Clamping and holding work

I didn't need much more than a good sturdy milling vise to get me started. You can make lots of clamps, jigs, and other work-holding fixtures in a good vise. Parallels are a vital tool to have when working with a milling vise, but since I have a bunch of square HSS toolbits of different sizes I haven't needed to go and buy parallels yet. I just stack some up under the work and I'm good to go. I just made a pair of V blocks for a project I'm working on (a plate bender). Since they're only made of mild steel I can't harden them, and even if I could I can't finish grind them, but oh well, they'll suffice for this project (milling a 3" long flat half way through a 2" diam. carbon steel bar) and maybe a few others.

Probably the most challenging thing about using a miller is figuring out how to set jobs up. As you find a need for a special item you can buy it and add it to your collection, much like people do with drill bits - purchasing only the ones they use often and not wasting money on whole sets where half of the bits never see a chuck.

Dave,

for small irregularly shaped items I use a low melt alloy (Cerrobend) - it melts in boiling water and can be poured round the item locking it into a frame that can be clamped. Works a treat and the alloy is infinately re-useable.

Andrew Mawson

Hi Dave, Another way to hold stuff is to make an extra table, from 1 inch thick plate. You can drill and tap holes in it to secure pieces. Also, drill and ream holes for ground pins for alignment. So, say you need to mill a rectangular workpiece on all edges, you set it against some pins and clamp it down so it hangs just off the corner of the plate. Mill the exposed to edges, then turn the work piece around so the other two edges are hanging off the table and mill those, the pins keep everything square. If you bolt some tangs to the underside and mill them accurately to the width of your main table slots, and mill around the edge of the extra table while you are at it, it will self align on the main table.

regards,

John

Jewellers use a vise that has a pair of plates with holes in 'em. The put steel pins in the holes, the work between the pins, then they screw the plates closer together. For really irrgular shapes something like that might work; take light cuts.

What is a useful amount of Cerrobond? At $35/lb (IIRC), I don't want to buy more than I'll need. Or less. Bob

You're certainly correct. Workholding is half the challenge. Its deeper even than this; design of good fixtures was what they did before CNC milling, and it still works pretty good for manual milling.

I would say my short list is:

1. Vice.

1. Vice with parallels.

2. Clamps.

1. Side clamps, those clamps that hold the part at the base like powerful fingers.

2. "pot it", or use low melting temperature metal to hold it.

1. Bolt or screw the workpiece to a plate.

For REALLY odd shaped workpieces, 6 cannot be beat. You get some extra screw holes - big deal. The part is held to a plate with complete access to all sides save the one face down. With most parts, it hardly matters if there is an extra screw hole, and if it does, it can be filled by various means.

You get some

Chuckle!

Apparently you've never worked where parts are built to specs. An extra hole is called scrap.

Harold

On 1 Sep 2004 22:49:37 -0700, galt snipped-for-privacy@hotmail.com (Dave) calmly ranted:

Nope. Dozens of entire books are dedicated to jig building. Most have much more sophisticated names for it, though. ;)

Hey Andrew:

I think the crux of this hobby, for many, is the creative parts. I've been working metal for just several years, not a lifetime. I've never had the pleasure of working on a Bridgeport, or a heavier mill. I have amassed clamps, vises and parallels, because I apparantly have not seen a set of parallels at auction that I didn't want to buy - for example.

I think your question is a good one, as it does get the creative juices flowing. But with my simple gear - and a rotary table (import) - the solutions usually offer themselves up after some study.

I think too, that we all get pulled into the overthinking trap.

I've been trying to figure out a way to tell if my garage door is open. I ran a remote switch to the house (can't get to the attached garage from inside) with 4-conductor wire. So, I'm pondering a way to utilize the other pair for some light or something. My good friend comes by and I miserate about the alternatives. He says, "why not put a mirror on the tree out front?"

Why not indeed.

Think extra lugs to clamp or screw down which get milled off in the last operations.

ffredd

... er .... John I think you mixed up questions and answers here - mine was an answer !!!!!!!

Andrew

Right you are Andrew.

To the original poster, stop worrying. You might mill for years before you come to a setup you can't do. Most stuff you can do in a vise. What you can't you can usually clamp to the table. When I get an oddball profile that isn't critical I just stick the part in the vise, mill off a little, turn it some, mill some more, and like that, ending up with a piecewise linear approximation just outside of the layout line, then I freehand sand to the line. I've made some pretty stuff that way.

Watch the machining mags. Some of the guys writing in there come up with some great ideas.

Grant

Gee Harold , I guess that you've never kept a farm rig running ;-) lg no neat sig line

Then I better not mention welding the part to a piece that's convenient to hold. Works great for turning discs or rings from plate in the lathe.

Ned Simmons

Probably. A good set of machinists jacks and a good tiedown kit will handle 99% of what you may run into. Sacrificial blocks beneath the part that you can cut through without worrying about hurting something else also come into play. Even cutting up to a clamp, stopping and moving the clamp to behind the cutter works quite well when the piece is thin. Clamps made of mild steel or aluminum that you won't be hurting anything by cutting into them also works. Just don't waste any more time making them than you have to, doesn't make any sense for something you're going to use once and toss when you're done. Reasonable milling vises are cheap, if there's money in a job to cover it, and you have to cut into it, that works too. Parallels, mine are all of mild steel, ground, and sometimes drilled and milled into, but cost is low. Use it once, either toss it or mill and regrind for the next job.

Not to say that some jobs are not tricky, but the answers usually don't have to be expensive or complicated.

The design of good fixtures for CNC work is often the difference between a "good" job, and a loser. Trust me on this, it's what I do.

For the OP, get some .25 x 1.75 aluminum rec bar stock and cut a bunch of 6" pieces. Cut a few pairs around 9' or so, also. Then you can make whatever height parallel you need, as required. You can even drill or mill into them without trashing your cutting tool. Some curved or bent spring steel or thinnish brass works nicely to keep said parallels in place.

I could go on and on, but I gotta lot of work to do.

michael

Aaarrggghhh! Welding? On parts for the aero-space industry? Man, you and Larry G.

Where I came from, something as small as an improperly deburred edge was rejected. You weld on a part, it's automatically scrap unless you see a requirement for welding included on the print. I guess it's all to do with the industry that you serve.

Harold

I know, can you believe that at the last place I worked, they used just tossed all those extra holes away! Don't tell, but I made off with a large bin full. I pretty well set up with holes for a while but it you need some, let me know. I've got diameters from about #30 up to 3/4" and the shipping is cheap!

Greg

PS. How many holes does it take to fill the Albert Hall?