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PStechPaul
06-29-2014, 10:10 PM
As part of my endless project of fixing my 6" four jaw independent chuck, I needed to make a 5/16" square socket, about 3/8" deep, in the end of the 3/4" round 4140 steel rod that will be threaded and turned as needed. I had prepared one piece for threading, and I decided to use that to attempt my proposed way to do it. Basically I would drill four holes 0.093" diameter on a 0.155" radius circle, and then drill through the center with a 5/16" drill. It would leave just about 0.02" of material to mill off with a 1/8" diameter end mill or diamond burr:

http://enginuitysystems.com/pix/tools/Chuck_Screw_Socket.jpg
The green square is the 5/16" size desired, and the green circle is the size of a 1/8" tool. I tried to drill the holes using my tool post rotary tool holder, but it was not very successful. So I rigged up a clamp and small vise and drilled them with the mill/drill, but they still did not come out very well:

http://enginuitysystems.com/pix/tools/Square_Socket_1318.jpg

Then I put it in the lathe and tried to drill out the center with a 5/16" drill, but it jumped around a lot and did not stay on center. Finally I used a spotting drill to get a fairly good guide hole and followed with larger bits, actually up to 21/64" (0.328"). Then I went back to using my toolpost rotary tool holder and I was finally able to use it to mill the inner surfaces of the socket, but only after I filed a flat on the tool's spindle and used a tool that I made so I could tighten the collet (chuck) properly:

http://enginuitysystems.com/pix/tools/Chuck_Tool_1330.jpg

Here is the result. It's not quite as deep as I would like, but the chuck key goes in at least 1/4" and it fits pretty well:

http://enginuitysystems.com/pix/tools/Square_Socket_1326.jpg

The tool facing right is the homemade chuck key that came with the chuck. It is a bit undersize and fits sloppy, but well enough. I made some video and I'll put together a little project movie. It shows my continued difficulties with the collet on the rotary tool getting loose, and then the camera batteries pooped out, so it doesn't show the much greater success I had after properly securing the diamond burr.

PStechPaul
06-30-2014, 12:35 AM
Here's the video:


https://www.youtube.com/watch?v=l-pKRpwwjxE

rode2rouen
06-30-2014, 01:12 AM
I'm not exactly sure about you're trying to accomplish, but being one to take the quick & dirty way out, I would use an 8 point socket............ welded, brazed or soldered into an appropriately sized hole bored into the end of the bar stock. Something in 1/4" drive would
likely do the deed.

http://www.mcmaster.com/#drive-sockets/=smmbv2


Rex

plunger
06-30-2014, 01:22 AM
This calls for making a rotary broach tool. You need 4 square holes so it easily justifies making a specialized tool,even if it costs a little more. There are nice plans for a rotary broach on the HMEM site

PStechPaul
06-30-2014, 02:18 AM
A rotary broach would be best, and I found one on eBay for $40:
http://www.ebay.com/itm/5-16-Square-Rotary-Broach-Punch-Fits-1-2-Shank-Holders-Made-in-USA-S0315B-/121141005958? (http://www.ebay.com/itm/5-16-Square-Rotary-Broach-Punch-Fits-1-2-Shank-Holders-Made-in-USA-S0315B-/121141005958?pt=LH_DefaultDomain_0&hash=item1c34910e86)

http://i.ebayimg.com/00/s/MjU3WDUwMA==/$(KGrHqJ,!p4F!YGqLT+7BQcvp)OEww~~60_12.JPG

However, the holders are $375, although I think it may not be too difficult to make one:
http://www.ebay.com/itm/NEW-Basic-Rotary-Wobble-Broach-Tool-Holder-5-8-shank-for-1-2-shank-broaches-/121372163309

I considered making one, using a 5/16" lathe tool. I even ground a broken 5/16" brazed carbide tip tool to try something like this but with a round starter point and notches to form cutting edges, but the shank is not hardened. It might be possible to make something like this with one cutting corner and press it into the hole four times at 90 degrees each. But it might not work well in 4140 steel.

Mostly (other than getting the job done) I wanted to see how this process might work, and I think now that I've fixed the loose collet problem and know how to drill the corner holes accurately, I think this could be a viable option. It is also able to make sockets of almost any size and shape, but especially the common square and hex.

