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Removing grub screws, best method.
Posted: Mon Aug 08, 2022 7:51 pm
by Gary Richardson
Hi
I have a problem with the M4 grub screws on the late Tiger axle/torsion rod assemblies. Having assembled and set up the axles and torsion bars a while ago I have decided to update and use 2.5mm spring roll pins on the axles for added security. Thanks Adrian for talking to me about this at the steam fair last Sunday.
I started trying to undo the grub screws locating onto the torsion bar flats but quite a few are rounding off. I have a good selection of the right size allen keys but it is not helping and even the newest ones are slipping. The grub screws had Loctite applied using the standard blue variety. As there are four grub screws per torsion bar this is becoming a real problem as I am getting one or two screws rounding off on each one. To remove one of the axles I had to grind the head of the grub screw off to allow the axle to be pulled through the bush then I drilled out the grub screw.
Is there an easy way to loosen the grub screws or break the Loctite bond bearing in mind the restricted space and the hull has been painted so a heat gun might ruin that. Hoping one of the more experienced builders or engineers will be able to help.
Regards
Gary
Re: Removing grub screws, best method.
Posted: Mon Aug 08, 2022 7:57 pm
by Donald Suttie
Hi Gary
best option is to get your best fit Allan Key (in my case its the cheapest AlDI one) and apply heat with a plumbers torch,this way it will free up the loctite and the expansion should break the hold its got,sadly the paint will not survive this process
the key is just the right amount of heat i use a rothenberger super fine torch which has already undone a green loctited screw on my build with no issues
hope it helps
Donald
Re: Removing grub screws, best method.
Posted: Mon Aug 08, 2022 8:01 pm
by Donald Suttie
To limt heat damage to your paint you could try and protect the area with Vermiculite blocks which will absorb the flames around them no problem
Re: Removing grub screws, best method.
Posted: Mon Aug 08, 2022 8:52 pm
by Jerry Carducci
One of many reasons why I don't like painting the inside of a model anywhere near mechanics...
That said. try small pieces of paper napkins/towels placed on the stubborn screw soaked with acetone or lacquer thinner.
The idea is the solvent will wick into the threads softening the locktite.
Please do this sans flames, heat guns or any other sources of ignition. Be mindful of your paint.
May not be instantaneous but should be effective given time to soak.
My go to method is a small gas torch or heat gun but the paint precludes this.
Jerry
Re: Removing grub screws, best method.
Posted: Mon Aug 08, 2022 9:01 pm
by Adrian Harris
Sorry
The plumbers mat used for the smoker wick might be easier to mould around the area.
I've also found a hot air gun seems to be able to heat things nicely but without the damage caused by the flame of a butane torch.
Adrian.
Re: Removing grub screws, best method.
Posted: Mon Aug 08, 2022 9:08 pm
by Vince Cutajar
Maybe a heavy duty soldering iron?
Vince
p.s. When eventually refitting the tornsion bars use hex head bolts instead of grub screws.
Re: Removing grub screws, best method.
Posted: Mon Aug 08, 2022 9:24 pm
by Shaun Hunt
Hi Gary,
I use a hot air gun
As long as the temperature is about 250deg it lossens the loctite great.
For bearings It works for loctite 638 also.
No flames to worry about and and if you can direct the heat to just where you need it not to much paint damage.
Regards
Re: Removing grub screws, best method.
Posted: Mon Aug 08, 2022 10:37 pm
by Gerhard Michel
I prefer a very small, but very hot butane / oxygen needle shape flame used for jewelry repair (hard soldering). It heats the screw in a few seconds without wearing the painting too much. To restore the hardness a single drop of water is used at the front end of the screw, then the allen key can be used.
Wherever possible, I avoid using Loctite for screws.
Re: Removing grub screws, best method.
Posted: Tue Aug 09, 2022 12:17 am
by Jerry Carducci
Gerhard Michel wrote: ↑Mon Aug 08, 2022 10:37 pm
Wherever possible, I avoid using Loctite for screws.
I agree, I'll use 2 set screws if the item to be fastened allows it; the second binds the first. Like using 2 nuts on a
threaded shaft with the second being a binding nut.
Jerry
Re: Removing grub screws, best method.
Posted: Tue Aug 09, 2022 8:51 am
by Gary Richardson
Hi
Thanks for all the replies, it seems heat is the most popular but will also try acetone wicked in to the threads. I found a Dremmel torch on the Screwfix site that can get up to 1200C with a short flame and looks small enough to use inside the hull. You can use a butane /propane mix with it which will give a hotter flame than just butane so will be ideal for silver soldering as well. I also ordered a new heat mat to protect the paintwork.
I have a hot air gun that produces a very hot jet but the nozzle is too wide so I am looking at modifying the fan shaped adapter to reduce the area it heats. Fingers crossed
Regards
Gary
Re: Removing grub screws, best method.
Posted: Tue Aug 09, 2022 10:28 am
by Gerhard Michel
Hi,
I use this one:
The green marked nozzle gives an extra fine needle flame with up to 3.100 °C
Re: Removing grub screws, best method.
Posted: Tue Aug 09, 2022 12:53 pm
by Shayne Sutton
Gary Richardson wrote: ↑Mon Aug 08, 2022 7:51 pm
Hi
I have a problem with the M4 grub screws on the late Tiger axle/torsion rod assemblies. Having assembled and set up the axles and torsion bars a while ago I have decided to update and use 2.5mm spring roll pins on the axles for added security. Thanks Adrian for talking to me about this at the steam fair last Sunday.
I started trying to undo the grub screws locating onto the torsion bar flats but quite a few are rounding off. I have a good selection of the right size allen keys but it is not helping and even the newest ones are slipping. The grub screws had Loctite applied using the standard blue variety. As there are four grub screws per torsion bar this is becoming a real problem as I am getting one or two screws rounding off on each one. To remove one of the axles I had to grind the head of the grub screw off to allow the axle to be pulled through the bush then I drilled out the grub screw.
Is there an easy way to loosen the grub screws or break the Loctite bond bearing in mind the restricted space and the hull has been painted so a heat gun might ruin that. Hoping one of the more experienced builders or engineers will be able to help.
Regards
Gary
Just a suggestion, maybe a Torx Hex Star Bit that can be tapped into the stripped hole.
Re: Removing grub screws, best method.
Posted: Tue Aug 09, 2022 6:27 pm
by Gian Marco Menozzi
in addition to the solution of heating the grain, there are extractors for spanned screws:
https://www.amazon.it/Estrattore-Diyife ... 2443&psc=1
https://www.amazon.it/Gebildet-Estratto ... 1119701587
have left / opposite thread,
in the positions that allow it, I replaced the dowels with standard hexagonal bolts
Marco
Re: Removing grub screws, best method.
Posted: Wed Aug 10, 2022 8:37 am
by Gary Richardson
Thank for the info Gian, I have also order hex bolts to replace the grub screws as I had 12 that rounded off and had to be drilled out despite the use of heat. This also required the tops of the grub screws to be Dremmelled smooth so I could withdraw the steel holders through the bushes.
Regards
Gary
Re: Removing grub screws, best method.
Posted: Wed Aug 10, 2022 9:31 am
by Adrian Harris
This may be a little late but I have found that stuck hex head bolts snap much more easily than HT cap head ones.
Adrian.
