Tool to find bolt sizes

[James Morse]

I was trying to match front splash guard bolts on the Lexus and I *think* they are M6.3-1.81 x 20mm. I already got some (not that exact size) that looked the same in the pack but threads are just enough different to not fit.
I do have one for an example to match, and my question here is, what's a good tool that will let me fit/try different sizes of bolts/threads so I can determine what it is, and/or try prospective ones against it. Advance has tests for some sizes but they are just for common plus I'd like to have one in my shop anyway. If they're not horrible expensive.

6.3mm sounds like 1/4" to me but I guess it's not. Heads are 10mm.
The example oem one I have goes in fine in the empty holes (threads take fine). The wrong ones I got, start ok, but fairly quickly seize up and to me that says wrong thread, just off by a tiny bit, which is enough. If it binds with finger pressure, I stop there and regroup.

I run into this kind of thing not often but periodically, enough to make me want to be able to measure it and say for sure "it's this size".

 

[pjtoledo]

look at the heads of the bolts.
markings like 4.8 8.8 10.9 12.9 are metric
anything with dots or short lines is SAE, they can look like pie cuts.

they (who?) sell gauge plates, a 4 x 8 with popular sizes of threaded holes.
also other measurements.

there are many special size & pitch fasteners in the automotive world.

search bolt identification for info.

 

[pjtoledo]

you have the equivalent of 1/4-14, that ain't a standard size.

 

[James Morse]

Thanks. Just as I thought, it's an oddball. There are bolts that seem the same, but when you look carefully at teeth vs teeth, they don't quite exactly match.
If I can't locate it at usual parts places, it has been suggested that body shop stores carry a lot of fasteners which makes sense. There's also a place in town that sells nothing but fasteners.
Or junkyard if they'd pull some for a couple dollars.
Stupid little task, but when she got it the splash shield was partly down under its mounts which makes a hole and you see it from the front and it looked like it's falling apart. Which basically it is since there are, I think 6 bolts and only 2 of them in there. So I tucked it back where it should be, doesn't look like anything wacked out as the holes all match up. Cosmetically it's a big improvement and you want that sealed there anyways that's its purpose.
It is a consequence of somebody owning a vehicle but never bothering to attend to these little things. But they can turn into big things, if all the bolts come out and the thing hangs down and catches on something then you have a whole different problem.

 

[Blmpkn]

Amazon.com

Every hardware store worth its salt should also have one of these down the hardware isle.

 

[ericbphoto]

Body fasteners are often non-standard. Often look like “sheet metal screws” with coarse threads to grab spring clips (u-nuts and j-nuts) or to thread into plastic. You might find something at a regular auto store in bible packs under the “help” or “Dorman” brands. Otherwise, a place that specializes in automotive hardware.

I keep a bin for stuff like that when I disassemble junk parts. It can be handy to have those later.

 

[ericbphoto]

By the way. You can get a screw/bolt measuring thin pretty cheap at Lowe’s, Harbor Freight, Northern or online. But it will only have the most common sizes and thread pitches. Won’t be a lot of use for that specialty hardware.

 

[James Morse]

Here's the item. No markings on head. Washer does not come off them not sure how they manage that, but you don't lose the washer. You've seen them before I'm sure.
Note the cutters one on each side. I believe it's a tapered thread which would make sense with the cutters.
These are holding together plastic so you can't reef on it much or you break things. I think over time with vibration they just work loose and fall out. Or else someone had it apart and lost most of them.
I have tons of stuff saved over the years and often I have a match but so far don't see one. Especially with the integrated washer, although I have washers so that's not important. I'm sure I can find them somewhere.

 

[ericbphoto]

Looks like the M6x1 body screws all over a Ranger.

You need a decent thread pitch gauge. That way you know for sure what the threads are and if something else doesn’t fit, it’s either wrong or damaged.

 

[James Morse]

I'm not pulling any off my Ranger!
yes thread pitch gauge that's it
thanks

 

[pjtoledo]

self tapping, drive it into a round hole. common in automotive world.
get one of these, comes in handy at least twice per year.
IRWIN 18 Leaf Thread -Gauge in the Standard (SAE) Thread Gauges department at Lowes.com

 

[ericbphoto]

self tapping, drive it into a round hole. common in automotive world.
get one of these, comes in handy at least twice per year.
IRWIN 18 Leaf Thread -Gauge in the Standard (SAE) Thread Gauges department at Lowes.com

And get the metric one, too

 

[sgtsandman]

Amazon.com

Every hardware store worth its salt should also have one of these down the hardware isle.

I was going to suggest the same.

To the OP the thread gauge, also mentioned, helps a lot along with a drill gauge. That is either a metal or plastic card with various hole sizes and markings next to each hole as to the size in SAE and metric.

Often times and ACE or True Value hardware store will have the first posted testers and a large assortment of fasters in coarse and fine thread to match. Sometimes you still have to break down and go to the auto parts store, where things aren’t as user friendly.

 

[19Walt93]

A thread pitch gauge is a good start. I bought a Snap On thread chaser set like this years ago and use it constantly, even when the threads aren't rounded off like your picture.
Actually, my set is bigger but you get the idea.