T
Tim Mn
Guest
Do you need an action fixture to true up an action, or can you just use a 4-jaw chuck and indicate it off of that? If you do need a fixture what is the purpose for it? Thanks.
The fixture holds the receiver while you indicate off of a tight fitting mandrel inserted in the bolt raceway. There are four screws in the front and four in the rear, they act as the four jaw and spider. I've seen other ways to do this but, this is the best so far. Take a look at Mike Bryants WWW, you'll get a better idea as to what I'm talking about.
Action Truing Fixture
The purpose of the fixture is to allow you to indicate both ends of the action, using a mandrel in the bolt raceway, so that the bolt bore is "dead true" or as close as possible. There are other ways to accomplish this, but a double spider type fixture seems to be the most popular. One drawback to this system is that the fixture may be long enough to extend the receiver face pretty far out from the headstock which reduces rigidity and increases the likelihood of experiencing chatter. Some gunsmiths have made up fixturing which allows the receiver to be inserted into the spindle bore if the lathe being used is large enough. Others have used a fixture or a combination of fixturing which employs the steady rest. Which is most appropriate depends on the size and type of lathe and the smith's preference.
Scott Roeder
The purpose of the fixture is to allow you to indicate both ends of the action, using a mandrel in the bolt raceway, so that the bolt bore is "dead true" or as close as possible. There are other ways to accomplish this, but a double spider type fixture seems to be the most popular. One drawback to this system is that the fixture may be long enough to extend the receiver face pretty far out from the headstock which reduces rigidity and increases the likelihood of experiencing chatter. Some gunsmiths have made up fixturing which allows the receiver to be inserted into the spindle bore if the lathe being used is large enough. Others have used a fixture or a combination of fixturing which employs the steady rest. Which is most appropriate depends on the size and type of lathe and the smith's preference.
Scott Roeder
A
AdamZx3
Guest
Heres a short video from SGR rifles that explains a little about it. I will be getting one from PTG my remington build.
Also from what I understand the outside of the remington receiver is not concentric to the bore and or bolt, the jig seems like a great way to do it.
Also from what I understand the outside of the remington receiver is not concentric to the bore and or bolt, the jig seems like a great way to do it.
Mike Bryant
Active member
Here's a link to the system that I use for truing Remington's...
action truing It seems to work pretty well. The mandrel that fits into the receiver has to fit fairly tightly or you'll work yourself to death trying to get it indicated in with both dial indicators. Indicating the receiver in takes more time than doing the actual machining to true everything up. Of course, the more often you do it, the easier it gets to do the indicating. The first one will take some time. Consider the set of 4 set screws closest to the chuck as working the indicator farther away from the chuck. The set of 4 set screws farthest away from the chuck work the the indicator closest to the set screws. However, any time you make an adjustment to either set of set screws, it will make both indicators move. You go back and forth from one set to the other set until both indicators indicate in to the run out that you want. .0002" run out or less on each indicator is my goal when I indicate in a receiver. Indicating bolts I'll shoot for .0005" runout front and rear or less depending upon how round the bolt is. Most of them are doing good if you can indicate them in to .0005" as very few are very round especially on well used actions.
action truing It seems to work pretty well. The mandrel that fits into the receiver has to fit fairly tightly or you'll work yourself to death trying to get it indicated in with both dial indicators. Indicating the receiver in takes more time than doing the actual machining to true everything up. Of course, the more often you do it, the easier it gets to do the indicating. The first one will take some time. Consider the set of 4 set screws closest to the chuck as working the indicator farther away from the chuck. The set of 4 set screws farthest away from the chuck work the the indicator closest to the set screws. However, any time you make an adjustment to either set of set screws, it will make both indicators move. You go back and forth from one set to the other set until both indicators indicate in to the run out that you want. .0002" run out or less on each indicator is my goal when I indicate in a receiver. Indicating bolts I'll shoot for .0005" runout front and rear or less depending upon how round the bolt is. Most of them are doing good if you can indicate them in to .0005" as very few are very round especially on well used actions.
D
Dennis Sorensen
Guest
Mike does it very well... but it is quite a handful to make and set up and do it for only one or a few actions...
I don't do a great volume so I made a sacrificial sleeve about 2 inches in length, that fits over the front of the 700 receiver fairly close. Then I have 2 set screws that engage the action about equal with the stock line on one side and 2 set screws equal with the stock line on the other side... when these are snugged up the sleeve is tight against the top of the action. I insert a tight mandrel and between centers with light cuts turn the outside of the sleeve concentric. I then hold this sleeve in my 4 jaw chuck (the jaws have been ground true) and dial the mandrel in using one dial indicator.. then I remove the mandrel and proceed with any machining I wish to do. This may not be as accurate as Mikes set up but it works very well. The sleeve will do several actions before it become too small.
I don't do a great volume so I made a sacrificial sleeve about 2 inches in length, that fits over the front of the 700 receiver fairly close. Then I have 2 set screws that engage the action about equal with the stock line on one side and 2 set screws equal with the stock line on the other side... when these are snugged up the sleeve is tight against the top of the action. I insert a tight mandrel and between centers with light cuts turn the outside of the sleeve concentric. I then hold this sleeve in my 4 jaw chuck (the jaws have been ground true) and dial the mandrel in using one dial indicator.. then I remove the mandrel and proceed with any machining I wish to do. This may not be as accurate as Mikes set up but it works very well. The sleeve will do several actions before it become too small.
Hi all. I'm new here but thought I would kick in my 2 pennies worth. I have done action truing both in the lathe and with a homemade fixture. They are both good as long as you take care and watch what your doing. If your doing an occasional job, the lathe works very well, but if your doing alot of action work then a fixture would be the way to go. Everyone has their own way of doing it. Its all good as long as quality remains the primary goal.
P
PPP MMM
Guest
When the outside and the inside of a receiver have a separate axis each that're tilted each of the other (which is the usual case) one can't zero the mandrel on both ends in a four independent jaws chuck alone. A spider fixture in a four independent jaws chuck is the quickest and the most reliable way for one to achieve that.
Shoot better
Peter
Shoot better
Peter
Last edited by a moderator: