[691175002]

Matec has build of an ER16 spindle here:
http://www.cnczone.com/forums/cnc_wo...dle_build.html

It can be somewhat vague, but it fully covers how to properly build a spindle from scratch.

The bearing arrangement he uses - AC pair in front, spring preloaded deep groove in the back - is essentially the generic universal arrangement.


If you track down a correct set of bearings, the hardest part of building a spindle is making it accurately enough. Everything needs to be flawlessly concentric and your bearing fits have to be bang on. The better bearings should have specs for proper fits.

Too loose and your spindle is trash, too tight and the bearings will have shortened lifespans or be outright destroyed. That being said, the Chinese can do it for 2$ an hour so if you have a micrometer you will probably be okay.

[waltpermenter]

you boys don't have a clue, the majority of real lathes use tapered roller or deep groove bearings for the spindle, Timken being a common brand.
walt

[aarongough]

The grinding alone will cost you more than the used spindle head. These Dunham things are over 3500.00 new. You'd certainly learn a lot by taking one of them apart. They are neat. They are almost like a baby Hardinge spindle.

So here's a question: is it possible to build a spindle of any sort without grinding? I know most spindles are ground into their final dimensions, but I don't have a grinder and wasn't planning to buy one.

It's worth noting that my accuracy requirements are low low low. If my spindle turned out as accurate as that on a 7x12 I'd be happy. The reasoning here is that I'm *never* going to be re-chucking parts. Any second operations will be done on another lathe.

Also worth noting that I'll probably be cutting the final bore and taper in-situ.

[aarongough]

Matec has build of an ER16 spindle here:
http://www.cnczone.com/forums/cnc_wo...dle_build.html

It can be somewhat vague, but it fully covers how to properly build a spindle from scratch.

The bearing arrangement he uses - AC pair in front, spring preloaded deep groove in the back - is essentially the generic universal arrangement.


If you track down a correct set of bearings, the hardest part of building a spindle is making it accurately enough. Everything needs to be flawlessly concentric and your bearing fits have to be bang on. The better bearings should have specs for proper fits.

Too loose and your spindle is trash, too tight and the bearings will have shortened lifespans or be outright destroyed. That being said, the Chinese can do it for 2$ an hour so if you have a micrometer you will probably be okay.

Everything I've done so far has been to relatively loose tolerances, so part of the idea behind making a spindle was to get used to machining bearing fits etc...

I actually have a nice starret 1" tenths micrometer that I got off a retiring machinist for $20, an amazing bargain! I'll need to buy 2" & 3" tenths micrometers too though.

[aarongough]

you boys don't have a clue, the majority of real lathes use tapered roller or deep groove bearings for the spindle, Timken being a common brand.
walt

I believe the newer turning centers generally have angular contact bearings in the spindle because they're more suited to running at high spindle speeds.

The reason I'm planning on using tapered roller bearings is because I'm planning to stick to lower RPMs (up to about 2500) and because I want as much stiffness as I can get for my money.

I agree that as far as I know most good quality older manual lathes use tapered roller bearings, not sure about the newer ones.

[aarongough]

So I have decided that the first step on my journey is going to be making a small ER20 collet spindle to improve my skills and get a feel for exactly what's involved without breaking the bank.

Initially I'll fit this spindle as a replacement for my 7x12, but I may build a complete small lathe around it as well, mainly for the purposes of learning.

[aarongough]

You might also want to go to the ArtSoft forum, and search for a thread from a couple of years back by user Simpson36, who has built several very high performance 4th axis units from scratch. He now sells them. He learned a LOT about building high quality spindles, and his adventures could save you a LOT of time, money and effort. It's a LOT harder than it appears. I'm sure he has a thread on CNCZone as well, but I don't know where it is, or what his username is here. Steve's a VERY sharp guy.

Regards,
Ray L.

Thanks for the great link there! As soon as I saw the thread I realized I had seen his work before... I've been watching Steve's YouTube channel for a while!

[aarongough]

I was thinking today and I have decided that if I'm going to do a small spindle I may as well make it a 3C spindle rather than an ER... For me a 3C spindle would actually have some utility, so on the off chance I actually pull it off then I will be able to use it.

