A mini ratchet handle build

[crueby]

Hi all,
I am taking a short break from my Holly pumping engine build to see if I can put together a mini ratchet handle to work with the 4mm hex shank Wiha tool bits that I have. Already had several places on the engine (and previous ones) where it would have been very handy to have a ratchet that would fit into tighter places. There are lots on the market for 1/4" square shanks, and Wiha does make one for the 4mm hex shanks, but they are all too bulky for small model work.


After several design starts, and restarts, and input from a number of others on the forum here, here is where I am at the moment. This first picture shows the ratchet all together:


The shop elves decided on the SnapToff brand name, since the SnapOn name is already taken.   
 This handle is double-sided with a one-way ratchet, which means that to reverse the bit has to be taken out and put in the other side. Small price to pay to keep it all very small!
A view from the bottom, with the bottom retainer/cover off. There is an o-ring there, a number 7, that just fits over a 4mm hex shank. It will act as a retainer for the tool bits so they dont just slide out of the center tube. That tube will be hex shaped on the inside, and has the ratchet gear on the outside. To make the hex without a hex broach, I am going to use small drills to make holes at each corner, then bore/file out the center using those holes as a guide.




For scale, the screws are 2-56 size. The unit overall is 3" long, the head is 3/8" wide and 3/8" tall - pretty small by ratchet standards. Here is a view of the insides with the top cover off:



The dark green gear/tool holder will be cut from one piece, and has 20 teeth that can be cut with the corner of a straight end mill, no special cutters needed. The dark red pawl pivots on the cover screw, and is pushed against by the blue follower on the gold spring. For the spring, I am going to use one out of a standard retractable ball point pen. The handle acts as the end retainer for the spring, and the handle is held in by a screw from underneath. All easily accessible and no special parts. Earlier version of this design used flat sheet springs and had a reversing control, but wound up much larger.

So - thats where it stands right now. I have the measured drawing made from the CAD file, and am attaching the initial version to this post so anyone who wants to can build one too. The chances that the build will go off without any changes to those plans? Pretty iffy - at best there will be dimensions that I missed, at worst something needs to be tweaked for clearance or to make it easier to make. When I am done I'll post any new versions of the plans on this thread. Shouldn't take more than a week, less if all goes to plan.
Chris
 
EDIT: My version of this tool is done, and I have updated the plans attached to this post with the changes made during the build - mainly missing dimensions, one hole changed size, and one screw is run in from the opposite end for easier assembly. Enjoy!

[cnr6400]

 

[Vixen]

Chris,

That looks like a real neat micro ratchet handle. You should be able to get into some tiny corners with that one. 

Mike

[Admiral_dk]

Looks like a nice design 

Thinking out loud - should you not have an o-ring on each side ...?
I know that the Wiha bits are long enough to reach the other side, but still 

The o-ring as the retainer (so to speak) can also kind of lock the racket - you know when the friction of the bolt, nut or screw isn't high enough to 'click the racket', and you 'just move them forth and back, instead of clicking one way' - so maybe a very thin washer between the cover and the o-ring ....

Maybe useful, maybe not ....

Hmm - maybe on second thought - do a small groove in the middle of the Hex, for the o-ring - so you have boths ends as a 'bearing in the covers' sticking a fraction out at each end .... and much less friction + control over the racket ....
Or should it be a single turn of music wire in that groove 

Per

[gadabout]

Would a small sprag  bearing be useful instead of the ratchet? Just turn it over when you want to go in the other direction.
Regards
Mark

[crueby]

Looks like a nice design 

Thinking out loud - should you not have an o-ring on each side ...?
I know that the Wiha bits are long enough to reach the other side, but still 

The o-ring as the retainer (so to speak) can also kind of lock the racket - you know when the friction of the bolt, nut or screw isn't high enough to 'click the racket', and you 'just move them forth and back, instead of clicking one way' - so maybe a very thin washer between the cover and the o-ring ....

Maybe useful, maybe not ....

