Trapdoor ........... perhaps

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Orville
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Re: Trapdoor ........... perhaps

Post by Orville »

Just finish turning a barrel down myself (22 k hornet) talking to an old long time machinest, said rollers on a steady rest for turning barrels is not a good idea, they impart stress into that spot on the barrel.
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mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

I don't have a follower rest Clark plus I don't see how they can work on a taper.
i never thought of that Orville as I don't actually have a roller rest but that makes perfect sense when I think on it.
Woody
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Re: Trapdoor ........... perhaps

Post by Woody »

Mike,

A follower is always in the same plain as the cutting tool. It follows the cut or precedes it, depending on the direction of the cut.

Woody
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mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

I'm familiar with them Woody, what I don't under stand is how the rest following the work on the opposite side of the cutting tool adjusts for the taper which is making the distance between the tool and the rest change as the table moves up or down the bed and taper angle.If your turning the same diameter it's full length then I see how they work but not how it compensates for the cross section diameter change.
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alfajim
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Re: Trapdoor ........... perhaps

Post by alfajim »

mdeland wrote: Mon Apr 26, 2021 3:46 pm I'm familiar with them Woody, what I don't under stand is how the rest following the work on the opposite side of the cutting tool adjusts for the taper which is making the distance between the tool and the rest change as the table moves up or down the bed and taper angle.If your turning the same diameter it's full length then I see how they work but not how it compensates for the cross section diameter change.
Do they make one with spring loaded follower fingers to allow for a constant pressure?

Jim O
mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

I've never seen one ! One of the techniques I have learned by trial and error to compensate for barrel flex is to run the tool forwards and back words over an area that is not being reduced at the same rate in a single pass as the taper angle dictates it should because the barrel flexes out of the way. Each pass back and forth will shave off a bit more without touching the cross feed.
mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

Here is where we are at presently. I got in a hour or two yesterday on it before getting off on another tangent responsibility. Should be getting to machining the integral sight lug in the next day or two. Hope I don't screw that up after all this work! New ground for me.
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mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

A lot of steel has to come off that 1.300 diameter blank to get down to the spindly trapdoor barrel profile that will fit back into the stock and barrel rings correctly. I left it a bit large and will have to draw file it to final fit after the sight lug machining is done.
The hope is to get the diameter draw filed to fit the two barrel rings correctly as this will be key to good accuracy I'm thinking. I can always shim them if necessary which I've read is common practice in tuning these style guns for competition.
I've got a lot to learn about trapdoors but it certainly is interesting!
mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

I'm almost there but this is the most technical taper I have ever turned because of having to deal with the correct barrel ring diameters. The set over calculation has to be tweaked to account for barrel flex and to blend the cut intersections which has to be continually monitored and adjusted. I have three tangent cut intersections on this barrel . One either side of the lug ring and the one at the steady rest about mid barrel.
I'm within .010 of finish at the action shoulder and a good bit out at the back barrel ring and the cut intersection so I have to reset the tail stock over until the intersection and ring diameter correspond to the original barrel diameter. I'll leave them about .010 proud in the lathe and strike/draw file them to final fit.
Now that I have the shoulder cut to diameter all I have to do is cut the other direction and tweak the set over until the intersect blends with the shoulder and front half of the barrel taper.
The front half of the barrel being thinner flexed more than the rear half and the set over has to account for it.
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mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

I'm going to have to be really careful when drilling and trapping for the Buffington sight screws on this thin barrel. The Sharpy mark on the lower picture is where the rear ring goes.
mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

Well she turned out well guys as far as we have come. The taper fits both rings, threading , chambering and extractor fit are all good and now the hard part , getting the lug machined to proper profile and at top dead center without messing anything else up.
It is radial filed and sanded to 320 finish ready for rust bluing.
After the lug is milled then I will need a bit of draw filing to match taper either side of where the lug ring was.
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mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

Some more shots of it:
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mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

This is back in the stock, all fitting well.
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mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

I couldn't try the fit of the front ring with the barrel lug still on but it fits the stock nose cap mortise perfectly and I see little chance it won't also fit the front ring.
mdeland
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Re: Trapdoor ........... perhaps

Post by mdeland »

The new barrel is within 1/8th of an inch the same length as the original although in the picture it appears a good deal shorter. Tomorrow before I set up in the mill I need to do a bit of clean up on the crown I forgot about before I mill off the sight lug which will be my steady rest bearing for the crown trim.
I decided to set the barrel up in my Forrester sight jig in the two V Blocks to mill the sight lug. I'll need to take light cuts with a small diameter mill so as not to break anything. I think once the lug location is established I can cut most of the lug ring away with a power hack saw with the barrel taped up to protect it from getting all scratched up.
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