MuskyGary

Drill bit for screw eye hole

16 posts in this topic

How do you decide what size drill bit to use to make the hole for a screw eye? The reason to make it is to stop the wood from splitting, but you don't want it to big or the screw eye might pull out; right?

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How do you decide what size drill bit to use to make the hole for a screw eye? The reason to make it is to stop the wood from splitting, but you don't want it to big or the screw eye might pull out; right?

Gary every screw has a certain drill size that is used. most can be found on the internet. searching for drill sizes for screws or screw drill sizes drill size charts etc etc

one thing to keep in mind is always have the size of the drill no smaller than the minor of the thread, maybe 10% bigger. when your drilled hole is smaller in dia. then the minor dia. of the screw thats what cause splitting

A minor is the part part on a thread that doesnt have the cuts in it. or the bottom of the "V" of the screw.

hope that makes sence.

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@ MuskyGary

Also depends on the kind of wood , that you work with and wether you have SSt screweyes or just brass ones .

As a basic rule of thumb you should drill the pilot holes at the same diameter as the screweyes shank thread core .

In softer woods like abache(quite common in Europe for crankbaits)you could go a fraction smaller , also no need to drill the hole as deep as the shanks length , 2/3(shorter shanks) to 3/4(longer shanks) of it should be enough .

When twisting in the eye , the point of the screweye taps into the soft wood , squeezing , but not breaking it .

In hardwood , you need to go a fraction larger than the thread core and at full depth , at least extend the upper portion of the bore diameter a bit by carefully pulling the rotating drill bit around the inner circumference of the hole , especially when mounting very long shanked eyes .

When twisting in the eyes gets too hard , I always take 'em out again and re-drill slightly larger at entry of bore the above described way .

I also set in my eyes with epoxy , for this purpose I'd extend the first approx. 1/5" of the bore to a bit more than double diameter , so that a kinda "glue plug" surrounding the upper shank could evolve there .

I would not recommend brass screw eyes in hardwood , since they easily break off , when too much force is used to twist them in .

In fact I have used up a mailordered batch of 50 or 100 in softwoods and after never again , since I had some real trouble with them in hardwood at the beginning of my luremaking career !

I haven't yet had a hardwood(or any wood) body split up , when the twisting in by pliers gets real hard and I forced the eye in , it would rather de-form and bend rather than cracking up the wood , at least with ordinary SSt eyes , can't tell about those XXX strong musky SSt eyes , they might damage the wood in that case .

good luck , diemai

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A tip for running screw eyes in and out.

Take a finish nail, 8d, and bend it into a Z, with 90 degree bends instead of the actual Z shape, and one of the ends at right angles to the other.

That way, you can insert one end of the nail into the eye, and use nail as a crank to run the screw eye in or out. I have two, one for in, one for out, but I usually use just the closest one for both, since it's not hard to reverse it and still make it work.

Like others have said, always predrill, even in soft wood. If you feel resistance when you putting in the screw eye, stop and re drill.

And put some epoxy on the threads before you do the final installation. I always run them in and out once before I glue them in, and put enough epoxy on so that it seals the hole where the eye is going and kind of seats the eye against the lure. Better too much than too little. A little Denatured Alcohol will clean off any excess.

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Which would be stronger, a dry screw eye installed with the correct pilot hole. Or a hole drilled larger than the maximum diameter, so that the screw eye pushed straight in, only loaded with epoxy.

I suspect the latter would be stronger. I have a twisted wire eye on pull test at the moment. It has been supporting close to 50Lb for three weeks now. I now have a severe algae and mosquito lavae problem.

It is all about the surface area of the contact. The larger the hole, the larger the surface area of grip. As I have said before, if you are not sure of something, exagerate the dimensions or parameters. Imagine a hole of 1" diameter, filled with epoxy. It would be stronger than a 0.05 dia hole. As for a dry screw hole, I would not bet my life on it.

On the various pull tests that I have conducted, any failures have been the wire pulling out of the epoxy and not the wood failing, even though I am using a wood of very low density. This is because the surface area of contact of the wire is much smaller than the surface area of contact with the wood.

Contentious with popular opinion, but food for thought. I hope.

Dave

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Mark, could you explain why " If you feel resistance when you putting in the screw eye, stop and re drill. "

Thanks

s54

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@ seeking 54

I am sure , that Mark is refering to a point , when the screweye gets too hard to turn in , because the pilot hole is not deep or wide enough .

It is a "feel" thing , because naturally this point would be shortly before having the screweye bent or even twisted off(brass screweyes) .

The more harder and dense your used wood is , the easier this case of re-drilling might occur .

greetz , diemai

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Doesn't redrilling again compromise the tap created by the initial screwing of the screweye causing the screw eye to lose it's bite?

When I first started building baits I experimented with red cedar, and gave up because the screw eye even with Gorilla glue would still turn. I would predrill with a 3/32'' bit and add the glue to the .092 ss srew eye tread.

I feel softwood lures are best with a wire thru design. I have since switched to harder density wood like, Ekki, Brazilian Cherry, Brazilian Ebony, Purpleheart, Santos Mahogany, and some of the harder North American hardwoods.

