Thread: Problem?

Hi Graham I think the centre being out may be part of the problem but it could also be the drill bit that you are using, I have had similar problems and got around it by starting my hole using an engineering centre drill bit and now dont have any problems. I know some people use a smaller diameter drill bit and do a pilot hole which also may work.

Cheers Rumnut

Graham,

Being from the "dark side" namely the metalworking forum , and just getting into pen turning I saw your post and thought I may be able to help....

I am assuming you are using a twist drill, jobber length or similar and not a brad point bit so if everything on your lathe looks square and true, you may find that you need to centre drill the spot first with a dedicated centre or spotting drill before you actually drill the hole with the correct sized bit. These are readily available in various sizes and quite cheap to purchase......in drilling metal, you would not start a hole without spotting it first to avoid the drill wandering......

It's a common misadventure when drilling in a lathe especially in harder materials for the hole to be off centre..happens for a variety of reason and also dependant on the type of drill you are using, ie 4 facet, 2 facet etc - it may also be that one face is biting in before the other and that causes the drill to go off centre, likewise any flex in the drill bit can cause similar problems when you are drilling to length, the error becomes more pronounced if you start slightly off centre....it happens frequently when using a cheaper brand of bit, or you have sharpened it incorrectly or it may have worn on one facet more than the other(s)......could also be the drill bit flexing under load??.....along with an incorrect feed rate for the drill.

Best to start from scratch and eliminate the easy bits first...get yourself a spotting drill, look at the facets of your bit and make sure they are correct and it's been sharpened correctly then try varying the feed and see if that cures the problem......think you'll find it does....hope that helps

Let us know how you go.....................Lee

Having a look at one of the pics, I notice that the points do not line up, it's pointing away from centre, which would be one of the causes.
1) Do you have sideways movement? You might need to push the front of the tail stock away from you to help line it up.
2) Have you recently moved the lathe? Even though the lathe is made from cast iron it can twist.
3) Is there any damage on the drill chuck taper? Check inside the taper on the tail stock, sometimes dirt, grime, dust build up, can cause this problem also.
A plastic taper reamer can clean out any debris inside the taper without causing damage.
Hope that some of these suggestions help.
Kryn

Thanks for the input guys, I will definately try the center drill bit as a start, I noticed that the drill did waver on contact, but when I drill a small hole to begin with it worked a lot better, so I think this will be a starting point.

In regards to the center points not meeting, after reading Kryns points I had a 'Doh' moment, I have recently moved and am waiting on a shed to be built, needing some pens for my daughters wedding i set the lathe up in the spare bedroom, timber floor, so no doubt that the whole thing is out, all I needed to do was adjust the feet, oh well at least I know what to do when I set up the shed.

Cheers

Originally Posted by gdf26562

I have a Jet lathe and recently have been making pens, I have noticed that when drilling the blank, the drill will slightly veer off center as it hits the blank (Acrylic) I have the speed low and no matter what I do, it will bend slightly as it hits the start of the blank. I have looked at all avenues, and have spoken to another guy and he has the same problem.

It looks as though the drill/chuck moves ever so slightly causing the entry hole to be slightly oblong (?) on entry but not on exit

I had the blank held in the chuck, so I took it out and put the drill point agains the chuck and found it to be out by about 3mm, as in when the chuck was hand turned the side of the drill touched one jaw and missed the other by about 2 - 3 mm.

So I checked the lathe itself, as in center to center, see pics, and as you can see looking down it is out about 1 -2mm, height is ok but the side is out.

Is this the cause of the out of round holes?

Did'nt seem to have the problem before, so I do not think it is the off center (Hopefully) and just the way i drill.

Thanks for your help
Graham

Question does this model have 4 cap screws holding the head in place ? Are they tight , can they be loosened and the head stock be re aligned and re tightened . Just a thought .

Graham,
Chuck up the blank as normal, and try using a counter sink to first drill a small pilot hole, then switch to your normal drill.
You don't have to drill a large pilot, just enough to guide the nose of the drill.
You can also invest in a "stubby" 7mm bit, it is about 2 1/2 inches long and stiff enough to prevent it from deflecting, and use that to dril a pilot.
Some driff will alway happen when you spin the material instead of the bit, unless you give the nose of the bit a starting point.
The counter sink or stubby will do just that.
When you spin the drill bit instead of the material, the cutting edge can grab and guide the bit, the other way around the material can flex the bit before it can grab.

Originally Posted by gdf26562

I have a Jet lathe and recently have been making pens, I have noticed that when drilling the blank, the drill will slightly veer off center as it hits the blank (Acrylic) I have the speed low and no matter what I do, it will bend slightly as it hits the start of the blank. I have looked at all avenues, and have spoken to another guy and he has the same problem.

It looks as though the drill/chuck moves ever so slightly causing the entry hole to be slightly oblong (?) on entry but not on exit

I had the blank held in the chuck, so I took it out and put the drill point agains the chuck and found it to be out by about 3mm, as in when the chuck was hand turned the side of the drill touched one jaw and missed the other by about 2 - 3 mm.

So I checked the lathe itself, as in center to center, see pics, and as you can see looking down it is out about 1 -2mm, height is ok but the side is out.

Is this the cause of the out of round holes?

Did'nt seem to have the problem before, so I do not think it is the off center (Hopefully) and just the way i drill.

Thanks for your help
Graham

Thats some discrepancy Graham firstly I'd clean out both shafts of the head and tailstock and refit the live and spur centres and see if its any better. If not try another of both. Try the same process using the drill and see how it lines up. Make sure th headstock is parrallel to the ways.

Good luck