# Need to tap threads in wood



## cagenuts (May 8, 2010)

Morning folks.

Thinking about tapping holes for machine screws instead of wood screws. Particularly for jigs and fasteners.


I've chosen machine taps so I use a drill press chuck to keep the tap perpendicular to the wood.

Soooo.

I can get the appropriate drill bits here but which of these two type of taps would be best for use on wood, taking into account the possibility of blind holes?


Spiral Flute Tap Set










or

Spiral Point Tap Set


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## richtink (Dec 5, 2012)

It will be interesting to see how it works out. I wonder if changes in humidity will have any effect at all. Will the screws be removed and reinstalled from time to time?


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## harrysin (Jan 15, 2007)

cagenuts said:


> Morning folks.
> 
> Thinking about tapping holes for machine screws instead of wood screws. Particularly for jigs and fasteners.
> 
> ...


As shown, I've tapped many holes in hardwoods without a problem. I use a middle tap but would follow this with a plug tap for blind holes.


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## williamm (Oct 10, 2011)

I would think that both would be needed if you will be tapping blind holes.

The pointed ones would be needed to start the holes because of the taper on the pointed end needed to start the tap.
Then the other set is needed to run the threads all the way to the bottom of a blind hole which the other set can't do because of the taper on the threads.


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## Skyewalker (Aug 30, 2012)

From my experience working with cast iron moldings, just use the flat bottomed bits, BUT only in a drill press. You'll never get them to start properly by hand but a press shouldn't have any problem. You'll also want the hardest wood you can get, 1. to hold the threads and 2. to avoid the soft wood from tearing.
Good luck, let us know how it turns out.


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## rwbaker (Feb 25, 2010)

Personally I do not tap wood but drill a hole and insert a helicoil - this is not going to tear-out and a generic version can be had at HF and of course there are the traditional brass inserts that screw in. I have hand tapped wood, and always hand tap metal but on wood these have worked much better for me and are much less expensive than the brass inserts. Good luck, Baker


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## waynecochran (Aug 2, 2011)

I tyr to use spiral taps as they seem to cut better in wood and metal. Some times I will run some super glue down the tapped threads and retap. Makes them a little stronger and durable.


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## Quillman (Aug 16, 2010)

Tap type, in wood: Essentially it doesn't matter.
Rosewood, Jatoba, soft wood, taps are so hard they don't feel a thing in wood, MDF or plastic.
Spiral, straight, multifluted, not to worry. I use them all, whatever is handy.
A bottoming tap will buy you a few more threads in a blind hole but even that is often unnecessary.
Example.


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## OPG3 (Jan 9, 2011)

Hilton,
I do this daily and simply use brass inserts, propel nuts, helicoil or simply thread the required bolt into the wood. The bolt is harder than the wood, so it will "tap" just fine. With any of these methods, using a [non-running] drill press works perfectly. I even use this method on Crepe Myrtle, which is the hardest wood I am familiar with! Good Luck!
Otis Guillebeau from Auburn, Georgia


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## JOAT (Apr 9, 2010)

richtink said:


> Will the screws be removed and reinstalled from time to time?


That's what I'm wondering. I was brought up being taught that you use screws only if the item is intended to be taken apart. If it is not intended to be taken apart, you use nails.


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## cagenuts (May 8, 2010)

Thanks for the input guys. I probably will be taking the parts apart from time to time.

I watched a video on TheWoodWhisperer about tapping wood, then looked up that article in Fine Woodworking by Pat Warner then of course Lee Valley tempted me with this beauty.

In hindsight, I may have been a tad over exuberant so I think I'm going to try the inserts first. On Saturday I found a cheap and nasty metric tap set for a whole $8 so I figured it will suffice for wood usage. If my metalworking takes off then I will cough for a proper set.

Thanks again.


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## JOAT (Apr 9, 2010)

Ah, just recalled. There are a few occasions when I do things I want to take apart, but rather than use screws, or tap wood, I drill thru and use a T-nut and a bolt. Works like a champ, under $1, and you can really crank the bolt down with no worry about striping out.


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## Stargate (Oct 2, 2014)

Quillman said:


> Tap type, in wood: Essentially it doesn't matter.
> Rosewood, Jatoba, soft wood, taps are so hard they don't feel a thing in wood, MDF or plastic.
> Spiral, straight, multifluted, not to worry. I use them all, whatever is handy.
> A bottoming tap will buy you a few more threads in a blind hole but even that is often unnecessary.
> Example.


