Dowelled butt joints strong enough?

greensalad

I'm looking to make a sewing table to replace my current one and am considering DIYing it, as getting what I need made will be quite expensive. I have some experience with woodworking from a while ago, but not very confident in lots of different joints. 

I plan to get the boards (velvet matt veneered MDF) cut to size for me as I know that part would be the most complicated, and then I was hoping to join together using butt joints and dowel/glue as I'm confident with that type of joint.

The design for the table is pretty basic, it's a solid sided table with a short support towards the back, I've done a sketchup design (although I'm rethinking the top to be a deeper 25mm board so I have more dowel depth to work with).

I am thinking dowels and glue would be enough, particularly in MDF?

Ectophile

Without a solid back that goes all the way to the floor, that desk is going to be very wobbly.  It won't have anything but gloe and dowels to stop side-to-side swaying.

km1500

might be worth attaching it to a wall for stability

greensalad

Ectophile said:

Without a solid back that goes all the way to the floor, that desk is going to be very wobbly.  It won't have anything but gloe and dowels to stop side-to-side swaying.

Would the support at the back not help with that? I could put that support all the way to the ground I suppose. It's just more material needed. 

Obviously as a sewing table it's going to have a lot of vibrations hence why I need it to be strong, but I'm just not confident enough building other joints myself.

What sort of joints do you think something like this is using? https://www.madeinply.co.uk/collections/custom-desks-with-legs/products/custom-plywood-desk-with-solid-sides?top_shape=Desktop&w=1200&d=600&hl=750&top_th=24&top_material=Natural&mat_top=Plywood Birch&sup_style=Solid Sides for Desk&leg_th=24&leg_material=Natural&mat_leg=Plywood Birch&cablehole_style=None&cabletray_number=None

jennifernil

I am not a fan of this MDF stuff, much prefer real wood!

My OH has made 4 tables to a design that we originally found in a Readers Digest DIY book, though, instead of mortise and tenon joints, he used 10mm diameter dowels.   The original design was for a table with an extra attached drop leaf that could be lifted and slid along to make a bigger table.  He made 2 like that........my original sewing table in 1978, still in use, it has an offset crossbar to allow for the sewing machine foot pedal, and a kitchen table for our previous house in 1983, which went with the house.

All the supporting frames are made in pine (sewing table) or Douglas Fir ( the other 3).    The sewing table has a varnished blockboard top.  The one we sold with the house had a 40mm thick Maple top.

Then he made the  2 tables for kitchens in our our present house, in 1989, one now passed on to our son.   They do not have the extra leaf.  The tops are made from 28mm thick beech block worktops.

Pictures below.

greensalad

It's a nice looking table but not quite what I'm, after. I want something with a melamine top surface as well, so was planning to buy pre-veneered wood. MDF makes it very cost effective, and then I was planning to finish with ply edge banding as I love the look of ply furniture but it's a lot more expensive than MDF and doesn't paint as well. If I could figure out if it's possible, I'd make the whole thing in beech ply and have only the tops be veneered, with the rest left as raw beech. 

flashg67

I'd be tempted to add a piece lower down too across the back -  - , just say a 1inch square section to give extra support? I've found mdf doesn't stand upto much abuse  -I prefer plywood personally  -not always that much more expensive?
Edit to add - I've used pallet boards to make a lot of stuff at home - there are lots of sellers on facebook selling the planks for £1 or so ready stripped

greensalad

I presume the larger the back panel, the stronger the table will be. I’m not against adding more material if it’d work:

https://theplywood.com/wp-content/uploads/2021/02/diy-sewing-table.jpg

ThisIsWeird

greensalad said:

I presume the larger the back panel, the stronger the table will be. I’m not against adding more material if it’d work:

https://theplywood.com/wp-content/uploads/2021/02/diy-sewing-table.jpg

That will be much stronger. If you use 18mm MDF for the sides and panel, you should be fine.

Don't skimp on the dowels, and have the end ones closish to the panel ends - 30-odd mm. And PVA the whole contact edges, not just the dowels.

It won't be dismantleable after this, of course.

Gavin83

What's the purpose of leaving the back open? Is it to allow more room for your legs? I think even some strips down each side, so the inside piece of wood forms an arch of sorts would provide the extra strength you need.

I also agree with the other suggestion, I'd be building this out of ply personally, but it would require you to apply some beading to the edges.

Ectophile

The deeper you make the back panel, the more rigid the whole thing will be.

If the panel is too short, the whole thing will be wobbly, and will collapse back into a flat pack if somebody bumps the side of the table too hard.