Limitation for use of abrasive grinding wheel

I'd have it checked by a dealer, or reliable brake shop.
Brakes are not a good thing to DIY.

Most likely your rear brake shoes are worn down far beyond the min limits and you now have metal to metal contact, which causes the grinding noise, overheating and poor braking. You most likely will need to replace the drums. The other rear wheel will probably be the same.

I could be a bad plug or a frade power cord. Whith the grinder unplugged make sure the grinding wheel turns by hand. If it does it could be a bad on off switch or the brushes in the motor could be worn.

3-Series (Except M3, M Roadster, M Coupe, 318ti & Z3)

1. Raise and support vehicle. Remove wheel(s).
2. Remove axle shaft. See appropriate AXLE SHAFTS article.
3. Remove brake disc. See BRAKE DISC .
4. Screw special tool (33 2 116) onto drive flange with wheel studs. Drive out drive flange with special tool (33 4 201/202/203). See Fig. 33.
5. If necessary, pull off bearing inner race using special tool (00 7 500) and a thrust piece. See Fig. 34.
6. It may be necessary to remove inner wheel bearing race with the following procedure:

• Detach wheel bearing inner race with special tool (33 4 400) through groove in bearing inner race.
• According to outside diameter of bearing inner race, use special tool 33 4 401 with: 33 4 405 for dia. 45-51 mm, 33 4 406 for dia. 50-55 mm and 33 4 407 for dia. 55-61 mm in groove. See Fig. 35.
• Tension special tool 33 4 401 with wrenches 33 4 403 and 33 4 404 until it can still just be turned in groove. See Fig. 36 .
• Screw in special tool 33 4 402. Detach inner bearing race.

7. Remove circlip. See Fig. 37 .
8. Remove wheel bearing with special tool 33 4 031/ 041/ 042/ 043/ 045. See Fig. 38 .

CAUTION: Do not reuse old wheel bearing.

9. Draw in new wheel bearing with special tool 33 4 041/ 042/ 043/ 047. For inner bearing race 42 mm use special tool 33 4 049 and for 39 mm use 33 4 046. See Fig. 39 .
10. Installation is reverse of removal.
11. Replace stretched or damaged circlip. Ensure correct seating.
12. Pull in drive flange using special tool 33 4 041/ 042/ 043/ 045/ 048. See Fig. 40 .
13. Install brake disc.
14. Install axle shaft.

I believe the thread is left hand, but close inspection should verify. Also you should never over tighten cutoff wheels or grinding wheels. You should be able to remove with a gloved hand while holding button on top with the other hand

Grinding chrome is not recomended on a bench grinder

You can use it down as far as you want,

TORQUE VALUE CHART

7/16" dia. 50 to 60 lb-ft

12mm dia. 70 to 80 lb-ft

1/2" dia. 80 to 90 lb-ft

5/8" dia. 110 to 125 lb-ft

*Use this chart to get correct torque values for each size wheel stud. I hope this helps and don't forget to rate my answer.