pen blank drilling

[Jensmith]

I posted on here a few weeks ago with a problem where I was drilling on the lathe and I was getting a screaming noise while doing so.

I seem to have resolved that issue in the main thanks to your advice but now I've run into another problem where the drill seems to stick when I've drilled about half way through the blank. It just gets tighter and tighter.

The wood I was using I think was zebrano and I also had the same problem with walnut. The drill was getting hot so I left it to cool but even when cold it was still sticking. It just stops being able to drill through and my fault light comes on on the lathe.

it's as though the wood is shrinking. It's a colt twinland lip and spur drill that I've been using

I've just got a little chinese made mini lathe so it's not the most high powered or best made in the world but I can't see why it would be a problem when drilling at low speed.

It seems to be the period of time where my inexperience is causing a whole heap of issues :?

Any ideas?

 

[laird]

Normally sticking is when the drill doesn't clear itself, and the sawdust builds up and jams it/cooks it. When you withhdraw the bit are all the cutting threads clean ?

 

[Jensmith]

Normally sticking is when the drill doesn't clear itself, and the sawdust builds up and jams it/cooks it. When you withhdraw the bit are all the cutting threads clean ?

Ah! No, it wasn't actually but I was only drilling a cm or so at a time and even tried to tap out any shavings in the blank itself.

Is there a way to resolve this? Is some wood worse than others? It was fine with a bit of masur birch I had.

 

[János]

Hello,

This is a common problem if/when drilling larger diameter (over 20mm 3/4") holes in hardwood. The wood shrinks onto the bit. Walnut, ash and oak are the worst offenders in this respect. Remedies are slow feed, and a low rpm, under 600, and a sharp drill bit.

Have a nice day,

János

 

[laird]

Normally sticking is when the drill doesn't clear itself, and the sawdust builds up and jams it/cooks it. When you withhdraw the bit are all the cutting threads clean ?

Ah! No, it wasn't actually but I was only drilling a cm or so at a time and even tried to tap out any shavings in the blank itself.

Is there a way to resolve this? Is some wood worse than others? It was fine with a bit of masur birch I had.

I think you might need some new drill bits, or sharpen the ones you have - including the threads, not just the tip.

 

[laird]

Oh and yes, some woods are worse, far worse, than others.

 

[CHJ]

Jen, how are you holding the blanks, 4 jaw chuck? are you by any chance compressing the blank?

 

[Jensmith]

Jen, how are you holding the blanks, 4 jaw chuck? are you by any chance compressing the blank?

I'm getting a 4 jaw chuck for xmas so no - I've been turning the blank round between centers and then drilling in my 3 jaw chuck.

It is possible I could be gripping too hard.... didn't think it could be that simple. It is when I get close to the chuck end.

It's just 7 mm slimline pens I'm turning too.

To answer laird's question - it's a new drill and it's only been used a couple of times on soft wood before this problem. I don't think it's blunt yet.

 

[CHJ]

Sounds as though you may still be drilling at too fast a speed, if you compact the wood chips at all before they can travel up flutes then they are going to create heat due to friction and jamb in the hole.

If you think about it the spiral on a twist drill is very shallow and ideally chippings should be travelling something like 20mm or so up the hole per revolution to clear correctly, even on a 7mm diam. drill, something very difficult to do with wood chips due to natural rough surface friction but the slower the speed the more realistic are your chances.

 

[Jensmith]

Sounds as though you may still be drilling at too fast a speed, if you compact the wood chips at all before they can travel up flutes then they are going to create heat due to friction and jamb in the hole.

If you think about it the spiral on a twist drill is very shallow and ideally chippings should be travelling something like 20mm or so up the hole per revolution to clear correctly, even on a 7mm diam. drill, something very difficult to do with wood chips due to natural rough surface friction but the slower the speed the more realistic are your chances.

The trouble I've been having is that if I drill too slowly the blank seems to stick as though there's not enough power, yet too fast and the chips get stuck.

 

[CHJ]

If your lathe is short on torque at slow speed, spindle stopping, can you try drilling with a smaller diameter drill to start with.

