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Hole saw diameter adjustment?

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Kaizen

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I need to drill fairly precise holes in plywood. The need to be 49mm.....perhaps 48 will work. 50mm is 2" so i bought a few of these
I have typical metal cutting and banging tools as well as welding. Is there a precise way i can reduce this diameter by a few mm on all teeth? I only need it for 30 holes so really don't want to pay to get a special bit made. Also don't want to drag to a cnc shop.
 
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nicholsmf

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I don't have a solution, I'm just curious what the project is that requires holes in plywood that can't be roughly 1/32 of an inch too big using the 50MM bit.
 
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whateg01

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For wood, it's not as big a deal but if you were to cut the saw and then reweld it, the temper on the teeth will be lost in the area of the weld. The bigger concern, especially since you seem to want this to be exact is that the saw will likely no longer be perfectly round. Hole saws are not generally considered to be precision tools.
 
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Kaizen

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nicholsmf said:
I don't have a solution, I'm just curious what the project is that requires holes in plywood that can't be roughly 1/32 of an inch too big using the 50MM bit.
Click to expand...
One of my hobbies is beekeeping. I want to drill a hole in their roofs and use a paint plug to seal the hole when not in use. The plug requires a tight friction fit to keep water out.
50mm and it is too loose.
 
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Kaizen

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Kaizen

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Garage Junkie said:
Why not just make a template and use a router to cut your holes?
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yea i think you are right. hopefully i have a combination of a larger holesaw and a bushing. All that i recall i have are not small like 2 mm.
Drawing and cutting a round hole would be pretty impossible. any other methods i'm not aware of to make the template?
 
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Kaizen

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whateg01 said:
For wood, it's not as big a deal but if you were to cut the saw and then reweld it, the temper on the teeth will be lost in the area of the weld. The bigger concern, especially since you seem to want this to be exact is that the saw will likely no longer be perfectly round. Hole saws are not generally considered to be precision tools.
Click to expand...
yea i think that idea is a fools errand. once i get it dialed in it will heat up and change
 
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Kaizen

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OccupantRJ said:
Adjustable fly cutter. Drill a pilot hole the size of the pilot of the fly cutter, but use a solid rod in the fly cutter to prevent drift.
Click to expand...
I'm using one to do this in paint lids and works great. i've never had much luck on wood with these things.
 
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kmacht

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You aren’t going to hold a 1mm tolerance with a hole saw. Your drill press likely has way more runnout than that. A router and template will probably do it but if you still want to drill it you will need an adjustable boring head and will likely be tweaking it on each and every hole to hold such a tight tolerance as wood doesn’t machine like metal and just the variation in the plywood layers is going to cause variation in the cut. Are you sure that the hole needs to be that precise?
 
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Kaizen

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kmacht said:
You aren’t going to hold a 1mm tolerance with a hole saw. Your drill press likely has way more runnout than that. A router and template will probably do it but if you still want to drill it you will need an adjustable boring head and will likely be tweaking it on each and every hole to hold such a tight tolerance as wood doesn’t machine like metal and just the variation in the plywood layers is going to cause variation in the cut. Are you sure that the hole needs to be that precise?
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Yea i'm sure. This is the plug. Second picture shows it upside down. the bottom lip is on the plywood top and that litle bump out is what has to make a friction fit.


IMG_0828.jpegIMG_0829.jpeg
 
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Garage Junkie

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Hmmm..... if only a standard 2" hole could be used and then a substance could be applied to seal any sloppiness between the plug and the hole. A substance that wasn't permanent, but is waterproof, non-toxic to bees, easily attainable and easy to apply. A waxy substance perhaps, liquid when warm and solid when cool...... It feels like the answer is just buzzing around in my head somewhere.......
 
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Kaizen

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Garage Junkie said:
Hmmm..... if only a standard 2" hole could be used and then a substance could be applied to seal any sloppiness between the plug and the hole. A substance that wasn't permanent, but is waterproof, non-toxic to bees, easily attainable and easy to apply. A waxy substance perhaps, liquid when warm and solid when cool...... It feels like the answer is just buzzing around in my head somewhere.......
Click to expand...
Thanks that made me laugh. Very creative. As they would not really be in contact with it i'd probably use a strip of tape if it comes to that. I only need it at that friction lip.
The bees keep the inside of the hive ventilated which keeps the combs made of beeswax from melting. As this is in direct sunlight it would melt and fall on the bees. Or some other mess. This is a sticky hobby.
 
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Kaizen

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Appreciate everyones input. I have a few avenues to try. I['m sure i'll get something usable.
 
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whateg01

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Have you considered a solution that has the hole and plug matched?

I'd have to look at what's available today, but used to be you could buy plastic speaker ports that you just got a hole close then glued them in.

Here's what I would either 3D print or machine from some sort of plastic. 49mm ID so your plug would fit in it and the hole in the box just has to be close.

1710880204581.png
 
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bluedog225

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Good idea. Maybe a pvc male and female threaded connection? Self flashing within the tolerances we are talking about.
 
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RegeSullivan

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Here is two suggestions. Either should take less than 30 minutes or so to make and last a few hundred holes..

Make one correct size hole in some scrap 1/2 or 3/4 ply using what ever method is easiest for you then tack or stick it where you want the hole. Drill it out with a smaller hole saw then use a pattern bit in your router.

Or

If you have a trim router you could probably make a small enough jig to just route a hole that size.
 
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Jswain

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3d printer can make an excellent router template too, in any size you could imagine. If you know someone or have one. Potentially even your local library or online
 
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danielbuck

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OccupantRJ said:
Adjustable fly cutter. Drill a pilot hole the size of the pilot of the fly cutter, but use a solid rod in the fly cutter to prevent drift.
Click to expand...
This. you can get pretty precise with a flycutter, and nice clean edges. and especially for holes small-ish like around 2", it shouldn't be much of a chore.
 
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JeepYJ

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This isn’t machining metal, it’s making holes in plywood for outdoor use, not fine cabinetry. Try 1 3/4”, 1 7/8” and 2” hole saws on a test piece. Either one of them will be close enough or you can sand the hole slightly larger or sand the plug lip slightly smaller. You seem to be chasing perfection where it’s not necessary or obtainable.
 
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gungatim

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JeepYJ said:
This isn’t machining metal, it’s making holes in plywood for outdoor use, not fine cabinetry. Try 1 3/4”, 1 7/8” and 2” hole saws on a test piece. Either one of them will be close enough or you can sand the hole slightly larger or sand the plug lip slightly smaller. You seem to be chasing perfection where it’s not necessary or obtainable.
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They are made for wood, not metal, at least mine is. I think I paid $10 for mine at Sears. In the WOODWORKING section. It's a common woodworking tool when you need precise holes.

Apparently i'm the only woodworker left on here who doesn't overcomplicate things.
 
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JeepYJ

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gungatim said:
They are made for wood, not metal, at least mine is. I think I paid $10 for mine at Sears. In the WOODWORKING section. It's a common woodworking tool when you need precise holes.

Apparently i'm the only woodworker left on here who doesn't overcomplicate things.
Click to expand...
I wasn’t referring to your hole saw, just hole saws in general. Holding .03” tolerance in outdoor plywood using a hole saw is a fools errand.
 
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