Author Topic: Lapping machine?  (Read 485 times)

Offline Scota4570

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Lapping machine?
« on: November 17, 2020, 08:01:39 PM »
I have lead lapped several barrels.  I have three I want to do.  Removing enough material to clean up a bore and create a choke is physically demanding.  I am not up to that anymore. 

I was thinking of making a machine to move the rod back and forth.  My first thought is using a lever that rotates on a spindle at low speed.  That could be done with a gear box or pullies.
The lever  links to a rod in a tube to straighten the movement.  That rod links to the lapping rod.  A 5" lever would give a 10" stroke.   The barrel could be moved back and forth in a carriage to cover the whole barrel.   

Has anyone made something that does this job?


Offline D. Taylor Sapergia

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Re: Lapping machine?
« Reply #1 on: November 17, 2020, 08:19:27 PM »
My experience with lapping is limited to only one rifle barrel.  The purpose in my case was to remove a frosting of rust in an otherwise good barrel.  the frosting was caused by the owner using boiling water to clean his rifle, for several years.  Each time the barrel flash rusted, getting worse and worse until loading was difficult and cleaning  between shots became necessary.
There is a feel happening in the process that tells you that the lap is actually cutting.  I think this contact feel would be missing in a machine operated system.
D. Taylor Sapergia
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Offline rich pierce

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Re: Lapping machine?
« Reply #2 on: November 17, 2020, 09:13:34 PM »
I agree with Taylor on this. I could also see tight and loose spots happening without that feel.
St. Louis, Missouri

Offline Scota4570

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Re: Lapping machine?
« Reply #3 on: November 17, 2020, 09:23:10 PM »
I must be doing it wrong.  I start with clover 120 grit.  I cast the lap on 10-32 all thread.  Jam nuts expand it as I go.  IT takes hours to remove any significant material.  Half a thousands takes most of the day.  I end up with sore shoulder and elbow with a blister on my palm. 

Is there a sharper abrasive I should be using?

I got this idea from the Ruger custom shop.   They use a machine to lap bores, or at least used to.  Their machine did cover the barrel length in one stroke though.

Offline Maineshops

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Re: Lapping machine?
« Reply #4 on: November 18, 2020, 06:36:14 PM »
I think I would get a car seat meter and rig a lever assembly to increase the stroke. Use a dpdt switch or micro switches t reverse the streak? Just a thought... or get a 5lead thread and nut and use a windo Moyer...Dan

Offline JPK

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Re: Lapping machine?
« Reply #5 on: November 18, 2020, 08:03:24 PM »
I lapped a number of barrels in my youth and have thought of making a machine to do it. The basic idea is a wheel that is turned slowly to operate a rod. Picture a steam locomotives drive wheel. The attachment point of the rod would  be adjustable on the wheel to alter the length of the stroke. This rod would attach to anther rod that would translate the movement into a controlled straight stroke to which the lapping rod attaches. With this contraption the length and location of the lapping would be selected by the operator and could be powered by hand but better yet a motor. Some one that feels they would lap enough barrels to justify the space and effort may want to build it.
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Offline Machinist John

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Re: Lapping machine?
« Reply #6 on: November 21, 2020, 03:03:18 AM »
This one works great.

Two ball bearings in the center portion.    A pair of file handles for putting a lot of thrust into the laps.  Even has a grease fitting on the end to lubricate the bearings.  The lapping rod is interchangeable to a difference size.  Note the stop on the rod, it is adjustable for position to prevent pushing the lap out of the barrel.   The rod/lap rotates with the rifling, the handle does not turn, the bearings take care of that.



The laps are made of leather about 1/8" thick, oversize for the bore groove diameter.  In between each is a aluminum washer, turned to a little under bore diameter.     Clover compound is smeared over the lap and replenished as required by extending the lap about half way out of each end.    Leathers and washers fit over a long 10-32  ( or larger) socket head caps screw threaded into the end of the main rod.   The screw is tightened as required for good lapping.   I can get the barrel warm when lapping, so some work is being done!



I have adapters that thread over a external threaded breech for that style of barrel.   And some adapters threaded to match breech plug threads for that type of barrel.  The adapters center the rod in the  bore and provide a return stop to prevent pulling the lap out of the barrel.

Start with coarse clover compound, then progress to finer.

The beauty of the leather washers is I can squeeze them to a snug fit in the barrel by tightening up the screw.   No time consuming re-pouring of a lead lap when it wears.   And the leather holds more compound than the lead.

I clamp the barrel in a barrel vise so it will not move. 

« Last Edit: November 21, 2020, 03:09:07 AM by Machinist John »

Offline Scota4570

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Re: Lapping machine?
« Reply #7 on: November 24, 2020, 01:45:20 AM »
I never understood fancy ball bearing rods.  I don't screw the lap jag tight on the rod and it spins freely. 

The "jag" is used the other day had opposing cones that were drawn together on the arbor by screwing the arbor deeper into the rod.  That expanded the lap as it wears.