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Bone screw machining

 
Machining challenge is to avoid burr formation in milled features in the tip when doing the thread whirling operation.
 
Benefits
  • Good surface finish
  • Secure process
Machining solution
  1. Turning of tip
  2. Milling of grooves
  3. Thread whirling of tip (for more information, see below)
  4. Deburring pass with mill
  5. Thread whirling complete 
Machining solution – thread whirling of tip
 
​​
​​Thread whirling
Tool:
​HolderCoroMill® 325, whirling ring
​Insert​325R16-150HAF01 1105​
 ​
​​​Typical cutting data for the operation:
​vc​50–90 m/min (164.–295. ft/min)
​fz​0.01 – 0.03 mm/tooth
(0.0004–0.001 in/tooth)​
     ​  
 
Selected component features

 

bone-screw-tip-060159.jpg

 

 
Machining the long and slender thread is preferably made by thread whirling to avoid bending and vibrations.
 
Thread quality is a challenge when high feeds are used in the thread whirling. Facets is a common problem. 
 
If the thread diameter is changed, the setting angle of the whirling ring has to be changed too. Use the calculator for correct programming.
 
Every whirling spindle has a gear box reduction, due to size restrictions of the unit. Remember to take this into consideration. The programmed rpm will not the actual output. In our case the reduction was 50 %. 
 
Benefits
  • Good surface finish
  • Good dimensional accuracy
  • Secure process
  • Productive
Machining solution (example) 

​Thread length​45 mm (1.772 inch)
​Total component ​length​50 mm (1.969 inch)
​Outer thread diameter​6 mm (0.236 inch)
​Core thread diameter​4.90 mm (0.193 inch)
​Maximal depth of cut​1.625 mm (0.064 inch)​
     
Machining solution – thread whirling
 
The cutting data as below will give a good cutting process with acceptable
sound levels. It is possible to surpass these values, but the sound level will
increase rapidly and facets are formed. 

 
​​
​​Thread whirling
Tool:
​Whirling cutterCoroMill® 325 whirling ring
​Insert​​GC1105 (325R16-150HAF01 1105)​ ​
 ​
​​​Typical cutting data:
​ap​~1.6 mm (0.063 inch)
​vc​50–90 m/min (164–295 ft/min)
​fn​0.01–0.03 mm/tooth
(0.0004–0.001 in/tooth)​
     ​  
 
bone-screw-thread-2-060159.jpg

Machining head

Machining solution – Head 

  1. Turning front of head
  2. Roughing back of head
  3. Finishing back of head
  4. Parting off
Benefits
  • Chip control
  • Secure process
bone-screw-head-060159.jpg

 
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