Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?

thanks

OM

ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?

thanks

OM

If money is not an object, get a core drill of appropriate length. Try
the local tool supplier, or McMaster Carr.

If you gotta do it on the cheap, turn down the shank on a 3/4" drill
or use a Silver and Demming type drill, and solder an extension onto it.
A little creative grinding and it will have it's own pilot.

12" isn't all that long a hole, in the scheme of things.

Cheers
Trevor Jones

ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?

thanks

OM


first question, is the bore of the stock finished or just the rough
cored hole from extrusion?

second what type of finish do you require and size tolerance on the
finished bore?



very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such


if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.

or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.


i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.

of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125

On Dec 17, 5:51 pm, Chris wrote:
ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?

thanks

OM

first question, is the bore of the stock finished or just the rough
cored hole from extrusion?

second what type of finish do you require and size tolerance on the
finished bore?

very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such

if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.

or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.

i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.

of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125

need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.

ol3_m3 wrote:
On Dec 17, 5:51 pm, Chris wrote:

ol3_m3 wrote:

Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?

thanks

OM

first question, is the bore of the stock finished or just the rough
cored hole from extrusion?

second what type of finish do you require and size tolerance on the
finished bore?

very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such

if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.

or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.

i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.

of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125


need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.

Bore the length oversize, fit accurate bushings to the ends, along
with wipers to keep the whole inside works clean.

On both size and location to decent tolerances is going to be a right
job to do. Never been around one, but it seems a job for a horizontal
boring machine, or a similar cobble-up from a lathe with a boring bar
between centers.

Cheers
Trevor Jones

ol3_m3 wrote:
On Dec 17, 5:51 pm, Chris wrote:
ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?
thanks
OM
first question, is the bore of the stock finished or just the rough
cored hole from extrusion?

second what type of finish do you require and size tolerance on the
finished bore?

very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such

if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.

or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.

i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.

of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125

need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.


strongly suggest you look at other methods for this part, 12 inches of
sliding / rotating contact ?


might want to look at thompson shafting, and a sleeve with either
bearings or pressed in bushings


you can get to bores on either end of a lon gpiece in line with little
fuss , just takes patience with a good .0001 indicator


the other thing to do is make both bushings od , and rough bore the id,
bore each end of the shaft to a good press fit to the od of the bushing

use a mandrel long enough to go through each bushing and after using
some lapping compound to get them running true with each other , turn
the od of the shaft concentric with the shaft between centers

still only going to get it withing .001 or .002 of play no matter how
hard you try.

is that good enough for your grinder?

might look at moglice too, form in place bearing material

http://www.moglice.com

On Dec 17, 11:12 pm, Chris wrote:
ol3_m3 wrote:
On Dec 17, 5:51 pm, Chris wrote:
ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?
thanks
OM
first question, is the bore of the stock finished or just the rough
cored hole from extrusion?

second what type of finish do you require and size tolerance on the
finished bore?

very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such

if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.

or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.

i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.

of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125

need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.

strongly suggest you look at other methods for this part, 12 inches of
sliding / rotating contact ?

might want to look at thompson shafting, and a sleeve with either
bearings or pressed in bushings

you can get to bores on either end of a lon gpiece in line with little
fuss , just takes patience with a good .0001 indicator

the other thing to do is make both bushings od , and rough bore the id,
bore each end of the shaft to a good press fit to the od of the bushing

use a mandrel long enough to go through each bushing and after using
some lapping compound to get them running true with each other , turn
the od of the shaft concentric with the shaft between centers

still only going to get it withing .001 or .002 of play no matter how
hard you try.

is that good enough for your grinder?

might look at moglice too, form in place bearing material

http://www.moglice.com- Hide quoted text -

- Show quoted text -

Pick up a cheap gundrill @ MSC.

ckoehler wrote:
On Dec 17, 11:12 pm, Chris wrote:
ol3_m3 wrote:
On Dec 17, 5:51 pm, Chris wrote:
ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?
thanks
OM
first question, is the bore of the stock finished or just the rough
cored hole from extrusion?
second what type of finish do you require and size tolerance on the
finished bore?
very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such
if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.
or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.
i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.
of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125
need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.
strongly suggest you look at other methods for this part, 12 inches of
sliding / rotating contact ?

