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I got some EZR Struders to replace the old EZ ones but the tiny allen wrench included does not tighten well and comes loose quickly.
I put lock tight on the belt drive pulleys but the HOBB drive does not lend itself to this. (to small)
Seems strange to have a 12mm diameter hobbed drive with a tiny M3 screw to keep it tight.
Anybody else have this problem and come up with a fix?

I am considering redrilling the holes to M4 with a better grub screw or two.

The screw isn't too small to use thread locker on. You put a dot of it on the end and go. Make sure you've got the grub screw contacting the flatted portion of the stepper shaft.

g.

I disagree. Its too small for this purpose. The provided allen wrench can't tighten the grub screw without stripping. I tried it on more than one. Same result. The lock tight would be potentially useful if the screw got tight. As I said if it was like the pulleys it would be OK.
Maybe you use a different allen wrench than the one provided.
Is there a good reason this grub screw isn't dual M4 like the pulley?

I've only built about 30 of them that way, so...

It's entirely possible that either the grub screw or the Allen wrench is out of spec.

SeeMeCNC manufactures the hobbed gear on site and they buy-out the GT2 belt gears. Two grub screws are typical for a fully round shaft. They're a bit overkill for a flatted shaft installation, especially when thread locker is used.

g.

@Gene,
So of your 30+ EZR struders, none of your allen wrenches that came them spin when you try to tighten the grub screw?
I have 5 and they all did. Something strange. They act like they are english and the screw is metric or vis verse.
Did you use the allen wrench that came with the kits or use your own higher quality one?

Wow. That's really not right. I've always used the included wrench. It almost sounds like the wrench isn't fully seating in the pocket on the grub screw.

You might want to contact support about it - if they got a bad batch of grub screws or Allen wrenches, they need to know about it.

g.

Looks like the best option is removing the M3 grub screw and drilling a new hole and replacing with a stainless steel M4 grub screw that will not strip "so easy".

Maddog wrote:Looks like the best option is removing the M3 grub screw and drilling a new hole and replacing with a stainless steel M4 grub screw that will not strip.

Will not strip??? Hold my beer!

If it's any consolation, i stripped out the grub screw in the Titan's hobbed gear while I was upgrading Red Sonja (massively modified v1). Of course the drive gear is in the wrong position... I need something like a 1.75mm allen wrench to fit it now.

g.

I still have no confidence in this M3 grub screw that came with the EZR extruder. It just not tight.
I finally decided to use the M4 drill bit and tap and use new grub screw.
I was surprised the metal it not hard at all. The drill bit sliced thorough the existing hole with little resistance.
I didn't spend that much on these metric drill bits.
I thought this hobbed gear should be harder metal so the grooves put in stay there.
Anyway, tapping the hole for an M4 grub screw went easy as well with the softer metal.
I placed this new improved hobbed gear in the EZR assembly (with a little lock tight Geneb) and it tightened up nicely.
Not going to have a problem with it coming loose now.

I used a 3.3mm drill bit to drill out the existing hole.

Your call, but the M3 screw is perfectly adequate for the task it does.

I did discover that I could loosen the M3 screw in the Titan by using a 1/16" Allen wrench. Go figure.

g.

geneb wrote:Your call, but the M3 screw is perfectly adequate for the task it does.

I did discover that I could loosen the M3 screw in the Titan by using a 1/16" Allen wrench. Go figure.

g.

Since the M3 screw didn't get tight, "perfectly adequate" sounds pretty silly to say.

I believe that in general, an M3 grub screw is sufficient. Assuming a class 12.9 grub screw (The ones I source are 14.9, so stronger yet), the proof yield is 970 Mpa, or 828 pounds of force (Assuming an area of 3.8, which is below what the specifications allow for minor diameter). The minimum yield strength is rated at 1100 MPA, or ~940 pounds of force.

Of course, as you mentioned, if the hobbed gear is unhardened, the yield of the hobbed gear is the point of failure, at a mere 323 pounds. Now, excuse me if I am doubtful that 323 pounds of clamping force is insufficient for something pushing molten plastic.

Much more likely is a low quality gear, allen key, or grub screw slipped through QC, which would be difficult to track down at this stage. I've also made assumptions that since I was using a metric screw, I should use a metric key, which at least for my and E3D's suppliers, is untrue (Which I found majorly weird, TBH).

Xenocrates wrote:I believe that in general, an M3 grub screw is sufficient. Assuming a class 12.9 grub screw (The ones I source are 14.9, so stronger yet), the proof yield is 970 Mpa, or 828 pounds of force (Assuming an area of 3.8, which is below what the specifications allow for minor diameter). The minimum yield strength is rated at 1100 MPA, or ~940 pounds of force.

Of course, as you mentioned, if the hobbed gear is unhardened, the yield of the hobbed gear is the point of failure, at a mere 323 pounds. Now, excuse me if I am doubtful that 323 pounds of clamping force is insufficient for something pushing molten plastic.

Much more likely is a low quality gear, allen key, or grub screw slipped through QC, which would be difficult to track down at this stage. I've also made assumptions that since I was using a metric screw, I should use a metric key, which at least for my and E3D's suppliers, is untrue (Which I found majorly weird, TBH).

The specs are great but if it don't work then specs are a moot point. It's not a "sufficient strength" issue. It's a quality problem or just too small.
I have had trouble with 5 units bought at the same time. Make that 6 units. I have 5 different allen keys that came in the kits. I think the allen keys are the wrong ones or just defective but could be the grub screws. Hard to tell what it is. Not like I can measure the inside of that grub screw for accuracy. After drilling out and replacing the M3 hole with M4 in 5 units I tried to replace the existing 6th unit but the supplied allen key could not remove the grub screw. It simply spun around doing nothing. The lock tight is not that good!
After going through an assortment of modular screwdriver tips I finally got the screw removed.
I will be drilling it and inserting the M4 grub screw in it as well. The M4s tighten fine and unscrew as well.
Not seeing how putting an M4 screw in instead of an M3 has any down side. I have had no issues with 6 M4s but the M3s suck.

Face it man, the M3 Grub Screw Cabal has it out for you.

g.