Reaming after pre-boring

[Rich S]

I've played with pre-boring on some practice pieces. I was tending to get a little chatter when starting the reamer. I ended up using a center in the tail stock to get started then switched back to the floating reamer (Bald Eagle). The end results were good and and chamber run out under a tenth. For the prebore, I taper bored the chamber to match the reamer taper about 0.005" under to about 0.10" of the finished length. I was a bit timid starting the reamer initially and likely had it loose to start. Any pointers is appreciated.

 

[Dusty Stevens]

You reckon it would have been faster and less risky to just ream it?

 

[WayneShaw]

Mike Bryant kind of made the "pusher" the thing to use when chambering. If you read his methods, he drills and bores the hole, then starts the reamer using a center. Then once in, he switches to the pusher. A reamer needs rigidity.

 

[DaveTooley]

Here's what I did with AI 40' chambers. Start by running the finish reamer in until you have about .050" of the body in. Then rough it out whatever way you feel comfortable with. I never bored on a taper after that.

 

[msalm]

You'll sometimes get a little chatter or squeal initially, I've found it helps to put pressure on the reamer against the pusher. With only cutting .010" or so on the diameter, you may have to feed a little heavy to start also, and vary your rpm to see what works best. The one thing that helped the most though was to push the reamer hard against the tailstock/pusher (for me anyway!) YMMV.

 

[Rich S]

You reckon it would have been faster and less risky to just ream it?

Whats the fun in that. You have to try/do it to learn it. If I wasn't willing to try new things I wouldn't be clambering my own barrels, truing up receivers, making my own tooling, making my stock, front rest etc...., Not all were a success the 1st try. How much sense it all makes I don't know but it sure is addicting. In the winter I spend more time in the garage than behind the trigger. I'm lucky to have an understanding wife.

 

[Rich S]

All - Thanks for taking the time to respond. I think I'll stick with starting off the tail stock center for now and be a little more aggressive to get the bore started.

 

[hammerjack]

You could try a boring straight in instead of tapered might help.

 

[Cloudrepair]

You reckon it would have been faster and less risky to just ream it?

It seems more risky without pre boreing to me ? Would you expand on that?

 

[Dusty Stevens]

It seems more risky without pre boreing to me ? Would you expand on that?

Id rather the reamer follow the hole it was designed to do. Thats why it has a bushing on the front. What if you bore your hole 2deg off? Im a simple guy i just ream away- and my work checks out straight and the same size everytime. Gotta do what works.

 

[boltfluter]

I have started a few chambers by hand reaming until you cut through the rifling. Works great for me with the Bald Eagle style of reamer pusher. Once you get beyond the speed bumps, it is smooth sailing. Many ways to skin this cat.

Paul

 

[Cloudrepair]

Id rather the reamer follow the hole it was designed to do. Thats why it has a bushing on the front. What if you bore your hole 2deg off? Im a simple guy i just ream away- and my work checks out straight and the same size everytime. Gotta do what works.

I think that would depend on how you dial a barrel in?
If your doing it the way Gordie does then I would think you would need a good three inches dialed in real tight to get away with that without having it give you a oversized chamber.
Now I guess that also depends on how tight the chamber needs to be for what you need.
Maybe I should put away my can opener cos I feel like I just opened a can of worms

 

[dskogman]

Just be careful with the bald eagle style holder. The reamer can hang on long chambers and the handle will swing around and hurt you. I got an ER visit and 25 stitches from one. Luckily I did not lose a thumb. I use a JGS now.

 

[Dusty Stevens]

Just be careful with the bald eagle style holder. The reamer can hang on long chambers and the handle will swing around and hurt you. I got an ER visit and 25 stitches from one. Luckily I did not lose a thumb. I use a JGS now.

Did it swing around and pin your hand between something? If mine hangs it just slips from my hand and spins free

 

[dskogman]

It swung around and gouged a piece out

 

[Dusty Stevens]

Ouch.

 

[Matt P]

I think that would depend on how you dial a barrel in?
If your doing it the way Gordie does then I would think you would need a good three inches dialed in real tight to get away with that without having it give you a oversized chamber.
Now I guess that also depends on how tight the chamber needs to be for what you need.
Maybe I should put away my can opener cos I feel like I just opened a can of worms

Without starting a "mines bigger than yours" if using a pusher/floating reamer holder how can the chamber be oversize ??
My issue with pre boring is any error in clocking the barrel in is doubled and when that happens the chance of the throat being off centre is increased. I used to pre bore but use the reamer the whole way (with a flush system), the result from a measurement point of view are more consistent and with the flush system take no longer.
Matt P

 

[John from MN]

I pre bored for a time, but eventually stopped. I don't do enough chambers to worry about reamer wear and a long stem indicator suggested results were the same as using the reamer from the start.

Either way works well enough.

 

[Cloudrepair]

Without starting a "mines bigger than yours" if using a pusher/floating reamer holder how can the chamber be oversize ??
My issue with pre boring is any error in clocking the barrel in is doubled and when that happens the chance of the throat being off centre is increased. I used to pre bore but use the reamer the whole way (with a flush system), the result from a measurement point of view are more consistent and with the flush system take no longer.
Matt P

I depends on how you dial a barrel in.
If you only dial in the first few inches you may not have any problem but if the bore is slightly out at some point the pilot will follow that curve and whatever it is out it will be doubled by the reamer at some point.
if it only drifts .0005 then the pilot fitment will probably accommodate if it drifts. 001 you will get an enlarged chamber by .001 if it drifts .002 the reamer will be forced off target by .0015 wich turns into .003 if your pilot fit the reamer with a .0005 slip fit.
This can happen. it may not depending on fitment and other factors affecting you tools,lathe,reamer holder/pusher.
I've seen all kinds of thing happen when we dont see all things affecting our work.
Experience a being a big one or lack of.

 

[Wiscohunter]

I also drill and pre bore but step bore rather than taper bore. I find it easier then trying to match the taper of the reamer. When I have had chatter it was usually because of lack of pressure on the reamer.