Ball Screws for custom mill, need advise

I have an X2, which I am upgrading the base on with a larger table. I plan to CNC it right from the beginning, so I plan to build it all ready to go. I am in need of advise when it comes to getting ball screws for it. The X axis is roughly 18", and the Z axis is 12".

Here are some pictures:
Attachment 117149
This is the factory mount of the X axis.

More of the X axis:
Attachment 117150
I can see how to make and attach a ball screw to the end, but what do I do about where the ACME screw goes though?

The Y axis:
Attachment 117151
This pokes out the back of the base so being over 12 is not an issue.

http://www.cnczone.com/forums/bencht...tml#post829885

I think he's going step by step in converting the exact same table. To add ballscrews your just going to have to mill away the cast iron nut and design a mount to hold the ball nut in it's place.

I figured I had to get rid of it somehow, but it seems I overestimated this ball screw job. Very good find, thank you.

I will likely take a sawzall to the majority of that threaded lip, then place the base on the X2 to flatten the area.

I am glad I just purchased the mini 7x10 harbor freight lathe today.

Hey Nateman!!!

I'll get those ballscrew pics up for you later today

Here are the existing threads that need to be replaced.
Attachment 117164

Will something like this be easier? Looks to be an all in 1 package that I can bolt to the bottom of the X axis.

THK BALLSCREW,TRAVEL 320mm,PITCH-16mm,16Ø, ROUTER - eBay (item 260452991622 end time Nov-17-10 04:21:54 PST)

You will need to do some design work here, there is no bolt-on ballscrew upgrade for these 6x18 mill/drill tables.

You can modify the base (Y) or the table (X) to accept bearing blocks, but the shortcoming is that bearing blocks don't have motor mounts, and the bearing blocks won't line up with M8 threaded holes in the base or table.

Or you can modify the piece that goes between the table and the handwheel to accept thrust bearings or angular contact bearings and a motor mount and then design your ballscrew end machining around that.

Or you can throw that piece away altogether (like I did), make your own bearing blocks, and then design your ballscrew end machining around that.

Generally, you probably want to look at your machining capabilities and decide how much you can (or want) to modify the table, saddle, and/or base. Then decide what sort of ballscrew nut you want to attach to the saddle and table, there are many options in size/shape. Then figure out how to you want to support the ends of your ballscrews (bearings) and how you will house those bearings. Then you can decide how to machine the ends of your ballscrews. With all of those decisions made, you can design and purchase and/or fab up the parts. I guess motors, couplings, and mounts come in there too, but maybe not so critical.

I completed my 6x18 ballscrew upgrade with a Sherline mill (to modify base, sadle, and table and make bearing blocks). I purchased my ballscrews from linearmotionbearings on ebay. I can probably dig up the dimensions on what I ordered if you're interested. It cost about $200 iirc (including end machining).

I have only the X2 alone to help with the modification. I usually buy something, and design around it. I figured if I purchase something like that which seemed like a complete kit, I could do enough milling, and drilling to make it work. If you could provide me with the dimensions or help and perhaps some pics I would be very grateful! thanks!

Quote:

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Originally Posted by Hans_G

I completed my 6x18 ballscrew upgrade with a Sherline mill (to modify base, sadle, and table and make bearing blocks). I purchased my ballscrews from linearmotionbearings on ebay. I can probably dig up the dimensions on what I ordered if you're interested. It cost about $200 iirc (including end machining).

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Does this one look good for the X axis?

1antibacklash ballscrew 1605-500mm-C7+BK/BF12+couplers - eBay (item 250470033352 end time Nov-14-10 07:12:50 PST)

I know the table is about 18", and this overall length is 19.6". What sort of end machining did you require? Is that how you couple the motors to these bearings?

I have to apologize ahead of time, my MS Paint-FU is lacking today.

