Which length is normally the one to buy to go through the plates here and into the T-Nuts? Will I need any other length besides this?
Many times yes. It hits the back of the extrusion slot. Luckily they are cheaper than the longer screws
It seems like each time I order extrusion, I add a few packs of M5x8's and some more T-nuts. Then I get closer on the counts of the other things I need.
Well, I am going to buy 500 so I was trying to narrow down if 10 or 8 as I don't want excess. Thank you. edit: I see a HUGE problem I did not notice before but all of these screws are black oxide and I cannot use black oxide here. When I first built my printer a few years ago I used all black oxide and within 2 weeks they all had rust on them so I had to replace with stainless steel and not an issue since (within 6 weeks the rust covered the entire screws, and nuts, I had left out to the point they were worthless to be used within 3 months). What options will work since these screws, with the ultra low heads, are made in the cheapest metal and the worst kind of screws to use if you live in a hostile environment to metal as I do? I looked online and the only stainless ultra low profile M5x8 I could find was from Misumi and each single screw is $3.36 up to 99 then 100+ $1.68
Well.....that adds a bit of stink to the poo, doesn't it! I think McMaster Car has screws with a blue protective coating, but I am not sure what it protects against. Do you need the ultra low profile? I would think regular SHCS in stainless might be cheaper.
I am not sure as I was thinking about it and wondering why one would need an ultra low profile. I can easily find 3.2-3.5mm low profile stainless M5 and way cheaper but do you have any ideas why anyone would need an ultra low profile? The only thing I can think of would be for the corner brackets The thing is I will be using the first and very possibly the latter as well in my final build.
Low profile is necessary when you run screws through a gantry plate in both directions. The wheels hold the extrusion out just far enough from the plate such that a screw can be run back up through the gantry plate for attachment of another plate, mounts or another extrusion. They are also necessary when you are using plates that need to keep the head recessed such that it leaves a smooth face on the plate for direct attachment of another plate or extrusion. The C-beam XL gantry plates are a good example of that where X and Z axis plates are mounted flush together.
I don't understand the first part of that about the wheels. Could you show an example because I seriously can't use black oxide anything here. Even my galvanized 10mm all threaded rods had surface rust on them in spots when I looked at them 6 months to a year later.
As Rick2.0 says, there are a few times when you NEED them, but is most cases it is for looks. I can get 100 black M5x8 or 10 for the same price as 25 of the ultra lows. I usually still us the lows, as I like the looks, and try to support OB when I can. My MendelMax XXL is build with SHCS and it still looks pretty good, but I don't have the rust issue that you have. I am assembling parts for a big delta as we chat and I have a mix of both.
Please don't take this wrong, but Makers should have a good supply of about any screw you can get! Since it is all open source, nobody seems to follow a set pattern or size. I can't think of a time where I used M4's, but some builds use them for the whole build!
Having a mixture of sizes is acceptable but having any that has absolutely no protection against rust is not. I can only imagine if I purchased one of those Chinese Tevo like printers as it would rust out here before the end of the year I lay odds. I find it odd that OB doesn't carry something besides just Black Oxide. Now the ones I can get in SS are low profile so 3.2-3.5mm vs the standard 5mm whereas these from OB are 1.5mm. I suspect 3.2mm will be fine for me.
Not a great example but the quickest one I could pull up from old files. This is from a hot wire cutter example. Reference the vertical extrusion mounted to the plate. Attachment is accomplished by running screws in from the back side of the gantry plate into T-nuts in the vertical extrusion as shown below. There is enough of a gap for the screw head to fit without dragging on the extrusion. As far as the shop not having stainless screws, give them time, it may happen at some point. Mark has built this business up from scratch and growth takes time. (Probably wouldn't hurt to put in a suggestion though.)
Applying a light coat of oil to the screw heads after you install them will prevent the oxidation. A cotton swab works well to get down into the allen socket.
Thank you Rick as that clarified it perfectly and is what I thought you meant. Yep, I know Mark has done that for sure but even when I look around I can't find a source for them so they would have to be special made in China or RoC (Taiwan) for him, and us. All I found was from Misumi and at 1.6 dollars, or more, for each screw I can safely say they have a screw lose if they think I would pay that for a M5x8mm. Joe, the thing is the entire screw rusts not just the head so within 6 months to 1 year the screw will have welded itself to whatever it was screwed into and if not the rust would be so bad you would never be able to unscrew it anyway.
