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Silicon Bronze Screws Snapping

Posted: Mon Feb 19, 2018 12:33 pm
by Mark Christensen
I did a few test runs with my taper bit and some SB screws. In the pic you can see the depth I set the bit to. They seem to go in ok without snapping, but as soon as I try and back them out, they snap. This is going into white oak. I believe these are cut thread and not rolled. What am I doing wrong?
IMG_4111.jpg

Re: Silicon Bronze Screws Snapping

Posted: Mon Feb 19, 2018 1:37 pm
by KMuller
with a taper drill, the tip of the screw is doing the bulk of the pulling as well as absorbing the most torque. SB is not strong enough. bore the hole deeper or just use a straight drill. In fresh water use ss screws.

Re: Silicon Bronze Screws Snapping

Posted: Mon Feb 19, 2018 7:14 pm
by mbigpops
What number screw is that ?

You need to be using the recommended countersink for hardwood (not softwood) for your screw size.

I have a chart if you post the screw size.

Mark

Re: Silicon Bronze Screws Snapping

Posted: Mon Feb 19, 2018 9:16 pm
by Mark Christensen
#8 screw x 2”. I used the tapered bit per the supplier. I set the countersink a little deeper and that seems to have helped for now.

Re: Silicon Bronze Screws Snapping

Posted: Mon Feb 19, 2018 9:40 pm
by jfrprops
I hope more folks will post on this....it seems odd to me?
John in Va

Re: Silicon Bronze Screws Snapping

Posted: Tue Feb 20, 2018 7:21 am
by Bilge Rat
When screwing into white oak, you may want to lubricate the screw threads to alleviate the torquing off the tapered point. I used to use a mainly beeswax compound by the name of Akempucky but it is no longer manufactured. There should be other lubricants still available. This helped greatly in preventing the dreaded snap-off.

Re: Silicon Bronze Screws Snapping

Posted: Tue Feb 20, 2018 4:14 pm
by Denis D
I add almost a 1/8" additional depth when drilling white oak. Then I dip the threads of the screw in a small cup of dishwashing detergent as a lubricant. That eliminated the snapping problem both going in and coming out.

Denis D