Gunsmithing Too much runout on action alignment rod

[Gene Poole]

We recently purchased a tool from a well known gunsmithing supplier for aligning Remington 700 actions for truing. It consists of two tapered bushings (0.700 - 0.705 tapered OD and 0.5000 ID) and a 0.4997 ground steel dowel that fits in the bushings. You've all seen the setup: the bushings go in each end of the action bolt raceway and the dowel is used with DTIs to get the action as true as possible for blueprinting.

The first tool seemed bent. It bound up in the bushings when installed so we put it in a couple of matched v-blocks and measured the runout with a DTI. It was on the order of 3 or 4 thousandths about 4 inches from the edge of the v-block which seemed excessive. We sent it back and they confirmed that it was out and sent us a new one just a few days ago. I went to the shop tonight intent on getting an action ready for blueprinting but after testing the new dowel and bushings, there is still 3-4 thou of runout. I thought maybe something was out with my v-blocks (matched set of Lufkin blocks) so I installed the bushings in the action and clamped the action in a vise and mounted the DTI. Same results. Am I doing something wrong? Am I missing something? See for yourself:

[video=youtube_share;_6LKZvKT-TA]http://youtu.be/_6LKZvKT-TA[/video]

 

[Turd in the Pool]

Damned! I trust you checked the rod to make sure it was round.

Does it say "Made in China" on it?

 

[Gene Poole]

I forgot to mention that I had my friend and mentor (a machinist with 30+ years experience) look at the first rod. He set it on the mill bed, held it on one end and tapped the other with his finger. Then he rotated it 180 degrees and tapped it again and it made a "clack clack" sound when he tapped it. He looked at me and said, "It's bent!"

I found the video from the first dowel. It was actually more like 5 or 6 thou out:

 

[stangfish]

Straighten it and move on. You have the indicators. Set it in two v blocks and mark the highs. Deflect until it relieves the stress using a 1inch travel next to the point of pressure. Go in increments of .025 until it yields. Then go in increments of .005 or .010 until it is free of R.O.

 

[LRI]

If your talking about the PTG rod, then just call David and get a new one.

Dave and I talk frequently and during a discussion awhile back he admitted that sometimes the rods warp over time. They buy stress releived material and take measures to ensure the grinding process doesn't cause a distortion, but every once in awhile one will "go banana" on you.

Just give him a call (if that's where you go it).

If you bought it used, it could be the result of someone getting heavy handed with it.

Good luck.

C.

 

[xringaccuracy]

Also consider where the bushings are riding on. That round hole in the action may not be round. Just food for thought.

 

[LRI]

Little update...

talked with the OP via pm and he stated that this is NOT a PTG part. Just wanted to clarify in case anyone had concerns.


C.

 

[skeetlee]

I make my own truing rods.no need to buy something you can make. lee

 

[eddieharren]

Lee, what kind of grinder do you use to make the rods?

 

[Killswitch Engage]

why couldnt you you just turn a rod? shouldnt be any big issue

 

[eddieharren]

If you want something nearly round, turn it. If you want something perfectly round, grind it.

 

[Killswitch Engage]

i realize thats the general consnesus but if you turn a rod in in a lathe and run an indicator on its length getting zero run out what do you have?

 

[Gene Poole]

I thought about turning one, but the best I could come up with last time I shimmed the tailstock was about 2 tenths. That will induce a bit of taper, but if it's concentric the taper shouldn't matter much. I'm more concerned with getting a good enough fit. I need 0.4997+-0.0001 consistent across a span between the bushings which will be tough.

 

[eddieharren]

Killswitch, you have an incredible amount of luck!

 

[Killswitch Engage]

Killswitch, you have an incredible amount of luck!

I like to think its a well set up machine but whatever works I suppose.

 

[skeetlee]

Doc
If my lathe isn't good enough to make an alignment rod, then why would it be good enough to true a rem 700 action up? My rods are not ground, but they work just fine. The last rem 700 I did for myself says so. Shoots itty bitty!!!! Lee

 

[eddieharren]

Lee, if you and your lathe are that good then you'll never have a need for a grinder. Somehow I expected your rifles to always "shoot itty bitty".

 

[JJones75]

Question for you guys turning your own indicator rod.
are you using a follow rest when doing this?
I have made some pretty tight tolerance pump shafts using a follow rest and turning between centers bit we are talking a 1"+ shaft over a 18"-24" span

 

[stangfish]

"1"+ shaft over a 18"-24" span" Wow! That is a long one Centerless Grinding would be ideal. Otherwise an O.D. Grinder is the way to go.

 

[stenger]

I know the rods he is talking about I had the same rod it had problems also