Turning square headed bolts

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neil_1821

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Thought I’d post this as everyone has their own methods.

On my next project, in order to keep in scale to the full size there is a requirement to have square headed bolts, more precisely over 300 of them.

They are not commercially available to buy so that means I’ve got to make them and I’m wondering what method would be best to use in order to keep a fairly tight tolerance on repeatability.

I was thinking of drilling a hole in some round bar, which would be the overall diameter of the square material from corner to corner, then having bolts on either side to clamp it while I turn it and thread it then part off. If anyone can suggest any other methods I’m all ears.
 
I didn’t know you could get square hole collets!

We do have a collet set so this could actually be quite viable if I can find one to fit
 
My take is you have square material already?
As of now the image projected onto my eyeballs is to turn from round and thread, then make a split threaded collet (square) , then use vise to squeeze the thread and flip for each side, milling just the edges.
Just a suggestion

300 threaded wow, I would prob turn green seeing that number
 
I haven’t got the material yet, I’m just tossing some ideas round to see what the best way is. It doesn’t help that the top face isn’t flat. Although it is a square headed bolt the face of the square will be slightly curved so will have to grind the right profile on the parting off tool. Thinking that a square collect might be best as they hold the material fairly central, more so than a 3 jaw chuck, which is handy for how small the bolts will be.
 
You did not say the size. If you have a collet holder, you can buy square collets up to 7/8" for 5ç collets. You can take a round bar mill a groove the size of the square, then mill a piece to fill the slot, use set screws to hold the stock.
A 4 jaw Chuck is slower than the others, but works.
Drill the depth of 4-5 nuts, tap the hole. Then profile, then part off.

I did a dozen nuts for a scale project. For 300 look around on the net. A guy with a turret lathe could knock those out fairly quick.
 
I forgot to say that you then thread the nuts on to studs, thread them until they jam, cut the stud not quite flush, then peen the stud, hit it with a belt sander, look like it was old.
 
What size bolts are you talking about? You should be able to find them someplace on the net. If not bolts, nuts are certainly available especially in the smaller sizes used in automation extrusions. You could easily weld the nuts to threaded rod.

Unless you are extremely patient, i cant see doing this on home shop equipment. Maybe 30 but 300 would drive me nuts.

Interestingly i believe it was Mr Pete that ran some videos on making square head bolts. If i recall correctly they where flanged bolts for a tool post so maybe not what you need. In any event the general idea is good, which is to use round stock that can inscribe the bolt head. The nice thing here is that the square can be simply done with a collet block on a mill or even a lathe.
 
The thread is probably going to be around M3/M4 so the head has to be fairly concentric to the shaft. As you can see on the picture they’ll be used everywhere on the engine, although the builder of this has used some hex headed ones we intend to stick with square. I don’t think patience is an issue, I can make some, do a bit more machining on the wheels then come back when I need a break.
36ACFD70-A032-4396-9232-ABF9176FF5F7-15150-000011792E708EBE.jpg
 
Here's an article on making square adaptors for round collets: http://www.homews.co.uk/page75.html

Looking at that photo, a lot of those bolts look decorative; in that situation you could just make square head rivets, (ie: no thread) drill a hole and soft solder them in place. It would be much quicker than threading and tapping.
 
Thanks for the link Baner.

I haven’t ruled out the possibility of using square head rivets, but being a double frame construction there will still be a considerable amount that need to be threaded. I think this will be a case of seeing how I get on. I’ll have to post some pictures and further info on my build page when I get round to starting it again.
 
neil_1821 said:
Thought I’d post this as everyone has their own methods.

On my next project, in order to keep in scale to the full size there is a requirement to have square headed bolts, more precisely over 300 of them.

They are not commercially available to buy so that means I’ve got to make them and I’m wondering what method would be best to use in order to keep a fairly tight tolerance on repeatability.

I was thinking of drilling a hole in some round bar, which would be the overall diameter of the square material from corner to corner, then having bolts on either side to clamp it while I turn it and thread it then part off. If anyone can suggest any other methods I’m all ears.
Click to expand...
 
Hi,

I use a four jaw self centering chuck and this makes it easy.

In fact I only have a 4 jaw self centering chuck for all my concentric turning, more accurate, and will hold even hex accurately.

Hope this helps!
John
 
I can find square head bolts down to 1/4-20 all day long. Im not sure how the head sizes compare to M4 bolts but if they are not too far off you might be able to easily trim the head to the size needed by the model.

Mind you those where found in the common places. If you look around you might find square head machine screws in size 10-32. When all else fails call some of the bigger vendors to see if they have a line on stock or special orders. As noted before square nuts can be found due to their use in automation extrusions.
 
Last edited:
Would regular hex head bolts have enough meat in the head to look correct if milled square?
 
tjwal said:
Would regular hex head bolts have enough meat in the head to look correct if milled square?
Click to expand...

Unfortunately not. I know you can get bolts with different sized heads, but it’s more the width of the head as well as the profile of it.

I think I’ll end up using a collet chuck as detailed in the link further up the page.
 
Here are a couple of crazy ideas:

Forged head: Take a set screw of the appropriate size, heat the end red hot, and using a purpose-made square punch and holder pound the head square.

forged.png


Add head to set screw: Start with a length square stock of the appropriate size; drill and thread for an M3 set screw. Thread the set screw into the square stock to a bit longer than head height, using permanent thread lock. Cut of the square head so that you cut through the set screw also; hopefully the join will be almost invisible. This will leave a bit of set screw in the remaining square stock - just cut off the end of the stock to remove it, and repeat with the next set screw (alternatively, you could insert the set screw into the stock hex-end first; then use a hex wrench inserted through the square stock to back out the left-over end.

cut.png
 
Everyone seems to want to do extra work! A new Chi-Com 5C square collet, either metric or Imperial is about $15 or less. Square 12L14 free machining stock is probably available, although regular key stock will machine easily enough. Three hundred screws is a lot, but at about 7 minutes each, with quick-change tooling, is 35 hours or a short week, not including beer breaks. You will need to chuck each screw twice, the second time with a round collet to nicely contour the top of the screw head with a form-shaped tool.
 
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