Drilling large clean holes.

[Apache_sim]

I want to drill 6 45 mm holes partially through an oak platter I am making to hold shot glasses.
I have used a forstner bit in my pillar drill in the prototype, which cuts cleanly and with a reasonably flat bottom to the hole. The downside is the point of th bit leaves its mark in the centre of the hole, and the shoulder leaves the tell tale cut around the perimeter of the hole.

Is there a way to cut perfectly flat bottomed holes?

 

[Myfordman]

Forstner bit plus short bearing guided router bit to finish to final depth.

 

[nathandavies]

router with guide bush and template

 

[Mr T]

Both router options are good, will give the cleanest hole. Another less satisfactory way would be to have two forstner bits and grind the central spur off one of them. Start the cut with the spurred bit then change to the spurless for drilling to final depth. This will at least get rid of the central blemish.

Chris

 

[Apache_sim]

Thanks everyone some great advice as usual.
I will try the router option first before grinding points off

Regards

 

[Cheshirechappie]

Another approach, if it's possible, is to change the design of the platter slightly to avoid the awkward operation of drilling a perfectly flat-bottomed hole. For example, would it be possible to make the platter in two thinner parts, one with through holes for the shot glasses, and glue them together after drilling? This may need a bit of thought to disguise the joint - maybe sinking a larger recess in the bottom of the main platter, drilling the holes, and afterwards glueing in an insert that covers all the holes.

 

[CHJ]

.....the shoulder leaves the tell tale cut around the perimeter of the hole.

....

Don't understand this part of your statement, what shoulder? all Forstener and equivalent brands including saw tooth I have used have a plain cylinder form that passes cleanly down the hole without marking the entry area.

I use the fix mentioned by Cheshirechappie to hide the point mark of a disc insert in the bottom.

 

[gmgmgm]

How about drilling the holes over-deep, then inserting a slice of dowel to give a perfectly flat bottom.

You could also finish the dowel more easily and perhaps add some contrast.

 

[MMUK]

Another approach, if it's possible, is to change the design of the platter slightly to avoid the awkward operation of drilling a perfectly flat-bottomed hole. For example, would it be possible to make the platter in two thinner parts, one with through holes for the shot glasses, and glue them together after drilling? This may need a bit of thought to disguise the joint - maybe sinking a larger recess in the bottom of the main platter, drilling the holes, and afterwards glueing in an insert that covers all the holes.

Or, drill through completely then fit a rebated base panel so the joint can only be seen if you lift the holder up and turn it upside-down

 

[Phil Pascoe]

.....the shoulder leaves the tell tale cut around the perimeter of the hole.

....

Don't understand this part of your statement, what shoulder? all Forstener and equivalent brands including saw tooth I have used have a plain cylinder form that passes cleanly down the hole without marking the entry area.

I use the fix mentioned by Cheshirechappie to hide the point mark of a disc insert in the bottom.

I think the OP meant the perimeter at the bottom of the hole - I had to read it more than once.

 

[CHJ]

....I think the OP meant the perimeter at the bottom of the hole - I had to read it more than once.

Ahh, got it, have never noticed anything significant in that regard with the bits I have, might be because there is a minute relief of the cylinder behind the cutting edge.

 

[Spindle]

Hi

Can you offset mount the platter on the lathe and turn the recesses?

Regards Mick

 

[nanscombe]

How about cut slightly deeper than required and drop (possibly glue) a circle of felt, or other suitable material, in the bottom of the holes.

 

[bugbear]

Hi

Can you offset mount the platter on the lathe and turn the recesses?

Regards Mick

Hell's teeth, that would require massive clearance when drilling the edge-most holes!

BugBear

 

[Spindle]

Hell's teeth, that would require massive clearance when drilling the edge-most holes!

Hi

My modest CL4 could cope with about an 18" platter

Regards Mick

 

[chipmunk]

+1 for Spindle's suggestion of offset turning but it'd be best done on the blank before turning the platter IMHO.

It could potentially result in the best holes (not necessarily "boringly" uniform :roll: )

Jon

 

[Tierney]

Similar to Cheshirechappie...If you have a bandsaw and planer - I would rip the piece in half, plane each face, drill the hole through one half with a forstner bit and then glue back together with waterproof glue. If it is for shot glasses, I don't think you need to worry about people spotting a glue line, plus if it is the same piece of wood ripped and glued back together, many woodworkers wouldn't notice the glue line anyway.

 

[nanscombe]

Or you could make a feature of the join by inserting a thin piece of contrasting wood.

 

[Apache_sim]

Some excellent solutions and advice.....
Chucking for each hole is not an option, although I did think about that.
My forstener bits (of fair quality) do leave a circular mark at the bottom of the hole equal to the diameter of the bit.. I guess that is how most forstner bits are designed so that they don't wander too much.

I like the router option using a template of suitable height... cant find a very short bit with bearing above.

Thanks everyone.

 

[rafezetter]

Or you could make a feature of the join by inserting a thin piece of contrasting wood.

I like this idea, or the insert false bottom in contrasting material or wood colour