What size is a 4-40 close to?

[Paul Taylor]

What is closer to the size of a 4-40 bolt. 5/65 or 3/32?

[Dick Fowler]

Try this.

http://www.engineersedge.com/screw_threads_chart.htm

[Paul Taylor]

Lots of info... but still over my pointed head.

[Lee Thiel]

Paul, you didn't mention wheather you were wanting to go over size or under size.  Never heard of a 5/65th size, which would be a 1/13th.  There again, never heard of that either.  3/32nds would be the next size up according to my chart.  Proper drill size for tapping female threads would be a #43 bit or .0890.  Hope this helps.
Lee TGD

[howard shenton]

Paul
thread sizes in common use are
4-40 Most people use a 1/8" drill for the mounting holes
6-32 a 9/64 or 5/32 drill these holes

Hope to see you at the Huntersviill, NC contests some time.
This year May 2nd & 3rs and Oct 24th & 25th

Howard Shenton
Mauldin, SC

[Gary Mondry]

Let's try it this way:

1/8  =  0.1250
#4 screw  =  .1120 O.D.
7/64  =  0.109375
3/32  =  0.09375
5/64  =  0.078125

Does that help?

[Paul Taylor]

OK - here is what it is looking for control rod retainer for a 4-40 push rod. One end it not threaded.
Brodak shows to sizes.

5/64 and 3/32

[Allan Perret]

OK - here is what it is looking for control rod retainer for a 4-40 push rod. One end it not threaded.
Brodak shows to sizes.

5/64 and 3/32

4-40 pushrods are .093 wire.  Use the 3/32 keeper.

[Jimmy R. Jacobs]

 The next close size is 5-40. It is all most the same as the super tiger uses in their engine, in fact they will work in super tiger thread size per inch but the pitch is slightly different.

                                        Jimmy Jacobs

[Steve Helmick]

The next close size is 5-40. It is all most the same as the super tiger uses in their engine, in fact they will work in super tiger thread size per inch but the pitch is slightly different.

                                        Jimmy Jacobs

Correct for OLDE Super Tigres, like the ST .60bb's, C.35's and G.21's, which were all 3m x .6 pitch. The G.51's (and other current issue ST's) use modern 3m x .5 pitch.

Near as I can find out, the standards were changed, for reasons pretty much unknown these days. The .6 (mealy meter) pitch would be coarser, generally a good thing for aluminum threads. I presume there would be a finer thread option in 3m diameter, but for the most part, it appears that all you find these days is 3m x .5's. FWIW. This suggests that perhaps they were just trying to cut down on the number of standard sizes by striking a happy medium, or maybe they were scared by the fact that 5-40's were just too close for comfort!?    Steve
 

[Dallas Hanna]

That 0.6 pitch was from an old SI etc European standard Steve.  The Japanese addopted that one somewhere in the late 1800s hence it's use on Enyas etc untill more recent years when they seem to have taken the ISO system on board.

Noted the bit on ST with the #5-40??  but put it in another post.

HH

[Dallas Hanna]

The next close size is 5-40. It is all most the same as the super tiger uses in their engine, in fact they will work in super tiger thread size per inch but the pitch is slightly different.

                                        Jimmy Jacobs

The ST thread is exactly #5-40 as measured with an optical comparator and thread mic... that is at least for the early 70s to early 80s 46 and 60 engines.  See other thread post.

HH

[Vince Mankowski]

Machine screw sizes have roots in the wire industry and there is a formula for the outside diameters.
Take the number of the size (for 4-40 it's #4) times 13 (4 X 13 = 52) and add 60
4 X 13, + 60 = 112  This is the size of the outside diameter in thousandths. (.112)

Works for 2-56; 2X 13, + 60 = .086
Works for 5-40; 5X 13, +60 = .125
6-32 comes out like 6X13, +60 = .138

#14 screws = .242 which is NOT a quarter of an inch
And #12 screws are .216 which inn NOT 7/32” that’s why these are little used.

