Making J Type Head

From Wiki

Version 6

Material: Brass Bar Stock, 1/2" Square, 1.000" Long

Finished Weight: ~11.3 grams (will need verified)

  1. Cut a piece of brass bar stock 1 inch long plus enough to adequately hold the stock in the lathe.
  2. On the brass bar stock, find the center of the axis of the nozzle. (The axis is centered at 0.250 +-0.001, from one edge, and 0.157 -0.000 +0.003 from an adjacent edge.) This can be done by various means ranging from using a milling machine to using marking fluid, a height gauge, and a surface plate.
  3. Mount the brass bar stock in a 4-jaw chuck on a lathe. Adjust the chuck so that the nozzle axis is on center.
  4. Turn the threaded end of the nozzle down to 0.3125 +0.000 -0.004. This section is 0.500 +-0.005 long.
  5. For the first 0.150 +-0.010, of the threaded section, down to an OD of 0.255 (6.5mm) +0.000 -0.002.
  6. Thread the nozzle to 5/16-24 up to the shoulder of the heater section.
  7. Drill out the center of the nozzle with a 3.5mm drill bit. This will create a heat chamber that is the entire length of the brass nozzle.
  8. Remove the work piece and mount it by the threaded end so that the threaded end is centered in the lathe.
  9. Cut-off any excess material.
  10. Machine the nozzle tip to the desired profile leaving the heater block section 0.325 thick.
  11. Drill the nozzle orifice.
  12. Using a size C drill bit, drill the heater resistor hole through the heater block section. The remaining brass, between this hole and the edge opposite of the melt chamber, should be 0.020 +-0.002 thick.
  13. Drill the thermistor hole. (Change this....)

20130209 revised process

Material: Brass Bar Stock, 12.7mm (1/2") Square, 24mm long

Finished Weight: ~11.3 grams (will need verified)

  1. Cut a piece of brass bar stock 25mm (1 inch)
  2. Mount the brass bar stock in a 4-jaw chuck on a lathe centered on the nozzle point (4mm in from 1 edge, centered on the other) leaving a machinable 12.5mm length exposed
  3. Turn the (to be threaded) nozzle top to 8mm OD for a length of 12.5mm.
  4. Turn the nozzle top to 6.5mm OD for a length of 3.75mm
  5. Drill out the center of the nozzle (heat chamber) with a 3.5mm drill bit for a (initial) depth of 22mm
  6. Mount in a 3 jaw chuck holding by the nozzle top
  7. Leaving the heater block section 8.5mm long, turn the remainder (to be nozzle tip) down to max 8mm (7.5mm looks nice)
  8. Turn the nozzle tip: starting 1mm in from the heater block, machine at a 60 deg offset moving towards the tip, until the  Machine the nozzle tip to the desired profile leaving the heater block section 8.5mm thick.  Total length should be ~24mm
  9. Drill the nozzle orifice to 1mm depth 0.33mm or 0.5mm ID
  10. Remove from lathe and finish drill (3.5mm) the heat chamber to total length - 0.5mm
  11. Thread the nozzle to M8 x 1.25 (5/16-24) up to the shoulder of the heater section
  12. Using a 6.147mm (size C) drill bit, drill the heater resistor hole through the heater block section. The remaining brass, between this hole and the edge opposite of the melt chamber, should be 0.5mm (0.020 +-0.002) thick.  Lindsay: Heat chamber is 3.5mm thick and 4mm in so side of heat chamber is 4+(3.5/2) = 5.75mm (~6) but block is only 12.7mm wide leaving only 12.7-5.75mm = <7mm for heater hole.., if drill 6.35mm hole only allows bugger all on sides = 0.65/2= 0.325mm!..  even drilling 6.1mm still only leaves <0.5mm so.. either way we drill at midpoint between heat chamber & side = 3.5mm in..
  13. Drill the thermistor hole