Accurately opening out a hole

[felixgogo]

Hi, I have a wooden workbench, which oddly has 15.7mm holes in it, and this is not compatible with most fittings, and I'd like to use parf kit and hold-downs which are 20mm.

How can I open out these holes accurately?

If I try to runa 20mm drill bit into the hole it'll not run parallel. I'm not sure how to approach this.

 

[sammy.se]

Hi, I have a wooden workbench, which oddly has 15.7mm holes in it, and this is not compatible with most fittings, and I'd like to use parf kit and hold-downs which are 20mm.

How can I open out these holes accurately?

If I try to runa 20mm drill bit into the hole it'll not run parallel. I'm not sure how to approach this.

Hmm, maybe not the cheapest optuon, but if you buy an MFT template, it comes with reference dogs that you can attach to your first hole, thereafter every other hole made using the template will be parallel.


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[9fingers]

I would buy some 5/8" dowelling and glue full depth sections into the holes. Then use whatever template scheme you wish to cut the new holes. most drills and forstners need a central support all the way through to stop them wandering. Even though you will be turning all the dowelling to sawdust, you will get a far better result and the cost will be trivial in comparison to the frustration of wonky holes.

Bob

 

[Coley]

How thick is the top ?

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[Woodbloke]

I would buy some 5/8" dowelling and glue full depth sections into the holes. Then use whatever template scheme you wish to cut the new holes. most drills and forstners need a central support all the way through to stop them wandering. Even though you will be turning all the dowelling to sawdust, you will get a far better result and the cost will be trivial in comparison to the frustration of wonky holes.

Bob

Yep, that's how I'd do it as well - Rob

 

[Pinch]

I would buy some 5/8" dowelling and glue full depth sections into the holes. Then use whatever template scheme you wish to cut the new holes. most drills and forstners need a central support all the way through to stop them wandering. Even though you will be turning all the dowelling to sawdust, you will get a far better result and the cost will be trivial in comparison to the frustration of wonky holes.

Bob

Yep, that's how I'd do it as well - Rob

Yep, me too.

:text-bravo:

 

[Woodster]

How thick is the worktop? If you have enough travel you could simply plunge cut the holes with a router firmly clamped in position. It would be much quicker than plugging and should leave better holes in terms of size, finish and being vertical to the surface.

 

[felixgogo]

Thanks all, I thought perhaps there would be some fancy tool that would do that, but perhaps not.

I think rather than plugging and redrilling, I'll just drill new 20mm holes in between the existing.

Thanks for the router idea - I don't have a router, so this maybe a great excuse to get one!