Hmm - maybe on second thought - do a small groove in the middle of the Hex, for the o-ring - so you have boths ends as a 'bearing in the covers' sticking a fraction out at each end .... and much less friction + control over the racket ....
Or should it be a single turn of music wire in that groove 

Per

Hi Per,
The hex shank on the Wiha bits are 1/2" long so they will go all the way through the opening and engage the o-ring from whichever side the bit is inserted from, so I dont think that a second one would be needed. I'll find out this coming week, easy enough to add another one if need be. Interesting idea about using the friction - another thing to experiment with.I considered putting the ring in the middle of the hex, but I dont have a boring cutter that could reach in such a narrow bore to make the groove deep enough - that hole is only 4mm across. A small bit could do the groove for a smaller diameter cross section o-ring, the rings I happened to have in the bin are 1/16" cross section, a thinner one would work too.

[crueby]

Would a small sprag  bearing be useful instead of the ratchet? Just turn it over when you want to go in the other direction.
Regards
Mark

Hi Mark,
I've never made a sprag bearing, though I did look around for an off-the-shelf one but could not find one in the right size range that could take the forces of the ratchet, the only small ones I could find had plastic parts that were too weak. The ratchet handle I have been using till now does have that kind of bearing, so it can work with a tiny movement, but it has a very large diameter end on it, three times the size that I am trying to make. This one will work the same way, flip over for other direction.

[gbritnell]

Hi Chris,
Can you buy the sockets separately? The only ones I could find came in a set with screwdriver tips, Torx bits etc.
gbritnell

[crueby]

Hi Chris,
Can you buy the sockets separately? The only ones I could find came in a set with screwdriver tips, Torx bits etc.
gbritnell

Hi George,
Yes - on the Wiha web site they sell them individually too. I have one of the bigger sets, but had lost one at a show and I got a replacement. If you google for 'wiha sys 4 bits' you can find some other retailers that carry the bits, though most just sell the sets.

Here is a link:https://www.wihatools.com/bits/micro-bits/bits
They call the ones with a 4mm hex shank a 'System 4' or a 'Micro' bit.
And looking at their site, and I mis-spoke in an earlier post, they do NOT make a 4mm ratchet - in the set with a ratchet handle, its a 1/4" drive and they include a 1/4" to 4mm adapter.

[crueby]

This morning I got a start on the ratchet handle build. Wanting to get the most complicated piece made first in case it turned up any issues with the design, I started with the gear/drive piece at the heart of the tool. Started with a piece of 303 stainless roundbar, and turned the profile for the gear piece.


I started the turning with a regular lathe too, but finished up the inside corners and the area on the left with a parting tool to get a better inside corner.
Then the chuck with the part still in place was moved over to the mill, on the rotary table set vertically. This is very similar to cutting a gear, but just using a normal 1/8" tip end mill. I set the height so the tip of the bit came in to the part about 45 degrees up from center - just eyeballed it. The depth of cut is .030", which leaves room for 20 teeth around the edge. Then made a pass across the part, turned the rotary table 18 degrees, another pass, repeat till done...

Then switched to the rotary table set flat on the mill table (I cheat on this part, years ago I picked up a second-hand rotary table so I can leave one set up in the vertical adapter, saves a LOT of time switching it back and forth). Centered up the part under the mill head, and moved out .07" and center drilled for the corner holes.

These holes will define the corners of the hex, and make it easy to get the final shape without needing any broaches or a lot of filing. Then put in a number 58 drill (small little thing!) and drilled each hole .45" deep, enough to get through the length of the part once it is parted off. With such a smalll bit, this took a while since I needed to peck at it, backing the drill out every turn of the handwheel to clear chips and add oil.

Now to remove the center material - a normal drill bit would catch the edges of the smaller holes and get pulled to the side most likely, so I first ran in a 1/8" end mill in a slow plunge cut, clearing chips a couple times - don't want it to start chattering.


Then ran in a 5/32" end mill, which is an elves-whisker smaller than 4mm.


On test fitting one of the bits, turns out that it went in about halfway - the top of the hole left by the mill was just a little oversize due to the chips and chatter from the interrupted cuts. Perfect!

