Creating hole with square mortice

[ajayre]

I have to create about 20 of these holes in plywood for a one-off personal project with a very short deadline. They have to be fairly accurate. I have a drill press, plunge router and a 3D printer. Any suggestions on how I can make these with minimum effort but high consistency? Willing to buy new tools to do it.

Thanks!

 

[ChaiLatte]

Are all the square holes in the same piece of plywood?

Do the sides of the square have to line up with each other or with an edge of the plywood?

 

[ajayre]

Are all the square holes in the same piece of plywood?

Do the sides of the square have to line up with each other or with an edge of the plywood?

Up to four holes per piece of plywood.

They will be in a row down the middle of the wood strips, so aligned to a center line, parallel to a long edge.

 

[Amplidyne]

Not impossible by any means, but a bit tricky with those 0.1 mm tolerances IMO.
Does it need to be that tight?
For the square hole I would make a simple template to cut it out with the router, and then square the corners by hand. It's need to be a good template, probably plastic or alloy though, and a good register on both (?) edges of the ply. Even then a router that will give that sort of accuracy on the plunge is needed.
You could use a drill guide of the right size that fitted in the square template to drill the smaller hole, it might need reaming though for that accuracy. Not sure how well ply reams? I don't think I've ever tried.
Again you could make a centred dowel to fit the smaller hole to drill the larger one, probably with a Forstener bit.
But then that all needs some metal turning equipment, sorry.
Anyway it's just ideas.

 

[bourbon]

0.1mm tolerance in plywood? Take it indoors and it will have moved by that much!

 

[ajayre]

0.1mm tolerance in plywood? Take it indoors and it will have moved by that much!

I hear you, but the stupid bolts and the material requirement are imposed on me.

 

[Amplidyne]

You say that it's a "personal project". Do the parts have to be removable, or can it be made a good fit in wood, by the time honoured method of making it just a tad tight, and then using a little persuasion to fit things together? Makes sure there is not play.
But as bourbon said, wood, even ply, isn't that stable. If you need a tenth of a mil tolerance for accuracy with something, you're looking more at metalwork tolerances than woodwork I reckon.

 

[Jacob]

I have to create about 20 of these holes in plywood for a one-off personal project with a very short deadline. They have to be fairly accurate. I have a drill press, plunge router and a 3D printer. Any suggestions on how I can make these with minimum effort but high consistency? Willing to buy new tools to do it.

Thanks!

View attachment 194046

All out of scale? Your measurements are all cocked up.
What are you trying to do with this?

 

[HappyHacker]

Outsource to a laser cutting company.

 

[gcusick]

1. Start by making some proper drawings, accurately to scale, and showing both the section (took me a while to work out your original sketch).
2. You’ll then see that the square hole is only 0.3 mm larger than the 4.9mm hole.
3. Trying to rout a 5.2mm square is a fool’s errand. If this is for the square shank of a coach bolt, just drill a 5.3mm hole and press fit.
4. As others have commented, 0.1mm tolerances in plywood are, shall we say, optimistic.
5. As an alternative, why not 3d print an insert with the square and 4.9mm holes, and glue it into a 10mm diameter hole.

 

[Deadeye]

I think your square bolt will strip through that hole if the 0.1mm tolerances move against you!

 

[okeydokey]

Sorry but however long I look at your sketch all I can see is a strip of plywood 24mm wide (no idea as to length or thickness) with 2 toothed sections (left and right) that are not joined to each other. So all I can see a a need for 2 bits of ply slightly different to each other.
I must be missing something here.

 

[Jacob]

Sorry but however long I look at your sketch all I can see is a strip of plywood 24mm wide (no idea as to length or thickness) with 2 toothed sections (left and right) that are not joined to each other. So all I can see a a need for 2 bits of ply slightly different to each other.
I must be missing something here.

It'd make more sense if the 5.2 and 10mm hole sizes were 52 and 100, the 0.1mm should be 1mm and the 4.9 to be 5mm.
If we knew what our logical positivist OP was actually trying to do it might help!

 

[ajayre]

Thanks for all of the replies. This is for carraige bolts into Far Eastern plywood. They have to be removable and insertable many times.

I am now thinking that all I need to do is crush the bolt into the wood the first time to make the square hole after drilling a 5mm hole.

I was reading that after doing this I could remove the bolt and use a thin epoxy resin to harden the impression but some sites I read said that it doesn't really work. Any thoughts on that?

Thanks!

 

[ajayre]

Sorry but however long I look at your sketch all I can see is a strip of plywood 24mm wide (no idea as to length or thickness) with 2 toothed sections (left and right) that are not joined to each other. So all I can see a a need for 2 bits of ply slightly different to each other.
I must be missing something here.

It is a cross section of the hole.

 

[ajayre]

All out of scale? Your measurements are all cocked up.
What are you trying to do with this?

What do you mean? It isn't a scale drawing.