Milling something larger than the table travel?

[silverhawk]

Just a quick question, how would someone go about milling something flat that is larger than the table's travel (without buying a new, bigger mill)? I have something I need to square up and cut a dovetail on, and unfortunately, it is longer than the table itself.

 

[MontanaLon]

How tight are the tolerances? You can usually get pretty close by putting pins in the t-slots to act as a register against 1 side of the work and clamping to the table. Slide the workpiece down and reclamp as needed.

 

[derf]

Swivel the head.

 

[cathead]

If a person is careful, one can use multiple set-ups and move the work several times. I did this to make new reverse
actuator and feed rod on my Monarch lathe. They are about six feet long each. I mounted a level securely on the
work as the work was round and also used secured vee blocks for positional accuracy. It worked out fine.

 

[Boswell]

I have done this multiple times. I ensure that I have a feature that I can register against that is common to the first and second setups. and then reposition the part and use the common feature to ensure alignment.

 

[silverhawk]

Tolerances are a bit unknown. I'm trying to make the taper attachment dovetail for a lathe, and it's a part I do not have access to (it was missing from the stock).

My fear is that the piece I'm working on does not yet have a registration surface (anything "flat"), and that would mean that any shifting away from the original tie down points could result in misaligned milling planes (not flat). I suppose I could repeat the process, just taking skim cuts on opposing surfaces and then flipping it over until I can drop a straight edge on and not slide an 0.0005" feeler gauge underneath (kind of like using a home-grown index plate to make the real index plate, increasing your accuracy each iteration). Once I have a flat surface on the long side and on the adjacent long edge, the pins/part-translation/re-setup technique should work up until I get to cutting the dovetail, but if I have it squared then I can use some table stops to keep it aligned for the dove tail.

Over night (sometimes sleep is good) I thought about adding another single axis table to "compound" the distance, but it would have to be low profile because of the cutting area. I do worry about rigidity, but if I use some clamps and move things around, I might be able to get that first side flat, and a long edge.

The stock is 18.5" long, 3.125" wide, and 1.25" think. It is larger than I asked for from the metal supply shop, so I have to get it to dimensions.

The mill is a "mini mill" from Harbor Freight. It has been a great little mill for what I had room for up until this point. The table travel is 9"x8"x4", so I know I'm good in two dimensions, it's that 18.5 vs 9 that stopped me dead in my tracks for a bit. So the question is :

a) Pins and skim cuts?
b) add another single axis table?
c) Something else I'm not thinking about?

 

[silverhawk]

Swivel the head.

This is a little tougher with what I have to work with. Another option would be to run it at an angle (a 45 degree angle bolted down would get it nearly there).

 

[mickri]

Post a drawing or picture of what you are making. That will help everybody to give you better answers.

 

[silverhawk]

Sure thing. Here's what I have to work with (stock on the table) :

Here's what I need to finish it as :

If I can get two sides flat (the bottom and one long edge), I'm okay with shifting the work piece (even with the dove tail, as I can use table stops to keep it lined up).

 

[silverhawk]

I just had another thought. If I used 1-2-3 blocks on each end instead of pins, that should give a large enough foot print on the stock to keep it the milling planes from getting too far out of whack. I should be able to do that and mill one surface with flipping the stock to use that newly milled surface as the next face. If I do that twice (with a rotation along the z axis in between, so a long end swap to keep it even), I should have it close enough. Then it's a repeat for the sides, and that should give me exactly what I need. I'll do a direct-to-table clamp once I have both registration surfaces. After getting it squared, (don't care about the ends, I'll be putting a bevel on them), I should be able to cut the dovetail using table stops to keep it lined up.