Pat,
I have a new Incra Router Table (MDF with laminate both sides). Instead of using the (12) #10 x 3/4" long pan head wood screws supplied to attach the router table to my Incra metal stand, I was thinking of using a wood tap and tap 12 hols to accept #10-24 Machine screws or Cap Head bolts rather than use brass inserts. What do you think? I really don't like the idea of using these #10 x 3/4' wood screws to fasten the Incra Table to the metal stand.


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## Mike (Nov 22, 2004)

Machine screws pull out of MDF way too easily.


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## Stargate (Oct 2, 2014)

Mike said:


> Machine screws pull out of MDF way too easily.


Mike, the laminated Router table top is simply sitting on top of the Incra metal router table stand. I have the roller wheel set on the metal router stand. Thus the whole router table stand unit will never get picked up from the table by itself, when moving it from one location to another.


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## Mike (Nov 22, 2004)

Larry, the larger threads of the wood screws have a better chance of holding in the MDF.


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## Ray Newman (Mar 9, 2009)

Shop rumor is that if you tap into wood, apply some Crazy Glue to finished threads. Supposedly the wood wicks up the glue and the glue reinforces the threads.


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## Ratbob (Apr 6, 2015)

Ray Newman said:


> Shop rumor is that if you tap into wood, apply some Crazy Glue to finished threads. Supposedly the wood wicks up the glue and the glue reinforces the threads.


That actually sounds plausible Ray - good tip! Where's Mythbusters when you need 'em.


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## Stargate (Oct 2, 2014)

Ray Newman said:


> Shop rumor is that if you tap into wood, apply some Crazy Glue to finished threads. Supposedly the wood wicks up the glue and the glue reinforces the threads.


Ray, that is exactly correct. The CA wicks into the threads in the MDF and makes them much stronger. After the CA (Cyanoacrylate) cures and you reinsert a wood screw or machine screw, it acts almost like a thread locker. This is exactly what I had in mind. Tap the Incra laminated MDF router table for #10-24 threads, then use Q-tips to CA coat the internal threads of the taped holes, let cure then use the #10-24 Machine screws or Cap head screws to fasten the MDF router table to the Incra metal router stand. - MDF threading .
I use super thin and or medium CA glues a lot with Balsa, Basswood in the hobby industry to seal and toughen up the wood.


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## Mike (Nov 22, 2004)

Take a lesson from pocket hole screws. In hard materials like Oak you use fine threads. In soft materials like pine you use coarse threads. Since MDF is even softer than pine it is logical to use the largest threads available. Machine screw threads are much finer than the fine pocket hole screws.


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## Stick486 (Jan 4, 2013)

I don't understand all the fuss...
top cut threads in wood unless they are Acme fail over time...
you can postpone or delay this but it happens sooner or later...

go to the head of the class and use T nuts or a variation of them...
install from the back side.. 
glue, screw, fitted recess, pressure fit or any way that pleases you...
lasts a long time and perform well...
hex headed sex nuts work really well to...


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## Stargate (Oct 2, 2014)

Stick486 said:


> I don't understand all the fuss...
> top cut threads in wood unless they are Acme fail over time...
> you can postpone or delay this but it happens sooner or later...
> 
> ...


Stick, Wood > Yes. But I'm talking about MDF. I don't exactly call MDF wood. I've never seen a MDF tree


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## Stick486 (Jan 4, 2013)

Stargate said:


> Stick, Wood > Yes. But I'm talking about MDF. I don't exactly call MDF wood. I've never seen a MDF tree


okay...
so w/ MDF you are even more handicapped....
now you really need the T nuts...

agreed on the MDF not bring wood...
I think in wood because I never use MDF...

MDF is a sheet of glue w/ sawdust, industrial fiber leftovers, either pulp mill stuff, sugar cane fiber, lignocellulosic materials or ground up paper bags for fillers...
it's not even in the same class as wood come strength, fastener holding or moisture resistance,...
not to mention the dust is very unhealthy...


