Help! Drilling straight holes in shafting, in an axial direction.

[jackofall]

Help!

What is the best way to insure that a hole is centered in a mild steel shaft?
I have squared the drill to the shaft, and center punched, yet I still have a problem with the hole starting off center.

I am trying to lengthen a shaft by drilling and taping the shaft, and adding another shaft on it's end. The addition will be turned and threaded, so as to be screwed into the lengthened shaft.

Any ideas on this is appreciated.


Regards,

 

[brucer]

center drill or spot drill it prior to drilling the hole.

 

[pdentrem]

Also make sure the drill point is of proper shape and sharp. Less likely to wander even with a center drill hole.

 

[Tony Wells]

Good suggestions so far. You could run a tool blank up to the drill as you start it to stabilize it, if it tends to wobble. Don't center punch, just spot or center drill.

You may want to consider finish turning the OD of the extension after locking it into the stub. That way the runout of the tapped hole isn't a factor on the concentricity to the main shaft.

 

[nctoxic]

Make a drill guide that slips over the end of the existing shaft to guide the drill. If made on the lathe the hole for guiding the drill bit should be concentric with the shaft hole.

Ed

View attachment 29827

EdK,
I like that idea. It would be especially useful when making many of the same sized items.


Tim,,,

 

[george wilson]

Can you drill them in a lathe? The best way: Center up accurately in a 4 jaw chuck. Drill a slightly smaller hole,then single point bore the hole out. It will be exactly true if your chuck centering job was accurate. Long shaft? Support the outer end on something,and run the lathe slower. You don't want the long shaft to suddenly bend 90º and fly around.

 

[atfab]

I've used the guide idea before and made it to except a drill bushing or just used a long split clamp shaft coller and a drill bushing it allows you to drill for a tap drill size in 1 operation. Drill bushings are available in lots of bores and outside diameters
MSC, McMaster Carr, etc.
An example drill 1/2" rod with #7 drill to tap 1/4-20
use a drill bushing 1/2" OD #7 bore clamp in a long 1/2" coller its quick and when the bushing wears out or you need a different size just change it.

 

[Mueller]

Some of you will remember I had to do this a while back. I needed to drill a 8 mm hole 4+ inches deep. I started with a spot drill and then a stub length drill bit. I moved to a jobbers length drill bit then on to a 8 inch long 8 mm Drill Bit. It went extremely well with no appreciable drift. Take mucho time but is a can do.

"Bill Gruby" :thumbzup:

That is the common and best technique. I would only add as a rule of thumb. 1st pass no deeper than 3 &1/2 times the diameter of the drill. 2nd pass no more than twice the diameter of the drill. Every subsequent pass no more than the diameter of the drill. Never crowd the drill or it will wander. Always lubricate with every pass. it should gp withput saying that you should start with drills that are evenly and well sharpened. It takes a long time but the results are worth it.

 

[Maglin]

Ty for the notes. I've also had to do this and a drill guide would have been a lot of help.