might want to look at thompson shafting, and a sleeve with either
bearings or pressed in bushings

you can get to bores on either end of a lon gpiece in line with little
fuss , just takes patience with a good .0001 indicator

the other thing to do is make both bushings od , and rough bore the id,
bore each end of the shaft to a good press fit to the od of the bushing

use a mandrel long enough to go through each bushing and after using
some lapping compound to get them running true with each other , turn
the od of the shaft concentric with the shaft between centers

still only going to get it withing .001 or .002 of play no matter how
hard you try.

is that good enough for your grinder?

might look at moglice too, form in place bearing material

http://www.moglice.com- Hide quoted text -

- Show quoted text -

Pick up a cheap gundrill @ MSC.


and get a high pressure coolant set up and some starter bushings too

On Dec 18, 5:45 pm, Chris wrote:
ckoehler wrote:
On Dec 17, 11:12 pm, Chris wrote:
ol3_m3 wrote:
On Dec 17, 5:51 pm, Chris wrote:
ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?
thanks
OM
first question, is the bore of the stock finished or just the rough
cored hole from extrusion?
second what type of finish do you require and size tolerance on the
finished bore?
very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such
if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.
or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.
i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.
of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125
need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.
strongly suggest you look at other methods for this part, 12 inches of
sliding / rotating contact ?

might want to look at thompson shafting, and a sleeve with either
bearings or pressed in bushings

you can get to bores on either end of a lon gpiece in line with little
fuss , just takes patience with a good .0001 indicator

the other thing to do is make both bushings od , and rough bore the id,
bore each end of the shaft to a good press fit to the od of the bushing

use a mandrel long enough to go through each bushing and after using
some lapping compound to get them running true with each other , turn
the od of the shaft concentric with the shaft between centers

still only going to get it withing .001 or .002 of play no matter how
hard you try.

is that good enough for your grinder?

might look at moglice too, form in place bearing material

http://www.moglice.com-Hide quoted text -

- Show quoted text -

Pick up a cheap gundrill @ MSC.

and get a high pressure coolant set up and some starter bushings too- Hide quoted text -

- Show quoted text -

Have a ten inch atlas lathe, do not want to get into an expensive
deep hole drill or high pressure coolant systems, any ideas on a low
tech solution to deep hole drilling.
any one have a source of supply for extra long drills and reamers?

OM

On Dec 17, 10:46 pm, ol3_m3 wrote:
ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?

need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.-

I'd save the bronze for something else and press flanged Oilite
bushings into the ends of a steel tube. You could make a half-round
reamer out of 3/4" drill rod and pull it through, so the near end
guides the shank while you cut the far end.

ol3_m3 wrote:

On Dec 18, 5:45 pm, Chris wrote:

ckoehler wrote:

On Dec 17, 11:12 pm, Chris wrote:

ol3_m3 wrote:

On Dec 17, 5:51 pm, Chris wrote:

ol3_m3 wrote:

Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?
thanks
OM

first question, is the bore of the stock finished or just the rough
cored hole from extrusion?
second what type of finish do you require and size tolerance on the
finished bore?
very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such
if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.
or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.
i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.
of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125

need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.

strongly suggest you look at other methods for this part, 12 inches of
sliding / rotating contact ?

might want to look at thompson shafting, and a sleeve with either
bearings or pressed in bushings

you can get to bores on either end of a lon gpiece in line with little
fuss , just takes patience with a good .0001 indicator

the other thing to do is make both bushings od , and rough bore the id,
bore each end of the shaft to a good press fit to the od of the bushing

use a mandrel long enough to go through each bushing and after using
some lapping compound to get them running true with each other , turn
the od of the shaft concentric with the shaft between centers

still only going to get it withing .001 or .002 of play no matter how
hard you try.

is that good enough for your grinder?

might look at moglice too, form in place bearing material

http://www.moglice.com-Hide quoted text -

- Show quoted text -

Pick up a cheap gundrill @ MSC.

and get a high pressure coolant set up and some starter bushings too- Hide quoted text -

- Show quoted text -


Have a ten inch atlas lathe, do not want to get into an expensive
deep hole drill or high pressure coolant systems, any ideas on a low
tech solution to deep hole drilling.
any one have a source of supply for extra long drills and reamers?

