Can someone please explain how to

[gray wolf]

I have been told, and read about using a split dowel with wet & dry paper to open a sizing die.
I understand how to do it with a metal rod and rolling it on a flat surface.
But I am not sure about the split dowel process. How do you get a concentric hole with a piece of sanding paper flopping around while sitting in the slotted dowel.
Can someone explain how this works ?
I would like to open a Lee push through sizer die.
I tried rolling it with the metal rod wrapped with the sand paper, but the area that does the sizing is small. That made the die wobble a little.
So I think I need a different approach.

Thank you

sam

[williamwaco]

Split the dowel.
Slide the paper into the slit and wrap it around the dowel so that the grit is "out" all the way around the dowel. Wrap it around about twice. At this point, the dowel with the paper wrapped around it should fit loosely in the die. If it doesn't, get a smaller dowel.

Chuck the dowel in your electric drill. When the drill spins, centrifugal force will force the edge of the paper outwards and into contact with the inside of the die. If you can keep the dowel reasonably parallel with the inside of the die the centrifugal force will keep it centered and the result will be concentric and perfectly round ( at least as round as the original die.)

The split in the dowel should be long enough that the paper goes all the way through the die do you don't have to work it back and forth.

[paul h]

If you really want to do it properly, use an expanding lap that you can get from a machine shop. Using a split dowel and sandpaper flopping around will produce a belled out sizer, and you really have no control or gurantee you'll be producing a round concentric hole.

As to why some use such techniques, they are cheap and easy, and not everyone is as concerned with preciseness of their end product.

[R.M.]

If you're only taking out .001" or so, how much damage can you do?

[randyrat]

Be careful, go slow,check often and save a little in the end to finish it with 400 to 600 grit sandpaper.
It doesn't take long to open a push thru sizer die 1K

[MtGun44]

Also don't push or pull it in and out too far, you want only a small amount of unsupported
paper hanging out the ends of the hole so that it doesn't start to cone out from centrifugal
force and funnel the ends of the hole. If it stays inside so that say 1/4" hangs out at most,
the hole will stay cylindrical.

Bill

[Guesser]

I have polished hydraulic control valve bores using the small "ball" hones, with great success, no out of spec "egging". Why wouldn't a ball hone with the die in a 3 chuck bench top lathe do the job?
I need to open up a 410 and a 430 and intend to do it with the ball hone.
Anyone?

[Plinkster]

Guesser that'd be a great method, most folks use the dowel and paper for speed and more so I would say from lack of lathe access. Lapping is preferred, paper is cheap lol.

[44man]

I use a split rod, steel or brass. I wrap the paper tight so I can barely get it forced into the die as it spins. If it wears, I reverse the paper end for end.
Takes a minute or so the get the right length so I start with a longer piece and cut off a little at a time until it goes in.
That will round out an oblong hole.
I do not like the "flop" method.
I use the rolls of abrasive cloth that machinists use.
I forgot, I use a variable speed drill, battery.

[Guesser]

I'm going to try the ball hones, I've got some of the right dimension. I'll report back.

[gray wolf]

Great Info guys,
but you got to remember this is shade tree work.
I have no access to any fancy machines. Has anyone ever tried a lead lap ?
As in a bullet with a cleaning rod screwed into one end and using compound.
The way they used to lab barrels.

[Longwood]

I'm going to try the ball hones, I've got some of the right dimension. I'll report back.

Good idea,,,
Honing with paper wrapped around a rod can make a hole out of round.
If you do stuff like putting tape in molds in order too cast oblong bullets, then go for the rod and paper wrap.

[76 WARLOCK]

I do it exactly as 44Man said and it works well.

[captaint]

I, too, have used 44man's method. It works. I only had to open my die .0015. So, go slow, check often. It works. Mike

[LongPoint]

Using either a wooden or metal split dowel, put enough wraps of wet-or-dry paper or emery cloth on it to make a few wraps on the dowel. It don't have to be tight in the die. It needs to stick out of both ends of the die so you can hold onto the paper. Stick the dowel and paper through the die and roll the die on your thigh a few back and forth strokes. As the paper wears, tear some off and go again. It only takes a couple minutes to lap a couple thousands out of a sizer die. I believe it was Buckshot that posted this a few years ago. Good Luck

LongPoint

[armednfree]

I've never done that too a sizing die but have done several dozen bushings for 45's. I never had any success with the sandpaper on a dowel rod. I always use the felt polishing pads from a dremel tool and lapping compound of progressively finer grit. Mounted in a drill press with the bushing in a vise.

Basically I take a screw with washers a bit smaller than the Desired diameter. I compress the felt between the washers and mount it in the drill press. I use a carpenters file to rough down the diameter of the felt. An old carpenters flat file, not one of these sheet metal pieces of junk.

Then I set the press at high speed and progressively reduce the grit until the hole is the right diameter. Of course as you change grits you also change the wheel. Takes time.

[wallenba]

I've done it two ways. First drill a small hole crosswise through the dowel to check the stop of the split. Wrap the emery around it in the direction of the turning. Slowly begin removing little bits of paper until you get a slight interference fit. Work it slowly at first, then 'wobble' it as you spin. Periodically, slug the die to check size. If it's slightly out of round it will be OK, as it will swage into the rifling when fired. Most I've done this way were round.

The other method I have used works a bit faster, so go easy. Cast a boolit (hard alloy), drill a hole in the base for a long drywall screw. Size the boolit with the die. Insert the screw in the boolit, cover it with lapping compound and lap the die using a cordless drill. Check as you go. The boolit really hangs on to the abrasive.

[leftiye]

Contrary to what some have said, the technique even when used with a drill motor to spin it does produce round holes. Remember, the rotation causes whatever part of the sandpaper might be "high" to contact the surface evenly all around. Kind of solves its own problems. Also, think for a moment on how out of round it is possible to get if only removing one, maybe two thousandths of an inch. Moving it forward and back on the hole further reduces the possibility of cutting one part of the die more than another. Torqueing the die on the dowell, on the other hand will most probly produce both out of round and uneven removal of steel from the die. Hold the die in the middle, and just enough to prevent it from turning in your hand. You could take it to an automotive machine shop and ask them to open it up on a Sunnen valve guide hone, but you may not get the diameter you specify, and you wouldn't be able to measure the difference between that and the one you rolled on your leg.