Lapping Suggestions

I looked at those Acro barrel laps. They are priced very fair! I didnt even bother looking at prices on laps before. I believe the wife wont even know if I purchased them. So I'm going to order a few. I was thinking laps would be more expensive. Guess not.

I will however research and try other methods such as the lead lap for fun. Plus I will need to use a lead lap for polishing the point form die when complete. I already have the "D" bit/spoon cutter for the bullets I want made. Just have to grind down one more and hone its edge.
 
joshua43214 said:
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.
Click to expand...

Would dead soft lead be better than a harder alloy? I have plenty of lead and can blend for pretty much any hardness I need. Just wondering what would work better.
 
It appears that you are intending to lap about 0.002 - 0.003" out of a 0.448"ish hole. That strikes me as a lot of material for a lap. Boring to 0.447±0.0005" is not to tough - then you have a lot less material to remove with the lap. Better yet, bore to 0.445, then use a D-bit and take it to 0.4475±a small amount, then you have even less to lap. As "Wreck" pointed out, the challenge will probably be in the measuring - both for actual size and then uniformity of size. 0.4485"±0.0005" over 1.8" should be doable (if it were me I'd likely end up with several scrap ones first). Consider numerous sized pins (for which you may need to make an OD lap) to determine if you have taper and a ball gauge and mike will get you close on size.

Interesting challenge. Let us know how it works out.
 
I've already bored out to .446". Just need .002" to go. I don't mind taking the time to do it. I made the boring bar I used from hardened O1 since I didn't have a boring bar this small on hand. While it's not the best, it worked to get me to .446". It doesn't leave too great of a finish. That's why I stopped at .446". And I already have pin gauges to check the bore when I get a decent finish started. As it sits right now, it has a rough finish from my crappy boring bar. If all else fails, I will make another one and learn from my mistakes.
 
I found one of the threads, it was over at the castboolits forum
http://castboolits.gunloads.com/showthread.php?75201-Home-made-dies
You will find it very informative. A long read but worth it.

I have been working on methods for forming jackets using copper tube since getting .30 jackets is really hard at times. It would be built around Richard Corbin's Walnut Hill press, though hopefully it will also fit the S-press or Mega-Mite.
I also have a few ideas for quickly forming cutters and laps combined with a way of making the dies that might seriously speed the whole process up. I hope to offer them for sale at some point in the future.
 
boostin53 said:
I've already bored out to .446". Just need .002" to go.
Click to expand...
Here is a cylinder liner lap progression I'm making for my model radial engine using Acro brass barrel lap. For the tool price it wasn't worth me making one, especially because barrels can be purchased separately. I think this pic may have been cast iron, but not sure, I experimented with a few materials.

2-thou doesn't sound like much but it can be depending on the material. Even with a nice visual boring bar finish, even relatively coarse lapping compound like 400-600 will highlight hills & valleys. The first thou or so will cut quite quick as its lopping off the tops of the hills but not the valleys. But its a mat finish like shown. Once you are past the undulations & fully lapping the entire bore diameter material, it slows down quite a bit. Once you start increasing grit to 1000+ progress seems to come to a crawl. At your particular bore dimension have you considered buying a sized reamer & go say 1-thou undersize? It will A) be a better finish than you can (easily) achieve with boring bar & B) that much less material to lap. Oh, BTW you are not supposed to use the same lap for different grits. Also remember to let your part temp stabilize & remove all signs of compound before measuring (tedious!). Not sure about your lapping compound but my silicon carbide grease seems best removed with WD40. Good luck!

IMG_0728_edited-1.jpg

400g lap step-1.JPG
 
...I've lapped out thousands of holes (Carbide and Tool Steel tooling) with both "store bought" and my homemade laps. All out of soft steel or brass with a split or spreadable eye at the end of the lap to pry ("spring out") for pressure and hold the lapping compound with usually coarse, then medium, then fine (IE Brown, then Blue, then Pink diamond paste)...
...However, remember that leaving so much stock in a hole can result in taper, "belly" and/or "bellmouth" very easily so when I didn't have a Sunnen Hone available for the bigger holes, I left no more than .0005 in the hole (actually, all holes that need to be lapped or honed to size and for finish I always tried to hit from the Machine Tool leaving no more than .0005 stock in the hole (with still a good finish like around 16 to 24 rms at worst) ) knowing that the longer I have to lap or hone, the more distortion (taper and/or bellmouth) I'm apt to get....anyway, leaving .0005 = a couple of "swipes" (in a lathe or mill or drill press or even by hand) with coarse, a couple of swipes with medium until the go gage barely starts or the telescoping gage or whatever reads, then high finish with fine to size (I even wrap a hone arbor with note paper and smear some fine paste on it for a mirror ID finish for waaaay longer life of the hole ifn' the hole is a wear surface or even a press fit with an OD

PS Always have/use a separate, specified laps for different grits of lapping compound as, for example, once you smear coarse compound on a soft lap and use it, it is now "charged" (imbeded) with coarse
 
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...oops, upon further thought and memory (Hey! I heard that!)...leaving only .0005 to lap or hone for a 1/2" hole may be cutting it a little close for a beginner...shoot for .001 stock left in the hole with a good finish...but my point is is much of this has to do with the finish in the hole now, what finish you want... and the more time you spend lapping or honing to size the more problems in the hole can happen
 
Add: In the olden days a steel bushing fit to slide on a post was usually left without a high finish in the hole of the bushing to "hold" the oil or lube...later; Steel Bushings with a higher finish and with a oil groove spireled machined in the ID of the hole were the norm (along with oilite bronze and ball bearing bushings)
 
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