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 Post subject: Question for gunsmiths.
PostPosted: Mon Sep 28, 2020 10:52 pm 
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I would be interested to know what is your prefered method of chambering a barrel.
Do you chamber between centres using a steady rest?
Do you chamber through the headstock using an outboard spider?
Also, what is your method of dialing in the barrel?
Does anyone use the Gordy gritter method of dialing in and do you have any comments on his method?
I have watched the video and it seems to be very different from the methods I have seen used by other gunsmiths.


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PostPosted: Tue Sep 29, 2020 7:48 am 
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Location: Lincolnshire Wolds
Inboard only, so 4 Jaw with brass inserts or copper band at the front and spider with brass faced screws at the back. PTG tapered rod with correct sized bushing (I sometimes make my own out of brass) I use a 0.01mm finger indicator and/or a 0.0001" as I am looking for deflection only.

Also, I initially align the barrel off a live centre (Stationary) then I clock off the outside with a 0.01mm Plunger to get a rough position. I know everyone says never clock off the outside, however this is to get in the approximate area and my plunger DTI's are a lot cheaper to replace than the Mitutoyo finger indicators which I finish off with.

No, I personally will not use the Gordy Gritter rods, to much scope for error to my mind. Maybe I will change my mind one day.

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PostPosted: Wed Sep 30, 2020 5:32 pm 
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I use the exact same method as Dave above. It works for me. A floating reamer holder would be nice.

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PostPosted: Wed Sep 30, 2020 11:54 pm 
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I rewatched the Gorrdy DVD and as I see it if your tailstock is not perfectly aligned to the headstock his dialing in regime does not work.
Yes/No


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PostPosted: Thu Oct 01, 2020 5:38 am 
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Exactly. Your tailstock will be maybe 8” away from the barrel with reamer and reamer holder fitted. So take a length of bar stock the same length and place it in the Chuck and support it with the tail stock. Now take a full length cut. Measure both ends and if there is any variation in diameter you have a problem in that you are turning a taper and the fritter system is not going to be as accurate as needed.

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PostPosted: Thu Oct 01, 2020 10:54 pm 
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I have ordered a ground calibration rod that will fit in my tailstock when it arrives I will set it up between centres and check the runout. I have probably given up on the Grizzly rod idea.
I will use range rods or indicator rods. Probably indicator rods to re crown the muzzle.


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PostPosted: Sat Oct 03, 2020 11:20 pm 
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Another question some barrels I have discovered have a cut out for the extractor. You obviously can not do this on the lathe. Is it a milling job how do you cut the slot. How would you set it up?

The Grizzly rods I bought that were not cheap were probably a bad investment. I invested in quite a few different sized bushings I am thinking maybe I could bore one out to slide onto the rod.
I could then insert the rod with the bushing it came with to engage with the lands then slide the bored out bushing onto the rod to about 1inch into the muzzle and indicate off that.


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PostPosted: Sun Oct 04, 2020 9:07 am 
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Extractor cuts are done on the mill. I use the solid carbide profiling/boring bars or a parallel reamer for the ID of the bushes when I make them, however I mostly make them out of brass and in one hit, so OD and ID whilst the job stays in the machine. Not wishing to appear harsh, however the chances of chucking up a bush accurately in anything other than a 4 Jaw are going to be slim and even then you need to get as close to absolute as possible, otherwise just stop with the rods and spend some time clocking the tail stock.

I use a ground gauge bar held in a micro adjust collet chuck and the tail stock and a measuring fixture I built myself which is held in the collet chuck and a sacrificial cut made every time I use it to ensure
concentricity.

I still maintain he easiest way is to do it on a teach CNC, measure the run-out and add the off-set, job done :) Sadly that feature is not available on my Fanuc controller...

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PostPosted: Sun Oct 04, 2020 10:58 pm 
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I checked the tailstock today for alignment. No, surprise it's out. So that needs sorting out. I don't have an issue using a four-jaw independent chuck now I know how to dial one in. I have more dial gauges than Cromwell tools.
I don't have a lot of spare time for messing with the lathe at the moment I am back at work apparently I am a key worker.


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PostPosted: Mon Oct 05, 2020 11:03 pm 
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The ground bar with an MT taper ground on to fit in my tailstock arrived today. I fitted it to the lathe and clocked it. I was pleasantly surprised it was hardly out at all.
I don't know what happened the other day. Actually, I think I do know what happened but I won't bore you with the details(Operator error and lack of adjustment not maintaining the lathe properly.)


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