[nateman_doo]

First time I am ever messing with them. Is is possible to pack too much grease into them? I slipped my grease gun onto the grease fitting and pumped away until it was busting at the seams with grease. Now I feel like its much harder to move.

Also, is parallelism to within 0.005 acceptable operation?
I made a jig and ran a 0.0005 gauge across the other rail.

[Connor]

I've seen talk about how to do rails.. and one method is to mill out a groove for one rail, and secure it to the base, and mill down the other side so it doesn't have anything to index against and let it "float". I've never done that.. or have any experience with it, but, like I said, I've read something about that on the forum somewhere..

[nateman_doo]

Im tempted to leave it alone since. 005 is pretty good number. At least i can drill the holes, and maybe get it a little closer

[nateman_doo]

I forgot to ask, how does one make sure the rails on the next level up are perpendicular?

[rowbare]

I suspect that you will have to do better than .005" otherwise things will jam up at one end or the other. Linear guides aren't especially compliant.

Here is a THK mounting guide.

https://tech.thk.com/en/products/pdf/en_b01_089.pdf

bob

[nateman_doo]

How do i know its not my strange mounting apparatus? It feels sturdy, but im not sure why the rails got harder to use with the extra grease. Since I don't know what I am talking about I will guess they are the pre-loaded type so they are naturally harder to use. Plus I got them off of ebay, so being used they were probably replaced since they were approaching the end of their useful life?

They are NSK LAH25BN/BNZ. http://www.nskamericas.com/cps/rde/x...near_Guide.pdf

[nateman_doo]

After staring at the problem for days I think I figured out a way to make the rails perpendicular to each other (on separate datum planes) using a vise, long clamps, and a dial gauge. More to follow on this process.

[scudzuki]

How do i know its not my strange mounting apparatus? It feels sturdy, but im not sure why the rails got harder to use with the extra grease. Since I don't know what I am talking about I will guess they are the pre-loaded type so they are naturally harder to use. Plus I got them off of ebay, so being used they were probably replaced since they were approaching the end of their useful life?

They are NSK LAH25BN/BNZ. http://www.nskamericas.com/cps/rde/x...near_Guide.pdf

You can over grease linear rail trucks.
Too much grease will create resistance for the ball bearings to move through the trucks, especially in the return tube.
I have heard of return tubes popping out and the balls coming out of the truck from "packing" the truck full of grease.
Maintenance for trucks on commercial VMCs can be as little as a few strokes from a grease gun after dozens of hours of operation.
There needs to be enough grease to maintain lubrication, and not much more... but running them dry can have disastrous results as I'm sure you're aware.

I would settle for no more than .001" out of parallelism between the rails and better if possible. Fix one rail, either by pinning it or locating in a slot, then aligning the second rail to the first (using an indicator rig like you have) as close as possible. Get it close, then snug one end and near snug the opposite end of the adjustable rail. Set the indicator to zero on the snug end, move the indicator to the opposite end, and use a small piece of aluminum or brass to lightly tap that end to zero, snug that end and move the indicator back, tap that end in (if it has moved), then work the center into place (if the rail is not straight).

I suspect that unless the rail is bent it could be aligned within a few tenths with some patience.

Joe

[nateman_doo]

I got it aligned to 0.0005". The problem I am now facing, is how to I project the hole pattern of the hold down screws to the piece I will be mounting to the rails. If I had some M6 studs that were turned into a sharp end on the other side I could simple drop the plate on and the points would mark the slab I am going to put on it.

[TXFred]

I got it aligned to 0.0005". The problem I am now facing, is how to I project the hole pattern of the hold down screws to the piece I will be mounting to the rails. If I had some M6 studs that were turned into a sharp end on the other side I could simple drop the plate on and the points would mark the slab I am going to put on it.

That is exactly what I would do if I were you.

You only need to mark two of the six holes on each slide. That's enough to position the slide and hold it in place while you mark the remaining holes.

I can't remember if you have a lathe. If not, you can use your existing milling machine. Hold the M6 stud in a collet or drill chuck. Mount a grinding tool such as a bench grinder, angle grinder, or dremel to the mill table. Run the grinder and the spindle, and you can use the grinder to grind a point onto the stud.

If you use a drill chuck to do this job, keep the cuts light so that you don't create too much side force and pop the drill chuck off of the jacobs taper.

Frederic

[nateman_doo]

Yup, I have a lathe. Good to know I am not the only one who thinks like that

I was planning on 4 of them at the least. The counterbore should allow for enough slop to move them around enough to align well. But if I am making 4... why not make 8 and idiot proof it?

[nateman_doo]

Here is where it stands now:

The 2 bottom rails are already aligned to 0.0005" and bolted to the bottom plate. The first step that needs to happen is to secure the X axis (top plate) to the bottom pillow blocks which will complete the Y axis. There I will use 4 pointed M6 studs and place the Aluminum slab down so the points mark it. Then drill the holes, counterbore and bolt down. Y axis done.

