Homebrew TS mill spindle

[Steenkamp]

Hi all. I have been contemplating for a while now the build of a new spindle for my Tom Senior M1 mill. Reasons as follows
1. Current knuckle head configuration utilizes a 45 degree helix gear set, the teeth on my set are worn sharp and dont like high speed or mild steel at all. Lots of noise gets generated

2. Head hight with the current head is very limited

3. High spindle speeds for very small end mills are impossible due to machine construction

4. Very limited angular movement of current head.

5. I would like to preserve the current knuckle head
in a working condition, thus need a replacement spindle before this one gives up the ghost.

After trolling the internet for ideas i saw some people fitted Bridgeport M heads to their TS mills. Bridgeports are extremely scarce in my neck of the woods, let alone parts or something as exotic as a M head. So i decided i will take the plunge and build my own spindle.

The spindle needed to be belt driven and not break the bank
I decided to use angular contact bearings for the spindle bottom and a deep groove ball bearing for the top. Will see to arrangement as i go along. Any suggestions?

Well i started to machine my spindle to be out of EN19T and it is slow going on my ML7!!

[bertie_bassett]

looks like a good start!

im sure iv seen photos of a spindle supported by the overarm and driven via a belt off the main drive. there were some pullys used to let the belt turn 90 degrees.

was the route I was going to go if I got an old horizontal mill.








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[Steenkamp]

Hi Bertie. My idea is to drive the mill spindle via VFD and a 3phase motor with belts and stepped pulleys.

[velocette]

Hi
One suggestion is that you use "Poly Vee Belts"  PJ section with 6 ribs and fabricate your own Stepped pulleys.
A variable speed drive DC or AC vsd   with the stepped pulleys give a very versatile power delivery to cope with anything you throw at it.
Personal preference is for Taper Roller Bearings with .25 mm brass shim grease retainers.
Angular contact ball bearing top and bottom will probably be better for high spindle speeds.

Eric

[Steenkamp]

Hi all, thanks for the suggestions. What would the best lubrication be for the angular contact bearings be? I was thinking about auto transmission fluid (ATF). Would that be too thin?

[PekkaNF]

Hi all, thanks for the suggestions. What would the best lubrication be for the angular contact bearings be? I was thinking about auto transmission fluid (ATF). Would that be too thin?

First question: Why ATF oil? Do you have excotic coupling/friction materials in it?

Second question: Why oil? You have vertical spindle, right? Oil has tendency to fall down to bottom bearing and drip out. You need some wics, capillaries or something to oil the top bearing and not to drown the bottom bearing.

I would first consider standard grease and seals. If standard grease is marginal, then a little of high speed grease and if you need more rpm than DN factor / temperature allows then you'll need oil.

Somewhat agricultural answer:
http://www.mcnallyinstitute.com/CDweb/d-html/d019.htm

I once calculated and had one mechanical engineer to check them and my conclusion was that on small milling machine is is hard to go too highs speed to warrant oil lubrication, when milling cutter is over 8 mm and taper is under ISO30. Very small milling cutters and large spindle bearings and then you have yourself in funny place quickly, but we are into hobby machines and we don't need the whole "Envelope".

Pekka

[lordedmond]

Just had a squint at the chart for some AC bearing that I use

Grease 40000rpm air/oil 63000rpm

That's with the correct pre load as speed in the designation letter on the bearing in question and the correct amount of grease

For that mill I would go for a simple taper roller bearing setup pre loaded with a belvue washer on grease you would be ok to about 5k any higher you need labyrinth seals

Stuart ,s 2cents

[Steenkamp]

Hi Guys. Pekka, thought ATF as its the best oil in our roundabouts. I was also concerned with temp increases as it would influence preload on ac bearings. Or am i reading too much into it? But as Stuart just mentioned, highspeed grease will be fine as i only want max RPM of around 3000. For bearing setup i was thinking in order from top to bottom: ac bearing, spindle centre, ac bearing and then deep groove. Deep groove to help with radial loads and ac for axial. Angular contact was what i could get, otherwise it would have been wheelbearings. Do you think my arrangement would be sufficient?

[PekkaNF]

What bearings/sizes you are using? I could look aup on tables and then ask trusted oldtimer mechanical designer what does he thinks.

I don't know how you are planning to use those bearings, Probably AC-bearings back to back and preloaded "justa about" or something in that effect on spindle nose and floating deep groove ball bearing in the tail, I vision?

Pekka

[philf]

Hi Steenkamp,

I've made two milling spindles.

The first made about 25 years ago was for my Aciera F3 which came with no vertical head and all the drive removed.

This one has a Myford nose and 2MT bore. It uses a preloaded 25mm bore double row a/c bearing at the business end and a floating single shielded deep groove bearing at the pulley end. The pulleys are 4-row J section Poly V. They are 3 step and have ratios of 1:1 (3,000 rpm max), 1:2 (1,500 rpm max) and 1:6 (500 rpm max). The motor is permanent magnet DC. The bearings are grease lubricated.



The most recent was for my CNC mill.

