Why not use some 'No Nails' or equivalent and stick a length of 2x1 prepared timber to the soffit and then fix your blind to the timber - unless of course your thinking of swinging from the blind!
Regards
Regards
Apologies for ole chesnut but now desparate
- Thread starter Longshanks
- Start date
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There are several different 'flavours' of self-tapping screws available, each designed for different purposes.
Some 'self tappers' just have a spire point which deforms the metal to follow the thread. IMO not really 'self tapping' more 'self forming', as they deform the metal rather than cut it. They are good for fixing thin sheet metal.
Some have flutes cut into their threads, so they can cut a thread as you wind them in. They are 'proper' self tapping screws, good for fixing into thicker steel sections.
There are self drilling fasteners. The tip is formed into a drill point to cut the correct size hole and the threads are fluted to cut a thread.
They drill their own hole, thread it and secure themselves in place in one operation - great when you've got a lot of fixings to put in.
You really do need the correct size hole, down to the last tenth, or even hundredth of a millimetre to use self tapping screws efficiently. Tool suppliers usually stock a more extensive range of bit sizes than DIY stores, including imperial, letter and number sizes, so you can select a drill bit size down to within a few thousanths of a mm of the size you want by using tables like http://www.tapdie.com/html/mm_equivalent_inch__no__letter.html You will see there are something like 25 different size drill bits available within the range of 4mm to 5mm diameter.
I agree with the comments about using a lubricant. A bit of lard on the screw points works surprisingly well.
I have no problems using a good quality carbon steel tap to thread the right size hole, using appropriate lubrication, but I agree HSS taps are more forgiving in terms of tapping hole sizes and lubrication.
Some 'self tappers' just have a spire point which deforms the metal to follow the thread. IMO not really 'self tapping' more 'self forming', as they deform the metal rather than cut it. They are good for fixing thin sheet metal.
Some have flutes cut into their threads, so they can cut a thread as you wind them in. They are 'proper' self tapping screws, good for fixing into thicker steel sections.
There are self drilling fasteners. The tip is formed into a drill point to cut the correct size hole and the threads are fluted to cut a thread.
They drill their own hole, thread it and secure themselves in place in one operation - great when you've got a lot of fixings to put in.
You really do need the correct size hole, down to the last tenth, or even hundredth of a millimetre to use self tapping screws efficiently. Tool suppliers usually stock a more extensive range of bit sizes than DIY stores, including imperial, letter and number sizes, so you can select a drill bit size down to within a few thousanths of a mm of the size you want by using tables like http://www.tapdie.com/html/mm_equivalent_inch__no__letter.html You will see there are something like 25 different size drill bits available within the range of 4mm to 5mm diameter.
I agree with the comments about using a lubricant. A bit of lard on the screw points works surprisingly well.
I have no problems using a good quality carbon steel tap to thread the right size hole, using appropriate lubrication, but I agree HSS taps are more forgiving in terms of tapping hole sizes and lubrication.
C
cmother1
A trick that I've done to attach to a 2.5mm thick box lintel is to use dry walling screws with a pilot hole 0.5mm smaller than the screw size. They're really tough and the threads are so sharp that they easily cut into mild steel. Miles better than self-tappers.
Do a trial on a scrap piece of metal first and lubricate with WD40.
Here's one I did a few mins ago. 3mm pilot drill. The red wire has 10Kg of scrap lead attached to it.
Don't know how thick your lintel is, but you might be able to get away with a smaller or no pilot hole at all with these screws.
Do a trial on a scrap piece of metal first and lubricate with WD40.
Here's one I did a few mins ago. 3mm pilot drill. The red wire has 10Kg of scrap lead attached to it.
Don't know how thick your lintel is, but you might be able to get away with a smaller or no pilot hole at all with these screws.
THese are known as "thead forming" screws - some also have the drill forged into the end and are self drilling thread forming. . .
If you go the tap route remember to keep turning the tap backwards to break off the swarf as you go - each half turn or so. Otherwise the tap clogs with swarf, locks up and snaps.
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A trick that I've done to attach to a 2.5mm thick box lintel is to use dry walling screws with a pilot hole 0.5mm smaller than the screw size. They're really tough and the threads are so sharp that they easily cut into mild steel. Miles better than self-tappers.
Do a trial on a scrap piece of metal first and lubricate with WD40.
Here's one I did a few mins ago. 3mm pilot drill. The red wire has 10Kg of scrap lead attached to it.
Don't know how thick your lintel is, but you might be able to get away with a smaller or no pilot hole at all with these screws.
I'm not sure if this thread is still ok to use, but:
I'm fixing some wood to metal gates 3mm wall steel. I have tried Screwfix and there' stainless steel screws stripped. You mention Drywalling screws, are these for fixing plasterboard to brick?
Or do you know of a supplier of good self tappers please?
Cheers, Camerart
With hindsight it's a good idea when you can to practice what you are trying to do on some piece of scrap metal.
Better to use grease on the screw.
When using a tap to make a thread using grease or oil on it will stop it from cutting properly. You need Cutting Paste or lube which is designed for the job.
Stainless self tapping screws are quite 'soft' compared to hardened steel screws and should only used in metal with care e.g. aluminium etc., or wood. In hardwood it would need a pilot hole.
Better to use grease on the screw.
When using a tap to make a thread using grease or oil on it will stop it from cutting properly. You need Cutting Paste or lube which is designed for the job.
Stainless self tapping screws are quite 'soft' compared to hardened steel screws and should only used in metal with care e.g. aluminium etc., or wood. In hardwood it would need a pilot hole.
I agree with those who say Stainless steel self tappers strip, I've tried different suppliers. (4MM screws) If they jam the heads snap off.
The screws that worked in 3mm thickness box section, are Galvanised steel, they have a kind of built in washer.
Trying different sized drills, I found 1/2mm smaller than the size worked.
I have a Torque setting on my drill. The stainless screws snapped over '10' if in a too small hole. The Galvanised screws could stand full torque '17' and stalled the drill.
The screws that worked in 3mm thickness box section, are Galvanised steel, they have a kind of built in washer.
Trying different sized drills, I found 1/2mm smaller than the size worked.
I have a Torque setting on my drill. The stainless screws snapped over '10' if in a too small hole. The Galvanised screws could stand full torque '17' and stalled the drill.
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