Drilling Tufnol
 

Is this the right place for this question? A 'workshop method' question associated with replicating a vintage part.
I need to drill some 30mm diameter holes through 20mm thick Tufnol, what is the best method?
I can envisage use of a hole-saw or maybe a woodworking flat-bit?
I want a nice clean edge to the hole on at least one side (the other side will be subsequently milled away) and clean sides.
Tufnol is expensive to experiment, so has anyone got experience of working with it?

Many thanks,

Andy

Re: Drilling Tufnol
 

I would suggest a 30mm hole saw, of the type that has a central drill bit projecting from it. This stabilizes the rotational axis of the saw and avoids the need to clamp the material, but if you can clamp it in the drill press all the better. These saws work well just with a hand electric drill too.

Once the bit passes through the panel I would cut about 2mm or so into one surface and then flip it over and cut the full thickness hole. Otherwise one edge can be rough, but it might not matter if you plan to machine that away later. Do it slowly with the occasional rest as this thick material can evolve a lot of heat if you try to pass the hole saw through it too quickly.

Re: Drilling Tufnol
 

A forstner bit works very well. Drill a small pilot hole first to give the tang of the bit something to follow. Cuts very cleanly indeed and gives a precise diameter.

About a tenner from my local emporium http://www.toolpost.co.uk/pages/Wood...__routing.html

You can get cheaper ones if this is a one-off hole.

Craig

Re: Drilling Tufnol
 

I use hole saws too - but I find that they are rather imprecise, even the high grade ones.

Re: Drilling Tufnol
 

It drills fairly normally with a few caveats.

Use a very sharp drill.
Use a pillar drill for carefully controlled feed.
Mount the work in a drill vice and bolt the vice down.

On your final size of drill, drill only half way from one side, turnover, carefully centre it up again and drill from the opposite side. This avoids breaking up the outer layers as the drill breaks through.

For a nice finish you can make up a tool with emery cloth on the outer or finish with a reamer.

If limited to stuff from a DIY shed, then pillar drill, drill vice and a hole-saw may be the best. Without positive positioning, the stuff does tend to make drills wander.

David

Re: Drilling Tufnol
 

All good advice Andy.

The only comment I will add is if you do use a hole saw once you've drilled the pilot hole replace the pilot drill with a piece of steel of the same diameter.

The shanks of pilot drills are often not of good quality, can be of odd sizes and the flutes can extend to be level with the teeth of the hole saw and cause a lot of wobble.

Practice first on a piece of scrap.

Jim

Re: Drilling Tufnol
 

I've used quite a lot of Tunol and phenolic Tufnol substitute, generally not thicker than 5mm. I dislike hole-saws with a passion and have always used Forstner bits up to 25mm diameter in a pillar drill, which cut very well with no jerkiness. One thing to bear in mind, is that for each rev at 30mm diam, that's 90mm of material to be cut at the periphery, so the drill speed needs to be slower than for smaller diameters or it will tend to stall - likewise it will stall if too much pressure is applied. Hole-saws do at least have the merit that the only material being cut is at the periphery - forstner bits and flatbits remove all of the material in the hole, so have to work harder.

I'd echo the comments about turning the material over as soon as the centre point have punctured through the material.

Whatever method you chose, it might be as well to practice on a piece of hardwood first.

Good luck with it.

(Makes a nice smell - well it does to my olfactory senses at any rate!).

Re: Drilling Tufnol
 

Some useful advice here, many thanks. The Forstner bit looks interesting, I don't have any of those, I suppose because I've always been happy with flat-bits for drilling wood. It looks like a cross between a drill bit and a hole-saw!
Jim, an interesting comment on hole-saw pilot drills. I have a set of Starrett hole saws, I think the drill bit can be removed from the arbor.
It looks like a bit of experimentation is on the cards. I can hold the item securely, I have a machine vice with X-Y movement on my drill-press, or I can use my milling machine as a drill-press, this does have the benefit of electronic speed control (although at slow speeds it lacks 'grunt')

Andy

Re: Drilling Tufnol
 

I've not cut Tufnol to quite that large diameter, but I would suggest if possible, use water as a lubricant/coolant.

Re: Drilling Tufnol
 

On the basis that 'a picture paints a thousand words', I've just drilled a 32mm (1.25") diameter hole in a 12mm thick piece of Tufnol with a Forstner bit. It took just 3 minutes at 680 RPM in a pillar drill with no lubrication - no dramas.

Hope that helps.

Re: Drilling Tufnol
 

David, that looks good! I'd better order a Forstner bit straight away.

Andy

Re: Drilling Tufnol
 

For DIY use, the sets sold by Screwfix are more than adequate. A set of five: 15, 20, 25, 30 & 35mm is £7.99:

http://www.screwfix.com/p/forstner-d...ails_container

(In stock at Preston branch!).

Have fun.