Ah I see. Usually bags of blackoxide screws have a bit of rust inhibitor mixed in. From personal experience they don't always have enough to coat everything and when that stuff dries up the bag turns into a pile of rust! I've received them dry too. Regardless, I usually add oil to the bag and mix to coat everything and seal them when stored. This has been working well. Here we have humid summer's and salt the roads in the winter. Corrosion is everyday life. Car parts rot quick! I've stripped off a few tire lugs over the years. If the threads are your concern then you might want to try a dab of antiseize, use oil for tapping, or maybe some light thread lock. Just remember to take the lube into consideration if you're torquing to a value. Protecting against corrosion is part of my machine maintenance and lubrication schedule just as it is with any machine tool. If it rusts then it's my fault for not taking preventative measures. I use steel guides and ballscrews and it's in an uninsulated non climate controlled garage. It's obvious they'll rust quick if left dry. A wipe of light duty oil is all that's needed. Adding, I try to stay away from mating stainless and aluminum where moisture will be present or with fine threads and tiny fasteners. There's been a number of times where I've pulled a stainless fastener out of an aluminium hole and had rotted brittle threads come out with it. They don't get along as well as plain carbon steel and aluminum. You'd likely be fine for years with the ss m5s though. If your machine is continuously exposed to a harsh environment(such as with a coastal location) maybe throw some oil or blue thread locker in there to force out some of the air as an added measure. Zinc plated would work well for a while too. What's the maximum head height you can have?
I agree but having to take each screw out to maintain them would be a nightmare. I am not used to this rust within 2 weeks environment so my black oxide screws rusted in my printer. So, I paid more for the SS but so much better and so much less hassle. I haven't had a single issue with the alum and ss after two years so far (I have removed and reinserted the screws a ton over the years too) but it all depends on what mix China throws at us too. The problem with adding anything to the screws is that it doesn't really coat the screw. I seriously wish Mark could get Zinc coated/plated or stainless steel M5 ultra low profile screws at least as an option. To be honest not much of a head height as the picture Rick showed is just about what I need to do so ugh. :/ My M10 all threaded rods I oil about once a year now and it seems to have helped but they are zinc coated too (yes, I had to remove each one and tear my printer apart to scrub and oil them when I saw the rust forming). I was going to use Vaseline but it gets so hot it would be a runny mess and be worthless on anything. A side question not related to this but is a Delrin nut for an ACME threaded rod better than a Brass nut especially when I see Brass nuts with anti backlash?
Well, with the screws you just oil the threads once and the oil should hang out in there. With blind holes anyways Due to the lower friction coefficient, you'll see slightly better efficiency and less wear on your leadscrew with the Delrin. It's more lubricious than brass (self lubricating brass is a bit better than plain brass, but the cost of legit selflub antibacklash brass acme nuts(mouthful!) is enough to make you puke). Brass is great for heavier loading. The thing about Delrin is that it likes to deflect a lot when you cut it. This explains why they're tight when you first install them. As recommended elsewhere(including by Mark in his OX vid I believe) it's good to run them in by handdrill on the screw to seat them in. Do this nonlubricated then lube after its seated snug. Joe
Alrighty, then I will use two of those babies for my Z axis then which is nice because I don't really need to do much to just make them work whereas the Brass nut I have to print something up to hold them or have someone CNC something so the nut goes in. With the Delrin it is just using the screw holes flush to the extrusion but no way and no how to do that with the Brass nut so makes it easier. I remember Mark saying that in a video I watched a long time ago now but it is very easy to warp it out because the leadscrew would need to be 100% true before you attack it with an electric drill.
Nah, there's enough meat on the acme nut to guide itself colinear with the screw axis. However, I don't see a problem with doing this installed on each actuator one at a time. Go for it.
Yep, just disconnect it so it doesn't burn the board up when it becomes a generator. I was reading and the best lube to use on the Delrin seems to be something called Dow chemical's 33 or simply Dow 33.
I'm not sure on that one. I think you could even get away with a dry graphite spray. Maybe even a light coat and wipe of dielectric(silicone) grease.
A wet lube can swell them which is why I leaned towards dry based lubes. Even then, swelling is minimal and not a big problem with Delrin. It really is a good idea to run them in until they heat up and reform to the screw prior to lubing. Throw on some silicone and forget about them for a while.
