CRP 24x48 build/community help thread

[yackback]

Hello everyone, I've been lurking here for a long time and finally took the plunge. With Ahren's help at CNC Router Parts, I purchased a 2' x 4' kit (the 4x4 is just too big for the space I have currently available). There have been a few snags along the way, but Ahren has been extremely helpful in getting everything worked out. I would highly recommend purchasing from him if you are on the fence. Before making my purchase, I was most concerned about buying from a business that would be responsive and help me along the way....because I knew I'd need help. I know that I made the right choice now.

I will be including a build log to hopefully help people in the future....and hopefully have the community help me, because truth be told, assembling this sort of machine doesn't come natural to me. I will include as many pictures as I can along the way.

Here's an image of all of the various components:


And here's picture of the rough layout of the machine:

[yackback]

Let me preface this by saying a I'm a perfectionist....this can be both a blessing and a curse, but I'm hoping some of the more experienced builders here can tell me when I'm going a bit overboard or when my pursuit of perfection really is justified.

I started assembling the base. Should be pretty simple right? Well my pursuit of perfection doesn't agree with me.

Alright here are my objectives:

I need to make the cross members square in these two ways:




And also I need the height of all the cross members to be equal so that the mdf spoil board will sit flat across all pieces:


I assume there can be a little bit of error here since the spoilboard will ultimately be resurfaced..but having these pieces significantly off wouldn't be a good thing.

Now for this kit Ahren has opted to forgo using the 90 degree brackets that are in the e-drawings on their website in favor of directly attaching the ends of the cross members to the slots in the extrusion. This is accomplished by drilling access holes in the x-axis extrusions. My pictures will do a better job explaining:



With the button head cap screws on the ends of the cross members:





Now as far as stability of attachment, this seems to be perfectly strong enough to hold the base together....but I do find it a bit cumbersome to perfectly align things this way. I'm not sure if having the 90 degree brackets would alleviate some of my headaches or not. Next post I'll go into the issues I'm having.

[yackback]

Now when attaching the cross members in this way, even though I can line them up with the holes that have been drilled, it's still possible to get a bit of play in how the pieces are aligned. The following pictures are over exaggerated but meant to show what I'm referring to:

Straight:


Play Left:


Play Right:



Now to alleviate this problem, I grabbed a square:


I do believe this should ultimately solve that problem, but when going to tighten things up with the small Hex key I have on hand, the tighter things get, the more of a tendency the cross members have to twist with the screw and end up not being square after they are tight. I'm going to pickup some T-Handle hex keys and I hope that this will provide some extra torque in fastening these....and perhaps that make keeping the cross members straight a little easier.


Now the other dilemma is getting things square on the other axis. I was able to get one cross member fastened tight then checked how square it was in the other direction....and it wasn't perfect:





Notice some space in the first picture and how I use my finger to rock the square in the second picture. I'm not sure if the 90 degree brackets would fix this or if I really need to shim. Or for that matter I'm not sure if I really need to be all that worried about those being perfectly square. Perhaps I'm wasting my time because the x-axis rails are what I'll really need to ultimately adjust. Those familiar with these kits would be more capable of helping me with that decision.

[ger21]

To keep it from twisting, I'd clamp it tightly together before tightening the bolts.

As for the outer square, try shimming it with sheets of paper. If it's not too thick, try cutting shims from an aluminum can.

[yackback]

Originally Posted by ger21 To keep it from twisting, I'd clamp it tightly together before tightening the bolts. As for the outer square, try shimming it with sheets of paper. If it's not too thick, try cutting shims from an aluminum can.

Thank you for the response Gerry! What sort of clamp would you recommend using? A lengthy one that can apply pressure to each of the x-axis extrusions?

I do have some brass shims that I purchased for setting up my jointer a while ago. So I'll look into using those.

[ger21]

Any type of woodworking clamp that's long enough, but it looks like you'd need one about 5ft or more?

[yackback]

If you mean clamping like this:


Then fortunately I really only have to have a clamp that goes a bit past 33 inches. That shouldn't be too hard to find.

[CarveOne]

I would suggest making a clamping plate from scrap 3/4" MDF or plywood that is sized to fit the cross member extrusion with a slip fit notch. Clamp the plate to the side extrusion on one or both sides of the notch. If you want it to self square with the side rail, glue a piece of MDF to the top edge of the plate (full width) so that it rests on the top of the side rail to hold the cross member at 90 degrees. You can still get to the screws to tighten them.

CarveOne

[yackback]

Genius! I'm going to give that a shot. Thanks so much!

Originally Posted by CarveOne I would suggest making a clamping plate from scrap 3/4" MDF or plywood that is sized to fit the cross member extrusion with a slip fit notch. Clamp the plate to the side extrusion on one or both sides of the notch. If you want it to self square with the side rail, glue a piece of MDF to the top edge of the plate (full width) so that it rests on the top of the side rail to hold the cross member at 90 degrees. You can still get to the screws to tighten them. CarveOne

[CarveOne]

If you think the MDF is not strong enough, glue two plates together before cutting it. This can be cut on a band saw, or with a hand saw if you are careful to make straight cuts at 90 degrees.

CarveOne

[vtx1029]

You may want to add the metal clip 8020 sells. It prevents some of the rotation and distributes out the clamping force.

http://www.ebay.com/itm/8020-T-Slot-...item562ee87dd8

[ahren]

Not sure this amount of out-of-square will matter in the end, as the rails have much more adjustment than this. However, we are planning on going to another angle bracket instead of the triangular gussets (easier to get a wrench on the nuts) and forgoing the cross holes to make it faster for us to produce custom kits like this. Justen, I'll get some of these out to you along with the fasteners -- we should have our stock in at the end of the week.

Ahren
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