. Everything is level. Before I take my table apart to re level the cross beam, anyone deal with this or read about it?
The center sags roughly around 0.01" before I surface it out. When I checked the beam today against a straight edge across the offending beam and the two on either side of it. It looks about ⅛"+/- lower. It doesnt appear to have adjustment room to remedy that either. Any bright ideas?
Are able to check if both Y rails are perfectly flat? Also verify the MDF is actually not flat.
Y rails are flat and level/coplanar. The MDF is very clearly not flat. The grid lines i cut in are almost completely gone front and back, but middle is crisp and deep. Its flat now, just seems like I shouldn’t have to surface a sealed spoil board monthly. Im going to further inspect that cross beam underneath it later today.
@Afterlife, are your machine legs splayed out? When measuring corner to corner at the top of the legs just under the table does that measurement equal the corner to corner at the bottom of the leg measurement? Splayed out will pull the center of your table down. Corralled in will crown the table surface. While the table and legs are stout, they do move around under aggressive machine movements. People have reported an improvement in table movement from adding crossmembers at the bottom of the legs. Hope you find the cause if this post doesn’t help.
I have a whole shelf underneath. All braced. I can see what you mean how it would cause the table to do that, but say my legs are all braced as they are, wouldn’t surfacing solve the dip? I surfaced many times now with the dip returning shortly after. I do have one single beam under the dip that is lower in the center than all the rest. Just cant figure out why its doing it. Im thinking im going to redo the entire top and thoroughly inspect everything
I’ve got 2 onefinity machines, and 1 is 4x4, i’ve not seen this yet on my altmill 4x8. the 4x4 is vacuum table and it pull hard on it. i bought supports amazon and put under it - now much better, the table i built for my 32x48 1f machine is much studier and while it flexes in middle, not like the others.
i do stand in middle of my 4x8 and weigh about 240. i’ve not noticed any flex, and when i surface, it stays consistent. when i cut profile cut outs. i use bottom as reference, and cut z+.003 and have no issues on my altmill, on my 4x4 1f, i do have to increase to z+.10 if it has been little more humid. and yes, mdf does move. i make shaker cabinet doors from mdf, and hdf. ive gone to 2 piece doors just to stop the flex. cut out fully on back side, cut rabbit, use vbit to .010 scribe on both of those lines to stop paint bridging rabbit is 1/2 deep, i use for center 1/2 mdf, and outer is 3/4 hdf. hope this helps.
btw, i have about 4400 hours cutting on all my machines. 2 1f machines in 68 deg year round shop, altmill not yet, but will be soon. also on 48x48 1f, i just braced it up more to stop movement and it seems to help. after i run a bit, i’ll reshim it to co planer and see how that goes.
Can you tell me about the bracing you used? Amazon link maybe?
