# Tapping Question



## wildbill001 (Feb 28, 2008)

Unfortunately, this question is not about tapping a keg of "adult beverage".

I'm working on a project/proto-type that looks like it will require tapping some holes. The size will probably be 1-72. Micromark sells a tap as well as two different drills. One is listed as the "tap drill" (#53), the other is listed as a "clearance drill"(#48). Do I need both sizes? I'm going to be cutting threads in some hardwood and/or possibly styrene if it makes a difference.


Thanks!

Bill


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## xo18thfa (Jan 2, 2008)

The tap drill is smaller in diameter. It is used to drill first, then run the tap into that hole to cut the threads. The clearance drill is just slightly larger in diameter than the tap. That's so the screw you are tapping for can pass thru when assembling parts. You will most likely need both.

Most plastics tap very well. Styrene may be a bit gummy, but should do OK. 1-72 into wood will not work at all. Best bet is to use a threaded insert. It is a wood screw on the outside and a tapped machine screw thread on the inside. McMaster-Carr has them in 0-80 and 2-56 thread. If you absolutely need 1-72, screw in a brass wood screw, a #8 or #10, then drill and tap into the screw.


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## Dwight Ennis (Jan 2, 2008)

For screwing into wood, you might also consider these brass hex-head lag screws[/b][/b] from Micro-Mark. They come in #0, #1, and #2 sizes, and I would think the head dimensions would be comparable to hex-head machine screws of the same size. These may also work better in styrene as well depending upon the thickness of the styrene.


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## Larry Green (Jan 2, 2008)

" 1-72 into wood will not work at all." From my experience of tapping a few hundred 1-72 holes into birch cabinet plywood, it is not a problem. I used a pin vice to hold the tap, rather than the usual T handle, and added a bit of soap to the tap. Have also tapped oak 2-56 and 3-48. 
The hex head lag screws from MicroMark work very well, but be careful in hardwoods not to shear off the head. Use a drill size or two larger than normal tap drill. 

Larry


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## xo18thfa (Jan 2, 2008)

Posted By Larry Green on 04 Aug 2009 09:30 AM 
" 1-72 into wood will not work at all." From my experience of tapping a few hundred 1-72 holes into birch cabinet plywood, it is not a problem. I used a pin vice to hold the tap, rather than the usual T handle, and added a bit of soap to the tap. Have also tapped oak 2-56 and 3-48. 
The hex head lag screws from MicroMark work very well, but be careful in hardwoods not to shear off the head. Use a drill size or two larger than normal tap drill. 

Larry 
I did not think of birch, you are right. Maple would work well too. Do you use the standard tap drill then?


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## wildbill001 (Feb 28, 2008)

All good info, thanks! Does anyone know what the actual diameter of those micromark lag screws are? I would need something close to the size of a 1-72 machine screw, which by my measurement is .072 (funny how that works out, eh?) Not sure what a #0 or a #1 works out to be.

As for threading wood, I've found that for most applications, if I'm working with a hard, dense grain, the tapping works pretty good. And in my application, I would not be screwing/unscrewing constantly. It would be more like a screw it together and leave it.

Thanks folks.


Bill


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## RimfireJim (Mar 25, 2009)

Posted By wildbill001 on 04 Aug 2009 09:12 PM 
All good info, thanks! Does anyone know what the actual diameter of those micromark lag screws are? I would need something close to the size of a 1-72 machine screw, which by my measurement is .072 (funny how that works out, eh?) Not sure what a #0 or a #1 works out to be.



The formula for machine screw diameter is D=0.060" + .013" X N, where N is the screw size number. So, a #0 is .060", and a #1 is .073". That number is the theoretical maximum major diameter of the threads, as if they came to a sharp point, which they don't, so the actual diameter is slightly smaller.


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## wildbill001 (Feb 28, 2008)

Kewl.... I did not know that











Thanks !

Bill


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## Larry Green (Jan 2, 2008)

Bob, I can't remember anymore, that was back in my days of building 1-1/2" scale rolling stock. Generally, I open up small tap holes one or two sizes for wood and plastic. 
For anyone interested in the challenge of drilling and tapping for ultra-small bolts, check out this site: scalehardware.com. I am now using these for my G1 modeling. 

Larry


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