100mm Screws
This topic contains 28 replies, has 7 voices, and was last updated by 
Mark68 3 weeks ago.
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Hey all
I need to drill a pilot hole for a 100mm length screw. The drill bit has to be 3.5mm in diameter but I can’t seem to find a drill bit (auger bit?) long enough. I’ve tried using the screw without a pilot hole but there’s no way that works.
Any ideas?
Thanks all.
"Sawdust? I think you'll find that's man-glitter."
Thinking about it, is there an applicable screw for the job of fastening the apron of my workbench to the legs? I want to make sure the fix is strong and permanent. I would use a nut and bolt but the screw doesn’t exit any timber so there’s no way to screw the nut on.
I was looking at the following two options (neither of which need a pilot hole, so that’s a bonus):
6.7mm diameter x 100mm length at £12.99
http://www.screwfix.com/p/timbascrew-flange-timber-screws-gold-6-7-x-100mm-50-pack/3374j
6.3mm diameter x 100mm length at £19.99 (smaller diameter but more expensive?)
http://www.screwfix.com/p/timberfix-flange-structural-timber-screw-brown-6-3-x-100mm-50-pack/23059
Would the above screws be sufficient or should I use something else?
Thanks all.
"Sawdust? I think you'll find that's man-glitter."
Would bench bolts or threaded nuts perhaps be suitable alternatives?
The attached link is for a Youtube video that some 7 minutes into it shows drilling for bench bolts
Sven-Olof Jansson
London, UK; Cambridge, MAHi Sven
Thanks for the video. I did watch most of it but the technique he uses is way above my skill level. I’ve seen the technique used on other furniture but I wouldn’t be comfortable using it. What a really nice looking bench though!
I was hoping to just screw some strong screws through the apron and into the legs. Paul mentions doing this as an alternative to coach bolts.
See here at 27m 17s:
"Sawdust? I think you'll find that's man-glitter."
If you use a twist bit in an electric drill or hand drill, just insert the drill into the chuck enough to hold it firmly, you don’t have to push it all the way in. That might give you enough length on the bit to drill far enough into the wood. May be worth a try.
I’m afraid to say it still wouldn’t be long enough
"Sawdust? I think you'll find that's man-glitter."
SPAX makes self drilling high strength lag bolt in a hex or star drive washer head style and they are available at your local orange box store or hardware stores. They will go in with a bp driver or a hand brace with the proper adapter.
https://www.homedepot.com/b/Hardware-Fasteners-Screws-Self-Drilling-Screws/SPAX/N-5yc1vZc2d6Z1bj
They also carry long shank bits – Often
called aircraft bits in small diameters if you want to use a pilot hole.If you lack said colored store there is always amazon.
Hi Larry
Thanks for the links.
Are they the same as the two possible candidates I posted above? They look to be:
6.7mm diameter x 100mm length at £12.99
http://www.screwfix.com/p/timbascrew-flange-timber-screws-gold-6-7-x-100mm-50-pack/3374j
6.3mm diameter x 100mm length at £19.99 (smaller diameter but more expensive?)
http://www.screwfix.com/p/timberfix-flange-structural-timber-screw-brown-6-3-x-100mm-50-pack/23059
The screws you posted, are thicker (if 3/8 = 9.5mm – which would be even better).
I have attached a pic of the problem I have. You’ll have to forgive my poor drawing skills but the point I am trying to get across is there is not enough apron for the coach bolt to go through. As indicated by the red circle, some of the coach bolt’s thread (more than what is displayed) would miss the bottom of the apron. I made my benchtop an inch or so thicker, and this is what I think has caused the issue.
"Sawdust? I think you'll find that's man-glitter."
After a bit more research, it seems these Coach Screws by Timco, are ideal:
The above configuration should hold it all steady. The bench won’t be disassembled or anything.
"Sawdust? I think you'll find that's man-glitter."
What about making your apron a little wider by laminating an extra (1″ or 2″ wide) board to it?
I was thinking of doing that but I’m not sure how strong the bond would be.
"Sawdust? I think you'll find that's man-glitter."
Well Mark, I’m at best an acceptably mediocre woodworker, but with use of a simple guide I managed to satisfactorily add bench bolts to my work bench. Some photos attached.
Sven-Olof Jansson
London, UK; Cambridge, MAWhat is that technique called? I’ll research it to see if I think I can manage it.
"Sawdust? I think you'll find that's man-glitter."
Isn’t your apron already made by laminating 3 boards?
A good glue joint is supposed to be stronger than wood.If that is the case, then I shall laminate an extension.
Thanks all for the feedback
EDIT: On second thoughts, it means having to cut out a mortise hole to requirements so I would much rather try another technique.
Perhaps using bolts in Sven’s suggestion is the way to go.
"Sawdust? I think you'll find that's man-glitter."
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