I’m working on a workbench and I have started drilling the dog holes using a drill guide and a 19mm (3/4") forstner bit.
I’m not exactly sure what went wrong, but a couple of the dog holes are not plumb.
The thickness of the top is 38mm and I’ve drilled them to about 3mm before exiting on the bottom. I planned to use a router with a template bit to finish the cut so not to damage the bottom with tear-out.
For the ones that are perfectly plumb, I think that’ll still work, but I’m a bit worried about the ones that aren’t.
If I use the template bit in the router, because the hole is not plumb, the bit will bite into a lot of wood at once and I’m not sure whether this is safe to do.
Do you have any advice on how to proceed?
How not plumb are they? And in what direction? Even if the router works fine your holes will be sort of oval shaped at the bottom which might make your dogs waggle around annoyingly in use.
Personally I would glue 19mm dowels into your bad holes. You might want to drill a small hole all the way through first to let the glue escape and avoid hydraulic lock. Once it has set you can cut off the top and level it. Then start drilling again from scratch.
On the other hand, if they are only very slightly out of plumb you should be fine. Unless I misunderstand you, the router will only be taking small amounts off gradually as you plunge. It might struggle with the last 3mm if you have a straight fluted bit as they dont really cut in the very centre. Avoid this problem by drilling a small hole through the center first.
I'm familiar with those long, 19mm router bits though and don't like them very much. A friend had one kickback and he dropped the router on his leg. It removed what the doctor described as "a satsuma sized chunk of flesh and bone" from his thigh. They deserve a lot of respect. I'd consider clamping the router down to the workbench before making each plunge.
Answered by Jambo on August 26, 2020
There is more than one way to avoid tear out. You can drill a small pilot hole all the way through then use your forstner bit to drill from both sides meeting somewhere in the middle. I would choose this method over a router.
Another way is to attach a piece of scrap wood to the bottom of bench where the hole will be drilled so when the drill bit is exiting the bench top it enters the scrap wood thereby avoiding tear out.
On the holes that are not plumb i think for a bench dog hole 3mm of off plumb is negligible and if the rest of the hole, 35mm, is straight and plumb, the dog will be fine. Drill the remaining part straight and true from the underside. (Put a piece of scrap over the misaligned hole and run the forstner bit, from the bottom, all the way up through the previously drilled 3mm to clear any material that would cause a bench dog to not line up correctly.)
Answered by Alaska Man on August 26, 2020
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