Sources for M7 (Metric) Hollow-Lock Set Screws?

I don't have a clue but that is an interesting little hardware item. I never knew they existed.

Found this....

https://www.alibaba.com/product-detail/hollow-lock-set-screw_60193922811.html?spm=a2700.7724857.main07.193.315d42af6urikl

Not bad. I don't know if ordering from them specifically will make sense (50,000 minimum order at a minimum price of $0.001 each, or $50 minimum), but that looks like a promising lead that I'll investigate further during daylight hours.

Well, you didn't say how many....haha, don't think you can beat that price...

How many indeed. If MMC doesn't list it, it isn't very common.

M7 is an unfortunate size for you as it is not commonly available in many ranges.

Why does it need to be hollow? It's not as if you can do anything with the lower screw once you insert the lock.

There are plenty of M6 or M8 short length set or grub screws available that you may be able to use in lieu.

Failing that, and depending on quantity, you may have to purchase longer M7 set screws and part them off in a lathe.

I do this for odd ones that I require, I use a short piece of 2" round stock with a bottomed out hole threaded to the size required and a smaller through hole that allows the key to pass through to loosen the screw after parting. It's a quick process to turn down a few but may be too time consuming if you have lots to do.

That's an interesting thought. I might end up doing that if I just want short set screws, but hollow set screws would be preferable because they let light through.

That said, they might sell longer hollow set screws in M7, which I could part down to the desired length.

If it is possible, you could re-drill and tap your holes for a standard 5/16-24 UNF set screw.

7mm is .275" diameter. The tap drill for 5/16-24 is .272" ( an "I" drill)

That is something that I considered. However, I don't believe I currently have a 5/16"-24 tap or time to get one. Additionally, the higher major diameter would require extra drilling and making the piece weaker than I would consider acceptable, while the 7M-1.00 tap drill is basically a 1/4" hole which already exists in my design.

A standard 5/16-24 tap will be easier and cheaper to come by than the non standard M7 setscrews that you are looking for. However, I can't judge the effect that the extra 1mm. in hole diameter would have on your design.

By the way, if your design already incorporates a 1/4" hole, which is actually to big for an M7 X 1 (6mm = .236" is the correct tap drill) it is just right for a 5/16-18 UNC tap.

Hmm. Looking at a tap and drill calculator, 1/4" corresponds to a 50% tap for M7-1.00 and about an 87% tap for 5/16"-18. Considering that I'm working with mild steel for this project, tapping for 5/16"-18 will definitely be a pain, but I feel like it's not insurmountable. I suppose I'll have to take a look at CAD just to see if there will still be enough material left after the tapping.

Thanks for the info, though. I assumed that a 5/16"-18 tap would be much more challenging.

Not quite the thread you were asking for: Fastenal 5/16"-24 x 5/32" Hex Drive Cup Point Grade 18-8 Stainless Steel Socket SetScrew - Hollow-Lock

Although, as already indicated, M7 is not very common, you could try https://de.misumi-ec.com/vona2/detail/221000551578/

Fastenal carries them. You can get any screw type available from Fastenal. They also carry a lot of other things as well.

I did check Fastenal for hollow-lock set screws, but like most hardware distributors, they don't carry them in M7-1.00.

That said, see @gringogreg 's posts. I think I'll go with some kind of 5/16 jam screw instead, assuming that I can find the tap in the machine shop today.

If they don't carry them then they will have them special made for your orders. They have their own machine shop too.

If you can't find a tap in your shop today (5/16-18 is one of the most common sizes), you can order it from what ever source you buy your set screws from: McMaster, Fastenal, etc.)

By the way, don't be afraid of tapping mild steel. It is one of the easiest materials to tap. Just buy good quality taps. The most expensive tool in your shop is a cheap tap!

Try Bayou City Bolt, Houston, TX. They are the go-to source for the Houston Oil, Gas, Petrochem and Pipeline industries. They may have to special order them, but if your set screws are to be found they probably can do it.

FYI: proper Texas spelling is yu'al, and when speaking to a crowd the preferred tense is all-yu'al.

Schrauben-Profi from Germany are offering stainless steel, 10mm long, M7 hollow-lock set screws (in Europe we call them grub screws) on Ebay (Ebay seller No 109224)

Have you tried to contact Grattan. I go to a local store, The Bolt Bin, in san Jacinto. To buy s.s. 1/4-20 button cap screws and set screws. I use the button screws to replace the inferior mild steel Phillips head screws and the set screws for some sheaves.

Dave Grattan & Sons, inc. www.grattanproducts.com

A few updates:

Apparently, the original McMaster-Carr link is no longer functional, and as such here is the updated link. I don't know if this one will continue to function due to the way that McMaster-Carr's website works, but fingers crossed.

I think I'll use a 5/16"-18 jam screw, as it is more readily available, and it turns out that I do have the proper size tap. If I have time, I'll try to finish what I was working on and put up some pictures, but it doesn't seem likely that I'll be done this week.