Help with milling setup for novice

Hi,

I have recently purchased a vertical milling machine to cut slots in front panels of enclosures for our prototypes.

The main 2 jobs are cutting small (10mm x 15mm) slots in 2mm aluminum flat plate (plate is 65 x 30mm). And cutting slots in the end of 1.5mm ABS plastic enclosures.

My main issues are.

  1. What is a good way to hold down the jobs. (I have a set of T-Bolts and threaded rods etc but not sure how to hold the jobs securely in place without marking them).
  2. What sort of jig or template could I use to repeat jobs (small runs up to 30)

Finally any good web sites for info on milling operation and/or jig making would be very helpful.

Thanks in advance

Reply to
David
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David,

I will leave that to others. I suspect recommendations will include putting something between the work and a stap clamp, but there could easily be a better way.

I have been using qcad to create and print heavily (purists would say "over") dimensioned drawings. If you read through some of the recent replies (particularly Harold's) to me in the past few months, you will pick up a lot. A short version is that you can set your dials to 0-0 at the top left of your work and then count your way to any coordinates you need; it's even easier if you have a DRO. Back to the drawings, dimension everything of interest from the top left, and it becomes a very useful map. I doubt you will need a jig.

If that sounds like too much trouble, you could make a mask and spray paint through it to mark the work, and mill out the stuff that got hit.

Especially with the Al, you can stack several pieces and mill them all at one time. They probably should be bolted or pinned together; again I will defer to those with more experience.

Good luck!

Bill

Reply to
Bill Schwab

I have been holding down single pieces of thin flat stock with double sided sticky tape. I put it on the flat part of the mill vice.

For cutting many at once, you might make clamp bars with holes that pinch a stack of sheets with nuts and bolts.

Look at two fluted cutters running very fast and making a loud squeaking noise when cutting Aluminum.

Reply to
Clark Magnuson

...

A vacuum plate would be just great for this. You have a straight edge on the top and one side to locate parts. The plate area has a bunch of small holes that connect to a vacuum pump. You make a sacrifical part that covers the entire plate and has holes to pass vacuum where your production part is. You wouldn't believe how high a hold force you can get this way and no marking, super quick to go to next part, located exactly. Make your own, buy on Ebay, or buy new.

Karl

Reply to
Karl Townsend

David wrote in news:WHNof.26205$V7.21554@news- server.bigpond.net.au:

A vise and parallels for the aluminum should work fine. If you are going to power tap, add a hold-down clamp on top. Clamp a vertical bar, or some other straight piece of metal to the table at one end of the vise to use as a solid stop. Use the shortest parallel and stack the parts as deep as the vise jaws allow, so you can make several at one time, one set-up. You didn't mention the size of the abs enclosure, but a vise would probably work for that also.

For a manual machine and repeatable work, a DRO (digital read out) is a must.

If you set the vise at one end of the table, you can fixture the abs housings at the other. Then using the DRO, you set one zero reference for the vise fixture, and another for the housings.

Reply to
Anthony

Anthony,

For the metal, how do you control buckling? Any tricks to holding them well enough w/o squeezing so hard that they distort? I see just such task for myself early next year, and am open to any/all advice.

Despite many years as a beginner, I am basically just starting out. With that said, I am becoming convinced that Harold is correct. A DRO is a convenience, but not necessary if one understands how to manage backlash. In fact, he is obviously correct, because people did repeatable work long before DROs existed. You might argue that modern or small machines are not as accurate as the early monsters??

This from a guy who had 0.01 inch errors on two of four parts in a run ;) One of the slips was (I strongly suspect) due to inadequate stops (soon to be corrected). The other has no explanation short of operator error; I suspect I read the wrong number from the drawing. Whatever happened, I blew it. I care only for practice, +/- 0.05 inch would be more than adequate for the parts in question.

Mistakes aside, by measuring +/- 0.1 inch and reading the dials in a backlash-friendly way, I get where I want to go often enough to suggest that with a little practice, a DRO will not be necessary. I am also discovering that once a slot or window is partially cut, or (extrapolating because I didn't know to do this the last time) a hole is drilled, all one needs is the dial reading; an error in the number of revolutions will be visible with some care and bringing the endmill/bit close to the work.

Just don't turn your back on the power feed, or better yet just reset the relevant stop if the abs is below the vise =:0 No, I haven't made the implied mistake, yet :)

Bill

Reply to
Bill Schwab

---snip---

I'd mount a good vice then make a T bed to support and locate the plate, with a top to clamp the piece and also serve as a jig. The trunk of the T would be clamped in the vice, the top of the T bolted to the bottom plate to secure firmly while cutting. You'd probably make two jigs due to the length of the piece, or flip it if a mirror image.

Reply to
Wayne Lundberg

2 mm aluminum in the size you are working with should not be buckling unless you are cutting away a lot of metal in the interior.