I spent some time this afternoon drawing up a concept:



(excuse the ****ty ball bearing drawings, apparently I don't have a compass at home and had to rough it in by hand)

The drawing is pretty much 1:1 scale, but I have avoided dimensioning it as I have drawn it without having the roller bearings in front of me for proper measurement.

The bearings in the spindle nose are both Nachi 32007 tapered roller bearings ($21 each), the bearing at the rear of the spindle is a 6207-RS sealed deep groove ball bearing (~$8). The lower bearing costs and decreased material cost of the smaller spindle means it's not the end of the world if I screw things up.

I also chose the rear bearing with a larger OD than the nose bearings so that the parts of the headstock bore that need to be close tolerance can be made as short as possible... If all the bearings were the same OD then the entire rearward bore of the headstock would have to be machined to the same close tolerance.

From looking at the bearing specs the spindle should be fine up to about 8000 RPM... Unlikely that I would run it that high though, more like 2500 RPM, we'll see.

Any thoughts on the design as it stands?

I'm not going to be starting on this for at least another few weeks as I have to wait to take delivery of the new lathe.

[waltpermenter]

you should have some amount of spindle protrusion so you aren't bumping your tools against the face of the housing. having the bearings that close isn't as necessary since you are going with the smaller 3C or even 5C. massive bearing support is for a lathe with big chucks.
walt

[aarongough]

Good point walt!

I'll do up another drawing with the spindle nose moved 1/2" forward.

[wizard]

I believe the newer turning centers generally have angular contact bearings in the spindle because they're more suited to running at high spindle speeds.

The reason I'm planning on using tapered roller bearings is because I'm planning to stick to lower RPMs (up to about 2500) and because I want as much stiffness as I can get for my money.

For this endeavor I'd go cheap, whatever type that implies as long as you can handle any accuracy issues that may arise from cheap bearings.

I agree that as far as I know most good quality older manual lathes use tapered roller bearings, not sure about the newer ones.

This isn't really true with respect to smaller lathes, Hardinge for example has used angular contact bearings for years. For what you are doing here, that is attempting to make a spindle for a collet lathe, I don't see bearing choice having a usable impact on spindle stiffness. This assuming reasonable quality bearings either way you go. From my standpoint angular contact bearings would be a bit easier to work with.

[wizard]

I was thinking today and I have decided that if I'm going to do a small spindle I may as well make it a 3C spindle rather than an ER... For me a 3C spindle would actually have some utility, so on the off chance I actually pull it off then I will be able to use it.

3C is very small and of course ER could imply a number of sizes. So I'd have to say which is better here is highly debatable.

I spent some time this afternoon drawing up a concept:

If you where doing angular contact bearings you could do them back to back and have the bearings seat against on shoulder and be clamped at the other end.

(excuse the ****ty ball bearing drawings, apparently I don't have a compass at home and had to rough it in by hand)

A pocketful of change has solved that problem.

The drawing is pretty much 1:1 scale, but I have avoided dimensioning it as I have drawn it without having the roller bearings in front of me for proper measurement.

The bearings in the spindle nose are both Nachi 32007 tapered roller bearings ($21 each), the bearing at the rear of the spindle is a 6207-RS sealed deep groove ball bearing (~$8). The lower bearing costs and decreased material cost of the smaller spindle means it's not the end of the world if I screw things up.

Always an important point in the learning process.

I also chose the rear bearing with a larger OD than the nose bearings so that the parts of the headstock bore that need to be close tolerance can be made as short as possible... If all the bearings were the same OD then the entire rearward bore of the headstock would have to be machined to the same close tolerance.

There are a number of ways to deal with that issue. If the nose bearing where seated in a pocket what happens at the other end of the spindle doesn't matter.

From looking at the bearing specs the spindle should be fine up to about 8000 RPM... Unlikely that I would run it that high though, more like 2500 RPM, we'll see.

That is assuming you follow lubrication recommendations, achieve the same level of precision in the machine as they will have and that you assemble everything like a surgeon.

Any thoughts on the design as it stands?

The big issue as I see it is getting the shoulders that the outer races butt up against parallel. It would be a critical feature for your design. You might want to reconsider that arrangement depending upon how well equipped your machine shop is.

I'm not going to be starting on this for at least another few weeks as I have to wait to take delivery of the new lathe.

