ModeratedUser

No, I'm not going to be using the larger sizes. Tell you the truth, it's mostly for working on my bike and maybe a foreign car in the future.

One thing I always though is how it works is that a 4mm wrench turns a M4 and a 5mm wrench turns a M5 and so on and so on. It doesn't work that way, does it?

Bill Kapaun

Other than Allen type bolts, NOPE.
The fact you are asking that kind of question kind of begs "what are you going to do with a thread gauge"?
It seems you are trying brain surgery before you've learned how to apply a band aid.

ModeratedUser

I never expressed any desire for a thread gauge, at least not intentionally. A thread gauge was first mentioned at post #4 by nfmisso.

Bill Kapaun

If you look at the title of the thread, it pretty much reinforces post #27 .

So, what IS a "bolt gauge"?

ModeratedUser

If you google "bolt gauge", what do you see in images? I see something like this.

Bill Kapaun

Well, whatever you do, DON'T Google "thread gauge".

ModeratedUser

OK so if a 4mm wrench does not turn a M4 bolt and a 5mm wrench does not turn a M5 bolt. Then what does a 4mm wrench and a 5mm wrench turn?

(I'm assuming I'd be able to deduct what a 6mm wrench turns after the answer.)

scott967

OK so I followed your link, and this is how Sears describes it:

Ensure Your Car’s Tires Remain in Good Shape with the Craftsman Screw Pitch Gauge, Metric"The tread on a car’s tires needs to measure at least 1.5mm, and Craftsman’s Screw Pitch Gauge, Metric makes it easy to check the tread periodically as part of your regular maintenance schedule. When winter approaches, you’ll want to make sure your car’s tires provide enough grip to keep you and your family safe on the road. Keeping this gauge handy in your car or garage will allow you to do just that. The pitch gauge measures thread counts between 0.45 and 2.5mm and features quality construction to ensure accurate readings."

Okey-dokey. Whatever.

scott s.
.

IthaDan 

Somehow I don't think you'll be able to deduct anything- for basic socket caps, a 4mm key turns an M5, a 5mm key turns an M6 and a 6mm allen key turns an M8 (eight). IIRC for button heads you go down another mm of allen key size.

Other than whitworth fasterners, which nominally sized the wrenches to the diameter of the fasteners, you'll pretty much always have these discrepancies in bolt diameter vs tool size.

Bill Kapaun

Maybe "somebody" should have asked a basic, simple question-
"What size wrenches do I need to work on my bike"?

IthaDan 

Wait, that's what this is all about?

really?

fietsbob

Sears.. because I knew you were too cheap for Sarrett Buy 52484 Starrett Stainless Steel Screw Pitch Gages from UseEnco

cradom

He was making fun of the Description on that Sears page... of a tire tread gauge, not a thread gauge.
Somebody got the copy mixed up.

ModeratedUser

Maybe "somebody" should realized we are in a bike forum.

And if in doubt on what the part is that is being sought after? Google it!

Amesja

This thread reads like a train wreck.

Remember Whitworth wrenches that were marked not on the size of the spanner but corresponding to the size of the bolt?

Maybe this guy is a real old-timer?

The size wrench that is needed is the that size which corresponds to the head of the fastener (which sometimes/often is NOT standard to the size of the threads on the fastener.)

A bike mechanic needs metric open-end wrenches from about size 7mm to around 17-19mm for the most part. Sockets are nice in some situations too. Allen (hex) keys/bits/wrenches from around 2mm to 10mm. Use the size that fits the head of the fastener, not the bolt size. There is no magic bullet which will tell you the size of the tool for any type of thread size/pitch.

I have a plastic bin with every common size of metric fastener for bikes from M4 through M8. When I want to know the size of a fastener I use my vernier caliper which is accurate to about 0.05mm -more than adequate. If thread pitch is in doubt then I use my thread pitch gauge, or just pull out my bin of fasteners and try it on one of the known fasteners to see if it fits (don't try it on a nylock nut though as those are supposed to bind up after a turn or so.)

This is not rocket science.

ModeratedUser

Well looks like my crap shoot on taking a chance on a gauge worked out. I just went with one of these babies and look to be pretty good quality. What's most important is that it covers the range I would be using working on bikes.

Seeing that I usually thank the person(s) that reference the item at this point. So I guess I'd like to thank myself for inspiring me to go with this gauge. Thanks self

sch

My experience matches BCRider, once you hit ~24TPI or under 1mm pitch it gets more and more dicey differentiating, especially when you are dealing
with short threads such as screws or nuts with only 3-6 mm of thread length. Of course a 4mm nut is going to be really hard to evaluate.
Known screws and nuts are the easiest way to go here.
When I was wrestling with my Di2 short battery mount, the threads were standard 3Mx0.5m but the allen head socket was NOT standard. I found some potential replacement screws out of hard drive mounts. I do have a set of thread gauges.

Bill Kapaun

Stick an 8mm crank bolt in the 8mm hole and report back.

wroomwroomoops

Why not? I just did and found an extremely useful tool which I actually need:
FREE SHIPPING Thread Plug Gage Stainless Steel Metric Screw Pitch 60 and 55 Degree Thread Measuring Gage Gauge-in Gauges from Industry & Business on Aliexpress.com | Alibaba Group

I bought it, too!

Bill Kapaun

Good for you-
I was replying to the OP and since you didn't follow the context of the conversation to that point, your post is totally meaningless.

wroomwroomoops

hahahh... I thought you were warning against googling for one of those cornea-burning images (as in "whatever you do, don't google tubgirl").

As you said, it turned out very well for me, so thank you.