I think this is what I am looking to do:
Attachment 117278

I am not sure where the 500 mm comes from, the overall length, or the screw length. The concept of what I sketched is the intent. I need a screw length of no less then 18", because I have to fashion Aluminum brackets with through holes to bolt to the side of the table, and that the motors can mount too. I am thinking .75" Aluminum would work.

So based on that assumption I would need a usable screw length of 19.5". So if that 500mm screw, is the overall length, it needs to be longer. If it is 500mm of usable screw, then I am in business for the X axis.

Send the guy (his name is Kai or Chai or something like that) an email telling him exactly what you want. He'll post an auction and then you buy it.

PM me with your email address and I'll send you the pdf with the dimensions of what he calls "normal end machining" and the markup I made to get my screws. I can snap a few pics tonight and send those too.

You are my hero dude =)
PM sent

Pictures are greatly appreciated!

The more and more I stare at the base the easier I get discouraged. I only have the X2 to do the work. If I have to make the original acme thread wider for the ball screws it will be impossible to do on the X2.

There should be no part of this conversion which would require a machine bigger than the X2 and 7x you already have.

Have you made drawings of the parts you need to make for this conversion? It helps.

I can't making drawings ahead of time all that well. Planning is not my stronger trait. Reaction is far better for me. I have to purchase something, and MAKE it work. Once I bought it, I am committed at that point to make it work. Not saying I can't plan, but its hard to plan when u don't know what your doing.

I measured the inner diameter hole for the existing threads, and I came up with an absolute diameter of .75". So whatever ball screw that I get, the widest part of the screw threads itself in order to slide into the Y axis needs to be .75"

Don't make excuses :)

You have the table so you can measure it. You know the dimensions of the ballscrews from the Chinese Ebay site. From here you can see how you need to do the end bearings:

5 Bears - Y axis ballscrew

Google has a free 3D drawing program that can be used to model the whole thing. You will save time and money if you discipline yourself to sit down and model it out.

heh, thanks. Don't get me wrong, I am doing the best I can to plan but when I have no idea what I am doing, it makes it a bit more challenging. You guys are far more experienced then myself so I just have to stare at it long enough until something comes to me-which it will eventually. We are all green bananas at some point.

What has come to me in the meantime is that I need a rotary table to help make this. I have no doubts in my ability to make it-just need to stare at more pictures.

Been staring at that 5 bear sight for a few days now and lots of ideas have come to me, but still need the rotary table to make it. Just trying to figure out which axis to tackle first. I figure the Y wouldn't be a bad place to start.

Why do you need a rotary table to make this? Obviously it makes drilling the flange holes easier but you can do them on the X2 by counting turns on the handles and using the scales.

Here is the link to Google Sketch up.
Google SketchUp

If you draw up you thoughts, we can offer advice and improvements.

So here is what I came up with paint. Can't install google anything on my work computer. :violin: ugh.


The Y axis:
Attachment 117606

Good start.

You only show a single bearing, and nothing to stop the ballscrew simply pulling back out of it. Here are a couple of pictures of how the block on 5 bears look(which is a copy of the way NSK, THK etc do it).

For Y, you need to design:

1/ The screw, including it's end machining
2/ The nut carrier which will join the nut rigidly to the saddle
3/ The bearing block including bearing, which will rigid locate that screw in the Y direction.
4/ The bearing block carrier which will rigidly mount that block to the base, while allowing some slop for adjustment during assembly.
5/ The standoff to space the motor out from the base
6/ the coupling to connect the motor to the ballscrew.

So you are a sixth of the way there.

You will be better off with a pencil, ruler and paper. You can post your drawings as photos. MS Paint is crap!

How long is the base (be exact - what are you measuring it with?)

Y will probably be a short screw, and will be rigid enough, and turn slow enough not to whip, so don't bother supporting both ends. Just a double AC bearing in a bearing block on the motor end will be fine.

Most bearings are metric. You will find a better selection, cheaper, if you design around metric here.

The hard part with these small retrofits is normally fitting the ball nut and it's carrier in the limited space between the base, the saddle and table.