Enco Compound Slide Table

You have it fixed in your mind that the accuracy is all in the table. Well, it could be, but really, Terry, the accuracy comes from *you*. Any table which moves and clamps should work if you use dial indicators to tell you where you are. I have played with the tables on import mill-drills which cost a fair bit (maybe $1000 new) and they aren't very good. I have never seen a cheap table which doesn't have play in it. Lots of times they move when you're locking them, for instance. The key is to know where you are when your table is locked.

Maybe I'm reading your posting wrong, but it sounds like you are saying a cross-vise (whatever that is) doesn't have the accuracy to drill small holes. Well, a vise is a workholding device. The spindle and the tool do the drilling. If the vise has the capability to move and re-lock, then it is up to the operator to know where the table is. Can you rely on cheap lead screws and dials? Probably not. Is that your only choice? Not in a million years.

Back in the '80s I used to drill PC boards for DIP sockets by stacking up shims and pressing the board against the stack, drilling, then removing a shim and repeating to achieve my step. The sockets worked. No cross-table, no lead screw, no vise a'tall. Just me and a cheap drill press and a master's degree that I had to find a way to earn.

Grant Erw> I have the need for a compound slide table and I have been looking around

Sometimes, yes, that's the happy answer. And sometimes it's junk. You're only at risk for the return shipping.

ENCO has free shipping on orders over $50, so there's another $14 saved. Use promo code NRPU45 when ordering.

Can't help with the quality issue.

Bob

To get 0.005 TIR accuracy you need to have a very good, small center drill held in a very good chuck. I would go with either a brand new small jacobs chuck or an albrect. Depending on what you are drilling you could spend your entire 0.005 on the centerdrill runout even if the workpiece positioning is perfect.

If you really wanted to do this on the cheap then the suggestion to purchase a pair of new, inexpensive imported one inch travel dial indicators is absolutely the best. You could mount those to your existing palmgren unit and be right there. Just remember that you need to hold the centerdrilll smack on center and is has to be a number zero or thereabouts. You will need a senstive drill press for this so you don't get 99% of the holes spotted, and then snap off the centerdrill point in the last one.

I spent an entire afternoon recently trying vainly to spot some holes within a couple of thou. The drill chuck I had chosen was only holding teh centerdrill at the very inner portion of its shank - the jaws on the chuck were worn by over five thousanths of an inch bell-mouthed. Even though the centerdrill was correctly sized and new, close inspection revealed that the point was wobbling around in a roughly 0.010 diameter circle. So all my holes were getting started with the same accuracy!

Jim

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I completely understand. A cross slide vise is similar to a sliding table but instead of a table it has a vise on it and slides in the x y coordinates. The accuracy I am looking for is across the table in both directions. For example. If I need to drill a hole at x=10mils, y=10mils and then another hole at x=4000mils, y=4000mils, I can not afford to be off by more than 5mils or so. This is where the cross slide vise is not as accurate. It is a nice American made vise, spend about $200 on it, but it just doesn't have the proper resolution to do what I need.

Thanks for the advice.

> When I studied the pictures, I could not find a single thing different about

I already am using a Jacobs 5/32" chuck mounted on a spring loaded shaft (finger operated to drill the holes), which is then mounted an a MT2 collet chuck. The only think I use the drill press for is the motor and to control the speed of the chuck. I drill the holes by pushing down on the spring chuck with my fingers. I am also using a 0000 centerdrill to start all of my holes. I have been doing this for a while, but I just need a bit more accuracy for this next project since there are about 120 holes I need to drill and most of them are .027" dia. across a 4x5" board. So as explained in my previous post, I need to be able to drill a hole at one corner of the board, and move to the opposite corner using the dials, and still be within .005" so my pogo pins will hit the proper spot on the PCB board. One guy mentioned free shipping on the Enco. So if it is a piece of junk, I can spend $14.00 to send it back. Small insurance to pay if it is junk. But big savings if it does what I need. I don't have a problem spending the $400 on a quality tool if that is what I need to do. But once again, if I can save $330.00, who wouldn't!

Thanks for the advice.

OK so it sounds like you have the 'small hole drilling' thing pretty well under control. As long as your sensitive chuck rig is accurate and does not introduce runout (actually it's tough to get a good one) then you should be all set.

You really should be using somthing like a Dumore sensitive drill press, those things are just what you are looking for, except for the price tag...

Put two dial indicators on your slides and you will be all set. Jim

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If you are going to be making a lot of identical test jigs, you could make a fixture with drill bushings. Careful layout one time and then zap, zap, zap. Thompson used to make something that would be useful. It was kind of a X Y table using ball bushings so it was easy to move the work piece to align it for drilling.

Dan

It sounds like you are making a fixture for pogo pins on a PCB. Why not just make a PCB with the proper holes? The accuracy will be there and small 2 layers boards are $80 to $120 for a lot of 5 boards.