This also used preloaded double row a/c bearing (this time a bigger section - 30mm bore) at the cutter end and two shielded deep groove bearings at the pulley end. The two deep groove bearings are preloaded together with a wavy spring. They are an easy fit in the housing so that they can float as the spindle warms up. The idea of using two deep groove bearings was that they tend to run quieter with preload. The spindle takes ER32 collets directly. The a/c bearings are oil lubricated with an oiler. The seal is a labyrinth with a drain so, in theory, I'm not sprayed with oil. This hasn't been entirely successful and I have a new design in the pipeline. This also has 3 step pulleys from 2:1 to 1:3. The belts are 5 step J section Poly V (easy to get as they are used on lawnmowers). The motor is a 3 phase Inverter rated motor which I run up to 5,000 rpm. This gives me a range of spindle speeds from 450-10,000 rpm. It's surprising how much of the time I use 10,000rpm. 8,000 rpm was the limit for grease lubrication.





Both spindles work very nicely but I have a feeling that the version with 2 deep groove bearings at the top is better.

You say you are considering one a/c at the bottom and one in the middle. Is there a good reason for this? As you run the spindle it will heat up and this will affect any preload on the a/c bearings. The bigger the distance in between, the more the preload decreases.

Hope this helps.

Cheers.

Phil.

[Steenkamp]

Hi Guys

Thanks for the sound advice. Pekka, i will probably just use some highspeed grease. Phil, how do you keep your spindle from being pulled down into the cut if you have a floating bearing at the top? Or am i going to the doctor before falling out the tree? Did you run a bit of I understand  what you mean with preload increasing and was worried about that with my configuration.

[Steenkamp]

Phil ,sorry, that one was sent waaayyy to soon. What i wanted to ask was whether you ran a bit of preload on your top deepgroove bearing to keep the spindle from moving in deeper sidemill cuts

[PekkaNF]

Phil ,sorry, that one was sent waaayyy to soon. What i wanted to ask was whether you ran a bit of preload on your top deep groove bearing to keep the spindle from moving in deeper side mill cuts

Hmm... on this bearing arragement double angular contact bearings should take all the machining forces. It is a textbook example an proven to work
http://www.skf.com/binary/21-3587/1__en__001_0212_tcm_12-3587.jpg
http://www.skf.com/group/products/bearings-units-housings/ball-bearings/principles/application-of-bearings/bearing-arrangements/index.html

I see what you mean, but the way I have seen, the preload in a single nonlocated bearing is used only if bearing is not loaded enough, here is a belt drive, that should give the bearing minimun load it needs.
http://www.skf.com/group/products/bearings-units-housings/roller-bearings/principles/selection-of-bearing-size/dynamic-bearing-loads/requisite-minimum-load/index.html

In order to this tail end bearing taking a significant cutting force the arbor should deflect and A/C bearings would yield or move, neither is desirable.

I think.....I'm electrical engineer not bearing engineer

Pekka

[philf]

Hi Guys

Thanks for the sound advice. Pekka, i will probably just use some highspeed grease. Phil, how do you keep your spindle from being pulled down into the cut if you have a floating bearing at the top? Or am i going to the doctor before falling out the tree? Did you run a bit of I understand  what you mean with preload increasing and was worried about that with my configuration.

Hi,

The double row a/c bearing is clamped in the housing and there is sleeve between the inner races the a/c bearing and the deep groove bearing. (On the version with two deep groove bearings there is also a spacer between both bearings). The nuts on top clamp everything together. The a/c bearings have the preloaded built in - the outer races just need clamping together.

The wavy washer just preloads the deep groove bearings.

Phil.

[Steenkamp]

Thanks guys, now its clear! Will be back home next week, so will put onto practice what i have learnt from you!

[Steenkamp]

Hi guys

Here is a pic of the spindle outside done, bearing journals polished to size, with bearing on to test fit. Inside is drilled through with 16mm bit. Had to use a long masonry bit to finish the last little bit in the centre to break through. Still have to cut the 2 morse taper and threads for retaining everything.

[Steenkamp]

Hi All.
After a long silence on the Tom Senior vertical spindle front i have started some work on it again. In the time between i have acquired a Chipmaster lathe and have been refurbishing it. As luck would have it, as soon as i started work on it I stumbled across a Maho MH600P vertical mill spindle assembly!




At a cost less than what the matched pair of angular contact bearings for the shop built spindle was!
Well sofar i have cleaned up everything and saw the power feed issues the previous owner had with it after dissasembly.
The first issue was that the powerfeed wouldnt move at high speed settings. I removed the small gearbox that drives it and dismantled it





I immediatly found tje problem... the little gearbox was opened before and who ever put it back together again never seated the key properly and thus minimal torque was transmitted


The second issue was that the dog clutch transmitting drive to the gear rack on the quill refused to stay engaged. That problem was caused by a tube that is supposed to have 4 ballbearing detents in them didnt have the balls in it. I found the balls in the pack of odd and ends the previous owner had thought had come from the assembly. Unfortunately my phone battery died by then so i could take no pictures.

I want to mount it in a similar way as the pic


For the horisontal bar i want to use a section of hollow bar and a flangeso i can use the heads rear drive to drive the spindle. Drive would be transmitted from the motor via belt and pulley arrangement to a driveshaft running in the hollow horisontal bar. I hope it comes across clearly.

Any advice?

[Steenkamp]

.

[hanermo]

Fwiw..
Using the proper grease
Kluber Isoflex NBU 15/ NCA15 - light loads, vertical or horizontal applications >500000 dN

The critical speed dN with 30 mm inner D bearings,
is 30 mm x 16.000 rpm = 480.000.

So you can use kluber grease and it will work at 15.000 rpm for a 30 mm bearing (like Bridgeport M head).