So, moved the chuck back to the lathe and parted it off to final length (0.422")


It needed just a few swipes with a triangular needle file on the one end to clean up the burs from parting and down the bore on one side to get the tool to fit in the bore. It looked like one of the drilled small holes had drifted in towards the center just a little - few file strokes on that side and it was a nice fit.

As you cann see from those monster fingers in the photo, this is going to be a small ratchet! I had exported the files to the slicer for the 3D printer, thinking that I could print a sample set of parts just to check function on the ratchet pawl, but there were too many places where the walls were too thin for the printer!

Next, will make the ratchet body. This is looking like it might be a one day project, maybe two.

[petertha]

Nice!

I am a Wera fan boy. Their Zyklop mini is a work of art & joy to use. The specs say 60 teeth which gives very nice action at this scale. But its 1/4" nominal hex shank tooling.
https://pdf.directindustry.com/pdf/wera-tools/catalog/88203-651310.html

[crueby]

Nice!

I am a Wera fan boy. Their Zyklop mini is a work of art & joy to use. The specs say 60 teeth which gives very nice action at this scale. But its 1/4" nominal hex shank tooling.
https://pdf.directindustry.com/pdf/wera-tools/catalog/88203-651310.html

That is a good looking one, should be very comfortable in the hand.   

[crueby]

After lunch got back in the shop, got a lot done while the shop elves were sleeping off their liquid lunch....

I did not happen to have any 1/4" x 3/8" flat bar, so I am using a 1/4" x 1/2" piece, will trim the edges after the shaping is done. First drilled a starter hole, then bored the hole through for the end of the gear shaft and counterbored to clear the gear itself. Had to use a rounded needle file to clean off the burs left on the corner to the smaller hole on the inside.

Referencing from that location, moved over and drilled the hole for the screw that holds the ratchet pawl and the o-ring retaining collar, after that did the hole for the handle at the other end (not shown in the picture)


Put in an end mill, and cut the opening for the ratchet pawl and the follower. This opening size is not that critical, needs to be a loose sliding fit on the follower and be large enough for the pawl to clear in its movement. In this picture you can see the hole for the handle, and a line where the block will be cut off to length.


Then cut off the excess on the handle end, and milled the ends/sides to final size. There is just a small wall left next to the gear opening. The end around the gear will be rounded off later.


Parts so far:

The hole for the handle overlaps into the cover, so the cover is up next. Drilled a matching pattern of holes in it, just like the main body. The hole at the gear end is smaller in the cover since it does not have to match the OD of the o ring.

With the cover screwed to the main body and using the body as a guide, the cover was trimmed off to match - again, no 1/8" x 3/8" bar stock but I did have 1/8" x 1/2".

And the parts so far:

Clamped the cover and body together, aligned carefully, and drilled the hole in the end for the handle. This hole also forms the opening for the pawl spring, the handle only goes partway in, then the spring sits at the end of the handle.

Cross drilled the handle for the screw through the body and cover, using the existing hole as a drill guide.

Quite a bit done - parts left to make are the o-ring retainer, pawl, and follower. Good place for a break!

[crueby]

Oh - and as I figured would happen, along the way so far have found some missing dimensions on the plan sheet.  Am updating that as I go, and will update the plans posted on this thread at the end!

[crueby]

After being outside most of the afternoon, got one more piece made, the o-ring retainer. Simple rectangle with a through hole and a larger one counterbored in to fit the o-ring. I had started with the larger hole being the same as the OD of the ring, but after a test realized that I need that hole to be at least as large as the OD of the ring when the shank of a bit is in it, otherwise it expands and binds. So, ran out the hole another 15 thou, much better. The holder is the piece in the lower right of the picture, also you can see the pawl spring set in place. The pawl and its follower are the last two pieces to make, that will be tomorrow.

And the parts so far, assembled. The end of the main body still needs to be rounded, and I am thinking that the sides need to be turned partially round, or at least beveled to a hex and the corners smoothed some, for comfort.

Quite a bit done today, thought it would take longer for these parts. The pawl and follower are more fiddly shapes, they will take a while tomorrow.