a rod in the V (make sure you use the none gibbed edge) to give you a straight edge to work from and a combination of 123 blocks and parallels to get it to the centre height.


See:
http://www.frets.com/HomeShopTech/Tooling/LatheSineFixture/sinefixture.html

*or turn a long parallel section on any old bar between centres

[bambuko]

thanks Bill,
Good link and good advice!
Haven't got sine bar, but intend to improvise using two ball bearing housings (on account of their accurate ground dia) and ground parallel bars.
Easy to work out all the distances and even with vernier caliper accuracy of 0.01mm should give me reasonable result.
Will report as soon as I have chance to try.