[chuckknigh]

Well, I went to one of those tool sales they hold out in the country -- some little company (Homier is a common one) sets up in the local VFW hall, and sells tools to us country folk. Today, it was Cummins Tools.

Well, while I was there, today, I found a drill press vise. It is essentially an X-Y table. In fact, it reminds me of a crude version of the X-Y facility on the Harbor freight mini mills.

http://www.cumminstools.com/browse.cfm/4,92.htm

It has acme lead screws which move the table in 2 directions, and a built-in clamp on the top. Surprisingly nice, actually.

It's a fairly rough casting, but it has dovetail ways and a built in facility for shimming them to remove slop! The actual sliding surfaces aren't too bad, either. Once I take it apart, clean it *properly,* and hopefully finish a few of the surfaces it ought to even look good!

I've not measured its exact capacity yet, but just eyeballing it, it looks like it's about 4x6 inches of movement, or thereabouts. The vise capacity is 4".

Anyway, needless to say, for $19.99 I picked it up. I think it'll make a nice complement to my wooden router, if I convert it to CNC. Might even allow me to do some light metalworking!

A question, though. The ACME nuts are part of the castings, so I can't remove, replace, or upgrade them -- is there any way to add backlash compensation, or just generally "tighten it up," perhaps with an injectable polymer compound? Something to take out, or at least minimize the backlash?

I'd just *add* nylon nuts to it, but they'd take up a bit of room, and basically eliminate half of its travel!

There must be a way to upgade the hardware itself -- relying on software to compensate is not an ideal solution.

-- Chuck Knight

[wms]

Chuck,

Run a search on this forum for "Moglice"

There are several thread that deal with just such a thing.

[Ken_Shea]

Chuck you mentioned to tighten up the acme backlash by the use of a polymer injection. In the auto repair field for many years I have used this method with great sucess on king pins, tie rod ends etc. This of course was with a special polymer but you may find that even the use of glue gun polymer that it may do what you need.

Just drill a whole in the center of the threaded area and inject the glue gun polymer and see what it does, cost nothing, is reversable and may just be a simple solution.

let me know if you do it and how it turns out.

Ken

[wms]

Ken,

That sounds like a good idea. Call the patent office.


And oh ya how about saw dust in the gear box?

[Ken_Shea]

Ward,
I know it sound like a hoot, but I have injected a bunch of this over the years with really great success, especially helpful in antique cars where the original parts are not available. Glue gun is actually not a glue but simply cheap polymer.

Does saw dust works well in old gear boxes.
Man that really ages us doesn't it Ward?
No one under the age of 40 would know anything about that.

I still have some polymer left you need an injection? great for worn out joints, knees, elbows etc.
Oh, I forgot I do have to drill a hole!!

[wms]

Ken,

I really do think that sounds like a good idea....


I just threw the sawdust part in for a laugh.

[chuckknigh]

Hey, hot glue is nothing more than a medium temperature thermoplastic. Nice stuff for a lot of uses.

A couple of concerns, though. Would it resist wear sufficiently to function as a lining for a screw drive?

It's somewhat springy, so would it introduce backlash into the system? (Tiny layer shouldn't be too bad, but it's still something to consider)

Would it introduce a lot of friction into the system? And, on a related note, would use at a "normal" speed generate sufficient heat to melt the polymer, thus ruining any alignment I had beforehand?

Is there a release agent for it? I'd hate to inject it, and have it stick to the lead screw.

A consideration about its installation, too. I'd have to practically bake the vise in the oven to heat it up sufficiently...the part would have to be hot, as well as the glue, since the glue would freeze "solid" the second it hit cold steel. Might be a bit of a practical problem in this...

Still, overall a good idea. Is there not a nice polymer that cures chemically, that would do the same thing? If I have to, I'll just go get some JBWeld and tap a new hole...but there's no guarantee the tap will align perfectly with the lead screw. They're rolled, not ground...thankfully they're short!

-- Chuck Knight

P.S. Moglice is essentially a granite hard epoxy, isn't it? Somewhat like the JBWeld I mentioned before. If memory serves, it's used to rebuild bearings...a good suggestion.

Is it possible to get a TINY bit of this stuff? I don't want to rebuild 2 nuts, and have buy a pound of the stuff. Since it's for machine tools, I have the sneaking suspicion that it's rather expensive.

P.P.S. On a 60 degree thread, there is a thin "sliver" of a nut called a jam nut, that I can buy at my local hardware store. Looks like "half" a nut. Is something comparable available in ACME? If so, I might be able to use it to adjust out any backlash, using some of the split nut designs -- this option would take up the least space possible, I would think...short of modifying the existing hole.

-- Chuck Knight

[NeoMoses]

you might take some all-thread and a cheap nut/bushing and try casting your own "moglice-like" nut out of JB-weld. Once cured, they both have very similar properties, so it just might work and be much cheaper.

[Ken_Shea]

Chuck never really gave the hot glue any serious thought, it just popped into my head and I threw it out as food for thought. There have been many times something said that was nut usable but prompted ideas that were.

I would not think you could turn these fast enough to cause any friction heat.

I have some hot glue that actually kinda hard and most hot glue melts at very low temperatures maybe 200f?.

