Making a Sub Spindle

[sbwhart]

Hi Chaps

Quite a few of you chaps have posted pics of sub-spindles is use either cross drilling, milling or Rose turning, they can be a very useful addition to a shop and have many applications.

I want to build a spindle that I will eventually use as a tool post grinder, as is my way I did a fair bit of investigation work into them, I've seen tool post grinders used when I was tool making and I've also seen John's in use, so I had a fair idea what they look like. I also bought a book from the Workshop Practice Series (No 27 Spindles by Harpit Sandhu ISBN-13:978-1-85486-149-8) and found it very interesting and informative, it covers the design and manufacture of various spindles for different application from milling, drilling, grinding and even a high speed spindle to take dremel tooling.

I will be following the design for a "Light weight tool post grinding spindle" modified for my own use.

This is a sanitized sketch of the spindle.



I've collected most of the bits needed together.



The bearing came from Arc Euro Trade £2 each, Johns started the ball rolling by putting a 20mm hole down the middle of the bar, this was a job that would have made my little lathe grunt (thanks John  ) this will eventually become the spindle housing. The housing will be bored to fit the bearings, so I'll need the bore clock, and has I'm going to hold the bearing in place with screwed caps I'll need to do internal and external screw cutting, I could have used adhesive to fix the bearing, but where's the challenge in that, so  I bought some HSS threading tools from Chronos ( just four days delivery including weekend  ), I've still to make a undercut boring bar holder, and I'm waiting for the electric motor that I bought on flebay to be delivered.

So I'm more or less ready to make a start in the next day or two.

Cheers

Stew

[Majorstrain]

Hi Stew,

You've got me interested,

It's one tool that I want to make as well.
What were the specs on the motor you ordered on flea bay?
Iv'e been thinking about a brushless DC and controller as used in electric RC aircraft 

Looking forward to seeing the progress reports.
Cheers
Phil

[sbwhart]

Hi Phil

Its a sewing machine motor 1/8 hp 6000 rpm you don't need a lot of power for grinding you're only taking a lick off.

I'm planing on having two sets of pulley one set giving 4000 rpm for external grinding and one set giving 16000 rpm for internal, thats what I'm aiming for anyway.

Its not arrived yet bought it over a week ago sent vendor a PM today asking where it is, hope its not a scam.

Cheers

Stew

[John Hill]

Stew,   this is very interesting!

I have started on a spindle too and I am interested in your comments re the motor size as I have started to build mine around a router motor, not a big router but a lot bigger than a sewing machine motor! 

I thought that by using the bigger motor and stepped pulleys I could use it as a drill too (for example drilling holes around a diameter in a flywheel or suchlike).

[bogstandard]

To all,

Even though you are normally only taking minute cuts, you do need the grunt there. If you are grinding a fairly large OD, say 3", that is over 9" circumference, it is the constant drag of the wheel that causes the problems. When I grind on my surface grinder say a piece 4" long at 0.0005" (0.01mm) cut, the 1/2 horse motor starts to slow down. So you have a choice, either more grunt to cut thru it, or super fine feeds so there is not as much grinding pressure.

The way to get your very fine feeds is not to use the crosslide for the feed, but the topslide which has been set over a couple of degrees, and the wheel set and dressed square to the job. Grinding angles then becomes a nightmare to set up.

With reference to motors, the original one used on mine (now replaced) was a 1/6th HP free running at 16K.

Bogs

[sbwhart]

Thanks for that John

I was looking for a slightly bigger motor but all I can seem to find is 1/3 HP ish with around 1800 rpm the sewing machine motor is the best I could find, but I'll keep looking, if I find something better, the sewing machine motor will be useful for something, I may even take up sewing.

Cheers

Stew

[Maninshed]

If you are using your spindle as a tool post grinder, a thing to be careful with is the bearing preload, I assume you will be using angular contact bearings, as these are better for this type of work they take the axial and end loads better. I built the quorn cutter grinder type spindle, looks very similar to your sketch, but it has a bearing preload system using springs giving about 10lb preload on the bearings. I would think  the book you have will make some referance to preloading bearings.

Martyn

[arnoldb]

Stew, very interesting.  I'll be closely following this one 

Cheers, Arnold

[sbwhart]

Martyn

I'm going to use ball bearings. Like you I thought taper bearings would be better, from the book the author discuses the use of the Quorn spindle that he thinks is excellent: however, it is best in one direction due to the pre load which is fine for the Quorn, but his spindle could be used in either direction, the author does admit that his solution is not ideal but its simple design makes it easy to manufacture and will allow the bearings to be replaced if undue wear accures.

