# What size drill.....



## jw2170 (Jan 24, 2008)

...do I need to drill a hole for a 1/4" and 5/16" t-nut and also same sizes in theaded insert. 

Can't seem to find the info and it looks like I need to update my drill collection...


----------



## steveo (Sep 10, 2004)

*drill sizes for t-nuts and threaded inserts*



jw2170 said:


> ...do I need to drill a hole for a 1/4" and 5/16" t-nut and also same sizes in theaded insert.
> 
> Can't seem to find the info and it looks like I need to update my drill collection...


This is what I've been using with success.
1/4" Tee nut, drill 5/16" hole
5/16" Tee nut, drill 3/8" hole

For the inserts...
1/4-20 drill 3/8" in soft wood and 5/16" in hard wood
5/16-18 drill 1/2" in soft wood and 19/32" in hard wood

hope this helps !


----------



## Quillman (Aug 16, 2010)

Depends on the design of the tee nut or insert.
Pronged, propeller, etc, describe.
Can always sacrifice one in a test.
This threaded insert (1/4-20 inside thread, 3/8-16 outside) use 5/16 as pilot hole for example.)


----------



## bdusten (Mar 22, 2013)

When we were using them for the trays at work we always used the same diameter, but we also put a little epoxy on them as well. The trays held 1000+ lbs. Never saw one come loose in 10 years. We would use a lag bolt and a few different washers to insert them. The pressure of the lag pulls the t-nut into the wood, if you use a mallet your more than likely going to have some play in the fit.


----------



## jw2170 (Jan 24, 2008)

Thanks for the info, guys.

I am going to use the inserts in Spotted Gum, a very dense hardwood. 

Thanks, Pat, for the tip on tapping the insert hole.

I must check with my 'Thread Detective' to see what outer thread is on the inserts.


----------



## Cherryville Chuck (Sep 28, 2010)

This is just slightly off topic James but you might find it relevant. Years ago, Lee Valley sold tap sets (tap and pilot drill) for wood which appeared identical to metal ones. They claimed that their tests showed that threaded holes would hold machine screw threads as well or better than wood will hold wood screw threads. I have some and have used them occasionally and I have found no reason to doubt LV's claims.


----------



## cagenuts (May 8, 2010)

Cherryville Chuck said:


> Years ago, Lee Valley sold tap sets (tap and pilot drill) for wood which appeared identical to metal ones.


They still do and the set comes with a clearance drill bit (for jigs) as well as the bit required for the tap.


----------



## jw2170 (Jan 24, 2008)

steveo said:


> This is what I've been using with success.
> 1/4" Tee nut, drill 5/16" hole
> 5/16" Tee nut, drill 3/8" hole
> 
> ...


Hi Steve, just went out to buy some new drills. They did not have 19/32" in stock.

Just checking the drill sizes. For 1/4 inserts you have the larger drill for the soft wood, but for the 5/16 inserts you have the larger drill (19/32) for the hard wood.

Is that correct? 

Anyway, i will go to the shed with what I have and make some practice holes......


----------



## bobj3 (Jan 17, 2006)

I use the letter drill bits

115 Piece Titanium Nitride Coated M2 High Speed Steel Drill Bit Set

Bosch BL0026 Wire Gauge A to Z Black Oxide 26 Piece Twist Drill Bit Assortment with Metal Index - Amazon.com

===


----------



## paduke (Mar 28, 2010)

James I cant remember stuff either I wind up using the holes on an old drill index to see if the object fits in the hole


----------



## jw2170 (Jan 24, 2008)

paduke said:


> James I cant remember stuff either I wind up using the holes on an old drill index to see if the object fits in the hole


Good point, Bill.

At least I tapped a 5/16 hole in some hard wood today, so I can just drill and tap to fit. 

My new tap and die set had 2 x 1/4"-28 taps and no 1/4"-20 tap, so off to Supercheap Autos to replace....


----------



## jw2170 (Jan 24, 2008)

bobj3 said:


> I use the letter drill bits
> 
> 115 Piece Titanium Nitride Coated M2 High Speed Steel Drill Bit Set
> 
> ...


That 115 piece set looks OK, Bob. I may see if I can find one in Oz.


----------



## jw2170 (Jan 24, 2008)

Prices vary quite a bit on Ebay....

115 piece drill | eBay

One set $392 + $80 postage......ROTFL.......


----------



## jw2170 (Jan 24, 2008)

*Trial and error./..*

Acting on advice from the forum, I went out and bought 2 new sets of drills.

1/16 - 1/2" in 1/64" increments and letter set A - Z recommended by BJ.

Does anyone have the measurements for this A - Z set? the A size is close to the 15/64" drill.

I then used a piece of hardwood (actually, a piece of machined fence paling) to drill test holes and see which one fit.

I got the results I was after, except for the 1/4" tap. 

i now have to wait until Wednesday to go to the Men's Shed to use their drill press. I only have a small bench top unit and the jig will not fit under the quill with the drill inserted.


----------



## jw2170 (Jan 24, 2008)

Quillman said:


> Depends on the design of the tee nut or insert.
> Pronged, propeller, etc, describe.
> Can always sacrifice one in a test.
> This threaded insert (1/4-20 inside thread, 3/8-16 outside) use 5/16 as pilot hole for example.)



Thanks for that, Pat.

My threaded inserts have a much coarser outer thread, and I cannot match it with my "thread Detective"...


----------



## cagenuts (May 8, 2010)

jw2170 said:


> Does anyone have the measurements for this A - Z set?


Here and see both attachments.

View attachment drill_bit_sizes.pdf


----------



## jw2170 (Jan 24, 2008)

*thanks....*



cagenuts said:


> Here and see both attachments.
> 
> View attachment 64482
> 
> ...



Thanks Hilton. Exactly what I wanted. Both saved...


----------