OM
Local hardware store.

Get a drill, some soft solder, some flux, some mild steel rod, 1/2
inch dia, and a short section a little smaller than your drill bit.

Turn the drill shank down to 1/2" if it is not already (like it would
be if you bought a stepped shank drill.

Turn the short section of steel to a 1/2" ID plus a little bit. (say 1
or 2 thou.)

Slide the sleeve onto the drill shank, insert steel rod, add flux and
solder using a propane torch.

Cut it to the length you need.

Cheap and effective.

Pick a drill a little smaller than your finished size.

Bore out the bore with a between centers boring bar, with the part
clamped up on the cross-slide.

You might even do the drilling in the lathe, holding the steel rod, in
the chuck.

Ugly, but cheap and effective.

Reamers long enough to cover a 12 inch hole are gonna be non-trivial
expensive.

Given the time you have spent asking how to accomplish this, do you
think that the project will ever get off the ground?

It sounds to me like the design came about without much thought to the
practical realities of how it was to be made.

Cheers
Trevor Jones

On 2007-12-21, Trevor Jones wrote:
ol3_m3 wrote:

[ ... ]

Have a ten inch atlas lathe, do not want to get into an expensive
deep hole drill or high pressure coolant systems, any ideas on a low
tech solution to deep hole drilling.
any one have a source of supply for extra long drills and reamers?

[ ... ]

Pick a drill a little smaller than your finished size.

Bore out the bore with a between centers boring bar, with the part
clamped up on the cross-slide.

Unfortunately, the Atlas lathe in question does not have T-slots
on the cross-slide for mounting a workpiece. They are somewhat less
common here in the USA than in your locale. The majority of the
cross-slide for this lathe is somewhat round topped -- or at best not
machined flat and fitted with T-slots.

The best bet for that would be a milling attachment for that
specific lathe, which mounts in place of the compound on the dovetailed
round projection around which the compound rotates.

Even my Clausing (a somewhat more robust lathe) has the compound
mounted by a round boss which projects down into the cross-slide, and it
is secured by T-bolts in a circular T-slot in the cross slide
surrounding the hole for the boss. Not exactly what you would want for
mounting a workpiece on the cross-slide.

Now -- if I had the cross-slide which was a companion to the bed
turret (capstan) for my lathe, it would have sets of T-slots.

A Myford, of course, would have the T-slots -- and is probably
what you are most familiar with.

You might even do the drilling in the lathe, holding the steel rod, in
the chuck.

Ugly, but cheap and effective.

Reamers long enough to cover a 12 inch hole are gonna be non-trivial
expensive.

Amen! I would say that learning to make a gun drill would be
the better approach.

Certainly purchased long drills (aircraft drills are available
in 12" lengths) would be highly unlikely to approximate a straight hole. :-)

Given the time you have spent asking how to accomplish this, do you
think that the project will ever get off the ground?

:-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

DoN. Nichols wrote:

On 2007-12-21, Trevor Jones wrote:

ol3_m3 wrote:


[ ... ]


Have a ten inch atlas lathe, do not want to get into an expensive
deep hole drill or high pressure coolant systems, any ideas on a low
tech solution to deep hole drilling.
any one have a source of supply for extra long drills and reamers?


[ ... ]


Pick a drill a little smaller than your finished size.

Bore out the bore with a between centers boring bar, with the part
clamped up on the cross-slide.


Unfortunately, the Atlas lathe in question does not have T-slots
on the cross-slide for mounting a workpiece. They are somewhat less
common here in the USA than in your locale.

Uhhh. DoN...

I'm in Canada. Really. We do pretty much get the same stuff as you
guys up here, just less of it. :-)

A bud of mine has a 10 inch Atlas POS lathe in his shop. If a lash-up
is required, a lash-up it shall have to be. If I had that lathe and that
job, a machined in place bed for the casting, with end grain hardwood
between the top of the cross slide (compound renoved) and the casting
would be a starting point.