In his design of what he calls his basic spindle that can be used for milling he uses three bearing a plane bearing at the back and at the front he uses a pair of radial and axial load bearings back to back to take the loads. (I think these are similar to wheel bearing in a car but i'll stand to be corrected on this)

I have looked at the Quorn with a view to making one how have you found it ?, would it be possible to post a few pics so the chaps have an idea what they look like. 

Cheers
 
Stew

[NickG]

Stew,

I would have thought taper roller bearings would be ok to deal with axial and radial load. But maybe ball or roller bearings along with thrust bearings would be better still.

I thought car wheel bearings were taper roller ... not sure ... I know mine need doing though!

Nick

[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

[sbwhart]

Thanks for the input and discussion on bearing selection chaps, very informative, its certainly helped me understand the issues, and help me understand the intricacies of the design. I now understand why the author stressed the importance of getting the spacer spot on between the bearings, I'll have a ponder which way to go but I may go with the plain ball bearings, I've had a look at the arc bearing and I think they have angular contact bearing that are the same size as the the ball bearing I bought, so I'll have the option to change at a later date but I will check this out.

Thanks again

Stew

[John Hill]

Some cars have a crushable spacer between the bearings.  I think Lotus ("Lots of trouble usually serious") use(d) they system in the rear hubs of some models.

[NickG]

 Slightly Bogs, you're right there, they don't make easy for us, just for themselves. I still tend to do a lot of work on my cars as I refuse to pay stealer prices! Having said that, I priced up the bearings on my Mini Cooper S and cannotget the bearing separately, it comes as part of the hub with the abs ring, hence £80 each!!! So I'll have to weigh up whether it's worth paying someone the labour on top of that or spending a day doing them ... these things usually need a day allowing because something usually doesn't go to plan! The one thing that makes it worthwhile is the sense of achievement you get when you do anything yourself.

Stew, can't wait to see this project, i've often wanted a spindle on the tool post, you might be able to use a change wheel to index, like when I drilled my holes in cylinder covers etc. If I had some proper indexing method that would have been very good as it's similar to being able to swap chucks to rotary tables like John does.

Nick

[Darren]

Hurry up Stew.....I want to build one too.........

[sbwhart]

Blimey

Talk about slave drivers, 

I know a man who'll make you a whip 

Anyway got on with the housing, this is made from a 38mm (1.5") dia * 150 mm (6") chunk of steel not quite sure what sort I was using but it was a bit tougher than mild steel, first job was to put 20mm hole right down the middle. John kindly did this for me on his more powerful lathe. Then setting it up in a four jaw, clocked it up, and skimmed the OD up for 120mm length. then cut the pocket for the bearing.

This is how the pocket should be sized



Boring the pocket



The bearing is to be a nice slide fit with no woble.

To cut the threads I cheated a bit, as its quite a fine thread and not very long I set the lathe gear train up for 24 TPI set the threading tool up square and cut the thread by winding the lathe over by hand, as my machine doesn't have a threading dial I kept the feed engaged and just wound the chuck backward a forward and nibbled the thread out.



With the first pocket I made the thread length as per the book (3 mm) but this barely gave 2 1/2 full threads, as I don't like things that look as though they well blow over with the fist puff of wind, I went to the brick **** house school of engineering: decided with the second pocket to make the thread length (5 mm), if I'm still not happy with the first one when I make the end caps I'll set it back up and cut it back a and re cut the pocket for a longer thread.

Setting up for the second pocket, the housing was carefully clocked up, take your time with this and get it right, clock it up next to the chuck and at the end other wise the bearing will be skewed .





Now for a confession I didn't use the bore clock, I had a practice and found it just to awkward to use so what I did was turn up a couple of plug gauges one 0.5 mm under size and the other 0.1 mm under size and work to these.

This is the finished housing with the plug gauge



And as you have to get the depth of the bearing seat spot on this is how I measured it.



Plan ahead my boy plan ahead 

Have fun

Stew


 

[dsquire]

sbwhart

Now we know why you built the depth gauge. Very clever.

Cheers

Don

[bogstandard]

Stew,

I'm going to have to stop you looking around my shop.

You are knocking up these bits of tooling (depth gauge) after seeing my commercial purchases, it just has to stop


John

[NickG]

Excellent Stew!

[Darren]

Thanks Stew, watching this one with great interest.....looking good so far....

[Gerhard Olivier]

Nice Stew -  keep it coming

Gerhard