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M6 thread locking/stiff screw

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modeng200030/09/2021 19:37:39
273 forum posts
1 photos

I would like a 12mm M6 screw, preferably socket head, that is stiff to turn in a normally tapped blind hole. I have seen thread locking screws but not in the size I want. I pondered slitting the screw that then might look like a threaded split pin or perhaps cross drilling and fitting a nylon plug. The screw must not damage the tapped hole.

These screws seem a bit rare hence the request for help.


John Hinkley30/09/2021 19:44:28
1199 forum posts
393 photos


I think you've answered your own question. I have used the cross-drill and nylon (strimmer cord) method a number of times with success. Just so long as the screw isn't subject to extreme torque, it should do the job satisfactorily.


Jon Lawes30/09/2021 19:46:10
700 forum posts

I never would have thought of strimmer cord, fantastic,

JasonB30/09/2021 19:46:15
21650 forum posts
2495 photos
1 articles

You could get a M6 socket head bolt and thread the plain shank with a die that has been fully opened up in a die holder and that hopefully will give you a fit with some friction saw off the unwanted length.

modeng200030/09/2021 19:52:05
273 forum posts
1 photos

Thats a briliant response, many thanks all.

I think I'll go with the strimmer cord, seemed to me to be a possible solution and as John has used it I reckon it should do what I need.


Frances IoM30/09/2021 19:55:51
1176 forum posts
28 photos
I have some fishing line - comes in various thicknesses (usually expressed as breaking strength or weight of hoped for catch) - any shop that deals with fishing tackle will stock it
Michael Gilligan30/09/2021 21:14:58
19323 forum posts
964 photos

If you can bear it … Pop over to IKEA and have a look in the ‘spares’ rack

At Ashton-under-Lyne this is ‘free access’ just after the check-outs smiley

They have [or did have] a good assortment of M6 screws with hex socket pan-heads and locking patches.

… on the other hand : Life may be too short.


Edited By Michael Gilligan on 30/09/2021 21:16:10

Richard Millington30/09/2021 21:23:04
38 forum posts

Locktite 243?

modeng200001/10/2021 10:18:20
273 forum posts
1 photos

Some interesting and useful ideas so thanks to all of you.


Gerhard Novak01/10/2021 10:18:50
64 forum posts
70 photos

I suppose Richards idea with chemical thread lock is a good one. Works very well on all kind of model helicopters. (Where you definitely have vibrations...)

ega01/10/2021 10:30:03
2329 forum posts
190 photos

Some cycle wheel builders use a product on the spoke threads that both lubricates to facilitate tensioning and then secures the nipple against rotation once the wheel has been finished. Apparently, linseed oil will do this but there is a proprietary product called SpokePrep.

blowlamp01/10/2021 10:30:50
1529 forum posts
98 photos

I've used a spot or two of super glue on the screw with good results.

Just apply to the thread and let it harden before screwing it in.


modeng200001/10/2021 13:05:19
273 forum posts
1 photos

I need to be able to re-adjust these screws from time to time.

The applcation is to improve the setting of the gib strips locating the saddle on a mini-lathe.

If you have experience of these machines you will know how much of a pain it is to adjust these for a good sliding fit.

There are 5 screws in each gib, the outer and centre ones are screwed into the saddle casting and the other two threaded in the gib, these two have lock-nuts. The intention is to not use the two lock-nut screws and make the three M6 screws into a friction thread version so that they retain their setting and do not rely on the pressure from the two lock-nut screws that are trying to push the gib away from the casting so giving some friction to the M6 screws.

I have been thinking about this for a while and have read all I can find about this adjustment and believe this mod will work. Time and experience will no doubt provide the answer.


Macolm01/10/2021 14:22:39
56 forum posts
10 photos

I have used PTFE plumbing tape for similar thread stiffening. You can vary the number of turns within reason for adjustment, it lasts quite well, and is quick and easy to replace.

Michael Gilligan01/10/2021 16:06:53
19323 forum posts
964 photos

It turns-out that my M6 IKEAscrounge screws are countersunk

… the plated ones with large pan-heads are M5



Apologies for the misleading information blush

… there may be other variants available.


modeng200001/10/2021 16:13:08
273 forum posts
1 photos

Malcolm, I should think the ptfe tape would work in this application.

I'll try it first before possibly making nylon loaded screws.

That's ok Michael, these screws are new to me.


blowlamp01/10/2021 17:14:07
1529 forum posts
98 photos

I would imagine nail varnish would work too - just apply it as show in Michael's post above.


Clive Foster01/10/2021 19:10:25
2889 forum posts
104 photos

Bit OT but Screwfix do M6 versions of the flat head hex socket screws in Michaels picture. 25 to 50 mm lengths. No locking stuff tho', just plain thread. Called joint connector bolts except for the 50 mm one which is a cross dowel bolt. Also joint connector nuts as the female thread version. M6 threaded cross dowels too. Not the highest of tensile ratings but worth remembering when you want a neat job. I usually have a part pack about the place.

Getting back to the OPs problem I've gotten away with insulation tape in the past. Unlike Malcom PTFE tape has never worked for me unless things are pretty tightly done up. Sort of tighness where I'm looking for the weakest loctite.


Edited By Clive Foster on 01/10/2021 19:11:26

martin haysom01/10/2021 22:15:24
60 forum posts

in my box of old screws/bolts is a few that have slightly triangulated threads they are tight in normal taped holes sadly i can only say i removed them from an oldish car and they are metric

modeng200001/10/2021 22:30:41
273 forum posts
1 photos

Martin, I think they are called tri-lobed screws.


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