Grizzly Rod upgrade

E

eddief

Eddie Fosnaugh
Lots of guys like and use the grizzly rods that Gordy developed a few years back. One of the biggest gripes and what I didn't care for, was having to hold one end in a drill chuck, mounted in the tailstock.

My take is you have to be inducing some flex into the setup (Grizzly rod) as the bore wanders when dialing in, albeit minimal. This is due to the Grizzly rod being held somewhat rigid in the chuck on one end while the piloted end follows the bore.

I'm not scientific, so I don't want to get involved in a lengthy, pick my method apart discussion. But I just wanted to share this because a lot of you guys do your own work, and I have had a lot of help over the years from some great smiths that were generous enough to give out info.

What I did to remedy this was....mill out some 5/16ths ball bearing and fit them to the end of each Grizzly rod.

This allowed me to mount that end in my Starrett No#828 wiggler, and then hold the wiggler with the chuck in the tailstock. This allows 360 degree movement of the rod at that end. Resulting in better indication.

I used high rpm and Garr tool carbide endmills in sizes 13/64, 15/64 and 17/64ths.

One was a press fit, the other was tight enough that I used Loctite 609. The other I used some JB weld.

RR3.jpg
 
Last edited:
Eddie, the wiggler joint is a good idea but how are you planning on keeping that ball on the crest of the land or in the bottom of the groove?
 
Jerry,

The other end is in the bore with a proper fitting pilot. I just wanted a better way to hold the tailstock end.

This just allows me to go into the throat and indicate better (in my eyes) before pre-drilling. I still go in after pre-drill and get a final direct reading on the throat with the DTI.
 
eddief said:
Jerry,

The other end is in the bore with a proper fitting pilot. I just wanted a better way to hold the tailstock end.

This just allows me to go into the throat and indicate better (in my eyes) before pre-drilling. I still go in after pre-drill and get a final direct reading on the throat with the DTI.
Click to expand...

So, the ball is riding in the bore of a pilot bushing? That should work.
 
Jerry,

No, the other end (not shown) has the fitted to the bore bushing like the tapered PTG range rods. The Grizzly Rods aren't tapered.

Grizzly-Rod-Example.png
 
How would this method be better than say a tapered range rod? I to use a grizzly rod, and i was under the impression that we want the rod to flex. Some fellas even hang a weight in the middle of the rod to add a little extra flex. Im new to all this, with a pedigree of 4 barrels under my belt. I find these topics very interesting. Thanks Lee
 
JerrySharrett said:
Now I get it , finally. The ball is on the wiggle joint end??
Click to expand...
This is an ingenious solution to a problem that is still the problem, i.e. You are still indicating outside the bore. Not only that, the farther you extend the rod toward the pivot the more you are reducing the movement of the rod where your indicator is taking its reading.
 
Don't you indicate the lands and grooves at the throat after predrilling? Predrilling allows my indicator with a short stiff probe to reach in and then indicate at the throat.
Maybe that will give you more jollys.
 
Jerry,
Wouldn't the difference between the outside and inside the barrel measurements decrease as distance from the end of the barrel to the pivot point (at the tail stock end of the rod) is increased?
Boyd
 
Butch,

Yes I do. This just allows me to go right to the throat for the initial dial in. Then I pre-drill and go in with Mituoyo DTI, take my direct reading, tweak the throat in as perfect as I can get it, and then pre-bore.

Sounds like we are getting the same results with a little different method or jollys as you put it.:)

For the record, I love the brashness and wear on my sleeve attitude around here. Makes me think back of my father and grandfather, god rest their souls. I can't stand people who tiptoe around crap and you don't know where they come from.

I appreciate all that is shared here from you all.
 
I thought holding the one end fixed in the chuck allowed the bore to be indicated quite well.

I grab very little of the rod in my tail stock chuck and I hold the pilot end down a bit when I tighten the chuck. This causes the pilot to be low in the bore. I also hang a 2 ounce weight in the middle of the rod so the pilot is held down in the bore when it is just past the throat area. My ten thou indicator measures up and down movement on the rod just outside of the chamber. I don't care what the actual movement measures, I dial it down as close to no movement as I can get.

I was going to solder ball bearings on the chuck end of the rods but I find I can 'cock' the rod down slightly in the chuck and have no problem with this method.

I just dialed in the crookedest barrel I have ever had from Shilen and the throat appears very concentric in the bore.
 
Eddie, I use Deltronic pins for my initial setup. I predrill and then use my Mitutoyo to indicate the throat. I taper bore to the throat. We are probably doing much the same thing.
 