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## Stargate (Oct 2, 2014)

Stick, I agree MDF dust is very unhealthy, thus the need for proper dust masks and eye protection when cutting and routing MDF. But then pretty well all real wood dust is unhealthy, and proper dust masks should always be used.
I do a lot of work with MDF, and real wood and various composite materials. When you look at the CNC people with their MDF or HDF spoiler boards, or audio speaker builders using MDF, you will see a lot of tapped holes being used with either threaded inserts for machine or cap head screws, or simply tapped threads in their MDF spoiler boards or speaker boxes. CA glues, and or products like Minwax Wood hardener are used to toughen up the tapped threads, and they do not swell up the wood.


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## Stick486 (Jan 4, 2013)

a lot of MDF products have shown up at the shop for repair put together 65 ways to sunday......
way way more than wood....
use to work on it....
then one day... no more...

it's all about making choices...
some days you do better than other...


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## Cherryville Chuck (Sep 28, 2010)

I made a zero clearance insert for my unisaw quite a few years ago and to level it I drilled and tapped it for set screws. I've never had a problem with it, however, there is only some down pressure on it as the saw table supports most of the weight of anything I pass over it. If all you are doing is basically pinning the top to a frame then line up pins in drilled holes would work. All the force is down and sideways.

There is another option too. Everywhere you want to put a screw drill a hole with a Forstner bit and install a wooden dowel. Drill a pilot hole in the dowel so you don't split it and install the screw in that. MDF will hold the dowel way better than it will hold a screw.


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## Ratbob (Apr 6, 2015)

Cherryville Chuck said:


> ...There is another option too. Everywhere you want to put a screw drill a hole with a Forstner bit and install a wooden dowel. Drill a pilot hole in the dowel so you don't split it and install the screw in that. MDF will hold the dowel way better than it will hold a screw.


 @Cherryville Chuck, I suggested this to Larry a week or two ago, along with the option to use threaded inserts.
@Stargate, If you're intent on using machine screws in MDF, and disregarding the sage advice from Mike, Stick, and Chuck, go ahead and build it. When it fails you can just repair it with a plug, threaded insert, or use a wood screw. Just don't keep trying to convince people that know better and prove them wrong (if you can).

Good luck, and post back in a year and let us know how your table is holding up.

~Jeff


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## Herb Stoops (Aug 28, 2012)

Ratbob said:


> @Cherryville Chuck, I suggested this to Larry a week or two ago, along with the option to use threaded inserts.
> 
> @Stargate, If you're intent on using machine screws in MDF, and disregarding the sage advice from Mike, Stick, and Chuck, go ahead and build it. When it fails you can just repair it with a plug, threaded insert, or use a wood screw. Just don't keep trying to convince people that know better and prove them wrong (if you can).
> 
> ...



Good one,Jeff. but by doing the arguing a lot of good information was brought out. Some that I didn't know anyway. I found out that CA glue was good for something.

Herb


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## Stick486 (Jan 4, 2013)

Herb Stoops said:


> Good one,Jeff. but by doing the arguing a lot of good information was brought out. Some that I didn't know anyway. I found out that CA glue was good for something.
> 
> Herb


one thing about CA glue and MDF is it make for a cold joint in the MDF where it stop being absorbed...
kinda like the slag on 70 series rod of a cold joint in concrete...
those treated threads will be be brittle...
VOE...


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## Ratbob (Apr 6, 2015)

True that Herb, I had never considered using CA. Now, after a little more reading I see that it's not an uncommon practice.


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## Stargate (Oct 2, 2014)

Old dogs (sages) and young dogs can still learning something new, but only if they are willing to.


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## Cherryville Chuck (Sep 28, 2010)

I usually just use wood glue and toothpicks to repair stripped screw holes. I either squirt some glue in the hole or get a glob of glue on the toothpicks, whichever is easier, and fill the hole up with them. The glue sticks the toothpicks in and hardens the surrounding material. Trim the toothpicks off flush when the glue hardens and reinsert the screw. I don't think I've ever had to make the repair twice and I've been using that method for at least 40 years.

I also use that method for straightening cupboard doors that have sagged a bit. Fill the holes up and when you reinsert the screw you start the ones for the bottom hinge at the edge of the hole that is closest to the door. On the top ones you start the screw at the edge farthest away from the door. This moves each hinge over a few thou and is often enough to cantilever the door back into position. Of course this for the old American Standard type door hinge.


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## cspink (Feb 19, 2016)

can you please tell me what these are called I am looking for type JNC


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