mvaughn's CNC machine worklog

[buscht]

Mark, you are doing a great job, that base is super. I just put my machine on an extra dinner table I had in the basement.

I prefer to either glue and wood screw MDF together or use Confirmat screws which are design especially for MDF. I have never tried to tap MDF, although it would probably work. It seems like alot of effort to me.

Always predrill your holes in MDF no matter what screw you use. The end grain strips out very easily.
Trent

[High Seas]

Mark - thats looking swell. Hope you're gonna stock the fridge with plenty of brews to celebrate when you "fire-up!"
Have you considered using a dado blade, slotting the mdf and gluing up? It would require you redimensioning any of your drawings a bit - but you'd have a pretty strong joint.
I did that on some 1/2 inch and it got a bit wiggly - but stabilized when dry. The biggest problem I had with that approach was the fact it was 1/2 inch mdf - really too light. Will move up to 1 inch on the redo, and dado again.
Cheers - Jim

[Patrick2by4]

glue and screw

[ger21]

I'd go with a 1/8" deep dado, glue and screw.

[mvaughn]

You guys have talked me into the glue and screw method. Seems simpler and more cost effective.

The dado is a great idea however I just finished cutting out all the pieces before I read this suggestion. I'll make a mental not for the next machine...

[High Seas]

If you think you might need more glue surface - you could make some glue blocks and lay along side the joints to add surface area. Just an extra 2 cents worth - you probably knew that, but I know in the "heat of construction" I sometimes forget the simple things and have to back up and add 'em in later too... I say that having spent all day on the master bedroom ceiling recessed/tray lighting - ughhhh added some extra blocks to support -- hehehe arggggh
Jim

[mvaughn]

Thanks for the tip Jim. I think I'll play it by ear for now and if I see a weak spot I'll probably glue in some gussets.

[mvaughn]

I managed to get a few more pieces cut out today. These pics are of the gantry pieces. The sides of the gantry have been the most challenging so far because of their shape. I used a harbor freight jig saw to cut them out after tracing them onto the mdf with a template.

I clamped the two sides of the gantry together so I could do a little touch up sanding to get them evenly squared up. I'm also going to drill the holes for the lead screws and bearing rods before I unclamp them to make sure they are true.

The I-beam shaped piece is the rear brace of the gantry. The other two pieces will join the sides of the gantry together at the bottom.

[mvaughn]

Here are the two table end pieces. They are clamped as well so I can drill the holes for the x-axis bearings and lead screw. I have also marked them for four notches that will hold the 1" square tubing table supports.

By the way... The lines for the notches really are square. The perspective of the camera made them all weird.

[Patrick2by4]

It's coming out great mark, keep those post and pictures coming.

[mvaughn]

I've been thinking about how I'm going to finish the mdf. I think I read someone saying that you should shellac (sp?) the mdf before painting it. Can you guys put your $.02 in and let me know how you would recommend finishing the mdf.

[Patrick2by4]

I use a oil-based primer followed by two coats of a oil-based enamel. It does a good job sealing the mdf. I would only use a shellac based primer/sealer if drying speed was a big consideration. It isn't as effective sealing in the chemicals use to make mdf (formaldehyde will off-gass for a long time) nor is it as good a vapor barrier as oil-based finishes. Stay away from Latexes, they make the surface swell and become a little rougher.