Once the top slab is mounted, I will take my CNC vise and clamp it to the left master rail as pictured here:

Yes, my MS-Paint-FU is strong.

Once the vise is pressed firmly against the master rail, the side of the CNC vise will be perpendicular to the master rail. Then I put a spare rail and clamp it to the side of the vise so now I have a perfect (damn close enough for me) right angle.

Then I clamp that floating rail with G clamps as tightly as humanly possible to the existing rails(pillow blocks already on there) & remove the vise. Then align a new "master rail" on the top slab which will be my X axis by means of the first picture posted in thread #1. Once the first X rail is aligned with the clamped rail, I bolt it down and lather, rinse, repeat with the non-master rail.

This is what I have come up with but as always I am open to suggestions.

[whitehedr]

How big are those plates? It looks like you are going to have decent travels with this device.
Have you decided on motors and drives yet?

RWW

[nateman_doo]

They are 24" rails. Should have close to 18x18x18 of travel. The bottom plate is 24x24
middle plate is 12x24, and the top plate is something like 13x18. I will be using the 520 oz keling motors and geko drivers.

[nateman_doo]

Here goes the pointed studs idea. Since I have honestly NO lathe experience, or knowledge I decided to give it a try and turn a point on the M6 screws.

Turning them on my lathe:

I went through every single tip of every triangle lathe bit. 5 bits, 3 points each, so yea.. chewed up 15 tips. The bolt kept riding over the tip and breaking it. One day I will learn how to use the lathe.


Installed studs:

Took me a while, but I was able to make 8 of them when I broke my last tip on the lathe.


I planned to make all 16, but that would require another trip out to the Harbor Freight store to get more bits. Maybe tomorrow I will go there anyway.

Once I had all the pointed studs "somewhat" even, I tried my best to align the slab "somewhat" centered on the studs.

You can see the 4 markings to the right of the larger table holes here:

It worked like a charm! I can always make it sloppy enough to work with anything. Also that is the top limit (Y+)

Y limit (Y-)


And Y centered

[TXFred]

I went through every single tip of every triangle lathe bit. 5 bits, 3 points each, so yea.. chewed up 15 tips. The bolt kept riding over the tip and breaking it. One day I will learn how to use the lathe.

Two things could be happening.

1. You have too much threaded stud hanging out, and it is flexing. If I was making that fixture, I would have drilled a through hole, then tapped partway through with a bottoming tap. That lets me screw the stud far in, turn the point onto it, and then remove it by using an allen wrench from the back side of the fixture. Also, use the outside jaws for this job. They will grip more of the fixture. With lathe work, you always want to run as close to the chuck as possible for maximum rigidity.

2. The lathe could be sloppy. It looks like a 7x12, so unless you've spent time tuning it up, it's going to give you trouble.

You got the point by using the entire edge of that triangular cutting tool. That means that the cutting forces were very high. This contributed to problems 1 and 2.

Once you finish the current project, it would be worthwhile to put some effort into the lathe. You can get substantial improvements by lapping the cross and compound ways and grinding the saddle. Tapered roller bearings are a good modification too.

Frederic

[TXFred]

I don't mean to hijack your thread. Since I brought up lathe improvements, I'll repost an email I wrote recently. It has links to good writeups of the major Mini-Lathe improvements.


For the cross slide and compound slide, I used this lapping procedure.
My ways were bad enough that I started with course valve grinding compound, then finished off with Mothers polish.
Mike Taglieri's Lapping Procedure

To get the saddle to fit the lathe bed, I used this method.
Mini-lathe mods - Saddle fit improvement
Home

Here's the info on how to install tapered roller bearings in the spindle.
C3 Mini Lathe Bearing Change

Here's how I did the compound bearing mod. I didn't exactly follow his plans, but I used the same general setup. I think the big difference for me was that I bought a bearing of the right size, so I didn't have to modify the leadscrew.
Add a Ball Bearing to the Minilathe Compound

Frederic

[Hans_G]

Like Fred said... use the compound to feed the tool in.

I tighten 2 nuts together on the thread, leaving as little screw hanging out as possible. Then close your chuck onto the first nut (the flats of the nuts won't line up). Sometimes it takes 2 or 3 tries with the chuck to get the screw to turn true, so open/close the chuck, test, repeat til it looks good.

[nateman_doo]

No problems with ANY hijack, since it really is related, and i was going to make a post begging for lathe links anyway. You guys saved me the trouble (as always)

Once this CNC is done ill look into lathe operations. So do u guys like the "Vise alignment" method to alighn rails on differnt datum planes?

[TXFred]

It seems like that system would be as good as your vise is.

One thing to know is that there is a way for Mach to compensate if you should be out of square. Let's say that you find that your Y axis moves 0.005" in X for every 1.000" in Y.

There's a Formula section in Mach, where you can tell it,"For every inch that you move in Y, move -0.005" in X." And that corrects for the error.

Sorry I cannot remember details. I haven't used it, just read about it in passing.

Frederic