Screw In Thermistor - How to...
Posted: Mon Mar 24, 2014 12:02 am
This mod works with the stock Rostock Max head as well as the E3D and a few others (like Hot Ends.com). I've known about screw in thermistors for a while but the challenge is that the ones I've found - I can't get taps small enough. Here's my home grown solution - it's probably not original but I haven't seen it...
Problem: Thermistor shorts, Thermistor blow outs and resulting dead hot ends. As you may know, once you blow a hot end (jam it), you might not ever get it back to normal.
Important note: This solution works with both the tiny 100k ohm resistors as well as those with the larger glass bead from Ultimachine.
1. Buy 4MM stainless set screws - length of your choosing, a 4MM .70 thread pitch tap, and a #29 bit by Irwin. I just picked a side where you are looking into the heating resistor hole. The #29 bit won't need a pilot hole since the metal is so soft. (Irwin blades are decent.) Buy an additional bit that fits into the set screw hole. Just make sure it fits into the hole.
2. Use Pliers or a bench vice...drill. With the #29, Drill enough to go almost into the hole to the heat break. This is the only way your tap will give you enough thread for the set screw.
3. Get your thermistor set up with PFTE tubing. Push it all the way down to the glass bead. Bend the ends of the leads to keep the PFTE secure.
3. Drill all the way through the set screw with the smaller bit.
4. Pull the leads through the hole in the set screw. Keep shoving until the PFTE is through as well. You might have to twist or thread it through. With your needle nose pliers, pull it until the tubing is about 1/4" away from the glass bead.
5. The Quick Steel takes about 24 hours to fully set. Be sure to knead it really well or it won't set up correctly. Smush some around the end with the PFTE and if your eyes are good enough, use a needle or small screwdriver and shove some into the set screw hole.
6. Make sure your PFTE is all the way down to the glass bulb. Pull the wire and tubing until it is either into the hole or can't pull through anymore. (If you have the larger glass bulb type, you'll know.)
7. Thread the set screw into your hot end. Use heat-proof thread locking compound. Caution: Don't tighten the screw so that you'll crack the thermistor. Leave a little room.
For extra security, I normally use a little Kapton tape and wrap it round the thermistor leads and heater cartridge leads.
Alternative - take those little screws that you see on PC cards - the ones that cables screw into. Find a matching tap for that and drill and mount. You can use the QuickSteel stuff with it as well. Most hardware stores do not seem to have the right drill and tap for them...I've been to a couple....
Problem: Thermistor shorts, Thermistor blow outs and resulting dead hot ends. As you may know, once you blow a hot end (jam it), you might not ever get it back to normal.
Important note: This solution works with both the tiny 100k ohm resistors as well as those with the larger glass bead from Ultimachine.
1. Buy 4MM stainless set screws - length of your choosing, a 4MM .70 thread pitch tap, and a #29 bit by Irwin. I just picked a side where you are looking into the heating resistor hole. The #29 bit won't need a pilot hole since the metal is so soft. (Irwin blades are decent.) Buy an additional bit that fits into the set screw hole. Just make sure it fits into the hole.
2. Use Pliers or a bench vice...drill. With the #29, Drill enough to go almost into the hole to the heat break. This is the only way your tap will give you enough thread for the set screw.
3. Get your thermistor set up with PFTE tubing. Push it all the way down to the glass bead. Bend the ends of the leads to keep the PFTE secure.
3. Drill all the way through the set screw with the smaller bit.
4. Pull the leads through the hole in the set screw. Keep shoving until the PFTE is through as well. You might have to twist or thread it through. With your needle nose pliers, pull it until the tubing is about 1/4" away from the glass bead.
5. The Quick Steel takes about 24 hours to fully set. Be sure to knead it really well or it won't set up correctly. Smush some around the end with the PFTE and if your eyes are good enough, use a needle or small screwdriver and shove some into the set screw hole.
6. Make sure your PFTE is all the way down to the glass bulb. Pull the wire and tubing until it is either into the hole or can't pull through anymore. (If you have the larger glass bulb type, you'll know.)
7. Thread the set screw into your hot end. Use heat-proof thread locking compound. Caution: Don't tighten the screw so that you'll crack the thermistor. Leave a little room.
For extra security, I normally use a little Kapton tape and wrap it round the thermistor leads and heater cartridge leads.
Alternative - take those little screws that you see on PC cards - the ones that cables screw into. Find a matching tap for that and drill and mount. You can use the QuickSteel stuff with it as well. Most hardware stores do not seem to have the right drill and tap for them...I've been to a couple....