I have never been quite happy with Gordy's method of indicating in a barrel so I tried something a bit different yesterday. First I indicate the outside of the barrel at the chuck jaws and at the spider end (muzzle) of the barrel. Once I get it running true there I switch to indicating using the range rods with the reamer bushings and once again indicate the barrel true at the chuck jaws. Then I would withdraw the rod and indicate again near the end of the barrel. This frequently gave me odd readings and TIRs that seemed too far off to be only 2 inches from the last reading. Then I got to thinking that being the end where the button or rifling cutter was started it was likely that the beginning part of the barrel might not be good enough to indicate off of and may actually give bad readings. Yesterday instead of indicating off this section of the bore I pushed the rod FURTHER into the bore and took an indicator reading about 2 inches further into the bore instead of at the end. I got a much more consistent reading off the range rod than I was accustomed to getting at the end of it. So good in fact that I didn't do any further adjusting at the spider end. Anyone else tried indicating farther up the bore rather than at the end of it?
Speaking of Gordy's indicating method
- Thread starter clowdis
- Start date
Boyd Allen
Active member
So...you think that the chamber end of the barrel may have been belled in a non-concentric manner during lapping? Interesting thought. I would guess hat this would mainly be a factor when the full length of the shank is being used, but it is an interesting point.
Just didn't always get "happy" readings Boyd. Seemed to get indications sometimes that a land was different from the others and that raised the question about OK where's center on this axis vs. center on the other axis. That combined with the fact that the manufacturers always want you to cut an inch or two off the muzzle before you use the barrel. Well, if that end of the barrel might not be exact then maybe the other end isn't either. I think I'll continue to indicate this way for a few barrels and see if the readings continue to be more consistent.
OK, I've only done a dozen or so barrels with this method but I've found lapping bells on all but one and most of the bells were definitely eccentric. This alone has been worth the price of Gordie's setup.
"Back In The Day" I didn't know about lapping bells. "Back In The Day" I'd perty much jam a center in each end and if it was really gonna' be copacetic I'd run an indicator in a half inch or so..... Then stuff in a "roughing reamer" and "finish with a finishing reamer". Now with complete sets of bushings, long-reach indicators and Gordy rods I see all sorts of runout in the ends of blanks. But it's dead easy to find, evaluate and quantify.v And then to decide HOW I want to align with the tunnel and drill and bore accordingly.
al
"Back In The Day" I didn't know about lapping bells. "Back In The Day" I'd perty much jam a center in each end and if it was really gonna' be copacetic I'd run an indicator in a half inch or so..... Then stuff in a "roughing reamer" and "finish with a finishing reamer". Now with complete sets of bushings, long-reach indicators and Gordy rods I see all sorts of runout in the ends of blanks. But it's dead easy to find, evaluate and quantify.v And then to decide HOW I want to align with the tunnel and drill and bore accordingly.
al
S
Superman
Guest
Have you ever had Gordy show you his method? He starts about an inch in the bbl at the very least and then goes another 2-3" deeper making adjustments at each point. The very beginning wouldn't be good because of the center cut and when lapping the barrel, the lap has to stop somewhere and start again.
JerrySharrett
Senile Member
Say what??
No, that's why you cut some off the muzzle end and put a chamber in the other end. I used to make some black powder barrels and I used a push reamer for the bore and every time it would bell the end of the bore a little bit before it got to running true. It would also do the same thing on the other end when it pushed through. I think this was mostly caused by the length of the reamer even though it was supported by a bushing where it started into the bore. When it broke out the other end there was around 3 feet of unsupported shank in the barrel and when the straight section of the flutes became very short it began to bell just a little bit. That is the reason that I got a better reading by taking an indication 3 inches into the barrel (at the chuck jaw where the round rod is clamping the barrel) an then going another 3 inches into the barrel for the second reading. Probably an inch into the barrel the bore is fine but I usually leave around 3 inches hanging out of the chuck for machining and I like to get my readings a little further apart than that.
T
tasy_ted
Guest
hi all
clowdis you have 2 choices make longer barrels then cut of the rough end or support the reamer rod
so that when the pilot leaves the barrel it is still on center and cant bell the end of the barrel.??
regards tasy_ted
clowdis you have 2 choices make longer barrels then cut of the rough end or support the reamer rod
so that when the pilot leaves the barrel it is still on center and cant bell the end of the barrel.??
regards tasy_ted
Ted,
I don't make barrels anymore. The reamer that I used came from JGS if I remember correctly and had no pilot. I was only taking about .005 so I really didn't need a pilot. I guess one on the shank might have helped. It reminded me of a forcing cone reamer but worked really well. Almost every barrel manufacturer will ask you to cut some off the muzzle end of their barrel. Lilja will make a saw cut at the point he wants the barrel cut off and I think Douglas for instance just asks you to cut 2 inches off the end of theirs.
I don't make barrels anymore. The reamer that I used came from JGS if I remember correctly and had no pilot. I was only taking about .005 so I really didn't need a pilot. I guess one on the shank might have helped. It reminded me of a forcing cone reamer but worked really well. Almost every barrel manufacturer will ask you to cut some off the muzzle end of their barrel. Lilja will make a saw cut at the point he wants the barrel cut off and I think Douglas for instance just asks you to cut 2 inches off the end of theirs.
K
kiwi smith
Guest
Clowdis,
Firstly, if you can, cut about 1" off the breech end of the barrel before doing anything else. Deburr it, etc. . I find with alot of button rifled barrels that they are tight at the very end, then loosen up (from honing and lapping) about an inch or so into the barrel bore.
Secondly, erratic readings can be due to having a too tight pilot on the 'gordy range rod', a too loose pilot, or mis-formed lands (more common on buttoned barrels). Or else your headstock bearings are just not up to the job, and causing in-consistent readings. Remedy for that is try tightening up the main spindle bearings, or get a new/better lathe.
Thirdly, if you are using the 'gordy/grizzly' type range rod that is loosely supported in the drill chuck, they are about 12" long. When you are checking the very breech end of the bore, and you have the DTI stem right up close to just behind the bushing, you will be pretty much reading about what the movement of the pilot bushing is. BUT, when you push it in 2 inches into the bore the readings on your DTI will not be 'true', you will be reading about 10/12ths of the actual movement of the pilot bushing. Go in another inch you will be reading 9/12ths of the actual movement. Therefore, the further in you go, the less run-out you 'perceive' you are getting.
That is assuming I have interpretted what you are saying correctly???
Cheers,
Dean.
When you are checking the very breech end of the bore, and you have the DTI stem right up close to just behind the bushing, you will be pretty much reading about what the movement of the pilot bushing is. BUT, when you push it in 2 inches into the bore the readings on your DTI will not be 'true', you will be reading about 10/12ths of the actual movement of the pilot bushing. Go in another inch you will be reading 9/12ths of the actual movement. Therefore, the further in you go, the less run-out you 'perceive' you are getting.
Dean,
I hadn't thought of that before but you are correct. The further back you read on the shaft the less runout you tend to indicate. I did thread and chamber a Brux barrel this week and in order to match the barrel channel I had to cut an inch off the breech end. Indicator readings seemed to be better when reading at the very end of the barrel. Maybe it was just the barrel?
Dean,
I hadn't thought of that before but you are correct. The further back you read on the shaft the less runout you tend to indicate. I did thread and chamber a Brux barrel this week and in order to match the barrel channel I had to cut an inch off the breech end. Indicator readings seemed to be better when reading at the very end of the barrel. Maybe it was just the barrel?