Forums: Whisstock Designs: finger joints on DXF files New Topic Post Reply
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dozigman
Posted: Apr 3rd, 2016 at 18:07   |   Subject: finger joints on DXF files
Hello George,

We have these files and they should speed up fabrication tremendously. Does one first locate a firm to do the cutting? And when the finger joints are cut, can the sections be glued up off the boat while maintaining accurate alignment longitudinally? Is that what the little marks on the ends are for?? Also, how does one glue up the joints properly for strength?

Thanks!
debenriver
Posted: Apr 6th, 2016 at 11:47   |   Subject: finger joints on DXF files
Hi Doug

Good to hear from you. Sorry for the delay replying.

If you can find a shop in your local area that does CNC cutting that is the best. Sometimes, smaller companies have CNC set-ups which they use for their own work, but don't look for outside work, but if approached, are happy to do the cutting for you – builders have found companies like those that manufacture custom kitchens for example, often have under-used capacity. So it helps to ask around the area. It's also quite a good idea to have a sample cut before embarking on the whole deal. Several builders have their materials cut in batches, to suit what they can handle at one time. With larger CNC companies, this can be costly because of set-up costs, but smaller companies are often happy to fit it in between jobs.

The planks can be glued up off the job, laid on a flat floor or a long bench. The finger joints are fairly self-aligning but the little lines are there to double check that the alignment is correct. If you stretch a taut string line from one end to the other (of the assembled plank), all the line marks on the planks should lay accurately under the string. If your floor is wooden, you can drive a few nails each side of the planks to keep them accurately in line.

To bond the joints, follow your normal procedure – wet out the bonding surfaces – perhaps wet them out twice in this instance, as the epoxy will soak into the end grain. Then use the thickened epoxy (WEST™/#403/#406 mix if you are using WEST™ epoxies). Make it a fairly thick mix and apply to both surfaces. The #406 Colloidal Silica improves the strength of the bond and helps prevent loss of material out of the joint. Then just slot together, check the alignment, and allow to cure fully. Make sure not to get a dry joint.

To add extra strength, epoxy/glass over the joints on the inside of the plank. You can do this as you bond them together. Or afterwards, once the joint has gone off and you have cleaned it up. Use about 6 oz cloth and run it about 6" or so each side of the joint.

Best regards

George

dozigman
Posted: Apr 25th, 2016 at 17:02   |   Subject: Thanks so much!
I think I forgot to reply thanking you for the comprehensive reply. Makes total sense.