Lapping Suggestions

[boostin53]

So I'm making some parts that are 1.8" long out of O1 steel. What I need is a thru hole that is .448-.449" with as smooth of a finish as my diamond lapping paste will give me. At the moment, I bored the holes out to .446" +/- .001" with a boring bar that I made.

Now I'm stuck trying to figure out how to lap it to final diameter. I could buy a lap that will work, but the wife wont allow me to buy anything at the moment.

So, what could I make to do the job? I was thinking of turning a taper on an aluminum rod that had a measurement of .447" on one end and maybe .444" on the other end. The shank would also be .447" for about 2.5" to allow me to pass the entire length thru the part. And chucking it in the tailstock, part in the headstock, lathe on the slowest speed and slowly hand feeding it in. My reasoning is that the lap is tapered and will work its way up to the final diameter. Then I could hand lap the last .001" for my mirror finish.

Anything seem wrong about this? Does anybody have a better idea, withought purchasing things? Lol

 

[joshua43214]

We need to put things in better perspective. In the long run, what is more important, a spouse that says "no," or a new tool that is always ready for you and will always say "yes?"
I'm pretty sure you can order a new spouse from overseas...
Just a thought

Lead or tin make the better laps. If you are a re-loader, melt some bullets down in one of your wife's pots and cast the lap right into the bore. drill a pilot hole in one end and run a screw into it and chuck it into the drill. Cut some spiral grooves in the sides with one of your wife's paring knives so there is a place for the compound to go. Lap away. When it gets too small, ovalize it with a light hammer until it is a snug fit again. Not only will you get a nice lap, your wife probably won't forbid you to buy a tool next time...

The classic method for making a lap is to use a dowel. Cut spiral grooves like above. Cut a groove around the circumference at the end for a binding wire. Saw the dowel in half up the length. Use paper shims in the saw kerf, bind the kerf closed onto the shims with soft wire. People have been doing this for ever, it really produces great results. Harder wood does make a better lap, but a hardware store dowel is probably fine. You can always make a dowel on the lathe from your wife's oak cutting board.

A tapered lap will produce a tapered hole. It is not bad to have a taper at one end for getting the lap started, but the body where the lapping takes place should be strait.

 

[boostin53]

My thoughts of the taper would be that the taper would gradually open it up closer to .449" as it gets deeper. And a long shank of the required size wouldnt be tapered. So using the taper to get to the final size. And the shank used to evenlt lap it out.

I am a reloader, and caster. I will try the lead method first. What I'm making are core seating dies for bullet swaging. Im making two sets of 45 cal then a 40 cal set. Making two sets of 45, one for me and another for a friend.

And about the wife, she lets me buy things often. Shes actually very understanding about the stuff I "need". But we recently had to do a bunch of repairs around the house and she doesnt want to get into our saving account for things that really can wait.

 

[Uglydog]

Ah...
I've attached a document I've found interesting.
She's a 1907 reprint of lots of stuff including making your own laps. Old school. Making your tooling instead of calling up ... and placing an order.
If you give it a go, please let us know how it works.

Daryl
MN

 

[boostin53]

Ah...
I've attached a document I've found interesting.
She's a 1907 reprint of lots of stuff including making your own laps. Old school. Making your tooling instead of calling up ... and placing an order.
If you give it a go, please let us know how it works.

Daryl
MN

I would love to study this document, but it's not showing up on my phone. It just opens another page and the page is blank. Im at work and don't have access to a computer.

 

[Uglydog]

25page pdf excerpt from much larger text.

Daryl
MN

 

[joshua43214]

There is a really long thread somewhere in this topic. I think it is at the PracticalMachinist, and it runs like 40 pages. Probably the best thread I have read on the subject. I also plan to do this at some point since Mr. Corby is not responding to my emails.
Search around for it, it has a bunch or excellent details on material selection and hole forming, I think the OP is the guy that sells the dies for converting 22lr to .223 jackets.
I am pretty sure he used lead laps in the end. I remember him posting a series of pics of the laps and the holes.

Keep us posted

 

[Uglydog]

If somebody finds links. Then please post them here.

Thank you,
Daryl
MN

 

[Wreck™Wreck]

Round lap, cast iron or brass like so.
http://www.newmantools.com/lapping/flexlap.htm, you can probably buy one from McMaster-Carr

I did one repeating job in the past that required such a tool, .5005 bore, .0005 large or .0005 to small and it simply would not work.

Adjust the lap with a Mic, charge it with abrasive and go to town, this is a maddening process on a manual machine.
Excellent finish and sizing however. Making one part as a hobby is different than making 100 for profit, I would not recommend making this a habit.
The only reasonable way to measure such a feature is gauge pins, a drawer full of Starrett inside micrometers will not do it. This is closing on air gauge land, you do not wan't to go there.

 

[boostin53]

There is a really long thread somewhere in this topic. I think it is at the PracticalMachinist, and it runs like 40 pages. Probably the best thread I have read on the subject. I also plan to do this at some point since Mr. Corby is not responding to my emails.
Search around for it, it has a bunch or excellent details on material selection and hole forming, I think the OP is the guy that sells the dies for converting 22lr to .223 jackets.
I am pretty sure he used lead laps in the end. I remember him posting a series of pics of the laps and the holes.

Keep us posted

I have a set of 22lr to .224" dies and use them a bunch. Mr Larry Blackmon made them, I also bought his BSSP press. Which is very similar to the SAS Mity Mit press. My 22lr to .224" projectiles are mainly for blasting/plinking ammo. I have J4 jackets to make accurate bullets. I also have a set of CH4D 101 swage dies in 40 cal. I want to make my own so I can control every aspect about them. Mainly in the point forming die.

The dies I'm making aren't for a standard reloading press. My next attampt will be a one step die similar to BTsnipers on the castboolits forum. I just cant justify spending more money on swage dies if I can make them. With practice, I should be able to make whatever I want.