[Swede]

Thanks for the update! An electric actuator is probably more convenient than a pneumatic actuator. How are you going to do the internal portions of the spindle? With my own spindle concept, I have no fear of turning the exterior, and then boring, but to really get the accuracy I want, I'm afraid I'd have to job it out to a grinding shop.

Metallurgists following this thread... any advice on a tough steel which can be turned and bored to a decent finish w/o grinding, and still deliver acceptable hardness and wear resistance without resorting to heat treatment and subsequent finish grinding? All I am truly experienced with are mild steels (too soft), tool steels (expensive and perhaps not suitable w/o HT), and 4000 series carbon steels.

Hendrix, didn't mean to push you into posting, I just wanted you to be aware that there are lots of thread lurkers interested in your project. Please post when you can, and when you are ready. Thanks!

[h3ndrix]

Hey Swede,

Yes I thought an electric actuator would be more suitable, thats why I used an electric actuator on my test setup and I was glad with the results I got.

As a side not, I do not want anything that works with air on my machine setup for safety and simplicity issues. Air power is good when you are in charge of it and next to it to keep an eye on it. The idea with a CNC is not to watch the machine while it works, but to be confident enough to let it work on its own. I am not a fan of letting anything that works with air work on its own, as I have seen enough compressors stopping because of an oil gasket getting blown and etc.

edit: Pressed the "post" button too early, heh

To answer your question, I think I will either go with 8630 or 4340 alloy steal. The 4340 comes in stressproof which is might be the better choice, but then again 8630 (or 8620 for that matter) is bearing grade stuff that heat-treats very well according to my research.

I have access to a lather that is pretty precise that I will use for the spindle, I will re-test the accuracy and make sure its at the rated 0.0002" before I begin the project. I am confident that the spindle will be relatively easy to machine and I will follow HFD's advice on how to check the taper for a nice fit (the lathe has a nice taper attachment on the carriage that has 24/7 taper cutting ability).

Hopefully it will be less painful, now all I am waiting for is those angular bearings to come up on ebay (ABEC-5 at least as per recommendations)

Thank you,

H3ndriX

[Bloy2004]

Originally posted by Swede


Hendrix, didn't mean to push you into posting, I just wanted you to be aware that there are lots of thread lurkers interested in your project. Please post when you can, and when you are ready. Thanks!

I'm one of those "thread lurkers"

[turmite]

nuther one here!
Mike

[RotarySMP]

http://www.profimaschinen.de/frame/frame.htm

This outfit in Germany is selling an ER25 collet spindle for 400 euro. With a body diameter of only 60mm, the bearings can't be terrible big.

[georgebarr]

What is the status of this project? Any further progress? I have a couple of questions for anyone. What is the part name of the light grey long cylinder like part that holds the red spindle? This part houses the belvelle washers, retention know, and sindle. Can you please provide some www links where I can find the cost of just this one part? Since this one part is the hardest to make, in my opinion, I can greatly simplify my construction by buying some and constructing other parts. Also, what is the name of the part in orange color that connects the power drawbar to the retention knob?

I know you can buy parts like the retention knob (blue part), spindle (red part), belvelle washers, bearings, etc. Maybe an easier way to construct this spindle assembly and get accuracy from it is to buy most of the parts and assemble/machine the rest yourself. Any comments?

Thanks,

[ESjaavik]

I don't want to throw any spanners in the works, but will try to explain how my spindles are built. It's almost the same on my mill and on one small and one big support grinder.

They have needle bearings at both ends. With long needles running in cages. The inner bearing surface is the spindle itself, and the outer surface is the housing. Then at the other end there are two angular contact bearings on the grinders and thrust bearings on the mill (max 2500RPM). The needle bearings are much stiffer than a ball bearing. They are also slim allowing the front bearing to be close to the wide end of the taper. On the mill spindle there is no labyrinth, it just widens out to the full diameter of the spindle housing with a fairly close fit. Anything that finds it way in will be thrown right out by the rotation.

I'll try to attach a pic of the mill spindle without housing.