Another option is to use a 1/4" or 3/8" square socket and then use standard square drive socket wrenches. In that case I could get a cheap 3/8 drive socket set or individual sockets. It should be easy enough to drill a hole for the OD and a deeper hole for the tip and then use a roll pin to hold it (or a force fit and Loctite, perhaps).

Arthur.Marks
06-30-2014, 03:50 AM
Some good ideas: http://rick.sparber.org/msh.pdf

PStechPaul
06-30-2014, 04:51 AM
That's an excellent article. Lots of good ideas. Thanks!

I like the idea of square holed sleeves, as available from:
http://sturdybroachingservice.liveonatt.com/products.nxg/#1

Not sure how expensive they are. I saw a couple on eBay for about $15:
http://www.ebay.com/itm/Sturdy-62-Square-Holed-Sleeve-/251177745053

They are also available from Stock Drive Products:
http://www.sdp-si.com/web/html/newprdrsleeves1.htm

I didn't see square hole sleeves in stock, but a 5/16" hex sleeve is about $11 for a 2.25" length.

I was able to clean up and deepen the hole in the steel rod I worked on, using my B&D "Wizard" hand-held rotary tool, with a new NiMH battery to replace the original NiCad that had died as they usually do after twenty years or so - I've probably had it that long. I paid $13 including shipping for this, whereas the B&D replacement is about twice that. I got the last one:
http://www.ebay.com/itm/221326024022

Dunc
06-30-2014, 10:03 AM
A stub drill might give more rigidity. Old machining texts suggest supporting the drill bit with a hss tool bit reversed in the toolholder and pressed lightly against the drill bit.

jlevie
06-30-2014, 10:14 AM
I would have purchased a bushing with a 5/6" square hole broached in it and silver brazed it into the tool.

Paul Alciatore
06-30-2014, 03:29 PM
Many excellent suggestions here, including Rick Sparber's great article. One that was missed is the way my wrench was made:

http://img.photobucket.com/albums/v55/EPAIII/Web%20Post%20Photos/Square%20Hole%20Wrench/MillWrench2_zpsbe9cb692.jpg (http://smg.photobucket.com/user/EPAIII/media/Web%20Post%20Photos/Square%20Hole%20Wrench/MillWrench2_zpsbe9cb692.jpg.html)

It shows no signs of any problems after years of use.

I take no credit for this as it came with the used chuck when I purchased it. The braze line is so fine and nice that I had to use a magnifier to see it. I was very curious as to how it was made. I suspect the design would work even without adding the insert if you used a better grade of steel.

PStechPaul
06-30-2014, 04:40 PM
That's another pretty good method, although making the insert seems a bit difficult. Of course, you could just use a piece of 5/16" square steel and then turn it to dimension after brazing/welding. Here is a similar idea that does not require any extra material except for welding rod or braze:

http://enginuitysystems.com/pix/tools/Chuck_Screw_Socket_2.jpg

I have not taken into account the thickness of the kerf from the saw, but it can be filled in, or taken care of when turning down from 0.75" to 0.728" as needed. There can be a small extension before the threads begin, as can be seen in this picture:

http://enginuitysystems.com/pix/tools/Chuck_6in_0970_800p.jpg

Paul Alciatore
06-30-2014, 05:27 PM
Paul, Looks like that would work too. If you do not mill quite so far, you will not have the half moon opening on the side.

And it would need a final, cleanup cut on the OD in any case if you want it to look nice.

Whoever made mine did such a nice job on the insert that you have to look close to see the braze joint. I imagine square or rectangular stock and file/sand the matching radius on the end. Then braze it in and turn it down as you say. But, as I said, I did not do it so I can't say for sure.

PStechPaul
06-30-2014, 08:22 PM
I'm trying to avoid welding or brazing. I have a small arc welder, but I've never used it. I don't have an oxy-acetylene setup (or any oxygen gas equipment). I do have a regular propane torch which I have used for sweating copper pipe, but I don't know if it is suitable for brazing. The videos I have watched all seem to use a welding torch with oxygen, and the one I found using a simple plumber's torch was actually silver soldering with SSF-6 "Muggy Weld".
https://www.youtube.com/watch?v=-oifC7fbQfY
https://www.youtube.com/watch?v=T2wYgQtPg4g

Similar product:
https://www.youtube.com/watch?v=I8zsBKvFfFs
$28 for 1 ounce kit:
http://www.ebay.com/itm/35-Silver-Brazing-Solder-1-troy-oz-1-16-AWS-A5-8-BAg-35-Flux-/301218935938

