Lathe Boring

[A Gilbert]

Hey all,

Fairly new to turning and I have a few questions on boring on the lathe.

For barrels:

I am having trouble getting an even hole throughout my blank. One end ends up with a slightly larger diameter hole. I am using a jaw chuck on the headstock and a jacobs chuck to hold the drill bit on the tailstock. It seems that its centered while drilling. Is there a preferred technique or method to use?

For inserts:

I am having trouble getting a centered hole. The drill bit I am using might be too long. Would a shorter drill bit help prevent this? Is there a good way to adjust for this or should I simply position the insert a certain way when setting it on the jig?

Im using a Rikon mini lathe that's only 6 months old; I dont think it is off-centered or out of whack. As in most cases, probably human error.


I appreciate all of the great info on this forum. It has been very helpful in getting started.

Thanks

[Henry H]

Pictures of the setup and results might help diagnose, but it sounds like the headstock and tailstock aren't perfectly aligned.  Put sharply pointed centers in each and, with the quill fully retracted, push the tailstock to the headstock until the centers just touch.  Are they perfectly point to point?  Back the tailstock up and extend the quill untill the centers just touch.  Are they perfectly aligned?  Differences between the two tests point to certain issues, too.  Could be adjustments necessary in either headstock or tailstock (or both), or the ways are uneven, warped, or twisted.  Have you checked the ways for level in all directions?  Just a few things to get you started.

[dogcatcher]

First try another drill bit, see if the problem is the bit or maybe run out on the lathe set up.  I have a 5/8" bit that drills 11/16" holes, same brand another bit drills 5/8" holes.

Marvin

[FDR]

Sometimes the problem is all about technique. Here is how I make an insert:

1.--I turn the exterior form of the insert between centers
2.--I mount the insert blank in a collet chuck using the live center in the tailstock to help align it in the collet. There is a technique associated with proper use of the collet chuck.  Details are here:
http://thogamecallsforums.com/index.php/topic,16405.0.html
3.--I turn the end of the blank insert square
4.--I use a center drill to start the hole. A center drill is short and stiff and made especially for this job. Here is the link.
http://www.use-enco.com/CGI/INPDFF?PMPAGE=51&PARTPG=INLMK32
5.--I drill my tone channel.
6.--I form my exhaust.

Works every time!

[dogcatcher]

I forgot, what kind of drill bit are you using? 

Marvin

[BigB]

When drilling on the lathe, always square the end of the piece you are drilling, and start a pilot dimple before drilling. Here's how I do it:

http://thogamecallsforums.com/index.php/topic,4196.msg35885.html#msg35885


Brian

[A Gilbert]

Thanks everyone for all of the help. I will do some experimenting and let you all know what worked for me.

Two questions:

 I visited Enco's website. Does it matter which size center drill?

Am I ok to be using a hand-tightened jacobs chuck to hold my drill bits, and is it important to use a drawbar in the tailstock?

Thanks again

[FDR]

Thanks everyone for all of the help. I will do some experimenting and let you all know what worked for me.

Two questions:

 I visited Enco's website. Does it matter which size center drill?

Am I ok to be using a hand-tightened jacobs chuck to hold my drill bits, and is it important to use a drawbar in the tailstock?

Thanks again

Something 1/2" or smaller that will fit in your tailstock chuck and you should match the centerdrill angle to your tailstock live center (usually 60 degrees) so you can use the center drill for other things. 

The draw bar is an important safety device and should always be used unless all you plan to do is turn between centers.  Chucks that screw on the the spindle nose do not need a draw bar unless your lathe will run in reverse which can then unscrew the chuck.  Some chucks have a safety locking screw to prevent this.

[dogcatcher]

I don't think the center bit is going to solve the problem.  But check these out at Harbor Freight a set for about $8.  http://www.harborfreight.com/5-piece-center-drill-countersink-set-60381.html

Still need the info on the type of bit you are using?   A pic of your process would also be helpful.

Marvin

[A Gilbert]

Still having some trouble with boring the barrel.

I am using a 17mm HSS bit, and the entry hole ends up slightly wider than the exit hole.

I have tried one with a 5/8 bit and got a nice even hole.

Here is a pic of the setup.

Thanks for the help.

[Henry H]

If you have gotten a good hole with the 5/8", then that eliminates alignment and chuck issues.  So, you may have an issue with the 17mm (not true width the entire length, slightly out of round somewhere, a burr on it somewhere, a slightly off-center or bent shaft)... or it or the wood used for that cut may have simply been slightly off or loose in their chucks.  I'm assuming your 5/8 and 17mm are roughly the same length and that length differences aren't causing the different results.

How much difference are you talking about between the in and out diameters?

[A Gilbert]

Not much difference between the in and out, but enough to matter. Re-tested the 5/8 and 17mm bits and got the same results. 5/8 drills even hole, 17 mm is off; I will try another 17mm bit.

Is a drill bit the best way to go? Can you use an auger bit or forstner bit?

Thanks

[Henry H]

I've had the best luck with Colt brad point drill bits with the twinland flute design.  The key with these large holes is giving the chips easy exit and not burning them... so large flutes, slow drilling, and small in-and-out increments.  Cleaning your bits regularly with some solvent to get resin of is also helpful.

[FDR]

Like Henry said here is the one you want:

http://www.amazon.com/10700058-TwinLand-Point-Drilling-8-Inch/dp/B005PKM18O/ref=sr_1_1?s=hi&ie=UTF8&qid=1409148508&sr=1-1&keywords=colt+twinland+5%2F8

Fred

[ben]

Another thing to consider is on the end you are drilling from, look at it this way, if the chips from the drilling cannot exit without resistance then there is going to be a difference from the entry hole to the exit hole because the bound up chips are going to act like sand paper, thus the hole will enlarge on the end started drilling from. There is probably just a minimal difference in hole size and it should not make any difference as long as the drill entry end is used for the blow end of the barrel.

ben