Drilling before reaming?

James M.

James M.

New member
Is there any advantage to using a piloted drill to remove most of the metal before using the chambering reamer? is this practice used to extend the life of a reamer or does it help produce a quality chamber. Also, who makes a piloted drill that uses interchangeable pilots? Thanks, James Mock.
 
Last edited:
I have never used a piloted drill but have used a common twist drill to rough chambers and still do so in some cases. A properly ground drill which is fed at a good rate will follow a hole , if not perfectly, very close to it. For precision chambering, I drill only to allow better access with the dial to measure runout at the throat then I bore to align the chamber with that.
A nice, straight barrel allows all sorts of variations in technique with good results. A barrel which is curved at the breech end is much more difficult and should probably just be sent back to the maker anyway. Regards, Bill.
 
I don't know anyone that uses a PILOTED drill. Many, myself included use a standard jobber drill about .030 to .050 undersize. I drill to about .100 short of the shoulder and then use a small boring bar to open the hole to about .010 less than the smallest diameter of the chamber. Although this method saves time reaming due to having much less material to remove (less chips), it is not so much to save wear on the reamer as to keep the chamber as straight as possible relative to the initial indicated setup.

As far as I know, all the major reamer makers make interchangeable pilot reamers. PTG, JGS, Manson, Hendrickson, Clymer, and others.
 
Last edited:
.

Same experience as Bill and Scott, non-pilot drill to within .040" diameter of finish reamed hole, drilled hole always shows less than .0002" runnout in match grade barrels so single point boring or piloted drilling are always unnecessary, final ream to size with chamber reamer to finish the job.
 
pacific tool has piloted drills. Uses their regular pilots. I thought about it, but for the cost, I will just drill with a normal drill, then bore it.
 
I use an end mill to rough my chambers. I follow this up by boring to within .010 of my final diameters. As far as crooked barrels go. I will have to agree with al in that some of my best shooting barrels were very crooked. By far the best 6br barrel I ever owned you could have played jump rope with the darn thing. That barrel was freaking fantasic. Don't know why but it was? Lee
 
Not speaking directly to anyone, but I hear people defend crooked barrels a lot..almost like being crooked is an attribute. I don't think it is. If nothing else, it makes dialing it in slightly harder. Wouldn't it be nice to simply indicate the end in and chamber it, knowing it's straight throughout? I've chambered literally hundreds if not thousands of barrels....if given the choice, I prefer them to be as straight as possible, but it's not a determining factor in good or bad. They can be straight and not shoot or crooked and shoot anyway. I do feel like the straighter it is, the better the chance of getting the chambering job as near perfect as possible, though. If barrels were truly straight, the od could easily be made straight to the bore and top notch chambering could be done in a good 3 jaw chuck.

I look at it like I do crowns....I prefer a flat crown for much the same reasoning, but both do work. --Mike
 
Bill Leeper said:
I have never used a piloted drill but have used a common twist drill to rough chambers and still do so in some cases. A properly ground drill which is fed at a good rate will follow a hole , if not perfectly, very close to it. For precision chambering, I drill only to allow better access with the dial to measure runout at the throat then I bore to align the chamber with that.
A nice, straight barrel allows all sorts of variations in technique with good results. A barrel which is curved at the breech end is much more difficult and should probably just be sent back to the maker anyway. Regards, Bill.
Click to expand...

I do exactly as Bill says here, and others, drill and bore. This takes a lot of wear off the reamer and since I indicate at the chamber neck and then bore it assures the reamer starts straight..

As to using a roughing reamer I have used one a few times but to me it is an added step hat increases the time to cut a chamber while not adding any improvement in finish, dimension or concentricity.

Indicating at the neck with a accurate indicator like an Interapid, I have always found some runout at the bore entrance. It might be very slight but it will have some curvature and I have chambered about every make out there made for benchrest.

.
 
If you guys were to drill, bore or taper bore before finish reaming, do you still use a bushing or let the reamer follow the drilled/bored hole?
 
NezRongero said:
If you guys were to drill, bore or taper bore before finish reaming, do you still use a bushing or let the reamer follow the drilled/bored hole?
Click to expand...

In the 6PPC chamber if you drill to about 1/32" smaller than the PPC shoulder finish dimension, stopping about 1/16" short of the finished shoulder, take a couple of light cuts to about 3/4 of that hole, then the bushing on the 6PPC reamer will engage the barrel bore as the reamer body engages the bored hole. Use care and measure to assure you don't over bore.

I feel it is important to take a couple of boring cuts to eliminate any runout at the chamber base.


.
 
After rough drilling I set up the taper attachment on one of my heavy 10's and bore my chambers leaving about .005 on a side. The front of the reamer does most of the cutting although I guess that's the case regardless of how you do it!
 
You must log in or register to reply here.
Back
Top