Oxy-Acetylene:
https://www.youtube.com/watch?v=ZojIpKCo4TQ

Brazing rods are cheap and easily available:
http://www.homedepot.com/p/Lincoln-Electric-1-8-in-Flux-Coated-Brazing-Rods-3-Pack-KH515/202715833

An Oxy-MAP torch kit is $60:
http://www.homedepot.com/p/Bernzomatic-OX2550KC-Oxy-Map-Pro-Torch-Kit-331673/203391033

56% silver brazing kit (1 oz) for $80 at Home Depot:
http://www.homedepot.com/p/Lincoln-Electric-Stay-Silv-56-Brazing-Kit-56KPOP/100672839

Don Young
06-30-2014, 09:22 PM
I have made some similar holes by first making a male pattern, drilling an undersize hole, heating the work red hot, and then driving the male pattern into the hole. Don't know how this would work with the material you used.

Paul Alciatore
07-01-2014, 12:14 AM
As I said, I believe the technique I showed would work even without closing the fourth side. The milled slot would function much like a standard, "C" shaped wrench, which has an open side. If you want to close it without welding or brazing, just cut it flat as your drawing shows and bolt a rectangular cap on it. Four 4-40 or 6-32 SHCS would hold it quite nicely. Round the edges a bit with a file.




I'm trying to avoid welding or brazing. I have a small arc welder, but I've never used it. I don't have an oxy-acetylene setup (or any oxygen gas equipment). I do have a regular propane torch which I have used for sweating copper pipe, but I don't know if it is suitable for brazing. The videos I have watched all seem to use a welding torch with oxygen, and the one I found using a simple plumber's torch was actually silver soldering with SSF-6 "Muggy Weld".
https://www.youtube.com/watch?v=-oifC7fbQfY
https://www.youtube.com/watch?v=T2wYgQtPg4g

Similar product:
https://www.youtube.com/watch?v=I8zsBKvFfFs
$28 for 1 ounce kit:
http://www.ebay.com/itm/35-Silver-Brazing-Solder-1-troy-oz-1-16-AWS-A5-8-BAg-35-Flux-/301218935938

Oxy-Acetylene:
https://www.youtube.com/watch?v=ZojIpKCo4TQ

Brazing rods are cheap and easily available:
http://www.homedepot.com/p/Lincoln-Electric-1-8-in-Flux-Coated-Brazing-Rods-3-Pack-KH515/202715833

An Oxy-MAP torch kit is $60:
http://www.homedepot.com/p/Bernzomatic-OX2550KC-Oxy-Map-Pro-Torch-Kit-331673/203391033

56% silver brazing kit (1 oz) for $80 at Home Depot:
http://www.homedepot.com/p/Lincoln-Electric-Stay-Silv-56-Brazing-Kit-56KPOP/100672839

PStechPaul
07-01-2014, 12:59 AM
Most of these methods may be problematic because I need to have the threads close to the end where the socket is. If properly brazed, silver soldered, or welded, it may not pose a problem. I think I'll finish the screw that has the socket in it, and see how it works. Then I will finish the screw that is already threaded, and see how that works out. The existing screws are 2.343" long including a small extension outside the diameter of the chuck, but I think it would be better to have it flush or slightly recessed. I have 3" of raw material for each screw so there should be enough extra to grip in the chuck to work on it before parting.

BTW, I'm wondering if it's OK to grip the screw in the three jaw chuck on the OD of the threads, or perhaps wrap it with some softer material like aluminum or copper foil. Triangular threads would be more susceptible to damage.

Paul Alciatore
07-01-2014, 03:38 AM
The square threads that you pictured in post #11 would be OK to grip on the OD of the threads if you do not bite too hard on them. I would not hesitate to do it that way. But, if you are worried, some shim aluminum to protect them would not hurt.

Richard P Wilson
07-01-2014, 05:58 AM
[QUOTE=PStechPaul;925757]I'm trying to avoid welding or brazing. I have a small arc welder, but I've never used it. I don't have an oxy-acetylene setup (or any oxygen gas equipment). I do have a regular propane torch which I have used for sweating copper pipe, but I don't know if it is suitable for brazing. The videos I have watched all seem to use a welding torch with oxygen, and the one I found using a simple plumber's torch was actually silver soldering with SSF-6 "Muggy Weld".