The majority of the
cross-slide for this lathe is somewhat round topped -- or at best not
machined flat and fitted with T-slots.

Build a tooling plate (wrong term maybe) to fit onto the compound
mount, and reinforce the surface to prevent rocking, with a little epoxy
or bondo type body fill cast in place. Use a film wrap or a spritz of
cooking oil to prevent it sticking down to the cross slide.

There IS always a way. Sometimes it is not an elegant or easy way, but
there is a way. There is a hundred plus years of back issues of Model
Engineer magazine out there proving that guys that really WANT to make
something with limited tooling CAN.

The best bet for that would be a milling attachment for that
specific lathe, which mounts in place of the compound on the dovetailed
round projection around which the compound rotates.

Depending on the size of the casting, that might be an option. It will
also provide one more potential location for the set-up to flex, as
well. All trade-offs.

Even my Clausing (a somewhat more robust lathe) has the compound
mounted by a round boss which projects down into the cross-slide, and it
is secured by T-bolts in a circular T-slot in the cross slide
surrounding the hole for the boss. Not exactly what you would want for
mounting a workpiece on the cross-slide.

Use the Tee slots to anchor a plate, drill and tap holes wher you need
them! :-)

Now -- if I had the cross-slide which was a companion to the bed
turret (capstan) for my lathe, it would have sets of T-slots.

A Myford, of course, would have the T-slots -- and is probably
what you are most familiar with.

I have a Myford S7 now. Just got rid of a 10 inch Rockwell Delta. Had
a beaten up South Bend 9, too. And another Myford, an ML7.
The availability of slots had little to do with my reasoning of the
method. Just that it is the most secure way to do a job like that on the
wrong machine. If it is the machine that is available, then make the
best use possible of it!


You might even do the drilling in the lathe, holding the steel rod, in
the chuck.

Ugly, but cheap and effective.

Reamers long enough to cover a 12 inch hole are gonna be non-trivial
expensive.


Amen! I would say that learning to make a gun drill would be
the better approach.

Yeah! Even a D-bit cutter running in a similar fashion to a gundrill,
where it is guided by its own hole, would be a good pick. Slower, but a
good pick.

No matter what, the guy is going to have to go slow and withdraw often
to clean out and check tooling, etc. He seems to think that all
gundrills run with high pressure coolant feeds. Gundrills were in use
for hundreds of years before someone thought to drive fluid through them!

Gundrill-
http://www.trackofthewolf.com/(S(444...UM=ROD-DRILL-7

Certainly purchased long drills (aircraft drills are available
in 12" lengths) would be highly unlikely to approximate a straight hole. :-)

No, I figure they would approxiamate one just fine! :-)

They would not make one though.

And the OP needs to drill through 12 inches, so he needs a longer
drill than that if he is to be able to hold onto it while it works.



Given the time you have spent asking how to accomplish this, do you
think that the project will ever get off the ground?


:-)

Enjoy,
DoN.

Cheers
Trevor Jones

On Fri, 21 Dec 2007 05:10:57 GMT, Trevor Jones
wrote:

DoN. Nichols wrote:


a general question on the same topic...

how did the old craftsmen drill their barrels?
some of these barrels, say for a shotgun, are almost too thin to hold
with any real purchase. similar for tapered barrels.

did they drill the hole through the blank, plane out the rifleing,
then turn down the outer diameter?

Stealth Pilot

ol3_m3 wrote:

Have a ten inch atlas lathe, Â*do not want to get into an expensive
deep hole Â*drill or high pressure coolant systems, Â*any ideas on a low
tech solution to deep hole drilling.

