Drilling on the lathe not centered

[spaceengravers]

I got what I needed for drilling on the lathe for Christmas. I'm using a Nova midi chuck in the head stock and a drill chuck in the tail stock. Putting the square blank in the midi chuck and a 1/4 inch drill bit in the drill chuck. When I move the drill bit up to the blank and start drilling, it is slightly off center. After drilling part way in, I can stop the lathe and turn it by hand and see that as it turns the bit wobbles slightly in blank (because it's off center and the blank is pulling it one way or the other as it turns).

I remove the chuck and the drill chuck and install 60 degree centers in the head and tail stock and push them together...they align perfectly.

Should I be marking the center of the blank, using a punch to dimple it, and moving the bit up the blank and set it in the dimple before starting to drill? I was under the impression that drilling on the lathe would ensure it is centered each time...What am I doing wrong?

Mike

 

[johnnycnc]

a quick question..are you locking the tailstock down,
and advancing the drill with the quill (round crank handle at rearmost of tailstock)?

Sounds like your drill is drifting location, it could also be walking off center when you start
drilling. I wouldn't mark (dimple) the blank before you go to the lathe, you won't be perfectly centered and that will only aggravate the drill starting on center.
You can use a center drill first before drilling, to help the drill start really well on center.

 

[BRobbins629]

Get a set of these:
http://www.use-enco.com/CGI/INSRIT?PMAKA=369-1810 on sale for less than $6

See the article in the 2009 library about drilling on the lathe and using these,

 

[dennisg]

Try dimpling like you suggested and run the live center in the tail stock up to the dimple before you completely tighten the headstock. That may help center it. If the blank is not real square you can have problem getting the chuck to center the blank. The other option is to turn the blank round and then chuck it up. hth

 

[Glass Scratcher]

Turn the blank round 1st, it will center in the chuck better. Use a center drill to start the center, then change bits to drill.

 

[jleiwig]

My guess is your using the standard jaws that came with the chuck and not the pin jaws that you need. You will never be able to get a decent enough grip on a 3/4" blank with jaws that were designed to close to a minimum 50 mm or 2". You either need a collet chuck or the pin jaw set for your chuck to drill accurately.

 

[jttheclockman]

I will never drill a square blank on my lathe. It just will not center up right. You are better off rounding the blank and using a collet chuck. If not then at least get a pin jaw chuck. Even that I do not trust. For drilling square blaks a drill press is the way to go in my opinion.

 

[TellicoTurning]

Should I be marking the center of the blank, using a punch to dimple it, and moving the bit up the blank and set it in the dimple before starting to drill? I was under the impression that drilling on the lathe would ensure it is centered each time...What am I doing wrong?

Mike

Mike,
I always mark and dimple the center of my square blank, I match the point of the drill to the dimple and then tighten the chuck on the blank... that way I think I'm aligned through the center... I also usually back the drill bit off the blank and run the lathe checking the blank to see that it's turning true... if your blank isn't perfectly square, it may be only held on two sides which can be a little askew.. by matching the drill point to the blank I can align the start and finish of the drilling .... as Johnny said, be sure the tailstock is locked down tight... mine will wobble if it isn't.

Using this method, I can nearly always get a centered hole through almost any shape blank... even a curved antler piece.

 

[rjwolfe3]

I had the same problem when I was putting squarish blanks in a 4 jawed chuck. I have since switched over to turning them round and sticking them in a collet chuck and have never had a problem since.

 

[thewishman]

I must have had different experiences from you guys. I find it easy to drill square blanks on the lathe with a Nova Midi chuck. I put a corner of the blank in the center of each jaw (I put the blank inside the chuck about 3/4 of an inch or more) and tighten the jaws mostly tight. Pull the drill bit in the tailstock up close to the blank and spin the headstock by hand. Move the blank (I tap it with the chuck bars) until it looks centered, then turn the lathe on (I drill at 500 rpm) and look to see if the blank is spinning true. Once the blank looks good, turn off the lathe and tighten the chuck all the way tight. Lock down the tailstock and begin your drilling.

This method has worked for me on hundreds of blanks - no center drill, no marking the blank, just load and drill. It takes a few tries to get things just right - but so does everything you try.

Good luck! You have all you need to drill like a pro with your set-up.

 

[spaceengravers]

Thanks everyone. Here's the answers to a few of the comments/questions...

The blank was perfectly square...I ran it through a planer to make sure because I thought this was the issue.

I was going to get a collet chuck but wanted more versatility.

thanks for the help! I'll keep working on it.

Mike

I am locking down the tailstock really tight because I noticed that it had some wobble otherwise.

I haven't tried dimpling yet, so I'll try that next. And I'll have to need to order some of those centering bits...that seems like a really good way to go.

I don't mind rounding my blanks first, so maybe I'll start doing that anyway.

 

[jleiwig]

I must have had different experiences from you guys. I find it easy to drill square blanks on the lathe with a Nova Midi chuck. I put a corner of the blank in the center of each jaw (I put the blank inside the chuck about 3/4 of an inch or more) and tighten the jaws mostly tight. Pull the drill bit in the tailstock up close to the blank and spin the headstock by hand. Move the blank (I tap it with the chuck bars) until it looks centered, then turn the lathe on (I drill at 500 rpm) and look to see if the blank is spinning true. Once the blank looks good, turn off the lathe and tighten the chuck all the way tight. Lock down the tailstock and begin your drilling.

This method has worked for me on hundreds of blanks - no center drill, no marking the blank, just load and drill. It takes a few tries to get things just right - but so does everything you try.

Good luck! You have all you need to drill like a pro with your set-up.

You call that easy? Man, that sounds like a workout to me!

 

[DozerMite]

I've drilled both square and round blanks with my Barracuda2 chuck. I noticed any variance is in the tailstock. I make sure it's pulled toward the front of the ways and it's perfectly centered. If you have a step bit, it can be used to start your hole instead of a center bit. They can be picked up at HF pretty inexpensively.

 

[mickr]

If you are starting with a "square" blank..it makes no difference how it drills..straight or not..IT WILL BE StrAIght once you put on your mandrel, as the lathe can do nothing else but make it centered on your turning..

 

[jttheclockman]

If you are starting with a "square" blank..it makes no difference how it drills..straight or not..IT WILL BE StrAIght once you put on your mandrel, as the lathe can do nothing else but make it centered on your turning..

To an extent that is correct. To do this one has to make sure the bit did not wander off too far to the outside edge so that when the blank is spun there is enough material left on the lower end of the pen.

Second, the ends must be milled so that the bushing are resting against the tube which is parallel to the mandrel when installed. That one trips some people up when they talk about off center blanks. The ends must be flat and not angled which is possible to get if sanding on a disc sander and not properly set up. Just a thought or two.

 

[rjwolfe3]

If you are starting with a "square" blank..it makes no difference how it drills..straight or not..IT WILL BE StrAIght once you put on your mandrel, as the lathe can do nothing else but make it centered on your turning..

This is assuming it is a plain jane blank and not a segment. If you have a design that needs to be centered perfectly to come out right, then drilling directly down the center becomes very important.

 

[mbroberg]

I watched Chris demo his method of drilling on the lathe at an IAP meeting and it is much easier than it sounds. I have since gotten a collet chuck, but have used Chris' method many times with great success.

You call that easy? Man, that sounds like a workout to me!

 

[bobindayton]

You said the points of a center in the spindle and the tailstock line up. Does the centerline of the tailstock quill line up with the centerline of the spindle? The points can line up and still have a tailstock that is sitting at an angle to the centrline of the spindle.

Bob