This should give you plenty of time to research ideas. Spend some time on the various bearing manufactures sits to down load app notes and design materials. There is a wealth of stuff out there to hone your design with.

[109jb]

Why not go 5C and use the guts out of a spin indexer for a starting point.

[aarongough]

3C is very small and of course ER could imply a number of sizes. So I'd have to say which is better here is highly debatable.

If you where doing angular contact bearings you could do them back to back and have the bearings seat against on shoulder and be clamped at the other end.

A pocketful of change has solved that problem.

Always an important point in the learning process.

There are a number of ways to deal with that issue. If the nose bearing where seated in a pocket what happens at the other end of the spindle doesn't matter.

That is assuming you follow lubrication recommendations, achieve the same level of precision in the machine as they will have and that you assemble everything like a surgeon.

The big issue as I see it is getting the shoulders that the outer races butt up against parallel. It would be a critical feature for your design. You might want to reconsider that arrangement depending upon how well equipped your machine shop is.

This should give you plenty of time to research ideas. Spend some time on the various bearing manufactures sits to down load app notes and design materials. There is a wealth of stuff out there to hone your design with.

Excellent! Your comment has made me have a number of realizations!

First, I realized that I had not really internalized the 'back-to-back' bearing arrangement. Makes a lot of sense. The preload is applied from the nose of the spindle, and the spacer between the floating bearing and the AC bearings retains them against the spindle nose.

One interesting thing that you also made me realize: if I use angular contact bearings then I can get sealed ones and I won't have to worry so much about sealing the spindle! That is definitely a big plus in the direction of using AC bearings.

Your note about having to make the shoulders parallel really strikes a chord with me as well... I'd like to give myself as much chance of succeeding with this as possible, so the simpler the better.

The machining of the headstock block would be much simpler with the proper back-to-back layout. I might even be able to set it up on the crosslide of the new lathe and do the entire thing without moving the block... Start by drilling, then line bore the smaller bore, then the shoulders from the back and front... Does that sound reasonable? Can't say I've done any line-boring before.

Thanks Wizard!

[aarongough]

For this endeavor I'd go cheap, whatever type that implies as long as you can handle any accuracy issues that may arise from cheap bearings.


This isn't really true with respect to smaller lathes, Hardinge for example has used angular contact bearings for years. For what you are doing here, that is attempting to make a spindle for a collet lathe, I don't see bearing choice having a usable impact on spindle stiffness. This assuming reasonable quality bearings either way you go. From my standpoint angular contact bearings would be a bit easier to work with.

Yeah cheap is the aim initially. I think there's a better than average chance of the thing being unusable on the first try, so I'd hate to be throwing away $1000 worth of bearings or something.

[aarongough]

Why not go 5C and use the guts out of a spin indexer for a starting point.

I'm mainly treating this as a learning exercise and an introduction to real close tolerance machining, hence why I want to build the spindle from scratch.

I definitely want to go 5C! Unfortunately even cheap bearings for a spindle that size are about $60 each... So I'm trying a 3C spindle first so that I can get a handle on the issues involved without killing myself on the cost. After I've got the process and design nailed down I will definitely be making a 5C spindle (and the lathe to go with it!).

Cost for a complete 3C spindle (bearings, steel for the spindle and cast iron for the headstock) looks to be about $150 or so, which is a pretty cheap price for something that's going to teach me a hell of a lot.

[aarongough]

I've decided to make my first go at all this a *little* more modest, by converting my old 7x12 lathe into a gang-tooled lathe.

The build thread is here: Build Thread 7x12 lathe gang-too CNC conversion - CNCzone.com-The Largest Machinist Community on the net!

I still plan to get started on making a 5C spindle from scratch, but I will be doing so in parallel with getting a CNC lathe up and running so I can keep making parts and money.

[aarongough]

And we're back!

After looking at the 7x12 a bit more I think that building a CNC lathe around it will leave me disappointed. I'm going to give it a good home somewhere else instead.

I've setup a build thread for the 5C spindle that I'm making here: http://www.cnczone.com/forums/vertic...dle_build.html

Rather than going with a full scratch-build I'll be using off the shelf components when I can.

One the spindle is complete I will be restarting this build thread to tackle the rest of the lathe!

Exciting times!