rear bumper bolt hole problem

[rmmchl]

I removed my rear bumpers  to have some touchup clear coat done. There are 2 bolts for each bumper plus the washers. One bolt hole will not allow me to thread the bolt in. It stops after a few turns. Maybe some clear coat got into the threads. I don't want to force the bolt in for fear it may break off. I do not want to tap a new hole either.  classic center has no idea of the original bolt size and thread size. Any ideas how I can screw something in the hole to straighten and clean up the threads.? They are original size bolt holes . Meaning they have not been modified

[johnk]

Can’t you run a tap in them to clean them out?

[Cees Klumper]

I know it's unlikely, but it does sound to me like you're not getting the bolt 'started' straight into the nut. A bit of clear coat should not cause this? This is a pretty large-size thread. Agree you can chase it with a tap.

[wayne R]

It may seem funny even with items like  bumpers, as you remove each bolt,
i place the bolts in a position on floor ,so that the same bolt can go back to its original hole,
Michael remove bumper , pre fit bolts before fitting bumper, put one drop of three in one oil,
on each bolt, thats in my tool kit all year round,.
Then swap the bolts around until they refit correctly, then refit bumper.

[mbzse]

.../...rear bumpers  to have some touchup clear coat done. There are 2 bolts for each bumper.../... classic center has no idea of the original bolt size and thread size.../...

The bolts are M10, with key width 17mm.  Length 30mm. Thick washer is swaged on

[rmmchl]

I have it threaded straight, it just wont thread past a couple of turns. I thank for you for the size. I will have to find the correct tap to use. hope I don't mess it up

[rmmchl]

any idea on the type of tap to buy. they come in different pitches for the different threads.

[mrfatboy]

Here is a metric set from Harbor Freight.  It has two pitch sizes for a 10mm hole. I am not sure which one you would require.

https://www.harborfreight.com/carbon-steel-metric-tap-and-die-set-40-pc-62832.html

[UJJ]

The thread is M10x1.5mm pitch. (No fine thread)

[mbzse]

any idea on the type of tap to buy. they come in different pitches for the different threads

Already defined. M10 is M10 (the pitch is then normal 1,5mm)
If it is M10 fine pitch, well then designation is M10x1,25 or M10x1

WIKIpedia has a useful table for all M-size threads (good when you own a Euro car)
https://en.wikipedia.org/wiki/ISO_metric_screw_thread

[rmmchl]

Thanks guys. It worked .  A quick fix. Size 10 tap with a 1.5 pitch. I threaded in the tap, then screwed  in my bolt. It worked nicely. Bolt is tight with no play

[johnk]

I bought the harbor freight tap
And die set just to clean all of the paint out of the holes as I put my car back together. It doesn’t have every size I need but it has most.