Help with angled holes...

[cliveso]

Hello

Newbie here. I would really appreciate some pointers for making the attached design.

The design is an air valve, a bit like a valve of an internal combustion engine. The valve shaft slides in a 3mm hole in a 20mm solid hard wood board (beech, I think) and covers a 11mm hole on the bottom side. The 11mm hole forks into two 8mm holes, which are 30 degrees off the vertical. I want to make sure that there is about 10mm left of the 3mm hole to guide the valve shaft. The 11mm hole must be clean on the surface to ensure good sealing. The 11mm and 3mm holes must be accurately aligned.

I realise this design might seem a bit awkward, but I have lots of space constraints so even this design took me a bit to come up with.

I'm trying to find the best way to drill the holes. My best attempt is to:
1) drill a 3mm through hole
2) enlarge the 3mm hole to 11mm from the bottom to a small depth using a twist bit
3) drill 8mm holes from the top using a drill guide set at 30 degrees with a brad point bit

I get tear out at where the 8mm holes meet the 11mm hole.

Any better solutions?

I don't yet own a pillar drill but am prepared to get one if it helps.

Thanks in advance.

 

[Orraloon]

Change the order of steps.
1 Drill the 11mm hole to depth
2 Drill 3mm hole from center of 11mm hole (up from bottom)
3 Drill 8mm angled holes. You can put a wood plug in large hole to help prevent tearout.
It will all work better on a pillar drill but should be doable with hand held if you can cut some guide blocks for the angles. Good sharp drill bits too.
As the valve seal is the bottom of the block some small tearout inside should not be the end of the world but can also be sanded smooth.
Try a couple practice runs on scrap wood first as its not an everyday job.
Regards
John

 

[woodbloke66]

If you have the latest Ax catalogue, have a look on the back cover at the new UJK Drill Guide - Rob

 

[cliveso]

Thank you, John. I think brad point bit + a little tear out will have to do, as I'll be making 125 of these!

Change the order of steps.
1 Drill the 11mm hole to depth
2 Drill 3mm hole from center of 11mm hole (up from bottom)
3 Drill 8mm angled holes. You can put a wood plug in large hole to help prevent tearout.
It will all work better on a pillar drill but should be doable with hand held if you can cut some guide blocks for the angles. Good sharp drill bits too.
As the valve seal is the bottom of the block some small tearout inside should not be the end of the world but can also be sanded smooth.
Try a couple practice runs on scrap wood first as its not an everyday job.
Regards
John

 

[Simon89]

Would it be possible to have the holes drilled vertical and a much larger counterbored hole at the bottom, that way it could be made to a much sloppier tolerance.

 

[cliveso]

Unfortunately not. The valve itself can't be bigger than 15 mm in diameter and I'd like to allow a 2 mm overlap of the seal, so the hole is 11 mm max.

I have considered various arrangements with several vertical vent holes surrounding the 3 mm hole (making a rosette, effectively) and I'll keep thinking...

 

[Eric The Viking]

If this is a batch production run, you should be thinking "jigs" from the outset. And a pillar drill. for repeatablilty and accurate depth control.

John is right: a Forstner drill for the large hole first and run the centre hole located by the pip in the middle (that bit is easy!). To eliminate tearout, use good quality drills, not jobber twist drills, which are designed and sharpened for metal. I use Colt, which are expensive but brilliant.

For the angled holes, start with a properly square block of hardwood or thick plywood. Mark a cross in the centre of one face, and extend those lines all round the block, as you would for tenons or other joint components: you should then know exactly where your drill will enter and exit. Drill through to size, check you exited on-target, then slice through the block at the 30-degree angle you want. Smooth the cut face carefully. You now have a guide block with good alignment marks.

At this point I was going to say, "do the geometry, and work out where you should insert a 3mm alignment pin, to allow you to locate your new angle jig, so it is held where you need the angled holes."

But it dawned on me: You are expecting too much of wood as a material. If this was scaled up by 2:1 (or even 3:1), you might make something that would work, but per your drawing, the hole dimensions are far too small for you to get good, repeatable results in wood.

A craftsman might do it, with really good quality stock, but what you really ought to do is consider using something else, either metal or possibly an acrylic, which will allow the precision at the scale you want. When people like Ikea manufacture with great precision, they are using high-tech machinery, and usually drilling faced man-made boards, which are both stable and smooth to start with.

So you can achieve something similar, but without a lot of messing about, probably only at lager scale in a home workshop. Of course that's only my opinion... (sits back; opens popcorn).