BTW the last number is the threads per inch, ie 4-40 is a #4 (.112 diameter) with 40 threads per inch

[Vince Mankowski]

BTW...........TAP SIZES
Take the threads per inch and divide into 1,
Subtract this number from the OD of the thread to give about 75% thread
examples;
¼-20 bolt:  1/20 = .050
¼ = .250 so,
.250 - .050 = .200 the tap size (any chart will say use a #7 drill which is .201. NOTE on sizes smaller then ¼” favor the next larger drill size to avoid tap breakage)

Try 3/8-16
1/16 = .0625
.375 - .0625 = .3125 the tap size (5/16”)

This can work for 4-40 threads if you know the OD
1/40 = .025
.112 - .025 = .087 the tap size (charts say use a #43 [.089] drill which again is to avoid             tap breakage on smaller sizes.)

just for grins – the watch maker crowd – there is a #0-80 screw.
It is 13X0 + 60 = .060” OD & 80 threads per inch

And the #00-80 is treated 60-13 = .057” OD. Tap drill is 80/1 = 0.125 & .057-.0125 = .0445 which you may want to round up to a #56 (.0465)

[Robert McHam]

I do love stuff like this but I have not heard of Class 2 and class 3 threads.
Could someone explain this to me?

Robert

[don Burke]

I copied this from an SAE web site:

"Tolerance classes
A classification system exists for ease of manufacture and interchangeability of fabricated threaded items. Most (but certainly not all) threaded items are made to a classification standard called the Unified Screw Thread Standard Series. This system is analogous to the fits used with assembled parts.

Classes 1A, 2A, 3A apply to external threads; Classes 1B, 2B, 3B apply to internal threads.

Class 1 threads are loosely fitting threads intended for ease of assembly or use in a dirty environment.

Class 2 threads are the most common. They are designed to maximize strength considering typical machine shop capability and machine practice.

Class 3 threads are used for closer tolerances.

Thread class refers to the acceptable range of pitch diameter for any given thread. The pitch diameter is indicated as Dp in the figure shown above. There are several methods that are used to measure the pitch diameter. The most common method used in production is by way of a Go-NoGo gauge."

[Bill Gruby]

 For a 4-40 you will have to go to number drills Paul

 Tap Drill is a #43 = .089
 Clearance Drill is  a #33 = .113

  "Billy G"   

[don Burke]

Anyone interested, HARBOR FRIEGHT has a coupon sale 4/20 - 4/26.
60 pc Ti-coated numbered drill set normally 19.99 $9.99!  Great buy!
I get the coupons by e-mail, not sure about how else to get them, maybe by contacting HF direct by e-mail.

[Larry Fulwider]

OK - here is what it is looking for control rod retainer for a 4-40 push rod. One end it not threaded.
Brodak shows to sizes.

5/64 and 3/32

So, it is a pushrod we're working on. I'm not clear on what you are piecing together, but here are some things that fit, or can be made to fit.

1. A normal hobby shop pushrod, threaded 4-40 on one end but not the other, mikes a tad over 3/32 where it is not threaded, maybe .096 or .097. 1/8" OD brass tubing .014 wall gives an i. d. of .097, so you can join a bare 3/32 pushrod to a threaded-on-one-end rod with a piece of 1/8 brass, no problem, just solder away. The 3/32 pushrod will be a bit sloppier fit than the threaded-on-one-end rod.

2. The Brodak "3/32" pushrods that come in their ARFs and ARCs are fatter, maybe .102 or .103 or so. Those will not slip into 1/8 tubing. We don't need much extra room, so slit an inch or so long piece of 1/8 tubing down about halfway, just on one side of the tubing -- not much hassle with a Dremel or a fine tooth metal saw. Slip the fat pushrod into the slit end, and the bare unthreaded part of the 4-40 into the other end. Solder with no worries.

3. Fully threaded 4-40 rod is also fatter than the OD of the bare rod, so a 4-40 thread will not fit into 1/8 tubing. In that case, make a full length slit (if using a Brodak ARF/ARC pushrod). Solder.

4. For a true 3/32 pushrod and a fully threaded rod, slit halfway as in number 2, but slip the 4-40 threads into the slit end. Solder again.

I've done all the above at one time or another, I think. The one I remember best is the one that rolled under the workbench and hid until I made a replacement. If you have a different combo than those listed above, beats me!

Larry Fulwider