[steveg]

Hi guy's I've been reading this thread with a lot of interest and decided to stop lurking and make this
my first post here.
First my background is about 18 years as a field service technician for a large CNC machine tool dealer.
mostly Japanese, with spindles from r8 and CT/BT30 up to 100' long 6 spindle CT50 wing spar machines

From this background I make a few observations. First NMBT tooling is a manual toolholder with no
provision for auto tool changing. CNC machines with ATC's use the ISO,BT,or CAT series holders
they do not have the straight section after the taper,(making them shorter) and they have a wider flange with a groove ,for the tool change and storage mechanism.

second the 2 bearing of your original design are MORE than adequate. there are several 30+hp 15000+rpm machines out there with 2 bearing spindles. (plus a 3rd at the far back end to hold up
that end)

As pointed out it would be good to provide a spacer for the inner bearing race. when a MATCHED PAIR
of AC bearings are made there is a preload factory set (in most cases about .001" or .025mm) when
these are held apart with a spacer set, the spacers for the inner and outer races are normally the same height.
There are bearing marked SU that can be bought individually and then mated but the best choice is
factory matched.

Many low power machines do not use drive keys and depend only on the taper and retention spring
for resisting torque. If drive keys are desired than a shot pin into the side of the spindle shaft was the
original method. almost all CNC machines now have electronic orient.

the coil spring for tool retention would most likely be fine up to 10000rpm but the belville springs
allow a more compact design.

If you don't already understand the belville spring principle it's actually very simple , when you
place two spring washers in parallel (back to face) you increase (double) spring rate, if you place two
spring washers face to face or back to back (series)you increase spring travel but the spring rate
stays the same.

for example if you have a washer with spring rate X and travel Y
4 washers in parallel would give you a spring rate of 4X and travel of 1Y
4 washers in series would give you a spring rate of 1X and travel of 4Y

Last about the retention mechanisim EVERY machine that I have EVER seen uses the retention rod
to push the tool out of the spindle It is absolutely necessary to do so. the tool will almost never
just drop out of the spindle, it must be unseated from the taper.
there is always a spring or deflection built into the tool change mechinism to accept the tool retention
rods push.

Hope this all helps in some small way.
Steve

[avsfan733]

Just my two cents on you comment about material hndrx

I'm no metallurgist but I have seen 4340 machined to an almost mirror finish on a lathe rpm was something like 40 rpm for facing a piece about .625 in diameter on the slowest feed the lathe would allow

[turmite]

Where oh where is our in house spindle designer?
We have been missing you! Finals???

Mike

[h3ndrix]

Hi guyz,

Sorry been away for so long, but I have been going thru very rough times financially and I had to put a hold on the project so I can buy myself food, literally.

The project is not forgotten or retired, but resting until I get things straightened out.

Thx to all who has shown interest,

H3ndriX

[turmite]

H3ndrix I do know what you are talking about on the financial! I won't go into it but I am going for an interview tomorrow for a job. I am having to turn my business into a part time for a while. Just don't get down and not let anyone know. There are a couple here on the zone that have lifted me up while I was down and it sure helps.

Keep us posted on the spindle though, we miss your posts!

Mike

[nicad]

yes, I know its an OLD thread.. but I found it be one of the most interesting ones as it was developing. Unfortunately the excellent images are no longer hosted-- does anyone have them copied? h3ndrix are you still around-- could you possibly email them to me?

Thanks-
Colin

[gbowne1]

Yes, I agree this entire post is a very helpful one. I enjoyed it when I first saw it.

Great design.

:-)

Love to see more of this!

Greg

[Salty72]

I would have to also agree we need the Photos back

are there any plans yet ?? Might be a way of boosting your income I have recently learnt to do drawing in AutoCad so if I can help I will only be to happy to do so....-Salty-

[paul3112]

Oh dear the last post. I was sooo excited to read, but then it has stopped devloping. My hope is for a BT 30 ATC spindle in the 0 - 18K rpm range. I am thinking that I will need to have a ratio change on the drive side .