I would highly highly suggest watching Brownells' video on lapping your upper receiver. It is also important to make sure that if you do this to check that the shoulder on the threads is perpendicular to the bore of the receiver.
After the first run, you had lapping compound on the tool where it contacts the bore of the receiver. An effective way to increase the diameter of the receiver and wear out the anodizing. Oil works better on that part of the tool.
Observation: For any mated surfaces ... If you are going to "TRUE" one side of a mated pair, you need to know (or make sure) the other side is also "TRUE". If you're going to TRUE the receiver, you also need a method to TRUE the "Stop Ring" on that barrel.
7 месяцев назад+2
What about the barrels shoulder mating surface how to we know its perpendicular to the barrels center line?
Bingo • I knew if I scrolled down far enough someone else had to ask. Purchasing cheap uppers isn’t recommended. I saw the bulge in the mating surface. That’s the foundation of cascading failure. A drill press and a method of guaranteeing perpendicularity ± .0001” isn’t unreasonable. If you can’t establish a control, your best bet is to purchase an upper receiver from a reputable manufacturer. And, you still have to inspect it.
I am an SDI grad myself! Something I have found that helps accuracy after the lapping process, is using a little green loctight on the inside of the receiver where the barrel extension slides in. I tried this on my LR build during school and it improved the accuracy very well.
Assuming the face was not square and flat (as measured with a precision instrument) I damn sure wouldn’t allow you to use a hand drill on one of my upper receivers. Your time would be better spent doing some 5S activities.
The number of people who do things just to do them and feel good about them without understanding what is going on... Trying to get a precision anything using an electric drill motor by hand in a plastic block you tossed in a vice? Don't do this.Theres no way you're going to achieve concentricity with this setup You could be just as accurate with a sanding block and 800 grit sandpaper to flatten the face evenly.
The mandrill has the entire shaft to track inside the upper receiver. And even if the lapping surface isn't completely perfect, because it's spinning its still lapping evenly. With hand sanding you'd have to make sure your receiver is perfectly level, and then also make sure your sanding block and hand is perfectly level.
Some dykem or sharpie marker will help you to see the high and low spots a lot easier.
I would highly highly suggest watching Brownells' video on lapping your upper receiver. It is also important to make sure that if you do this to check that the shoulder on the threads is perpendicular to the bore of the receiver.
After the first run, you had lapping compound on the tool where it contacts the bore of the receiver. An effective way to increase the diameter of the receiver and wear out the anodizing. Oil works better on that part of the tool.
Suggestion… use a sharply marker to color the portion of the part you are truing so that you can have a much better visual indicator of your progress.
A little tip us to color the reciever end with sharpie and then it's super obvious when your flush
This is basically want you want to do for a legit SPR build. It's a basic part of accurizing the rifle.
Observation: For any mated surfaces ... If you are going to "TRUE" one side of a mated pair, you need to know (or make sure) the other side is also "TRUE". If you're going to TRUE the receiver, you also need a method to TRUE the "Stop Ring" on that barrel.
What about the barrels shoulder mating surface how to we know its perpendicular to the barrels center line?
Is the lapping compound aluminum oxide ? That's what I use in my shop ...just curious
i use valve lapping compound .
How do you address an uneven surface on the mating face of the barrel ring?
Those barrel extensions are machined as such that it is nearly impossible for that face to not be perpendicular to the cylinder.
Sooooo your gonna check headspace now right
Bingo • I knew if I scrolled down far enough someone else had to ask. Purchasing cheap uppers isn’t recommended. I saw the bulge in the mating surface. That’s the foundation of cascading failure. A drill press and a method of guaranteeing perpendicularity ± .0001” isn’t unreasonable. If you can’t establish a control, your best bet is to purchase an upper receiver from a reputable manufacturer. And, you still have to inspect it.
Headspace is not affected by this, but it's good you're thinking about it!
You should put some oil on the mandroll when you put it in the receiver.
Wouldn't this change the headspace?
Do you grind until all of the color is gone from the face of the receiver?
Thank you for the video; going to help a lot. May 22nd, looking forward to school and learning.
I am an SDI grad myself! Something I have found that helps accuracy after the lapping process, is using a little green loctight on the inside of the receiver where the barrel extension slides in. I tried this on my LR build during school and it improved the accuracy very well.
Assuming the face was not square and flat (as measured with a precision instrument) I damn sure wouldn’t allow you to use a hand drill on one of my upper receivers. Your time would be better spent doing some 5S activities.
Made me cringe, no oil on the guide and to high of speed.
Thank you for the awesome video I love sdi
This is dumb and not needed if your upper receiver was produced this millennia.
Can't wait to start my school, I start June 19
There are so many things wrong in this video.......
Can't recommend this method. Please look elsewhere folks
nothign wrong with it. I have done dozens.
The number of people who do things just to do them and feel good about them without understanding what is going on...
Trying to get a precision anything using an electric drill motor by hand in a plastic block you tossed in a vice?
Don't do this.Theres no way you're going to achieve concentricity with this setup
You could be just as accurate with a sanding block and 800 grit sandpaper to flatten the face evenly.
So how should be done then? What is the closest to perfect method in your mind?
The mandrill has the entire shaft to track inside the upper receiver. And even if the lapping surface isn't completely perfect, because it's spinning its still lapping evenly.
With hand sanding you'd have to make sure your receiver is perfectly level, and then also make sure your sanding block and hand is perfectly level.