Shop made screws

[GordonL]

Folks talk about making their own to scale hex head screws. How do you machine something that small? When you are making something like 1/8" dia or less x 1/2 to 3/4 long the piece just bends away from the cutter no matter how sharp the tool may be. Is there some way to cut front and back at the same time?

[eKretz]

There are quite a few ways to do that. One is to start with larger, more rigid stock and take a deep cut right to finish size with a low feedrate. Another is to use something like a box tool that supports the stock as it is cut sort of like a follower rest. Yet another is to leave extra length on the workpiece and use a center to support the outboard end, then remove that extra length later. For threading, the center method can work if single point is necessary or a die can be used.

[GordonL]

I have used the method of making it too long and using a center but it is very time consuming. I have always used that method when making valves but then I am only making a few pieces. I can envision some kind of a box tool but I don't know where to buy one or how to make one. Any link to either a purchase unit or plans on how to make one?

[Rich Carlstedt]

I am writing a article for Home Shop Machinist magazine on building this unit, so this may be a preview.
it is a Box tool for doing what you may need.
I go down to 0-80 thread size (.060")
You first get your length , then you thread it with the die

The advantage with this box tool is that the stock can be any shape
I have used Round, Square, and hex raw stock to make the screws.
The front running work bushing is sized for the stock
You feed the material in using tour carriage and when it hit the stock, you withdraw the carriage,place the die on the boss and feed in , all without stopping
The threading is controlled by hold the knurled Die holder with your hand and you release when full thread is reached.

Another method is to use a Geometric Die head.

Rich



the lathe

[GordonL]

Rich:
I have seen something similar to that before but I don't remember where. How do you adjust the cutter to obtain the correct diameter? Do you just keep advancing the cutter until you get the correct diameter?

[ezduzit]

https://www.youtube.com/watch?v=X-TkuQDWdbA

[J Tiers]

That's the same thing I have done, although I've never done it to THAT extreme. I use HSS, same deal, small nose, cut on the face. I use a "slicer" high rake tool, but it obviously works with that carbide as well. I think I have posted doing that to make custom counterbore noses.

They may have an 0.062 shank, and might be pretty good size on the nose part, maybe 5/16" for that shank. Depends what counterbore you have and what shank it needs.. They usually don't need any longer than about 1.25 inches in length.

Gotta be sure the tool is dead-on-center if you go to the extent he did.

[Rich Carlstedt]

Rich:
I have seen something similar to that before but I don't remember where. How do you adjust the cutter to obtain the correct diameter? Do you just keep advancing the cutter until you get the correct diameter?

Back in the early 1990's there was a article in Model Tech magazine with a box tool for threading , then my friend Richard Vandenberg improved that design about 1999, and then I made even more changes.
Setting the cutter is one of my several changes, its as simple as pie and here is a picture showing how with a Depth Mike.
The anvil of the Mike touches the toolbit and you measure the test result (OD Mike) and then adjust the depth mike to get the diameter you want ( Half the difference of OD reading from ideal size)
Then slide the toolbit to the Mike and clamp- Done
Rich

[GordonL]

OK Thanks. That should work well.

I also just did an experiment on cutting full depth with a single pass and it works well. I have always tried to take multiple cuts which results in spring back. I will have to try that technique the next time I make valves. No reason why that should not work. Like I said I have always used a center in the tail stock and removed the end after I got the stem to the correct diameter.

Thanks.

[BCRider]

https://www.youtube.com/watch?v=X-TkuQDWdbA

I haven't used that method "in anger" yet but I did try it to see how well it works. And it works extremely well!

Rich, that is a very well thought out tool you made. Apparently a team effort with each new idea I'm sure. The only thing missing is an easy way to part off the turned and threaded bolt.

My own lathe does not do well at stopping on a dime so if I were using such a threading fixture I think I'd make it so I was only hand holding it so it spins in my grip when it bottoms out against the head of the screw. Or at least that I could let go when it's threaded on far enough. Then shut off and unscrew the die by hand after retracting the main tool body. Is that how it works for you use or do you slow down the RPM and use the set screw all the time?

It would be a fair bit of work to make up an all in one box tool of that sort. But the nice thing is that it's highly adaptable to a pretty wide range of small screw sizes.

[Rich Carlstedt]

...............Rich, that is a very well thought out tool you made. Apparently a team effort with each new idea I'm sure. The only thing missing is an easy way to part off the turned and threaded bolt.............................................. ..............................................that it's highly adaptable to a pretty wide range of small screw sizes.

BCRider, After the "Threading" operation, - I mount the die with my left hand while holding the carriage wheel with my right, and then bring the carriage "in" until the die starts-
The boss makes sure we are on center 100 % and the work picks up the die (threading) and when I see that I am threaded almost to the desired end of thread, I back off the carriage and only grip the die lightly. When the die hits to end of my desired thread length, i release the die and it spins with the work piece ...even down to 0-80 thread !.( its balanced and spins nicely)
I stop the lathe and go into reverse and lightly grab the die and it spins off ( carriage out of the way of course). No brake on the lathe, just normal start/stop.

I have parted off in the lathe but do not usually do that . If you want to part immediately. then mount the Box Tool in the Tail Stock and that frees up the tool post for a parting tool
This I only do when I have Hex Stock as raw material in most cases so I have a finished screw with parting. (Parting Tool is ground to leave a chamfer on the hex portion as we normally see)

Most of the time, I deal with "Sticks" ..That is round material cut into 6-8 inch lengths. and have maybe 4 to 12 of those and then turn and thread both ends, Then put them into a Collet Block
and mill them for Square or Hex heads where the threaded portion ends ( Not the whole stick ). Then the sticks go back into the Lathe and get Parted off and I start all over with shorter sticks.

Rich

Edit
One of the advantages of sticks is rounding the end of the screw - easily done !
Remember it's threaded , but the start of the thread may be rough.
So I approach the Scotchbrite Wheel ( on a pedestal grinder) with the stick at a 45 degree downward angle
and kiss the start of the thread, while spinning the stick and then gradually lower the stick til it is horizontal in about two to three seconds
You get a nice crowned end on the screws

[old mart]

The screw could be held on an er collet in one of the hexagon collet blocks, or a straight shank one if it was to be held in a chuck on a rotary table. This is for milling the head.
For the shank, also use a collet in the lathe spindle and start with only a short length overhanging, then move it out and repeat as often as the length requires.

[mklotz]

Folks talk about making their own to scale hex head screws. How do you machine something that small? When you are making something like 1/8" dia or less x 1/2 to 3/4 long the piece just bends away from the cutter no matter how sharp the tool may be. Is there some way to cut front and back at the same time?

Usually there are lots more fun things to make on a model than fasteners. You might want to give a thought to buying rather than making...

https://www.microfasteners.com/home.php?cat=576

[BCRider]

Thanks Rich. That describes the full process neatly.

I like your "sticks" idea for the reason you gave.

I was also thinking like you of a parting step that also chamfers or rounds the head at the same time. But with that extra load do you not find you end up with center nibs that need addressing?

All in all though I do have to agree with Marv that where the sizes fit perhaps machining with our charge card might be the handier option... I find the prices from Microfasteners to be very attractive.

[Tim Clarke]

A while back I made a run of 4-40 hex head screws. I used 5/32 12L14 hex stock. It was my first use of my rear mount tool holder, and turret tailstock.