Gallery, Projects and General > How to's
Making a Sub Spindle
Maninshed:
Hi Stew.
Angular contact bearings are not taper roller bearings, they look similar to a ball type standard bearings. A standard deep groove bearing if you try to push the inner race laterally out of the outer race (finger pressure) in either direction you cannot. However with an angular contact bearing if you do the same there is some detectable lateral play between the inner and outer races, the idea of the preload is to take this out. The races on an angular contact bearing (sometimes there called magneto bearings) are not a compete 'C' shape there are like half a 'C' in opposing directions, therefore the loading angles are different so they can take tangental loads better. I think the type of bearing you use is more critical if you are going to make a high speed spindle for grinding eg tangetal loads as on the perifery of a wheel, or a milling cutter, if the spindle was for lateral loads only eg drilling I guess you could use a standad deep groove bearing. I hope you can understand my drivel, I just copied the quorn spindle out of the Quorn book. I only lurk on this site at the moment, so have not figured out how to do the photos & attachments yet.
Maninshed:
NickG.
Its down to the RPM rating on the bearing, taper roller bearings can go up to about 9,000rpm a standard deep groove bearing can get up to 80,000rpm and the angular contacts can be up to 28,000rpm obviously these max speeds depend on size. Another problem when designing a high speed head is making it compact the footprint of a taper roller is quite big compared to a standard or angular contact bearing.
Darren:
Cars wheel hubs mostly use taper rollers (I think we can agree they can quite take some side and axle loads), my mini lathe now has tapers and my Smart and Brown has a pair of ball races at the front, great big ones that i hope I'll never have to replace and a taper at the back.
The best bit about tapers is you can fine tune the pre-load. But you can over do it as well and ruin the bearing quite quickly.
My pillar drill has one thrust and one roller at the nose and two rollers at the other end.
bogstandard:
You might find that car wheel bearings on trialing arm vehicles have gone away from the tapered type to just plain ball bearings.
At one time you could tweak them up and regrease them as well, they would most probably last the life of the car. My car is now 7 years old, and it is now showing signs it needs the rear bearings doing again, last replaced 3 years ago.
Do you honestly think car manufacturers nowadays will make something you can easily change or fix yourself. I could do it and most probably you people could as well, but the average man in the street who would normally have tweaked them up himself, is now forced to pay a couple of hundred squid to get them replaced at their dealership.
With regards to Stews bearing dilemma. I have made a few spindles in my time, and personally, I think the standard bearings he has are plenty good enough for what will be a little used grinding spindle, as long as care is taken in getting the spacer the correct length so that the bearings are not stressed, but running perfectly central when the shaft is tightened up. Pre loading shouldn't be required for what he is doing.
For a more dedicated type of a machine like the Quorn, then yes, make a proper preloaded spindle.
Bogs
Raggle:
It's worth remembering that the Unimat SL headstock uses E-13 magneto bearings. Preload is set by the length of the spacer tube between them and a pair of belville washers.
Plenty of SLs have been doing good service for 40-50 years with widely varying loads and I doubt many owners have replaced these inexpensive bearings more than once, if at all. Offhand I'd say they were good for speeds in excess of 6,000 rpm. The Unimat cartridge is 35mm diam which is not over large considering it has a rack and a keyway. Not too difficult to duplicate.
There'll be a drawing of it somewhere on the Yahoo site
http://finance.groups.yahoo.com/group/UNIMAT/
Arc Euro carry E-10s at £6.50 each and angular contact from £6 a pair
http://www.arceurotrade.co.uk/Catalogue/Bearings/Angular-Contact-Ball-Bearings
HTH
Ray
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