Boyd Allen said:
Jerry,
Wouldn't the difference between the outside and inside the barrel measurements decrease as distance from the end of the barrel to the pivot point (at the tail stock end of the rod) is increased?
Boyd
Click to expand...
Yep, the amount of runout in the barrel is more than what will show part of the way up the rod toward the tailstock. Therein lies the problem.

i.e. If the throat area of the proposed chamber neck is out 0.001", the amount that would be shown on the rod where the indicator rides would be showing less.
 
I roughly did the trig on the measurement difference for an 8" long rod stuck 2" into a bore with an initial .0005" of runout as seen by the bushing. I come up with .00016" difference between the runout at the bushing as opposed to what the indicator sees just outside the bore. With a 12" long rod (I believe the Grizzly rods are 12" long) the difference drops to .00008". If we reduce the runout as seen by the bushing to .0001" the difference in the two points would be .00002". So if the bushing sees .0001" the indicator sees .00008". I would think for Eddie's purpose of indicating the bore at the throat for predrilling he's doing just fine.
 
Last edited:
Dennis Sorensen said:
I thought holding the one end fixed in the chuck allowed the bore to be indicated quite well.

I grab very little of the rod in my tail stock chuck and I hold the pilot end down a bit when I tighten the chuck. This causes the pilot to be low in the bore. I also hang a 2 ounce weight in the middle of the rod so the pilot is held down in the bore when it is just past the throat area. My ten thou indicator measures up and down movement on the rod just outside of the chamber. I don't care what the actual movement measures, I dial it down as close to no movement as I can get.

I was going to solder ball bearings on the chuck end of the rods but I find I can 'cock' the rod down slightly in the chuck and have no problem with this method.

I just dialed in the crookedest barrel I have ever had from Shilen and the throat appears very concentric in the bore.
Click to expand...

This is just one of those "you don't have a freakin' clue until you TRY IT" deals ain't it? Once you CAN see crookedy barrels there's no going back :)

al
 
JerrySharrett said:
This is an ingenious solution to a problem that is still the problem, i.e. You are still indicating outside the bore. Not only that, the farther you extend the rod toward the pivot the more you are reducing the movement of the rod where your indicator is taking its reading.
Click to expand...

Jerry you repeated contention that you're "indicating outside the bore" is completely understood by all........ but here's the real deal. You use the Grizzly rod to get 'er done and then, with the chamber cut you CAN REACH IN DIRECTLY in some cases and measure the way you prefer.

And the two methods invariably AGREE.

Anyone who's capable of running a lathe understands perfectly well that you lose resolution the further you get from the point being indicated. This is true whether you're using a long probe or a Gordy rod. But as long as your methods are sound and repeatable and you understand this you just work with what you have. For myself I chamber enormous rounds where I have to reach in 3-4 inches beyond the lapping bell. I tried to get a 16" or 20" long rod in 338, I finally gave up and bought the short one and shorter rod works OK.

BTW, Back when I started with these big rounds nobody would/could do this (except Gordy, who manages to stay booked out for half a year) and several really good 'smiths tried to convince me that it was unimportant.... basically that even though it's WICKED important with the PPC it's "no biggie deal with a 338 Lapua, just aim the reamer in the general direction of the hole and let 'er fly...... hope for the best...."

So I did it myownself.

Just for your enjoyment I HAVE dialed in a blank, marked it, REMOVED IT FROM THE LATHE, covered my marks with tape and reset........ 4 times on three different days.

No surprises.

And I've indicated flexure in the chuck, the effect of various securing methods, the effect of torquing the muzzle around etc.

Ohhh, and the barrels shoot where I point 'em, predictably. I can predict within 2 inches at 100yds, even when impact is 6" or more from center.

Regarding your contention that the muzzle must be "in front of the chamber" I understand this too, I just don't necessarily agree :) IMO "centerline" of the recoiling system includes the stock and (also IMO) the two methods are equal as far as flexure of the barreled action unit.

I could be WRONG but it's not because I don't hear and understand what you're saying. Offer some alternatives, some evidence, even some stories and I'll listen.

al
 
In rereading my question to Jerry, One thing that I was trying to bring up, but completely failed to communicate, was that for certain applications, such as the one that AL has mentioned in his last post, that simply extending the rod would improve the ratio of outside to inside the barrel measurements. Perhaps an old automotive push rod could be pressed into service, with suitable adapters. In any case, I think that the longer the rod, the less difference there will be between outside and inside measurements, particularly at the throat.
 
You must log in or register to reply here.
Back
Top