These are only small parts, you should not have any difficulty silver soldering the closure piece with any reasonable propane torch.
Silver solder will be plenty strong enough for you to cut the short length of square thread through it. Holding a square thread in the 3 jaw for follow up operations will be fine, you start to loose concentricity if you use shims/packers.

Richard

SGW
07-01-2014, 07:24 AM
I've made a couple of hex sockets by drilling and milling. Try drilling the corner holes so they touch the corners. Drill the center hole a bit undersize, then use a 5/16" end mill for the final plunge cut. It won't wander. Then use maybe a 1/8" end mill to skim the sides and clean up what is left.
http://i1338.photobucket.com/albums/o686/sasgw/5-16-socket_zps2bdcd2dd.jpg (http://s1338.photobucket.com/user/sasgw/media/5-16-socket_zps2bdcd2dd.jpg.html)

PStechPaul
07-05-2014, 03:20 AM
Lots of good ideas, but for now I will just continue as I have. Finally I finished one of the chuck screws to the point where I could install it in the chuck. I had to shave a little bit off the OD of the threads and the "necks" to make it fit well, and it seems to work quite well. When I get all of them made, cleaned up, and installed in the chuck, I'll put a video together and a new thread on lathe chuck repair. This is how I started turning the necks down to size. The parting tool cuts very nice smooth square grooves which I locate at the desired width points, and then I move it one "click" of the leadscrew (1/16") to make overlapping cuts:

http://enginuitysystems.com/pix/tools/Chuck_Screw_1352.jpg

I used the same tool to do the parting. At this point I had to regrind it a bit so it would go all the way to the center:

http://enginuitysystems.com/pix/tools/Chuck_Screw_1356.jpg

Here is the screw in the chuck. I drilled four 0.094" holes at the points of the square socket, and then drilled out the center, which made it just the right size for the homemade smaller chuck key:

http://enginuitysystems.com/pix/tools/Chuck_Screw_1358.jpg

With the chuck key:

http://enginuitysystems.com/pix/tools/Chuck_Screw_1359.jpg

J Tiers
07-05-2014, 09:17 AM
Another technique that may or may not work there, is to drill a ROUND hole down the socket space. Use a drill slightly oversized so it takes out as much as possible, even if a portion of each side is left "pouched out". Drill deeper than the socket.

Then bore out behind the socket depth to a diameter that clears the corners of the socket to give file clearance

Now take a needle file and file the corners square. If you have an appropriate chisel, you can chip them out first.

The idea here is that corner drilling takes away material just where you need it, unless the holes are perfectly placed so that you still ahve to clean them up with a file. The IMPORTANT material in the wrench is the *corners* of the socket. The center of the sides has no part in turning the screw. The *corners* are what does the work, and they need to be complete and solid.

dp
07-05-2014, 10:50 AM
Make a simple rotary broach and tool holder - it's not a difficult project:

http://mikesworkshop.weebly.com/rotary-broaching.html

Paul Alciatore
07-05-2014, 05:05 PM
Another technique ...<clip>...

The idea here is that corner drilling takes away material just where you need it, unless the holes are perfectly placed so that you still ahve to clean them up with a file. The IMPORTANT material in the wrench is the *corners* of the socket. The center of the sides has no part in turning the screw. The *corners* are what does the work, and they need to be complete and solid.

J, That is not exactly true. While the center transmits almost none of the torque, the exact corner is not really necessary. As many commercial wrenches illustrate, what you do need is an area near the corner.

If the "corner" holes are small and placed properly, they will leave about 80% of the sides while removing only about 10% at each corner. Then if you mill or file the sides flat, you will have quite enough of the side left to work well. And, as a bonus, without the sharp corner, the stress riser effect there will be less so the socket will actually be stronger.

I will give you another thought. Unless the socket and square tool are made perfectly, it is likely that two of the corners will transmit most of the torque while the other two are only in light contact or not in contact at all. Thus, a hole formed like this would probably function just as well as one that is actually square:

http://img.photobucket.com/albums/v55/EPAIII/SquareMeter.bmp (http://smg.photobucket.com/user/EPAIII/media/SquareMeter.bmp.html)

The illustration was for a rectangular switch cutout, but the idea is the same. Use a small diameter milling cutter to form two opposite, full length sides by going past the ends by the radius of that cutter on both ends. That cuts right to the point of the corner. Then form the other two sides without going past the ends. Those two full length sides should transmit almost as much torque as a full square. And you still get the reduction in stress at the "corners".

