Author Topic: Barrel Laps  (Read 878 times)

Offline cfellows

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Barrel Laps
« on: August 28, 2018, 03:43:23 AM »
Bought a used set of Federal Flexolaps on Ebay and they arrived today.  Unfortunately, the one I needed most, 3/8", was pretty well worn.  Replacement barrels, in general, are not expensive, but couldn't find anything explicitly for the Flexolap.  Acro and generic seem to be all that's available.  And, not knowing if the thread and taper sizes match, I decided to just make my own.  Here's are the three parts to each lapping tool...

This particular one is about .400, maybe metric.  Anyway, the thread size on the 3/8" lap was M8-1mm.  The pilot hole for the 8mm thread extends in about 1/2" before the taper begins on each end.   The tapered pin is pretty close to 7 degrees.  The thread sizes changes for the bigger and smaller laps, but I expect the taper remains the same.  The smaller, through hole in the barrel is a smidge larger than the tip of the tapered pin.   There are 5 axial slits around the circumference of the barrel.  I cut these with a .032" slitting saw.  I also made a D-style taper reamer to ream the inside of the brass barrel.

After seeing how this thing works, I suspect a simple wooden dowel with one slit through the middle for an expansion shim would have worked just as well.  Oh well, live and learn.

So many projects, so little time...

Offline Mcgyver

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Re: Barrel Laps
« Reply #1 on: September 09, 2018, 03:20:08 PM »
I think you did well.   imo its not a wasted effort in that I don't think the wood would be satisfactory.  It might have polished the bore, but lapping lets you get a bore that is also very round and straight.   Have you used it, how did it work?