Proper way to Blue print a bolt

nksmfamjp

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Joined
Jan 5, 2004
Messages
598
Another good instructional Video to aid the newer Gunsmith in doing the proper work.


Enjoy

J E CUSTOM
Interesting, I was surprised to hear him basically slightly oversized the receiver threads with the idea that torquing to the face, lug, shank will hold it square.

The other camp says you have to single point cut them...

Which do you do? Has anybody done much testing both ways?

For the bolt, he clamps the bolt running true to about 0.001”, the cuts the aluminum holding jig, then reclamps to the jig and spider. The jig seems to add variation, But can the spider be dialed to remove that variation?
The other method being to hold the bolt with a truing jig and adjust until the bolt body has minimal runout. Seem similar methods. Is one better, more direct?
 
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J E Custom

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10,380
Location
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Interesting, I was surprised to hear him basically slightly oversized the receiver threads with the idea that torquing to the face, lug, shank will hold it square.

The other camp says you have to single point cut them...

Which do you do? Has anybody done much testing both ways?

For the bolt, he clamps the bolt running true to about 0.001”, the cuts the aluminum holding jig, then reclamps to the jig and spider. The jig seems to add variation, But can the spider be dialed to remove that variation?
The other method being to hold the bolt with a truing jig and adjust until the bolt body has minimal runout. Seem similar methods. Is one better, more direct?
There are many ways to achieve the desired results and many times you have to decide which way is best for that receiver. I will single point if the action has poor threads and are not concentric with the bolt bore, sometimes if they are true, I will chase them to remove any high spots. (If you look close at the threads you will often see a line perpendicular to the threads where they stopped cutting without backing off) these threads need to be single point cut for sure. I always clean up the threads with a quality tap to remove the thread sealer that prevents you from testing/inspecting the action threads.

Then after the inspection the decision can be made. (No two actions have the same problems)
If you single point the threads, it enlarges them and the barrel threads have to be cut to fit properly, so if the thread are good quality and concentric with the bore centerline less is required and the thread size remains In spec.

The bolt set up works If the lathe chuck is accurate. (I have my 3 jaw down to .0003, but for a higher degree of accuracy, the 4 jaw will normally get you closer to .0000 (Almost impossible to achieve) by cutting the aluminum Mandrell off the bolt barrel It trues the mandrel to the center line. (But you must do it each time you true a bolt because the threads inside the back of the bolt are never the same) Mine started at more than 2 '' and has been replaced several time when the chucking shaft got smaller then 3/4 " from re cutting/truing.

Some smiths like/prefer looser threads so they can self center, I prefer well fitted threads that I know are centered with everything else so there is less chance of any misalignment to the absolute center line,but extra steps have to be taken to prevent galling.

As far as which method is best, I don't think there is any good way to tell because of the other variables that could falsifier/misdirect the results.

The only thing that I have noticed is that the better the truing, the less finicky it is to different loads. Results are what counts, the method used is a personal preference based on the smiths
consistent results. The Video shows the items that need to be addressed, and if another method works best for the individual action it should be used.

J E CUSTOM
 

nksmfamjp

Well-Known Member
Joined
Jan 5, 2004
Messages
598
There are many ways to achieve the desired results and many times you have to decide which way is best for that receiver. I will single point if the action has poor threads and are not concentric with the bolt bore, sometimes if they are true, I will chase them to remove any high spots. (If you look close at the threads you will often see a line perpendicular to the threads where they stopped cutting without backing off) these threads need to be single point cut for sure. I always clean up the threads with a quality tap to remove the thread sealer that prevents you from testing/inspecting the action threads.

Then after the inspection the decision can be made. (No two actions have the same problems)
If you single point the threads, it enlarges them and the barrel threads have to be cut to fit properly, so if the thread are good quality and concentric with the bore centerline less is required and the thread size remains In spec.

The bolt set up works If the lathe chuck is accurate. (I have my 3 jaw down to .0003, but for a higher degree of accuracy, the 4 jaw will normally get you closer to .0000 (Almost impossible to achieve) by cutting the aluminum Mandrell off the bolt barrel It trues the mandrel to the center line. (But you must do it each time you true a bolt because the threads inside the back of the bolt are never the same) Mine started at more than 2 '' and has been replaced several time when the chucking shaft got smaller then 3/4 " from re cutting/truing.

Some smiths like/prefer looser threads so they can self center, I prefer well fitted threads that I know are centered with everything else so there is less chance of any misalignment to the absolute center line,but extra steps have to be taken to prevent galling.

As far as which method is best, I don't think there is any good way to tell because of the other variables that could falsifier/misdirect the results.

The only thing that I have noticed is that the better the truing, the less finicky it is to different loads. Results are what counts, the method used is a personal preference based on the smiths
consistent results. The Video shows the items that need to be addressed, and if another method works best for the individual action it should be used.

J E CUSTOM
Thanks for the response. Being able to converse with a real expert is quite valuable. Thanks for posting these technical posts and answering back.
 

Tommytrees

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Jun 7, 2020
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69
Location
FloridaGeorgiaLine
Another good instructional Video to aid the newer Gunsmith in doing the proper work.


Enjoy

J E CUSTOM
I did not quite understand what truing the bolt etc was, but this helped clear up some of the why, how and need for this work. Thank you for the informational video. Hopefully others will be forthcoming.
Be safe Be well
Tommy
 

GLTaylor

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Oct 11, 2019
Messages
499
Location
Cedar Bluff, Al
Excellent and instructional. I have an even higher regard for my smith. I've watched some of this and didn't fully follow what I saw! Thank you!
 

ntsqd

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Nov 16, 2015
Messages
712
Location
Upper SoKA
He briefly mentions something that I've noticed and I wonder how many others caught it. He mentions seeing "the flash" after his first pass truing the mandrel to the bolt body and says that it means that the tool was deflecting from the interrupted cut. Without ever realizing what I was doing I too have long been taking a very light cut after I cut past the interrupted surface in any lathe work.

He does need to make the trivial investment in a box of Harbor Freight 1" paint brushes. I use them as chip brushes all over the shop.
 

J E Custom

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Joined
Jul 29, 2004
Messages
10,380
Location
Texas
I did not quite understand what truing the bolt etc was, but this helped clear up some of the why, how and need for this work. Thank you for the informational video. Hopefully others will be forthcoming.
Be safe Be well
Tommy

Thanks.
Many people don't understand what goes into a TRUE blueprinting/truing and I just thought this would clear up some of the questions. This is also only half of the job, the receiver is just as important and is the foundation for the bolt work, and must be done with the same care.

Many people say just buy a custom action and save the cost of blueprinting, In general, they are/should be better dimensionaly But many are not. Being true has to be proven because the customs are machined the same way and with the same human mistakes in programming and quality control. Normally the quality control acceptance is much better than factory actions, but having checked everyone of the custom actions I have dealt with many were not perfect and needed some tweaking is certain areas.

The other reason for showing the Video is to help people understand what is involved and that they may not be getting a true blueprinting from some smiths. I have worked on many rifles that the owner was told that there smith had blueprinted the action, and after the barrel was removed
they were shocked to find out that it had not been done or was only corrected in one or two areas. These were documented with pictures and videos and presented to the owner before any work could start.

Absolute quality is/should be the goal of any good Gunsmith and is/should be continuous for his career. Many forget this and stop trying and unfortunately ruin their reputation in the end.

J E CUSTOM
 

pcrider53

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Joined
May 28, 2020
Messages
7
Location
alabama
Great video, enjoyed it. I have a much greater appreciation for what is involved in higher levels of accuracy
 

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