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Velmex makes high quality
lead screws by rolling through precision dies.
They are used in our positioning
equipment. You
can also buy the lead screws alone. Sizes
And we can combine
left and right hand threads on a single shaft for together
+ apart motion. |
Photo 1 |
Material
Our lead screws are 303 stainless steel,
except the 5 and 10 pitch (Code: W1, W2 and P5, P10) lead
screws which are electroless nickel plated, cold rolled steel. |
Lead Screw Accuracy
The linear accuracy of Standard lead screws is 0.007”/10" or less.
The linear accuracy of Graduated Knob Model is more accurate. Called Precision Grade it is 0.0015”/10” or 0.033 mm/20 cm of length. See Velmex screw
letter codes. |
Thrust
Bearing Design
A15 and A25 lead screws are constrained
and supported with pre-loaded DelrinŽ thrust bearings (except
A25 W1, and P10, which have pre-loaded ball bearings). A40,
A60 and B90 lead screws have pre-loaded ball bearings. Details |
Back driving
Because of their steep helix angle,
5 and 2.5 pitch screws (W2, W4, P5 and P2.5), may back drive
(coast back down) when supporting a vertical load or, if horizontal,
a linear thrust load is applied. If you want the slide to stay
where you put it, be aware of this characteristic and use a
finer pitch screw and/or lock. |
Available lead screw diameters and pitches.
| Pitch |
Diameter |
| Turns
per inch |
English Thread Lead
Screws |
| 0.25" |
0.375" |
0.50" |
| 2.5 * |
no |
yes |
yes |
| 5 * |
no |
yes |
yes |
| 10 |
no |
yes |
yes |
| 20 |
yes |
yes |
yes |
40 |
yes |
yes |
yes |
| Maximum
length available |
3 ft. |
8 ft. |
8 ft. |
| Turns
per centimeter |
Metric Thread Lead
Screws |
| 7 mm |
10 mm |
14 mm |
| 5 |
yes |
yes |
yes |
| 10 |
yes |
yes |
yes |
| Maximum
length available |
3 ft. |
8 ft. |
8 ft. |
*Not recommended for vertical units because it
will back drive.
Lead Screw Letter Codes
In Velmex model numbers, lead screws are specified by a letter/number after
the base length. This table defines the letter. Accuracy
Pitch |
UniSlide Letter Code |
XSlide
Code |
BiSlide® Code |
Turns
per inch |
Advance
per revolution |
|
|
|
Standard |
Precision |
Standard* |
Standard |
2.5 |
0.400" |
W4 |
P2.5 |
E04 |
E04 |
5 |
0.200" |
W2 |
P5 |
E02 |
-- |
10 |
0.100" |
W1 |
P10 |
E01 |
E01 |
20 |
0.050" |
B |
P20 |
E50 |
-- |
40 |
0.025" |
C |
P40 |
E25 |
-- |
Turns
per cm |
Advance
per revolution |
|
|
|
Standard |
Precision |
Standard* |
|
5 |
2 mm |
K2 |
Q2 |
M02 |
M02 |
10 |
1 mm |
K1 |
Q1 |
M01 |
M01 |
* More accurate screws are optional. Call Velmex.
Drive Nuts
 
| Photo 3a Tension adjustable UniSlide drive
nut made of Delrin AF®. XSlide also uses Delrin AF. |
Photo 3b Tension adjustable BiSlide drive
nut made from low friction polymer |
| Photo 3c Tension adjustable XSlide drive
nut made of Delrin AF®. >>> |
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End Bearing Block and Thrust bearings
The End Bearing Block supports and constrains the
lead screw
Photo 4: This design is for small diameter (1/4"
or 7 mm) lead screws.
It uses Delrin bearings and threaded retainer nut.
Photos 5 and 6: Threaded retainer nut and wrench P-N A15-A25W
Photo 7: Split Delrin thrust bearings
Photo 8: All other lead screws use
steel bearings and snap ring retainer.
Used with 3/8", 1/2", 10 and 14 mm diameter lead screws
Photo 9: Lead screw with two R4 Bearing separated by 2 E clips.
In the photo below the regular end bearing block has been replaced
by translucent pink plastic.
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