Thread: Drill holes.

Hi
Do you turn the outside of the pen first?
Are you trying to drill it to size in one go?
Are you using a center drill to get started?
Thats a pretty deep hole and will wander a bit. Better off drilling the holes then turning the outside to match the hole.
If you have a stub drill you could start with that and switch to a full length one.
If you must turn the outside first you could drill halfway then turn it around and drill from the other end. It wont line up spot on but it should be good enough for a pen as long as you arent using the brass tubes.
You can get gun drills for drilling deep straight hole but I wouldnt even know where to look.
Hope one of therse helps.

Stuart

Originally Posted by Stustoys

Hi
Are you using a center drill to get started?

And have you got it going fast enough for the centre drill

This should be an easy job to do. If you are drilling metal, make sure the drills are sharpend perfectly to begin with. Many a new drill I have used has needed to be resharpend before it could be used to even make chips with. A wandering hole is almost always caused by a poorly sharpened or shaped drill. I had to drill a hole 9/32" dia, thru two pieces of stainless steel 20 inches long and only 1/2" in diameter. I had to lengthen the drill with a 0.250" round MS rod to get the length needed. The holes were drilled from both ends and they all matched perfectly. It only took 30 minutes to drill each bar. A properly sharpened drill is the answer plus use the correct speed and don't force the drill but let it cut at its own rate. Using a full flow of coolant from a pump is a must. Try using a short drill to start with and then progress to a long series drill if a standard jobbers drill is too short. Make sure the tailstock is perfectly aligned with the axis of the lathe bed or you will have lots of trouble to drill a deep hole.
If you are drilling wood, it's also easy to do. The grain of the wood will throw the drill off even from the start of the hole. The way to tackle it is to make up a "D" bit or cutter. The reason the standard jobbers drill is wandering is because the drill is following the easiest pathway along the grain. The only problem in making a "D" bit is to find the size of round HSS that you want for the diameter of the hole. If you can't find the size needed, you can make a bit from Silver Steel (which is a bit expensive) or make it from round bar Spring Steel. Both of these steels can be hardened and tempered to do the job perfectly. Silver Steel machines beautifully and is quick to polish to a smooth bright finish. Spring Steel on the other hand, is a pain to machine to get a good finish but it can be done and it's very cheap to buy . The secret to getting a good finish is to have very sharp tools and take three or five finishing cuts of only a few "thou" deep. This will get you a good finish. Both of these steels are very easy to heat treat and temper. Grind/file/machine the "D" to the correct shape before you hardenen the tool. Any grinding that overheats the tool turning it blue after it is finished being made will destroy the temper and the tool will need to be rehardend.
You can feed the tool straight into the wood but it would be better if you start off with a pre-drilled center. I would make the "D" section of the cutter at least 20 mm (3/4 inch) in length. Hold the cutter in a good quality drill chuck and clear the "cuttings" every 4 or 5 mm depth as you cut the hole. You may need to play around with the speed to find the best speed (rpm's) to do the job. I would start off around 400 rpm and go from there either up or down in revs. The main problem you will have is the friction of the shank of the "D" bit producing heat when it's cutting at depth into the wood. You could try relieving the shank of the "D" bit behind the "D" section but you will need to have at least 15 mm length of full diameter to guide the cutter. These "D" bits work wonderfully and will do what all other drills can't, ie, make a straight and true hole.
If you would like a drawing of the "D" bit, let me know and I will post a drawing for you. I will need to know the length and diameter of the hole/s you are making. And of course, try the cutter out on some scrap wood first. The "D" bits can also be used on the metals you have listed but care is needed not to seize the cutter in the hole as you drill it. The "D" bit is perfect for drilling holes in brass. For drilling the copper and aluminium, it is essential take small increments in depth/length of cut. A lot of heat can be developed and this can produce steam from the coolant that can create a dangerous pressure if not relieved often.

Gents. Thanks for your advise. I start by using a small drill to make a pilot hole. When drilling I have the speed at approx 500 rpm and slowly drill just letting the drill take small cuts before withdrawing it. Coolant is used, but only on the outside of the pice being drilled. There are times the drill grabs and less presure is applied to get it cutting again. Currently I am drilling up to 11mm dia with brand new bits bought from H & R.
Kody if you can send me a copy of your "D" bits I will give that a go. Oh yeh th depth of my holes vary from about 8cm to 15cm deep. So as you can see they are not real deep.
I will keep trying untill I get it right.
Once again thanks for the advice.
Cookie

Cookie,
last week I drilled a 4mm hole right through a 12mmx150mm mild steel bolt. I used a long 4mm Sutton twist drill and drilled 75mm in from each end. The two holes lined up perfectly. Towards the end of the cuts I was only drilling about 5mm each time before withdrawing the bit and brushing off the swarf. Before reintroducing the bit I gave the hole a squirt of CRC cutting oil using the thin extension tube to get the oil right into the hole. Good luck.

Cookie, I would think that 150mm is quite a deep hole and I would certainly drill that length from each side.

I second the use of centre drills.

Copper is a b*tch to drill. DAMHIKT

Aluminium is a soft material and it easy for a drill to wander off centre a bit in that, particularly with the smaller drill sizes. You would also need to ensure that the centre of your tailstock lines up perfectly with the centre of your headstock.

You haven't said whether you drill before finishing the OD, if you don't then perhaps try and drill first and then finish the OD mounting the drilled blank on a suitable mandrel and supporting it with tailstock, that way your ID and OD should line up perfectly.

The other thing to look at to get perfect sized holes is to drill slightly undersize and finish the hole off with a chucking reamer.

Dont forget that the reamer will follow the hole.
The hole should be bored then reamed.

Originally Posted by cookie48

I start by using a small drill to make a pilot hole.
Cookie

Hi Cookie,
That, might be where you are going off line, make sure you are using a center drill to start the hole.
A small drill will flex more easily, so you might be starting off line.

Just to be perfectly clear, this is what a center drill looks like...




Start the hole by drilling with the center drill, only go about half way up the taper section.
So that you end up with a tapered lead in that is centered on the spindle axis.

Then you can drill your pilot hole. and go from there to your finished size.

Regards
Ray

Thanks gents. I drill my holes before I turn.
RayG. Will get those centre drills. Currently I use 3mm drill as my pilot. That seems to be a no no.
Will try out all ideas and keep trying till I get it right.
Cookie