The screw eye with these types of woods does not even require any type of glue added to the treaded shank. I screw the screw eye with a dental pic until it is flush with the base and even a little further in. A little bit of marine epoxy with 2 final coats of E-tex ensures no movement at all.

s54:)

Edited by seeking 54

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@ seeking 54

If the hole wasn't deep enough before , and you re-drill it deeper , the screweye would find a new bite , and the applied epoxy on final assembly takes care of the rest .

In hardwoods I drill exactly as deep as the shank length of the screweye .

Especially longer screweyes have a good portion of their upper shank unthreaded , so most likely it gets too hard twisting in the eyes , when this part has entered the hole .

So you only have to re-drill that particular length on the entry of the bore , leaving the lower tapped portion untouched .

I do not take a larger bit for this , but would "stir" around the original bit in that hole to widen it a bit .

What has happened to you with the Red Cedar really shows , that the wood grain might not be suitable for screweyes at all !

Did you drill the pilot hole on full length of shank ?

In softer woods it is of advantage to make the pilot holes only 1/4 to 1/3 of shank length deep , just for direction guidance , the self tapping ability of the thread would do the rest .

greetz , Dieter

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Dieter,

Yes, I was drilling the full lenght of the screweye in the cedar. Now that you've suggested going 1/4 or 1/3 of the depth, I will try it again. Thank you for the advice.

Sorry to highjack this tread with this question, but I was thinking about this theory: Would relieveing the moisture from the wood by leaving it indoors, with a screw eye in it, strenghten it even more as it contracts?

s54

Edited by seeking 54

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@ seeking 54

Sorry , but I can't tell about that , I'll leave this to Mark , since he's a chippy for almost a lifetime :yay:!

But why having moisture in wood for carving lures :huh:?

I guess , that it should be dead dry and well seasoned , so that exactly those contractions won't occur , since they might ruin not only the paint job and topcoat , but also the entire lure , as it might split up , soak water and get out of balance:yes: !

Or you are thinking to carve your lures out of "green" wood , install the screweyes and after let it set dry before painting.......?

Well , I'd better leave this to Mark as well , sorry:huh: !

Greetz , Dieter

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Hmmm.....let me see if I can sound intelligent at 4:00 in the morning. ;)

All wood has some moisture. Even kiln dried.

If you have any "free" moisture in a wooden lure, it will make the finish fail because it will cause the wood to expand and contract too much when the temperature changes. Most finished can't stand up to too much movement.

Air dried wood which has reached the same relative humidity (moisture content) as the surrounding air is pretty stable, as long as you don't live in a really humid area, where relative humidity is high all the time, like the tropics. But it still has more moisture than kiln dried, unless it's been sitting in the desert. That's actually a problem when people in Arizona buy wood products like furniture and pianos from other parts of the country. The wood dries out more in their dry climate, and the joints open up, even kiln dried wood in furniture. The outer layer of kiln dried lumber is exposed to the moisture in the air surrounding it where it's stored and milled, so it can dry out when it gets shipped to the desert areas.

But wood that's kiln dried is more stable, less susceptible to movement, than air dried wood, because it is not only lower in moisture content, but the process of kiln drying seems to keep the moisture content low if you store it inside.

If you seal the wood well before you paint and topcoat it, you eliminate the wood movement headaches.

I've settled on using Minwax Wood Hardener as a sealer for my wood lures after I've carved, sanded, and drilled them with all the holes for hinges, ballast, hook hangers and line ties. It's a penetrating sealer that is drawn into the pores of the wood and reinforces their cellulose structure by coating it with something. Don't remember what.

The softest wood I use is sugar pine, which is buoyant and easy to carve, and the hardener makes it strong enough to hold hardware.

I pour some into a coffee can, drop in the lure parts one at a time, slosh them around for about ten seconds, and then drip them out over the can for another ten seconds and hang them to dry for a day.

Even though the wood hardener wicks into the cells of the lure (you can see the air bubbling out of the end grain as it's displaced) and down into any holes that I've drilled, I still use glue on my screw eye threads.

I know Snax has found a better hardener product, but I've found the Minwax works for me. I use it at work on exterior wood products that I want to seal before installation, and my painter uses it to repair damaged wood before he bondos and paints, so I know it works.

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@ mark poulson

Very intelligent early at daybreak , Mark:yes::lol: !

Nice and interesting explanations , thanks for sharing your knowledge :yay:.

Greetz , Dieter

Edited by diemai
misspelling

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Dieter,

Yes, I was drilling the full lenght of the screweye in the cedar. Now that you've suggested going 1/4 or 1/3 of the depth, I will try it again. Thank you for the advice.

Sorry to highjack this tread with this question, but I was thinking about this theory: Would relieveing the moisture from the wood by leaving it indoors, with a screw eye in it, strenghten it even more as it contracts?

s54

I realized after I finally woke up that I didn't really answer you question.

If there's enough moisture in the wood that it would dry out by leaing it inside, it would also shrink slightly. That means that the holes would probably open up a little more, since wood shrinks toward itself, and, in the case of a drilled hole, away from the center of the hole.

At worst, the screw eye would tend to be looser afterwards.

In reality, unless you're using const. lumber that's full of water, it probably won't make a difference, one way or the other. But even a small "extra" moisture content in the wood can affect the bond of both the glue you use to set your hardware, and the bond of the paint scheme to the wood.

It pays to just use dry lumber, and some glue in the screw eye holes, and not have to worry about those extra variables. Goodness knows there are enough variables we can't eliminate as it is.

Vote early, and vote often! :lol:

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