A final suggestion here would be to use a small diameter milling tool and just keep the radius that it leaves at the corners. Then round or bevel the corners of your square wrench to fit. Frankly, I like this one best as it will produce less stress and leave more meat at those corners where failure would likely occur.

There's probably dozens of ways to do this one.

PStechPaul
07-05-2014, 05:13 PM
Another way to do it is to use the idea behind the "Metrinch" type sockets or the "lobed" type that use a sort of cam action. I have illustrated it here:

http://enginuitysystems.com/pix/tools/Chuck_Screw_Socket_Lobed.jpg

The corners are drilled 0.188" (3/16") diameter such that the edges just touch. Then a small amount of material on each edge is removed to clear the diameter of the square key. This leaves "lobes" which contact the key as it is turned (in this case 12 degrees). It is actually stronger because it distributes the torque over a fairly wide, flat area, rather than the point that is provided with a perfectly square slightly oversize hole. And it works just as well with a key that has sharp points or rounded corners as shown (which are preferred anyway). I think I will try this for the other two screws.

The difficult part for me has been accurate location and drilling of the four corner holes, and it will be even more difficult when they intersect. But I might be able to use a spotting drill and a short, stiff 1/8" drill followed by a 3/16" end mill. A ball end mill might be best because it will follow the pilot hole better. My mill may not be stiff enough or accurate enough to use the table x-y dials for location. And I think much of my problem has been locating the initial point and using the center punch accurately. Plus I don't have a really good clamping method for holding the work perfectly vertical. I'm using my small (ugly) vise which has small V-groove, lying on its side so the work can be gripped along most of its surface, and a V-block on the other jaw. But I'm using a C-clamp to hold it to the table, and it's on the edge and not very secure. I need to get or make some clamps for the T-slots. I may get this kit for $50:

http://www.ebay.com/itm/58-PC-PRO-SERIES-5-8-T-SLOT-CLAMPING-KIT-BRIDGEPORT-MILL-SET-UP-SET-1-2-13-/111368133024?pt=BI_Tool_Work_Holding&hash=item19ee0ed9a0

http://thumbs1.ebaystatic.com/d/l180/pict/111368133024_1.jpg

But just drilling the five holes produced a socket that is quite usable, although it will need to be enlarged just a bit for the correct full size key:

http://enginuitysystems.com/pix/tools/Chuck_Screw_1360.jpg

Paul Alciatore
07-05-2014, 06:58 PM
I love it. I wonder if a CNC program could be written to do that.

PStechPaul
07-06-2014, 01:06 AM
Here is what I was able to do with just a 3/16" end mill, using the mill table dials for location, and being sure to hold the slide gibs tightly:

http://enginuitysystems.com/pix/tools/Chuck_Screw_1364.jpg

The smaller homemade chuck key just barely fit:

http://enginuitysystems.com/pix/tools/Chuck_Screw_1365.jpg

I milled the center with a 5/16" end mill, and then I used a 1/8" ball end mill:

http://enginuitysystems.com/pix/tools/Chuck_Screw_1367.jpg

Now the full size chuck key fits well, but the smaller one twists too far to be used with much torque.

http://enginuitysystems.com/pix/tools/Chuck_Screw_1368.jpg

This was just a piece of scrap, to see how it works. I also realize now that I milled the holes at 0.094 from the center and not 0.133 as they should have been. I should have noticed when the holes overlapped. So I just need to try again. I have just about finished all the screws now and I'm just fine tuning them to fit the chuck.

I might make the socket a bit smaller than the 0.312" and mill or grind a small notch on each of the larger chuck key faces so that they clear the "lobes". It won't affect its use on the 4" three jaw, but it should make a nice fit in the four jaw, and the smaller key will fit better, so I can use the two-key trick when adjusting the opposing jaws.

J Tiers
07-06-2014, 01:14 AM
The corner drilling works with a small drill, because usually the corners of the wrench are radiused anyhow.

A file won't make a totally clean corner in general either so you won't have to fret much about stress risers, and of course you shouldn't worry, unless you habitually use a cheater on the chuck wrench.

The wrench or hole will be fine.