E.

 

[cliveso]

But it dawned on me: You are expecting too much of wood as a material. If this was scaled up by 2:1 (or even 3:1), you might make something that would work, but per your drawing, the hole dimensions are far too small for you to get good, repeatable results in wood.

Hi Eric, thank you so much for your comments. I think it might be back to the drawing board for me...

 

[Droogs]

If no tearout can be allowed, may I suggest the following method:
1. Using a guide block that has a 90deg hole at 3mm dia which has been securely mounted, drill a 3mm hole using a forstner bit from the botttom ensuring that there is a backing piece at the exit point deep enough to allow the forstner bit to pass into at least as deep as the teeth/cutter edge to ensure no break-out

2. Plug the hole with some melted bees wax (this will help prevent internal tear-out during next stage)
3. Again using a backing piece and a guide block that has a sized hole and has been planed or sawn to the appropriate angle, locate it on the correct position for the entry of the 8mm hole on the bottom and using a 8mm forstner bit drill out the angled holes
4. do as for 2.
5. repeat 1. but use an 11mm forstner bit.
6. heat up the part until the wax melts and flows out. Whats left will act as a sealing and lubricating agent for the valve
THIS IS FOR HARDWOOD ONLY
hth

edit typos

 

[xy mosian]

To eliminate tear out in the 11mm hole. Turn the stock the other way up and drill from the 11mm hole outwards. That way any tear out is in a place where it is more easily dealt with.
xy.

 

[Astrobits]

Have you considered multi angled drill bits? Drill a vertical hole down and then across to meet the 11mm hole halfway through the wood. Avoiding angled holes completely.
https://www.toolpak.co.uk/multi-angle-drill-bits.html
Don't know enough about your requirements so this might be a non-starter.
Nigel Wakefield

 

[AndyT]

What is the valve going to be doing?
The world already has thousands of designs of valves - one of them must exist which would solve the problem - and could be fitted into whatever you are making. It could even be disguised by hiding it underneath something made of wood which looks like a valve but is just a dummy.

 

[Eric The Viking]

... drill a 3mm hole using a forstner bit...

Do such things exist?

I have a feeling my really posh Colt set only goes down to 4mm, and those are more similar to lip+spur (although the tip shape and grind is quite different).

I know you can make lovely crisp 8mm holes in hardwood, but the 3mm one gives pause, especially as something is supposed to rotate in it, apparently with accuracy and consistency.

I like Andy's idea of finding a manufactured substitute, and then hiding it

 

[Droogs]

https://www.aliexpress.com/i/32956373793.html

 

[Eric The Viking]

Uh... OK, I see they describe them as Forstner bits, but wouldn't be what I would immediately think of.

I checked: my Colt set does go down to 3mm, but I don't think you gain much advantage from thegrind at that size. They're these (Colt "Five Star"): https://www.youtube.com/watch?v=LPGG9wCMLoc
I have some of their "twinland" ones as well, which are almost as nice, but not quite.

 

[profchris]

... drill a 3mm hole using a forstner bit...

Do such things exist?

I have a feeling my really posh Colt set only goes down to 4mm, and those are more similar to lip+spur (although the tip shape and grind is quite different).

I know you can make lovely crisp 8mm holes in hardwood, but the 3mm one gives pause, especially as something is supposed to rotate in it, apparently with accuracy and consistency.

I like Andy's idea of finding a manufactured substitute, and then hiding it

4mm brass tubing from a modelmaking shop has a 3mm internal diameter. You could just glue some in as a bushing.

 

[cliveso]

What is the valve going to be doing?
The world already has thousands of designs of valves - one of them must exist which would solve the problem - and could be fitted into whatever you are making. It could even be disguised by hiding it underneath something made of wood which looks like a valve but is just a dummy.

It's for a musical instrument, some sort of organ. The pressure on the bottom side will be about 50 mm of water. The valve will be partly kept shut by the pressure, and partly by a light spring (20 g of force perhaps). As you can see, the whole setup is extremely light duty - far below most industrial applications - and I very much doubt I could get the correct valve off the shelf...

Also, I need 125 valves, so it'd cost £2.5k even if I could find a valve at £20 apiece...!

 

[cliveso]

Thank you all for all your contribution! I've been sufficiently deterred by any kind of angled holes...

I've gone for a rosette design, with five 5 mm vertical holes surrounding and overlapping the 11 mm hole.

This is likely to cause a little more pressure loss but I suppose I'll have to live with that...