Charter oaks 12z cnc conversionmill with linear guides

[gearhead406]

I have owned this mill for almost 2 years and have just started my cnc conversion. Wanted from the start to use linear rails. Did not realize what I was getting in to. But this is my progress so far. 25 mm double ballnut and screws from hiwin. 20 mm hiwin rails for XY and Z. Hgr20cc heavy duty bearing blocks. I wanted to keep the integrity of the machine by leaving the dovetails intact so that the machine could be put back to a manual machine. I have the Y axis rails set up. I am eliminating the saddle and using a 3/4 inch piece of 6061 aluminum. Machined pockets on bottom and will add another 2 inch thick piece of 6061 on top of that to bolt the X axis bearings to and the Xaxis rails will go on the bottom of the table with aluminum spacers just like the Y axis. The Y axis is very smooth. Thish as taken me a while to do this so far because I only have the one machine I have to take the machine apart to measure and put machi e back together to machine and so on.

[gearhead406]

]Will take more pictures of the machine and post as I go.

[atomarc]

I certainly have to give you an A+ for your work. Having to disassemble then measure, then reassemble and machine the parts would be way beyond my patience level. Keep up the good work, looks good.

Stuart

[pippin88]

Interesting idea (using spacer blocks under the rails).

Won't you lose a lot of Z height? Or will you extend the Z rails up? Top of Z travel is usually only used for tool changes anyway.

[gearhead406]

Interesting idea (using spacer blocks under the rails).

Won't you lose a lot of Z height? Or will you extend the Z rails up? Top of Z travel is usually only used for tool changes anyway.

I will extend z.because I eliminated the saddle it brought the height back to a similar height.with all the measurements I have taken I have lost 1 in in height but will gain in z when I build that.when I was researching rails I did not realize I could have bought shorter style rails and bearing blocks. Which would of helped. But these are supposed to handle the loads.

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[CS900]

yeah, very clever adding the spacers to avoid the dovetails. Have you checked to see how parallel your rails are to the original dovetails?

[gearhead406]

yeah, very clever adding the spacers to avoid the dovetails. Have you checked to see how parallel your rails are to the original dovetails?

I used left dovetail as a reference datum . When I got the rails set up the parallel was no further than .0005 .and I used a hand drill and tap to do all that.

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[gearhead406]

I used left dovetail as a reference datum . When I got the rails set up the parallel was no further than .0005 .and I used a hand drill and tap to do all that. I was impressed to get the rails that close with hand tools. Then I used a dead blow hammer to straighten even more .

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[CS900]

really? over the entire travel? It doesn't look like you've shimmed the rails or anything. That seems almost unbelievably good.

[gearhead406]

really? over the entire travel? It doesn't look like you've shimmed the rails or anything. That seems almost unbelievably good.

I did shim right rail . when I surfaced the spacer it was tapered about .004 .So I shimmed up the inside of the rail so bearing blocks would not bind.
Wish I had another machine. And a granite table to check some of this but seems to be going ok. I sit in front of my machine and look for ideas and solutions. Then I proceed.

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[AutomatedIngen]

Any updates on this build?

I like the idea of using spacing blocks as opposed to milling off the dovetails. Would you mind providing the height of the spacer blocks? I'm trying to get some idea of how much I can expect to spend on steel for spacer blocks for all three axis on a similar sized mill.

[gearhead406]

Any updates on this build?

I like the idea of using spacing blocks as opposed to milling off the dovetails. Would you mind providing the height of the spacer blocks? I'm trying to get some idea of how much I can expect to spend on steel for spacer blocks for all three axis on a similar sized mill.

If you use bearing blocks without flanges you will not have to use spacers or cut off dove tails. With the spacers you will lose alot of z height . But if you do want to use spacers ,I would go with about 1/2 inch and then what ever bearing block you use will clear your dove tails. If you don't use spacers and use none flanged blocks I would use 20mm rails no bigger.

