Anyone got any tips for maching parts way bigger than the travels?

[digits]

Hi guys has anyone got any tips, or even better pictures of setups for machining parts that are way bigger than the travels of their machine?

What I need to do is surface (face mill) a couple of 1100mm long bars of 50x50mm steel. I probably will need to skim all four faces to get it square, but most of all, I need 2 perfectly parallel surfaces 1000mm long as I want to mount linear rails on them. My machine has about 550mm travels, and a 840mm long table. It should be man enough to cut full-width, but I'd probably only want a 0.5-1.0mm DOC so I'd probably have to take a couple of passes on each side.

I look forward to hearing your suggestions and seeing your pics!

Cheers.

[hoss2006]

I milled a column on my X2 in stages using slot pins to keep it parallel as I moved it along each pass.
You could clamp like I did and mill half of the face at a time, then flip the clamps to the other side.
Sounds like you have enough table width to use toe clamps on either side leaving the face free for full width milling.
I didn't have room to use the clamps I have like these.



Mitee-bite make some pretty compact ones.
Hoss

[vlmarshall]

Hoss' toe clamp idea is a good one, they're really useful.

I use them, teamed up with doublesided tape, when skimming material flat when I want to cover the surface in one pass.

Tape will hold the part down and toe clamps will hold it in place. You'll WANT to take multiple passes, to get the curve out of the material, instead of clamping it to the table and forcing it flat.

Leave the tape out for the finish passes, to eliminate any height change, and if you can, leave the mill head at cutting height while moving your part around, to avoid repositioning errors.

[digits]

Thanks for the replies guys

Hoss, I don't have any toe-clamps, but I might invest in some. I do have a couple of 4" vices which might be suitable for clamping. I couldn't think how to get them both lined up straight, but then I remembered I have some long bits of aluminium tool-plate lying round. I'm thinking I can dial in one vice. then clamp the tool-plate thickness-wise in both vices and the other vice will be close enough to dial in exactly. Alternatively I could just dial in along 300mm or so of the tool plate between the vices.

vlmarshall - I've heard of using tape before, but never had the balls to try it! I'm not sure it would work that well with this steel stock as it has mill-scale all over it. I also need to be able to reposition several times to mill the full length, but I will keep it in mind for when I've got the stock almost flat.

I'm going to have a quick go at mocking up the two-vice setup. I'll try and post a pic or two.

Cheers.

[hoss2006]

I was going to suggest 2 vises, but who has 2 vises.
sounds like a winner.
Hoss

[krutch]

As far as locating details out of the travel limits, when possible, make a hole in a known point to use to locate after moving work to new position. In a work piece in which I was milling round and rectangle holes, to relocate for those be on the travels. I would drill and plunge an end mill to pick-up after moving work to reach remander of features. The end mill plunge was to give a round hole for easier pick-up. If the tolerance is tight, ream the hole. I sometime use a dowel pin for pick-up.
Krutch

[digits]

Originally Posted by hoss2006 I was going to suggest 2 vises, but who has 2 vises. sounds like a winner. Hoss

I'm actually considering getting a 4th vice - another one of these:


as they are so nice, but the do weigh 40kg!

I'm also lusting after a proper CNC vice with ground parallel sides and matched heights between pairs of vices like these ones: http://www.glacern.com/gdv_416fe

I've got the tool bug bad! I haven't really made anything yet - except for more tools!

[digits]

Originally Posted by krutch As far as locating details out of the travel limits, when possible, make a hole in a known point to use to locate after moving work to new position. In a work piece in which I was milling round and rectangle holes, to relocate for those be on the travels. I would drill and plunge an end mill to pick-up after moving work to reach remander of features. The end mill plunge was to give a round hole for easier pick-up. If the tolerance is tight, ream the hole. I sometime use a dowel pin for pick-up. Krutch

Thanks Krutch - I was thinking about doing that, I'm glad to hear it really works!

[BobWarfield]

Originally Posted by hoss2006 I was going to suggest 2 vises, but who has 2 vises. sounds like a winner. Hoss

Hey, that's mean to make fun of people with 2 vises, Hoss!



Those are my new Vise Jaws of "Doom" spanning 2 6" vises, one a genuine Kurt, and one a very nice Glacern.

Looking forward to having some fun with that bad boy!

Cheers,

BW

[hoss2006]

Boy, Digits should borrow that setup.
Hoss

[BobWarfield]

I wound up putting that vise setup together because I was doing some engraving and the surface finish was terrible. Trying to hold the piece in one 6" vise and it was too long, leaving the ends unsupported. Even though it was 1/4" 6061 plate, it was still too floppy.

I had seen big jaws like this in Widigtmaster's threads, and since I have one vise for each of my two mills, it was a no-brainers.

Digits, if you have 4 vises, you should definitely try something like this. I reckon I could even put on temporary tooling plates like pallets using the silly things.

Best,

BW

[digits]

Nice setup Bob!

I've only got 3 vices at the moment, two small and one large, but I'm going to give it a go now with some 123 blocks to match the heights between the two cheap vices.

I don't think I need monster extended jaws just yet, but they do sound necessary for think work.

Cheers.