A D-bit reamer. Done by yourself. Needs some trying and fiddling to get it
running and make a nice and smooth surfaces.
I'm making a variant of a D-bit. I call it G-bit. Looks like a D-bit, except
I cut out only one segment (thus the G) and not two segments (the D).
The "G-bit" has better support.
Not the fastest way to drill a hole. :-)


Nick
--
The lowcost-DRO:
http://www.yadro.de

Stealth Pilot wrote:
On Fri, 21 Dec 2007 05:10:57 GMT, Trevor Jones
wrote:


DoN. Nichols wrote:



a general question on the same topic...

how did the old craftsmen drill their barrels?
some of these barrels, say for a shotgun, are almost too thin to hold
with any real purchase. similar for tapered barrels.

did they drill the hole through the blank, plane out the rifleing,
then turn down the outer diameter?

Stealth Pilot

Shotgun barrels started out with straight sides, and then get the
contour put on after the bore is finished. The walls are quite thick
enough, if you look at the chamber end.
First the hole through, then the reamers up to just below size, then
the lapping/polishing out to final dimensions. Some chokes were done
using tapered reamers, some by swaging down the outside of the blank
after polishing, some are machined in the bore after manufacture.

It is said that Harry Pope, one of the legends of rifle barrel making,
used a twist drill on an extension to drill his barrels. His barrels are
still sought after.
Proof that great work can be done with less than optimal tools!

If you get a chance, find a copy of the video "Gunsmiths of Colonial
Williamsburg". It follows through the whole process of building a
Flintlock rifle, using a forge welded barrel blank. The interesting
thing is to see the drills and reamers used to open and clean up the
bore there. Really low tech, but effective stuff.

Another video that covers a lot of the detail, is the Lautard video of
Bill Webb's Rifling Machine. It covers a little more modern approach of
drilling, with a pressure coolant fed gundrill, and a cut rifling head.

Most barrels these days are button rifled. It is a fast, accurate
enough process that leaves a decent barrel in one pass of the rifling
cutter, and does not require near the investment that a hammer forging
machine requires. The rifling is done by a carbide button being driven
or pulled through the barrel by hydraulics, usually.

Modern rifle barrels start out as a large diameter round bar. The hole
is drilled, the rifling installed, and the outer contour cut. At least
for barrels other than hammer forged, which are a whole different
process, that will never be suitable for anything but volume production.

Cheers
Trevor Jones

On Fri, 21 Dec 2007 14:32:03 GMT, Trevor Jones
wrote:

Stealth Pilot wrote:
On Fri, 21 Dec 2007 05:10:57 GMT, Trevor Jones
wrote:


DoN. Nichols wrote:



a general question on the same topic...

how did the old craftsmen drill their barrels?
some of these barrels, say for a shotgun, are almost too thin to hold
with any real purchase. similar for tapered barrels.

did they drill the hole through the blank, plane out the rifleing,
then turn down the outer diameter?

Stealth Pilot

Shotgun barrels started out with straight sides, and then get the
contour put on after the bore is finished. The walls are quite thick
enough, if you look at the chamber end.
First the hole through, then the reamers up to just below size, then
the lapping/polishing out to final dimensions. Some chokes were done
using tapered reamers, some by swaging down the outside of the blank
after polishing, some are machined in the bore after manufacture.

It is said that Harry Pope, one of the legends of rifle barrel making,
used a twist drill on an extension to drill his barrels. His barrels are
still sought after.
Proof that great work can be done with less than optimal tools!

If you get a chance, find a copy of the video "Gunsmiths of Colonial
Williamsburg". It follows through the whole process of building a
Flintlock rifle, using a forge welded barrel blank. The interesting
thing is to see the drills and reamers used to open and clean up the
bore there. Really low tech, but effective stuff.

Another video that covers a lot of the detail, is the Lautard video of
Bill Webb's Rifling Machine. It covers a little more modern approach of
drilling, with a pressure coolant fed gundrill, and a cut rifling head.

Most barrels these days are button rifled. It is a fast, accurate
enough process that leaves a decent barrel in one pass of the rifling
cutter, and does not require near the investment that a hammer forging
machine requires. The rifling is done by a carbide button being driven
or pulled through the barrel by hydraulics, usually.

Modern rifle barrels start out as a large diameter round bar. The hole
is drilled, the rifling installed, and the outer contour cut. At least
for barrels other than hammer forged, which are a whole different
process, that will never be suitable for anything but volume production.

Cheers
Trevor Jones

thanks