Hobbed Bolt Hi guys. Living in Argentina makes hard and expensive to source some parts for a printer. Now im dealing with the hobbed bolt. Iv seen that i can build one with a dremel, but i have a friend who owns a machine shop, so i can have access to a cnc lathe and stuff like that. We where talking about making a clone of the hyena hobbed bolt, but we are having some trouble with the grooves. How many of them should the bolt have?, how deep? Do you have any recommendations for the hobbed bolt? https://reprap.org/forum/read.php?1,158152,158152#msg-158152 Sun, 06 Sep 2026 20:24:42 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,158152,161784#msg-161784 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,161784#msg-161784 Cleaning of the hobbled bolt seems necessary when I frequently feed filament sections into the extruder.]]> peddiparth General Sat, 20 Oct 2012 01:33:24 -0400 https://reprap.org/forum/read.php?1,158152,161604#msg-161604 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,161604#msg-161604
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nophead
In normal use I don't clean my hobbed bolts. They produce a small amount of dust, that's all. If I have a jam for some reason then it will strip the filament and fill the teeth. In which case I remove it and clean it with a wire brush, but when everything is working properly the teeth stay clean. They may have some loose dust on them, but that is not the same as being clogged with torn off plastic.

ditto.]]> rhmorrison General Fri, 19 Oct 2012 05:36:09 -0400 https://reprap.org/forum/read.php?1,158152,161593#msg-161593 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,161593#msg-161593
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How frequently does everyone clean their Hobbed-bolt to avoid clogging while using PLA?
Is it possible to have an extruder design that auto-cleans the Hobbed-bolt?

In normal use I don't clean my hobbed bolts. They produce a small amount of dust, that's all. If I have a jam for some reason then it will strip the filament and fill the teeth. In which case I remove it and clean it with a wire brush, but when everything is working properly the teeth stay clean. They may have some loose dust on them, but that is not the same as being clogged with torn off plastic.]]> nophead General Fri, 19 Oct 2012 04:03:37 -0400 https://reprap.org/forum/read.php?1,158152,158719#msg-158719 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158719#msg-158719 BAMCNC General Thu, 04 Oct 2012 19:00:40 -0400 https://reprap.org/forum/read.php?1,158152,158537#msg-158537 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158537#msg-158537 GITRDUN General Wed, 03 Oct 2012 22:06:29 -0400 https://reprap.org/forum/read.php?1,158152,158531#msg-158531 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158531#msg-158531
I will head to the machine shop, so, if we have time to make something i will post pictures.]]> nic0laz General Wed, 03 Oct 2012 19:55:46 -0400 https://reprap.org/forum/read.php?1,158152,158520#msg-158520 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158520#msg-158520
Given that it appears most people have good results using a tap to form the "teeth", I am sure it is a good way to go. Regarding the concern I expressed that a tap fabricated bolt might tend to twist the filament, it was only a conceptual concern, not something I experienced.

I think the analog to the tap fabricated bolt is a worm gear (filament) with its corresponding worm wheel (tap fabricated bolt). At many typical "pitches", worm gear sets are not back driveable i.e. if you try to spin the worm wheel, the worm gear doesn't spin (due to the gear ratio being very high and the friction). If the analogy holds, this (no spinning) is what is desired in the filament drive; i.e you don't want to "back drive" the filament i..e spin the filament...you want to push it out. So no twist...too high an effective "gear" ratio and too much friction. Anyway, fun to think about...practically, many different ways to go with tap fabricated bolts a proven design.]]> mars bonfire General Wed, 03 Oct 2012 18:54:25 -0400 https://reprap.org/forum/read.php?1,158152,158424#msg-158424 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158424#msg-158424 Is it possible to have an extruder design that auto-cleans the Hobbed-bolt?]]> peddiparth General Wed, 03 Oct 2012 10:57:31 -0400 https://reprap.org/forum/read.php?1,158152,158326#msg-158326 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158326#msg-158326 jamesdanielv General Wed, 03 Oct 2012 03:23:50 -0400 https://reprap.org/forum/read.php?1,158152,158233#msg-158233 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158233#msg-158233 xiando General Tue, 02 Oct 2012 16:08:19 -0400 https://reprap.org/forum/read.php?1,158152,158231#msg-158231 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158231#msg-158231 droftarts General Tue, 02 Oct 2012 15:59:16 -0400 https://reprap.org/forum/read.php?1,158152,158217#msg-158217 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158217#msg-158217
Do you mean the method of using a tap to produce the hob?]]> xiando General Tue, 02 Oct 2012 14:58:36 -0400 https://reprap.org/forum/read.php?1,158152,158216#msg-158216 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158216#msg-158216
Isnt the slot necesary to avoid filament lateral movent?]]> nic0laz General Tue, 02 Oct 2012 14:58:27 -0400 https://reprap.org/forum/read.php?1,158152,158213#msg-158213 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158213#msg-158213

May well have already been covered but I thought I would share a method that I experimented with this weekend to make the friction drive wheel for an extruder. Based on some reprap research, looks like people are using the hob method (use a threading tap to hob teeth into a bolt...sort of like hobbing a worm gear) and others, using a press in insert that has gripping ridges.

I have a CNC taig mill with a fourth rotary axis (I built the rotary access...hobbed the main drive gear using a tap). My approach was to chuck the axle rod (bolt equivalent) in the rotary axis and mill a groove into the circumference of the axle using the edge of a simple straight 1/8" endmill. Looking at the end of the rod, the mill "kisses" the rod at 45 degrees so it results in a groove cut with an included angle of 90 degrees. Cut one groove, rotate the rod axis and repeat until you go all away around the circumference. For this test, I milled grooves every 10 degrees on a 0.25" diameter rod to a depth of 0.015"...so a total of 36 grooves. The attached pictures show the test cut and the mill with rotary axis. The resulting teeth are very sharp and straight...I worry a little about the hob approach since it generates a spiral cut...does it tend to twist the plastic filament? For the real extruder, I mill mill into stainless steel for wear...brass was just easy to cut for a test.]]> mars bonfire General Tue, 02 Oct 2012 14:54:15 -0400 https://reprap.org/forum/read.php?1,158152,158184#msg-158184 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158184#msg-158184 If you want to cut it with the dremel blade, you'll need an indexer like further down the page I linked above, or a tool like this one [www.thingiverse.com] (but you'll need a printer to print it). This lets you turn the bolt accurately, so the cuts are consistent.]]> droftarts General Tue, 02 Oct 2012 11:35:43 -0400 https://reprap.org/forum/read.php?1,158152,158156#msg-158156 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158156#msg-158156
Thanks]]> nic0laz General Tue, 02 Oct 2012 09:32:08 -0400 https://reprap.org/forum/read.php?1,158152,158155#msg-158155 Re: Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158155#msg-158155 reprap.org]]]> droftarts General Tue, 02 Oct 2012 09:27:49 -0400 https://reprap.org/forum/read.php?1,158152,158152#msg-158152 Hobbed Bolt https://reprap.org/forum/read.php?1,158152,158152#msg-158152
Living in Argentina makes hard and expensive to source some parts for a printer.

Now im dealing with the hobbed bolt.

Iv seen that i can build one with a dremel, but i have a friend who owns a machine shop, so i can have access to a cnc lathe and stuff like that.

We where talking about making a clone of the hyena hobbed bolt, but we are having some trouble with the grooves. How many of them should the bolt have?, how deep?

Do you have any recommendations for the hobbed bolt?]]> nic0laz General Tue, 02 Oct 2012 09:08:21 -0400