Fixing a marking gauge

[Wend]

Hi folks,

I have a malfunctioning marking gauge. If I remove the sliding piece, then I can screw the thumb screw all the way in, and all seems to be fine. However, when it is assembled, if I try to tighten the thumb screw then it just slips, and will spin forever and never tighten.

I was thinking that I could fix this by drilling the hole a little bigger, covering the outside of a threaded insert (assuming I can work out what thread type I need) with hot glue, and pushing it into the hole.

Is that likely to work? Is there a better answer?


Thanks
Wend

 

[Trevanion]

It sounds like either the threaded insert in the head has lost its grip in the wood and is slipping (If there is an insert) or the thread has stripped in the insert / wooden head.

I'd take the screw completely out and see if there's a threaded insert and if it's properly secured or not, if not superglue it.

 

[Steve Maskery]

A photo or two would really help, I think.
It's almost certainly fixable, one way or another.
S

 

[Wend]

I'm not sure how well I can show the problem with photos. Do those below help?

I think that currently the wood is tapped directly, rather than having an insert. I assume that the screw is just slipping over the wood.

 

[MikeG.]

When that happened to mine, I turned it over and drilled a new hole on the other side. When that failed some while later, I started making my own.

 

[Trevanion]

Ah, sounds and looks like the wooden threads have stripped then.

The best course of action would be a threaded insert like one of these:

Figure out what size insert you need, drill a hole the correct size for the insert into the head, wax the outside of the insert (To make it go in easy) and thread it into the wood with an allen key, voila! Fixed

 

[Wend]

Hmm, those look like they have threads on the outside that would be just as likely to slip again. That's why I was wondering if some sort of glue might be more secure.

 

[Trevanion]

I doubt whether the insert itself would slip, the threads going into the timber will be quite large and very snug fitting since they won't be cut in, they'll be squashed in. You could always glue it for extra security.

 

[Wend]

OK, thanks!

 

[Steve Maskery]

They won't slip, the outside is a coarse thread. Just make sure you drill out to the correct core size, first.
BTW, they are called Threaded Inserts.
https://www.screwfix.com/search?search=insert+m6

 

[Orraloon]

Making a gauge is quite easy and a bit like clamps you can't have too many. Think I have 7 now.
Regards
John

 

[ED65]

I assume that the screw is just slipping over the wood.

Seems likely from your description of the problem that the threading has stripped or degraded up at the top where the threads do the most work in day-to-day use. Might well be due to the threads not being done well initially (kinda looks like that might be the case) rather than simply through wear and tear.

Anyway it's child's play to repair the wood threading if you want to, or alternatively you can fill the hole, drill and re-tap from scratch IF the brass thumbscrew is a standard thread like M8.

For both jobs you can use filled epoxy (epoxy + sanding dust). You can also fill the hole with a solid-wood plug or a dowel, although the second will give weaker threads they can be significantly strengthened by dribbling in some runny superglue afterwards.

 

[Wend]

In case anyone's interested in how it turned out, I ordered a cheap set of metric threaded inserts, and the knob didn't fit in any of them. So I also bought a couple of the cheapest M6 2cm brass thumb screws I could find. I wasn't sure if the body would survive without cracking, but one 9mm hole later and the insert easily went in with a hex key. Now better than new!

Thanks again everyone for all the advice.

 

[Steve Maskery]

That looks quite a nice thumbscrew. Where did you find that?

 

[adrspach]

Just today I was cleaning 2 marking gauges and when I took them apart there was square plate inside with the thread in it. I did not know about is until the piece fell out when I dropped it on the floor. Once I got the pieces together is was easy to reassemble.

 

[Wend]

That looks quite a nice thumbscrew. Where did you find that?

https://www.aliexpress.com/item/4000065766049.html (although it was £1.88 for 2 at the time; other sellers may now be cheaper).

 

[Steve Maskery]

They look better in your picture than in theirs.
Is 15mm the overall length or the length of the thread? That is either short or ridiculously short.
S

 

[woodbloke66]

... I started making my own.

Same here. One of the easiest tools to do yourself; I use several Japanese style gauges (at least four) with cutters made from an off-cut of an old hacksaw blade - Rob

 

[Wend]

Is 15mm the overall length or the length of the thread?

I bought the 6x20 size, and the threaded section is 20mm long. The whole thing is 29.6mm.

That is either short or ridiculously short.

I bought the size that fitted the task at hand . There are probably other listings for larger sizes.

 

[Steve Maskery]

I bought the size that fitted the task at hand .

Can't argue with that!