Ask your customer/PCB person for a PCB file that just has the Holes, annular pads and no traces.

Paul

Ah. A cross-slide vise. I had a couple of those and would certainly get one again. If you break down your answer it looks like you are now talking about the errors built into the vise. Is the fixed jaw of the vise dead parallel to the X axis way machined into the vise? Is it dead perpendicular to the Y axis way? Are the X and Y axes machined precisely perpendicular? If your part has much thickness, you also must worry about is the fixed jaw of the vise perpendicular to both the X and Y axes as well.

You can answer all of these questions with $20 worth of dial indicators and some know-how. Also, you can remove the fixed jaw and use cigarette papers for shims behind it to correct some errors. For example, if you set up your cross-slide vise on the drill press, and open up the jaws wide, then set up your dial indicator so it touches one side of the fixed jaw, then you crank the X axis across to the other side while watching the dial indicator. If it moves, then (I think) the fixed jaw isn't parallel to the X axis way so you would need to shim the fixed jaw to correct that problem. I bet you can easily get that correct within .001"/4" even on a cheap cross-slide vise. Then comes the acid test: put a precision machinist's square (a little one) so the short leg is against the fixed jaw and the long leg is out the side of the jaw and running along next to the vise. Then set up your dial indicator against one end of the long leg and then crank it 4" using just the Y crank while watching the dial indicator. I believe (if I've thought this through correctly) then if the X and Y axes are parallel then the dial needle should move less than .001" in your 4". If those two tests work out, then you can use your cross-slide vise as is. But what if they don't?

Well, say you are out .010" in 4" as far as square. You could certainly just correct it, couldn't you? Meaning, if you crank it 2.000" in the Y direction you know you have to crank it .005" in the X direction? Ah, that's how a skilled machinist can do precision work on un-precise gear!

*That's* what I meant!

Grant

Terry G wrote:

A couple of dial indicators would be great. But I only have ones that are

1" or less. I would need to have at least a 6" indicator accurate to .001". I don't know if they make something like that, and if they did it would probably be pretty expensive!

Yes, a dedicated machine would be nice.

I went ahead and purchased the el cheapo Enco table. At $68.00 shipped to my door I couldn't resist. I'll see if it is worth it or not, and just return it if it doesn't work out for me.

Thanks for the > >

Never thought of this before. It was be a piece of cake to do this since I already laid out the board. The template is already there. I would just select my test points and change the hole sizes of the vias to accommodate the pogo pins. I might actually give this a try. I'll still use a compound slide table to make it go quicker. But I wouldn't have to worry about the accuracy as much.

Thanks!

a lot of 5 boards.

annular pads and no traces.

That's expensive! You can 'step-and-repeat' with a one inch indicator but it's cumbersome. Your real trouble is that you are relying on inexpensive lead screws to be accurate within a thou over six inches. If you think about that, this would be one part in six thousand which is tough to do.

There are two other options you could pursue.

One would be to instrument the table with a Shooting Star digital readout setup. This would probably run you several hundred dollars. Good for +/- one thou.

Another would be to purchase two new Mitutoyo six inch digital calipers, and fit them to the cross slide. That would give you sub-thousanths resolution. Cost, probably three or so hundred total.

Jim

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Or set up your two 1" indicators in combination with using the standards from a 0-6" micrometer set. (For example, say you want to move exactly

4.000". Take the standard for the 5" micrometer, which is 4.000" long, and put it between the table and the indicator so the indicator goes to some handy location. Then remove the standard and move the table and when the dial indicator goes to that location there you are 4.000" away.) Using the standards assumes you can get within a degree or so by eye, remember that for small angles cos(x) is very close to x ..

Grant

jim rozen wrote:

I will take a look at the Shooting Star Digital Readout setup. I have had my eye on these. That would be nice to have for a bit more accuracy.

I'll just have to play around with my table a bit and get a feel for what exactly I'll need.

Thanks for the > >

I think that there's a lot of technology in the world that gets by where it otherwise would not, if only because of that single approximation.

Jim

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You can always extend the range of the dial indicators by putting in something of known size between the dial indicator and the place you are measuring. Those cheap 1 2 3 blocks would work for that.

Dan

Note that you can mount some angle iron (or aluminum) to the ends of the ways (oriented like this -- "\/") to hold a stack of cylindrical gauge blocks arranged horizontally. You can put a stack of whatever is needed (1.000", 2.000", 4.000" will cover your total range with a 0-1.000" dial indicator. You measure the end of the stack with the dial indicator. This is done on very accurate machines (e.g. jig borers) to get precision. The sets of cylindrical gauge blocks can be obtained without having to spend too much, as even a cheap Chinese set would be sufficiently accurate for your needs. And a 0-1.000" dial indicator can sometimes be picked up for as little as $8.00 (Cabin fever a few years ago.)

Enjoy, DoN.