Perplexed - A Little Help Needed

A couple more thoughts.
My calipers is off by .009 when measuring depth. I always have to adjust the zero before each depth measurement and then adjust it back for "normal" OD measurements. Check yours and also double check your DRO with something of a known dimension.

The slot being to narrow could be the caliper reading incorrectly for inside dimensions, or it could be flex of the machine and or the cutter. 1.248 deep x .126 side cut is a pretty big cut, something is bending. Are you climb milling or conventional milling?
Use the DRO and the calipers to measure the slot width. if they do not agree then you need to get something with a known inside dimension to find out which is correct.
 
I'm certainly no expert.
Just curious, why carbide? Aluminum likes sharp HSS end mills in my experience.
Accuracy is not an accident. Good for you to make practice cuts on a blank.
Someone will be along with more than worthless information.
I tried cutting one of those 80% lowers on my wore out Bridgeport. Accuracy was not part of my experience due to the slop in the table, gibs, quill, spindle etc.
Good luck.
I hope that was before they were outlawed in Ca., Jeff ------- I had one that had to be "destroyed" because of being in an illegal form, did the 80% lower thing and re registered it with mods to make it legal, then came the new law, presently in force; I had a licensed dealer (class 10) friend sell it out of state; lost money, seems the bottom dropped out of the AR market. Besides the law, it was not to my taste, I like vintage big bores.
 
Did California make a law after this last earthquake that makes it illegal for people to work on their own cars at home? I heard that somewhere and couldn't believe it.
 
I understand wanting to keep your neighbors from going full on Fred Sandford and all but that is Ridiculous!
 
I've been telling my friends that eventually personal internal combustion will be so expensive as to be essentially impossible for the non-wealthy
In fact, if the government rescinds the smog exemption for pre-'75 cars there will be riots in the streets, especially in LA
This has been a public service message.
 
I have lived in Sacramento for almost 60 years, work on my car regularly in the garage, quietly with the door closed, don't use my automotive air tools, and am not concerned in the slightest about this legislation. It is a non issue. I am in an ordinary neighborhood and my neighbors and I all get along well. I have always gone out of my way to not make annoying noise when people are sleeping or on early weekend and holiday mornings. I get annoyed myself when someone is making too much noise during quiet hours, even if it is from their lawnmower. This is mostly about people doing things that are well beyond normal working on their own stuff. I have zero concerns about this legislation, though it does reek of silly ninnies. 'Nuff said...
 
I have lived in Sacramento for almost 60 years, work on my car regularly in the garage, quietly with the door closed, don't use my automotive air tools, and am not concerned in the slightest about this legislation. It is a non issue. I am in an ordinary neighborhood and my neighbors and I all get along well. I have always gone out of my way to not make annoying noise when people are sleeping or on early weekend and holiday mornings. I get annoyed myself when someone is making too much noise during quiet hours, even if it is from their lawnmower. This is mostly about people doing things that are well beyond normal working on their own stuff. I have zero concerns about this legislation, though it does reek of silly ninnies. 'Nuff said...
+1, you go Bob! If you read the reply's there is some interesting stuff, mostly nattering ninnies menthinks.. I do next to no auto repair anymore, thankfully. But I do all the service work on our cars with no problem. I guess it depends on the area but I don't have any problems and I have neighbors who's wood working equipment and yard equipment is way louder than my metal working stuff. I'm very carefull to work during the day when 90%of the neighborhood is gone. I have one neighbor who seems to be a collector of marginally operational transportation with 4 cars(two barely functional) two motorcycles, a scooter, gas powered rubber raft, and the latest a gas powered golfcart. Nice guy but firmly in the what we called the "rev to repair" camp. The golfcart is just worn out. Smokes so bad, stinks and will barely start. And when it does they spend all their time trying to rev it up over and over. The only reason I don't ask him to stop is the smoke blows right into his house. :) Thankfully it's parked. My other neighbors car died over 6mo ago and is just sitting in their driveway. And as long as it's in the driveway and not an eyesore seems nobody cares.
 
This is all well and good but what does it have to do with the original posters machining problem. Remember this is a machining forum we should be talking about machining and solving this guys machining problem.

Just my 2 cents
Roger L
 
Nyala,
Have you ever checked the accuracy of your equipment?
The reason I ask, you may need to make adjustments to improve accuracy or the ability to repeat cuts.
I haven't done this yet on my newer equipment but out of curiosity I drew a plan and tried to produce the part with my old Bridgeport.
I found if I locked the table and quill whenever I could the accuracy improved.
The reason I say this is you seem to be struggling with under and over cuts.
A DRO is a great tool as it measures movement regardless of backlash. As I was making an X cut I noticed the Y was drifting = not good.
Food for thought.
The beauty of the AR platform is it's versatility and endless ways of adapting or personalizing your firearm.
Don't own any since the new laws. Not worth it if you can't even go to a range without worrying about getting arrested or having your investment seized.
 
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