Calibration question

[wmgeorge]

IF someday my special order spoil board yes its 5x8 feet comes in I hope to get this done on mine. Meantime I have a $100 job to do in the morning regardless. When you faced your spoil board did you take off a lot? I ran a dial indicator on two of my cross supports and was off .036 inch on one, ant the other at the back only .020. So do I face the spoil board first and then try to square?? Suggestions welcome.

[ger21]

I would face it first, removing as little as possible.

[difalkner]

Ditto what Gerry said - always face it first. I take off only as much as is needed to get the entire board flat. Unless I'm in a hurry I start with about 1/32" just to see where the high/low spots are but that's probably just me being curious and a bit on the conservative side.

David

[GME]

This was the key, Gerry. I loosened and/or removed the 24 fasteners required to square the gantry at least 5 times before I got it dead perfect. You can see in the spoilboard how many rectangles I cut so I could measure the diagonals. I cut multiple rectangles of 23x46, 22x44, and 20x40 and kept sneaking up on 'perfect' until I finally got it to where no matter what size rectangle or square I cut the diagonals are identical. At least, they're as identical as I can see with 3.0 reading glasses and getting right down on the tape to compare each measurement.

At one point the diagonals different by 3/16" on the 23x46 rectangle. And I don't have to be concerned with temp and humidity because the shop is climate controlled 24/7 but that aside, neither temp or humidity will have enough effect on MDF in the span of a few minutes to cause a change. I'm comfortable enough with my measurements and methodology at this point to say this is as close in calibration as I can get this CNC machine.

You can see here how many times I cut for these tests (patience is one of my strong points - LOL!) -


David

Congratulations on getting your gantry squared.

Just curious; how did you keep one side of the gantry at least semi-fixed while you adjusted the other side?

Gary

[GME]

IF someday my special order spoil board yes its 5x8 feet comes in I hope to get this done on mine. Meantime I have a $100 job to do in the morning regardless. When you faced your spoil board did you take off a lot? I ran a dial indicator on two of my cross supports and was off .036 inch on one, ant the other at the back only .020. So do I face the spoil board first and then try to square?? Suggestions welcome.

I second Gerry and David. Surface first.

I used a pencil to scribble wavy lines all over the top and then took a few thousands off at a time until all of the pencil lines were gone. I used a 1-1/2" (1/2" shank) bottom cleaning bit to do the surfacing. As long as you're trammed, it does a nice job and the it's inexpensive for a bit this size. The Yonico 14976 sells for $22.95 with free shipping.

[DDgitfiddle]

I second Gerry and David. Surface first.

I used a pencil to scribble wavy lines all over the top and then took a few thousands off at a time until all of the pencil lines were gone. I used a 1-1/2" (1/2" shank) bottom cleaning bit to do the surfacing. As long as you're trammed, it does a nice job and the it's inexpensive for a bit this size. The Yonico 14976 sells for $22.95 with free shipping.

Another decent deal is the CMT 663.004.11 bit. It sells for about $77 on Amazon and is 2 3/8" diameter with indexable carbide inserts. It is a little pricey, but a good deal compared to others of similar size. The only down side is that it has a 12mm shank instead of 1/2 inch. A 1/2 inch collet doesn't really squeeze down that far. Also nice for facing large slabs of rough-cut lumber. Helpful when you don't have a 12" jointer to go with your 12" planer.

-Robert

[GME]

Another decent deal is the CMT 663.004.11 bit. It sells for about $77 on Amazon and is 2 3/8" diameter with indexable carbide inserts. It is a little pricey, but a good deal compared to others of similar size. The only down side is that it has a 12mm shank instead of 1/2 inch. A 1/2 inch collet doesn't really squeeze down that far. Also nice for facing large slabs of rough-cut lumber. Helpful when you don't have a 12" jointer to go with your 12" planer.

-Robert

Thank you for the information, Robert. I just ordered the CMT. I also ordered a Techniks ER20 12mm collet on Ebay. I bought them mostly for wide lumber facing (wider than my planer). I have t-tracks, 1/4-20 screws and blocks for hold downs, and virtually never cut into my spoilboard. I zero to my spoilboard, do a g90 move to the nominal thickness of what I'm cutting and reset Z=0 at the nominal thickness of the material. If I'm not cutting full thickness anywhere on the piece, I zero off the top of the material.

Thanks again,

Gary

[wmgeorge]

You must of retapped your table holes as mine are 6mm. I have a 1/2 inch (I hope) shank facing bit to use.

[GME]

You must of retapped your table holes as mine are 6mm. I have a 1/2 inch (I hope) shank facing bit to use.

Sorry. I didn't provide enough info. I currently have an 80/20 extrusion 4x4. My spoilboard is mounted with 5/16" screws and t-nuts. I'm thinking about upgrading to a Saturn 2 and will deal with the tapped holes and spacing with it.

I like the rigidity of a 1/2" (or 12mm) shank for most things that don't absolutely require a smaller shank.

If you're interested in a T-track setup, you might want to look at Orange Aluminum as a source. Best price I've found, and they are good quality.

Gary

[wmgeorge]

Thanks Gary. I have my T slots and whatever. I did also come up with a drill pattern for the 4x4 machine I have, so I am happy not to have to locate and drill 30 holes.