Full length sizing die fail

S

savet06

Mike Suhie
I am hoping to learn from my mistake and understand better why my attempt failed.
I bought a newlon blank that was externally threaded, had a pilot hole for the reamer and was already drilled and tapped for the decapping assy.
I dialed in the die blank to as close to zero as I was able to measure the whole length of the pilot hole.
The die was supported in a steady ( first mistake?)
Used a floating reamer holder (second mistake?)
Got a nice wallowed out chamner cut .005 over.
Tried to salvage it but no go. Round file it went.

I have since bought a ptg blank that has a pilot hole all the way through and the chamber dimensions are perfect using the same technique.

What should I have done with the newlon blank instead? My immediate thought was that the reamer would have had to be held rigidly and the tailstock/spindle axis alligned perfectly for this to work. Or my floating reamer holder which is homemade and similar to a bald eagle type had too much float for the system.
Should I have chucked ober the threads instead of letting it hang out and needing the steady?


Any thoguhts welcome.
Mike
 
savet06 said:
I am hoping to learn from my mistake and understand better why my attempt failed.
I bought a newlon blank that was externally threaded, had a pilot hole for the reamer and was already drilled and tapped for the decapping assy.
I dialed in the die blank to as close to zero as I was able to measure the whole length of the pilot hole.
The die was supported in a steady ( first mistake?)
Used a floating reamer holder (second mistake?)
Got a nice wallowed out chamner cut .005 over.
Tried to salvage it but no go. Round file it went.

I have since bought a ptg blank that has a pilot hole all the way through and the chamber dimensions are perfect using the same technique.

What should I have done with the newlon blank instead? My immediate thought was that the reamer would have had to be held rigidly and the tailstock/spindle axis alligned perfectly for this to work. Or my floating reamer holder which is homemade and similar to a bald eagle type had too much float for the system.
Should I have chucked ober the threads instead of letting it hang out and needing the steady?


Any thoguhts welcome.
Mike
Click to expand...

First, you must hold it TIGHTLY but without distortion and dial to the length of the center hole...... in three dimensions......Of the dozens of PTG's I've dialed in they're all bananananananana'd ooops banana'd

I now use a jiggable collet for this. I use'ta' use threaded support rings, yes, "over the threads."

Seconde, ye must prebore.....to get rid of part of the bananananananana.....and this is a Muther-ucking-Bother-Brother.

I leave the inside (left side) running truest and cut out the runout best I can. (later you'll have to flip it and re-dial to the "straight" portion. And, if you can, reach 'wayyyy in with a bent flibbertygibbit and try to get a read on the inside (left side))

T'urd, Ye got's to chamber the die using a pusher.......it is physically/scientifically/mechanically and metaphysically IMPOSSIBLE to cut consistent holes with the reamer mechanically fixed in place, even if it theoretically "floats".... IMO it must be PUSHED with a self-compensating ring and held with fingers for the drive, allowed to both float and flex stress-free, IN A PRE-BORED HOLE....... Just reaming without prebore guarantees the reamer to cut oversized because the reamer humps up like a kitten on a yarn ball and the unsupported portion kinda' wallers it's way in. Even if the hole is straight. It does this ANYways, even in a pre-bored hole but with at least 3/4 of it supported in the pre-bore it just kinda' ripples up and down it's length, cutting here-then-there but maintaining a good hole within a few tenths....and holding wit' de' fingers allows one to work out the screechin-chatter if it tries.


A 2.5" diameter round, wheel-shaped hand-drive works good for this, and safe........altho I still prefer handles. For safety's sake you can jerry-rig (Is That Racis'??) a stop bar at the back if you're worried about slapping your fingers....


"Steady's" are best left in high schoole IMNSHO....


And now, once't you've GOT a good die made. It Must Be Hardened.

This also sux.

I'm still working on this issue, home'ade hardening.
 
You should have held the die blank firmly in a chuck. Then indicated the OD, rough drilled the bore, then taken a couple of light boring cuts to established a concentric relationship of the OD to the ID.

THEN, using a floating holder for the reamer, reamed the die. The reason for using a floating holder in this instance is because it is very likely the centerline of your tailstock is probably not exactly on the same centerline of the rotation of your workpiece.

Rigidly holding the reamer, if thentailstock is not on the same exact centerline, the reamer, being off center, would act as a boring tool. So, if the tailstock is misaligned by, say. Only 0.003", it could cause an oversized hole of 0.006"!!!



.
 
Newlon Dies

I use a steady rest..... chucking only on a small part ( 1/4" ) of the blank
reason..... that way you can dial in the die at 2 points......
pre-bore.... to straightened out hole and to make less work for the reamer
push reamer with tailstock center......IF your machine is in alignment...if not use a fore giving type pusher......
bill larson
 
Straight linement

Here is the only way I have found to accurately every time get the bore alinement to .0001 each end then drill and bore it to size. Very fast and accurate each time. I use aluminum strip's under the set screws .
Chet


P1010050.jpg
 
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Thanks, guys.
I appreciate the info and the lesson in the why as well as the how.
Looks like a small boring bar is in order.
I will give it a go and see how we do on the next go round.
Mike
 
coyotechet said:
Here is the only way I have found to accurately every time get the bore alinement to .0001 each end then drill and bore it to size. Very fast and accurate each time. I use aluminum strip's under the set screws .
Chet


View attachment 17594
Click to expand...

To the op, Chet's right on altho I'll have to disagree re "very fast" as it always takes me some time to get dialed in ;) BUT.....

This is the method I used when I mention bearing off of rings.

I've used AL and brass shims, pennies and AL pads and found it easy to warp the die body with the four-jaw. Maybe I'm just ham-handed.

I tried sections of thicker AL with 45* grooves, even bored and slitted apart some heavy fitted shims but in the end found that FOR ME bearing off of threaded die lock rings on the threads was safest.
 
Mike, regardless your alignment and support method, your reamer is either greatly oversize or you were forcibly holding it off center for it to have cut 0.005" over. When you insert the reamer in your finished die if it does not fit really snug, you had the reamer held in a bind.

Why use a steadyrest for a workpiece that short?

.
 
When reaming a hole to a specific dimension and shape, the entire success of the operation depends on not allowing the reamer to get in a bind, whether by mis-alignment of the parts involved, or allowing shavings to become clogged in the flutes.

Follow Jerry's advice.
 
Straight Boring

coyotechet said:
Here is the only way I have found to accurately every time get the bore alinement to .0001 each end then drill and bore it to size. Very fast and accurate each time. I use aluminum strip's under the set screws .
Chet


View attachment 17594
Click to expand...


that is a correct set-up........... same way a receiver is done...... same effect as steady rest..... adjustable at both ends...........
bill
 
alinwa said:
To the op, Chet's right on altho I'll have to disagree re "very fast" as it always takes me some time to get dialed in ;) BUT.....

This is the method I used when I mention bearing off of rings.

I've used AL and brass shims, pennies and AL pads and found it easy to warp the die body with the four-jaw. Maybe I'm just ham-handed.

I tried sections of thicker AL with 45* grooves, even bored and slitted apart some heavy fitted shims but in the end found that FOR ME bearing off of threaded die lock rings on the threads was safest.
Click to expand...
Also, size does matter. For myself I had no issues with PPC's, BR's, even 308/30-06, but once't I got into bigger/fatter stuff the items I mentioned became problems.
 
Would the fact that the reamer becomes unsupported after about 1/2" of introducing it to the blank cause the oversizing?
My second attempt with the ptg blank went very well and it has a through hole the lengh of the die.
Well...perhaps a relative term, but for as well as I am able to measure.
 
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