If you do, take care when you open up with larger drill that it does not grab and pull into the hole too quickly, make sure your tailstock is clamped and feed slowly.

 

[Jensmith]

If your lathe is short on torque at slow speed, spindle stopping, can you try drilling with a smaller diameter drill to start with.

If you do, take care when you open up with larger drill that it does not grab and pull into the hole too quickly, make sure your tailstock is clamped and feed slowly.

I did try that.... but it was with just a 4mm wood drill.

 

[CHJ]

I would have said 4mm was ideal, if rather on the short side if a standard bit for full depth drilling of your blank.

Drill type is not too relevant, as long as you find one that works in the material you are drilling.

There are so many differing wood characteristics, far in excess of drill forms that no one type is ideal, admittedly some forms will on average perform better but don't get hung up on type.

Did drilling smaller pilot hole help?

One thing that may be happening, because you are turning them round before you drill, is that they are deforming due to lack of support when you drill the holes. I.E. collapsing into an oval due to grain direction, an amount not aparent to the naked eye would be enough to cause your problems.

 

[Jensmith]

I would have said 4mm was ideal, if rather on the short side if a standard bit for full depth drilling of your blank.

Drill type is not too relevant, as long as you find one that works in the material you are drilling.

There are so many differing wood characteristics, far in excess of drill forms that no one type is ideal, admittedly some forms will on average perform better but don't get hung up on type.

Did drilling smaller pilot hole help?

One thing that may be happening, because you are turning them round before you drill, is that they are deforming due to lack of support when you drill the holes. I.E. collapsing into an oval due to grain direction, an amount not aparent to the naked eye would be enough to cause your problems.

You are right - the 4mm drill was too short. I think it did help but the further I drilled with the 7mm drill the harder it got.

I think you must be right about deforming the blanks - I can't guarantee they were perfectly round so that must be happening.

 

[Melinda_dd]

I'm no expert but the one bit of advice i will give is this.... just keep at it, and don't give up... for the blanks that don't fulfill their blankly destiny... there's always the one that does and that's the one that will make your heart swell with pride when it's finished. just keep at it!

 

[Jensmith]

Thanks Melinda

 

[SVB]

One thought does come to mind. In you initial post you say you have a small, low powered lathe. Even after having allowed for that, I am sure even the most basic lathe should be expected to drill a 7mm hole!

How is speed control achieved - by changing pulleys or is it electronic?

If it is the latter, and you have the 'high range' pulley in use with the electronic control turned right down to achieve drilling speeds then the torque will be very low and this could be part of the story. Much better to select the low range pulley and therefore use a higher motor speed to achieve the drilling spindle speed desired.

If, however, it has fixed pulley speeds / mechanical variable speed ignore the above.

One final tip, a wipe of wax (finishing wax etc is fine) over the drill will reduce / stop screeching and reduce friction which is both more pleasant and may help overall.

BRgds
Simon

 

[CHJ]

One final tip, a wipe of wax (finishing wax etc is fine) over the drill will reduce / stop screeching and reduce friction which is both more pleasant and may help overall.

BRgds
Simon

May not be conducive to good adhesive bonding of the blank though.

 

[SVB]

Good point Chas although getting a hole in the first place seems a problem at the moment!! :lol:

Simon.

 

[Jensmith]

One thought does come to mind. In you initial post you say you have a small, low powered lathe. Even after having allowed for that, I am sure even the most basic lathe should be expected to drill a 7mm hole!

How is speed control achieved - by changing pulleys or is it electronic?

If it is the latter, and you have the 'high range' pulley in use with the electronic control turned right down to achieve drilling speeds then the torque will be very low and this could be part of the story. Much better to select the low range pulley and therefore use a higher motor speed to achieve the drilling spindle speed desired.

If, however, it has fixed pulley speeds / mechanical variable speed ignore the above.

One final tip, a wipe of wax (finishing wax etc is fine) over the drill will reduce / stop screeching and reduce friction which is both more pleasant and may help overall.

BRgds
Simon

It is variable speed with an electronic switch but you can change the pulley between 2 manually. There's a high and slow speed but not sure which it is on. I will have a look.