I like the idea of the JB weld mentioned by NeoMoses, you could call the company and ask them what a good coating would be so it would form to but not stick to the acme thread. Get a syringe minus the needle from a vet or doctor and use that to inject it . My guess is it would not take much. I have seen epoxy glues already in a syringe and it mixes as it comes out.

good luck, and let us know what you end up with.

[HomeCNC]

I used HOT glue on both exposed ends of my home made pre-loaded ball nuts as a wiper to keep chips out. It works great! Forms to the screw but does not stick because of the thin layer of oil on the ball screw.

[cbcnc]

Hi,

Polyvinyl Acetate or PVA is used when laminating with epoxy in molds. It might stick to a clean leadscrew and not allow the JB Weld to bond to it.

Chris

[chuckknigh]

Well, I have an email in to the JBWeld people, to see if anyone has tried this before. Surely I can't be the first...

Turns out they're located in Sulphur Springs, TX...less than 100 miles from me. Who knew?

Anyway, I did a little digging on Moglice, and other than a friction reducing component, they seem to be essentially the same stuff. Same properties, and everything.

Hopefully it won't be too difficult to make this thing, successfully -- I really don't want to modify the original casting, if I can avoid it.

That way lies madness.

-- Chuck Knight

[chuckknigh]

This is a picture of the unit in question. It's a fairly cheap ($20) cross slide vise, but it seems to work pretty well.

I saw instructions for "lapping" lead screws to fit better, so I may try that. I've adjusted the ways so they run true, now, and it seems to work pretty well overall.

Now, if I could just make the backlash go away, I'd have a good platform on which to build!

-- Chuck Knight

[cbcnc]

Yup, just like mine that I have had for about 10 years now. Down to the "100" on the casting. It is a low precision drill press vice. If you tighten the gibbs to get rid of the slop the cranks become a bear to turn. The dials are graduated in 5 thou increments. The dials also function to hold the leadscrew to the plate. Watch out there as the leadscrew has a step in it and rides in a hole in the plate. That is the bearing, steel on steel. If filings get in there they will wear out both pieces. It happend to me.
You might consider fitting some bronze bushings and proper shaft collars.

Chris

[chuckknigh]

Precisely -- it's not a bad unit, but it's a bit "rough."

The markings are in 5 thou increments? I did not yet know that...thank you for the information. It's not like it came with documentation!

The "hole in the plate" is for the upper section (haven't decided if it's X or Y, yet), and will be addressed soon. But, first, I want to get it running smoothly, overall.

It looks to be a pretty "modular" design, and as if it could be upgraded with relative ease. My primary concern is the lousy cast-in nut for the upper segment. I've gotten a few ideas from this site, and from the CAD_CAM_EDM_DRO list...we'll see if any of them pan out.

-- Chuck Knight

P.S. I figure that it's hard to go wrong at this price...even if I end up just taking it apart completely, for the fun of it all.

[NeoMoses]

Yep, that's almost identical to the cross-slide vise I've got on my drill press. It works well for drilling, but I'm not sure if you could get enough of the backlash out of it for milling. Good luck!

[anoel]

I've got one of those Cummins Cross slide vises. It's way crude... I had to take it apart and file the ways and do some major tweaking to get it to slide even remotely smooth. Honestly I can't imagine trying to adapt a set of motors to that thing. It's way too crude... I use mine for drilling on the drill press. it works OK for that. Now for a good deal on a pretty decent cross slide vise take a look at the Grizzy "Shop Fox" 4" model http://www.grizzly.com/products/item...emnumber=H0967

One of my buddies has that one and it's very smooth out of the box, not at all crude.

[chuckknigh]

Mine isn't very crude, really. I can easily turn the lead screw cranks with one finger, except at one point in its travel (needs lapping?)...shouldn't be too hard to make everything work. My example is not as crude as yours, apparently. Don't you just love Chinese quality control?

Someone on the CAD_CAM list told me that they had done such a conversion, and they used "accelerated wear" to adjust the fit. Basically they lapped the lead screw, and then used 500 grit abrasive inside the ways, and just ran it back and forth for a while -- once it was "worn" it worked fine.

Someone else sent me this video of their unit in action -- a good video, really. They used it as proof of concept for some steppers, and cobbled it together over a weekend, but it's the same idea. Notice, they also upgraded the lead screw.

www.electronicsam.com/video/VIDEO1.mpeg

On mine, the only real problem it has is the roughness and backlash in the lead screws. Apparently someone over at MaxNC has also done this conversion and even sells plans. The important part in their approach is to replace the lead screws...he used 1/4"x20 allthread, which surprised me, but it does give a lot of mechanical advantage. Apparently he made an "adapter" that threaded into the cast ACME nut, and which was held tight with a set screw.

I might try something similar with JBWeld. Cast nuts would be easier for me to work with, anyway.

-- Chuck Knight

[anoel]

Your's must be a lot nicer than mine, I just got mine about 3 weeks ago. when the Cummins show came through Bloomington. I got my bottom slide to work decent. The top slide is still a little rough. The cast nut and leadscrew are the problem there. I'l get bored and take it apart.

The vise screw turns very nice though.

[chuckknigh]

The first unit I got was even smoother, but when I took a good look at it, there were voids in the castings, ON the dovetail ways. Unacceptable.

I returned it and had the guy go through a couple of them, till I found one with some potential. Reasonably smooth action, etc...

Cummins, HF, etc may not have much in the way of QC, but I sure do. I picked the "best" one I could find, quickly.

-- Chuck Knight