DanielBauen.com
Prazi MD65 (SD300) Lathe
Click here to view a Tear Down of the Prazi Lathe at the Take Aparts website.
Made an incredible find on Craigslist. A Prazi MD65 (SD300) lathe and BFE65 milling head brand new in the box, straight from East Germany in 1988!
Quick Change Tool Post (QCTP) Holder
- 0XA Tormach - Designed for mini-lathes, but have to check height on the prazi. Maybe necessary to mill down the cross slide, or just remove it.
- Omni-Post - nice simple design. Indexable tool holders http://www.krfcompany.com/krfcatalog.pdf
CNC Conversion
Adding stepper motors to the lathe, primarly for threading, so I don't have to mess with the frustrating change gears.
Drive Side Dimensions
Handwheel Side Dimensions
Components!
Stepper Motor:
A belt drive with a 1:2 ratio will be used, so a ~280 oz-in stepper should suffice.
- NEMA 23 Stepper Motor: KL23H276-30-8A (1/4" Single Shaft with flat) 282 oz-in Specification Price: $39
Stepper Motor Driver:
- Stepper Motor Diver G251 1 Axis driver, $63.95, Specification from http://www.kelinginc.net
- Digital Stepper Driver KL-4042D, Heat Sink is included. Specification $59.95 from http://www.kelinginc.net
Drive Pulley:
XL timing belt drive pulley. Stepper has a 1/4inch motor shaft.
A 6A 3-16DF03708 has 16 teeth
Lathe Pulley:
The lathe drive shaft is 12mm in diameter. Stock Drive Products.has an XL timing belt pulley (0.200 pitch) with a 12mm bore.
A 6A 3M32DF09512 has 32 teeth.
Thrust Bearing:
There's already one thrust bearing on the drive side (left side of the lathe where the gears are) of the screw. To remove axial backlash for the stepper drive, another thrust bearing needs to be added to the right side of the screw, between the handle and the lathe.
- Metric, fits over a 12mm shaft, but not sheilded. A 7Z 7M1224
- Banded (Shielded thrust bearing), but closes size is 0.5in S9912Y-TB050121
Drive Belt
XL Timing Belt, 12.51 inches long according to CAD model.
The closest size SDP carries is 12.6 inches, which will work great! A 6R 3-063037
Drive Pulley Specs
| Part Number |
Pitch
|
No. Of Grooves
|
Material
|
Belt Width
|
Bore Size
Inch
|
Flange & Hub Configuration
|
Pitch Diameter
Inch
|
Outside Diameter
Inch
|
Overall Length
Inch
|
Hub Diameter
Inch
|
 A 6A 3-16DF03708 |
.200" (XL) | 16 | Aluminum Alloy | 0.375 | 0.250" | 2 Flanges / With Hub | 1.019" | 0.999" | 0.813" | 0.69" |
Lathe Pulley Specs
| Part Number |
Pitch
|
No. Of Grooves
|
Material
|
Belt Width
mm
|
Bore Size
mm
|
Flange & Hub Configuration
|
Pitch Diameter
mm
|
Outside Diameter
mm
|
Overall Length
mm
|
Hub Diameter
mm
|
| A 6A 3M32DF09512 |
5.08 mm (XL) | 32 | Aluminum Alloy | 9.50 | 12.00 | 2 Flanges / With Hub | 51.70 | 51.20 | 23.00 | 37.00 |
Thrust Bearing Specs
| Part Number |
Bore Size
|
Outside Diameter
|
Bearing Thickness
|
Mat'l(washers&balls)
|
Mat'l(retainer)
|
Load Rating
N @ 15 rpm
|
Load Rating
N @ 100 RPM
|
| A 7Z 7M1224 |
12.06 / 12.19 | 23.98 / 23.80 | 6.22 / 6.44 | Hardened Steel | Molded Nylon | 881 | 472 |
| Part Number |
A
Shaft Dia.
|
B
Outside Dia.
|
D
Bearing Width
|
Mat'l (washer&balls)
|
Mat'l (band)
|
Dyn. Capacity
lbf
|
Static Capacity
lbf
|
Max. Speed
rpm
|
| S9912Y-TB050121 |
0.500 | 1.219 | 0.563 | 52100 Chrome Steel | Low Carbon Steel | 3850 | 5600 | 7000 |
Timing Belt Specs:
Cost $5.89
| Part Number |
Belt Type
|
Pitch
|
No. Of Grooves
|
Belt Width
Inch
|
Material
|
Tension Member
|
Pitch Length
Inch
|
| A 6R 3-063037 |
Single Sided | .200" (XL) | 63 | 3/8" | Neoprene | Fiberglass | 12.60" |