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[gearhead406]

If you use bearing blocks without flanges you will not have to use spacers or cut off dove tails. With the spacers you will lose alot of z height . But if you do want to use spacers ,I would go with about 1/2 inch and then what ever bearing block you use will clear your dove tails. If you don't use spacers and use none flanged blocks I would use 20mm rails no bigger.

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CS900 is doing a similar build he is further along than I am. His build is very nice and has some good ideas.

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[AutomatedIngen]

If you use bearing blocks without flanges you will not have to use spacers or cut off dove tails. With the spacers you will lose alot of z height . But if you do want to use spacers ,I would go with about 1/2 inch and then what ever bearing block you use will clear your dove tails. If you don't use spacers and use none flanged blocks I would use 20mm rails no bigger.

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What about putting a riser block under the z axis column to compensate for the lost height from the spacer blocks?

I haven't purchased the new mill I wish to convert yet but I'm strongly leaning towards purchasing two PM-940M's and converting both. I'll use one to make the parts for the other then I will CNC them both at the same time.

I like the approach of the riser blocks for the dovetails because I'm thinking about rising the ballscrew and ballscrew mount completely out of the casting for the Y and Z axis and filling the mill base with epoxy granite. Basically I want to do what mrsimpson does in his video below, on both axis:

If I do decide to go with these mills and convert them to full linear rail CNC's I want to get the weight from the 1200 pounds they weigh stock, to around the 2000 pound mark, and hopefully increase rigidity. I think your solution of the dovetail riser blocks is a solid approach to to get me to what I want to achieve.

I am following both you and cs900's builds, and am grabbing ideas from both.

Keep up the good work, and keep posting pictures and videos.

[gearhead406]

I finally found some time to work on my mill. I put 4 bearing blocks under y axis and 6 under x axis.Tapatalk Cloud - Downlaoad File 20180727_164147.mp4

[gearhead406]

[QUOTE=gearhead406;2202064]I finally found some time to work on my mill. I put 4 bearing blocks under y axis and six under x axis because of all the canter levering of the table.

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[gearhead406]

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[AutomatedIngen]

Your build is still looking good, for a minute I thought this was going to be another dead project but glad you provided the update.

The motion from your video looks very smooth. I'm assuming the 6 bearing blocks under your X axis didn't take up away from any of your X travels?

My approach to solve the counter levering on my machine is to use the original mill table and invert it so I can install bearing blocks on it, and the mill table only move in the Y direction, then get plate steel and fit linear blocks to it, so it can sit on top of the mill table and move in the X direction. The plate steel will be a smaller width then the mill table but will be able to move towards the full extents. My approach does eat up some Z height but I do have a plan to counter that (column spacer, in the form of epoxy granite).

I'm in the process of finishing up my 1/4 scale 3d model of my design now, after that I will start a thread of my build.

Keep it going your build has inspired me.

[gearhead406]

Your build is still looking good, for a minute I thought this was going to be another dead project but glad you provided the update.

The motion from your video looks very smooth. I'm assuming the 6 bearing blocks under your X axis didn't take up away from any of your X travels?

My approach to solve the counter levering on my machine is to use the original mill table and invert it so I can install bearing blocks on it, and the mill table only move in the Y direction, then get plate steel and fit linear blocks to it, so it can sit on top of the mill table and move in the X direction. The plate steel will be a smaller width then the mill table but will be able to move towards the full extents. My approach does eat up some Z height but I do have a plan to counter that (column spacer, in the form of epoxy granite).

I'm in the process of finishing up my 1/4 scale 3d model of my design now, after that I will start a thread of my build.

Keep it going your build has inspired me.

Lost a little x travel haven't checked to see how much yet. But won't be a lot. Since left side of table will be used for third axis eventually I'm not real worried. Table is real smooth. I'm very happy, it won't take much for motors to run it. Sorry it took this long to get here to this point .I had a accident at work. Cantwait to see some pics and videos of your machine.

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[gearhead406]

I have done some more work to my machine. Have had a troublesome couple of years. Hopefully things are going back on track. I have purchased 400 watt servo motors and drive for x and y. With 2 to 1 ration pulleys . In the process of making brackets for the servos now.

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