Direct Indicating the Bore...

[tobnpr]

Grizzly rods have been my go-to for indicating, then check with a long-stem indicator. Whenever I've needed to tweak, it's the rod back in for that job.

So I want to experiment, eliminate the rod step and see if it saves time.

I know this sounds like a "machining 101" question- and mebbe I'm having a senior moment here- but how TF can you dial in the grooves, when they do not align with the jacking screws on the inboard and outboard spiders (and their locations change constantly as you travel down the bore).

I played around with this for the first time this evening on a barrel I'm chambering, got frustrated after about 15 minutes and am about to just go back to the rod.

This ain't get high/low, split the difference in 90 degree increments.

 

[Dusty Stevens]

You got confidence in the rod- go back to it

 

[B Nettesheim]

Are you using 4 screws currently?
Maybe 6 would be better

 

[Doug Beach]

Use the rod, then the indicator. You should be very close. Make tiny tweaks on the nearest jaw.
If I use a reasonably tight bushing, and dial the rod in to as close to zero as I can get, then check with an indicator, I am very, very close.

 

[Alex Wheeler]

When dialing a 5 groove in with 4 screws I dont go 180 and split the difference. I look at each groove to get an idea how far off the center of the bore is. So spin it 360 and find the extremes and zero the indicator between them. It will not be as quick as a 4 or 6 groove no matter what. Just be sure to measure each groove in the same spot as there is often a tenth or three of ratchet or radius error in a groove. I think once you compare the finished product to the rod you wont go back.

 

[tobnpr]

When dialing a 5 groove in with 4 screws I dont go 180 and split the difference. I look at each groove to get an idea how far off the center of the bore is. So spin it 360 and find the extremes and zero the indicator between them. It will not be as quick as a 4 or 6 groove no matter what. Just be sure to measure each groove in the same spot as there is often a tenth or three of ratchet or radius error in a groove. I think once you compare the finished product to the rod you wont go back.

Thanks for the feedback, the radius error is a good point- I'd noticed this and it was sort of frustrating when I couldn't figure out what was causing the slight variations. Couldn't put my finger on it and when I read your post the light bulb went off... the indicator stylus is sweeping inside a radius . Smaller the stylus tip, the more deviation I'd see in the same groove when rotating it slightly. I've been using a tenths B&S but it's so overly sensitive it drives me nuts, just found a smoking deal on a refurbed/certified B-15 so I'm going to be switching to that.

 

[Danny1788]

Use the rod, then the indicator. You should be very close. Make tiny tweaks on the nearest jaw.
If I use a reasonably tight bushing, and dial the rod in to as close to zero as I can get, then check with an indicator, I am very, very close.

I do it very much the same as Doug but I even go as far as using range rods. They get me close and I find them easier to get the barrel some what roughed in faster. Then it’s strait in with a DTI set as close to parallel with the bore as possible. I use an intrepid long stem

 

[Tucker65]

When using an indicator to dial the bore in. What is more important the bottom of the groove or top of the land?

I'm assuming it's the top of the lands as that is what the bushing would be riding on. I've seen slight variations between the two in some of the barrels I've worked with. Could of also been just one or two of the grooves being slightly deeper than tbe others.

John

 

[Alex Wheeler]

Thanks for the feedback, the radius error is a good point- I'd noticed this and it was sort of frustrating when I couldn't figure out what was causing the slight variations. Couldn't put my finger on it and when I read your post the light bulb went off... the indicator stylus is sweeping inside a radius . Smaller the stylus tip, the more deviation I'd see in the same groove when rotating it slightly. I've been using a tenths B&S but it's so overly sensitive it drives me nuts, just found a smoking deal on a refurbed/certified B-15 so I'm going to be switching to that.

I use interapids. I really like the large spacing between delineations. I can consistently dial in to LESS than .0001" tir with the long stem indicator. You have to get used to using one though. You can get real picky with them, the needle is fine enough to actually center it in the tenth mark on the dial face. You can tell if its on the left or right edge.

 

[butchlambert]

When using an indicator to dial the bore in. What is more important the bottom of the groove or top of the land?

I'm assuming it's the top of the lands as that is what the bushing would be riding on. I've seen slight variations between the two in some of the barrels I've worked with. Could of also been just one or two of the grooves being slightly deeper than tbe others.

John

For me the groove is most important.

 

[Spook]

use a relatively tight fitting bushing and indicate off the inside of it.

 

[butchlambert]

use a relatively tight fitting bushing and indicate off the inside of it.

Still indicating the bore and not the groove.

 

[Alex Wheeler]

Still indicating the bore and not the groove.

Plus added error from the bushing id/od runout...

 

[boltfluter]

If you think the bushing concentricity is bad, put a range rod on two v blocks and check the run out with a good indicator. You most likely will be shocked. Nevertheless they are handy for getting close. More or less! Lol

Paul

 

[Alex Wheeler]

I used a rod one time. I got it dialed then went in with my long reach indicator to check the throat area. That was the first and last time I used one.

 

[Will Henry]

I have always indicated off the lands and still do. The pilot rides on the lands. WH

 

[GenePoole]

I always check them and if they are not straight, I send them back. For some reason, they seem to switch from grinding between centers to centerless grinders (probably to save time and/or money) which is not the right tool for a part like this. I've had this argument with machinists at Manson tool and they eventually send me ones ground between centers.

 

[DaveTooley]

I indicate on top of the lands with a long stem Interapid. I also have the ball above the centerline. It puts a bit of a side load on the stem which keeps it in the same location when you stop rotating the barrel. No bounce of the needle. I've done so many 5 groove barrels that using 4 screws is not a problem. The key is don't fully tighten the screws until you are very near your number. Then it's just spin, tighten and tweak while watching the indicator.
If the barrel is setup properly and the chamber is roughed in concentric you don't need bushings. I just did some barrels with the bores .003" and .005" over. Obviously I didn't have any bushings that size. Upon inspection the throats were perfectly concentric. The reamer is going to the middle of the hole.

 

[gme]

I too indicate primarily on the top of the lands but rarely see much difference in the high end barrels we use, I made up this little tool for reaching in to indicate the throat area, .0001 CDI indicator but because of the distance between the tip and fulcrum it works out to .0002, works very well

 

[Hal]

Gary that clever.

Hal