When that is a problem, you use a sacrificial fixture, or "scab plate". This is some suitable piece of scrap that can be held in the vise (or bolted to the table if large) and the part is bolted to it. In some cases, the panel needs holes in in, so you drill the holes and then bolt through the panel's holes into threaded holes in the fixture. This clamps the interior, making it stiffer.

The fixture can have clamps or bolts placed at good locations to hold and align the part.

Jon

Reply to
Jon Elson

Jon,

I think you are confusing me with the OP. I noted that the plates are fairly small in that case; mine will be larger, and yes, they will be fairly well splattered with slots.

That would work. The only other concern I have is how to get the holes in the right places so they line up in all of the plates. Thinking out loud a little, perhaps only the relative spacing would be critical, so I could clamp them to the fixture (using holes and clamps as you suggest), put a couple of holes at known locations in each, and the bolt the whole stack and clean up the edges. Getting the edges in relation to the original holes might be a problem, but if the first holes are in waste, it would not matter, or it might simply not matter.

Am I making any sense? Is there a better sequence?

Thanks,

Bill

Reply to
Bill Schwab

Any chance of posting a drawing of the part? DXF, IGS or DWG formats would fine It is easier to offer suggestions if there is a clear picture to work from.

Post to the Dropbox at

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If you have not used it before the directions are simple and easy to follow.

Errol Groff Errol Groff

Instructor, Manufacturing Technology H.H. Ellis Technical High School

613 Upper Maple Street Danielson, CT 06239

New England Model Engineering Society

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Reply to
Errol Groff

Bill Schwab wrote in news:r3Xof.6216$ snipped-for-privacy@newsread1.news.atl.earthlink.net:

If you stack these pieces 1-1/2" - 1-3/4" deep in the vice (whatever your end mill will take and keep on the flutes), there will be very little to no bucking, as it acts more like a 1-1/2" thick piece of solid material. You may get a little bucking on the top piece, if you do a hold-down clamp from the table should be all it takes.

While a DRO isn't absolutely required, it is a handy addition. If you are setting this up as a small production type situation, adding solid stops, two stations, and a zero point for each is nice.

Should be no problem then, however, one should strive for accuracy whenever possible.

Reply to
Anthony

Anthony,

Am I correct in thinking that the pieces need to have fairly consistent width for the clamping to work? If so, then would you put them in the vise on end to square them first?

For my related job, I will be starting by rough cutting sheets.

Very true, and I was quite pleased with two of the four, and even the "rejects" were better than most work I did in the past. I can't bring myself to scrap them; metal ain't cheap and time is priceless.

I mentioned it in fairness given the side I took on DROs ~:0

Bill

Reply to
Bill Schwab

(I was replying to the thread, not necessarily to a particular person.)

I noted that the plates are

Here's a procedure I used for making some parts that had a round exterior. I cut squares out of sheet stock, and clamped them to the fixture. I had holes in a recessed part of the fixture, beyond the part OD. Clamps held the blanks on the fixture. I then center-drilled and then drilled through all the holes. Under these holes were tapped holes in the fixture. After drilling the holes, I then blew out the chips with compressed air, and inserted clamping bolts into three of the holes. I then could remove the clamps around the OD, and mill the entire OD without any interference.

This is much easier with CNC, but can be done with a manual machine, too.

Jon

Reply to
Jon Elson

Yes. Even when I gang-machine the plates together, and then put them flat between the jaws, some will try to slip. You can put a sheet of paper between the jaws and the plates. Sometimes, I put a piece of soft wood between the plates and the movable jaw. (The fixed jaw is the reference jaw, so you don't want anything crushable there.)

I used to have badly worn leadscrews on my manual Bridgeport, and couldn't figure out why two parts wouldn't align well. When I got an optical measuring system (forerunner to DROs) I found out that the screws were unevenly worn, and therefore quite inaccurate from point to point, even if you stayed to one side of the backlash. There was an error of almost .050" over 9". Once I had accurate measurement of machine position, I no longer had to file out bolt holes to get two parts to bolt together.

Jon

Reply to
Jon Elson

Jon,

Understood.

Ouch! Is there a way to replace the leadscrews?

That would defeat the purpose of having a precision machine tool.

Thanks!

Bill

Reply to
Bill Schwab

Bill Schwab wrote in news:pN6pf.6499$ snipped-for-privacy@newsread1.news.atl.earthlink.net:

Yes, the width needs to be exactly the same, so I most definately would square up the material first if you are cutting it from sheet. Put a bunch of pieces in the vice on edges, take a clean-up pass to get them all one height, then turn them over and finish to size.

Reply to
Anthony

Anthony,

Got it - thanks!!

Bill

Reply to
Bill Schwab

If the parts are large enough, I like to clamp them together with C clamps. Square all the sides before removing the clamps.

Reply to
Dave Lyon

Why, yes, of course! First, I got a Bridgeport optical readout, and then converted the machine to CNC with high precision ground leadscrews that I was lucky enough to come across.

Right, when it WASN'T precise, I had to file the holes to fit. I don't have to do that wretched stuff anymore.

Jon

Reply to
Jon Elson

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