Anything special I need to know about adding a second set screw to a hub?

[ebinmaine 68,446]

I have at least 7 hubs on different tractors that I would like to add a second set screw to.

 

I have an older but good quality floor model drill press.

I have the tap set.

I don't recall ever using the tap set to do anything other than clean out threads. Not make my own thread set.

 

Can anybody give any particular advice?

[953 nut 55,845]

If you will be drilling that many hubs I would suggest making a gig to hold the hub upright and steady while drilling. A piece of 4 X 4 with a "V" notch cut in it attached to a piece of plywood so you can clamp it to the drill press would probably do the trick.

The other thing that would help out would be to find a small socket wrench to fit the tap or weld a tap wrench to an old socket extension so you can use a ratchet to tap the threads. Sliding that little handle back and forth on the tap wrench would get old real fast.

[roadapples 6,983]

Should have a flat spot where lock nut contacts

 

Edited June 17, 2018 by roadapples

[lynnmor 7,354]

If you have been using that tap to clean threads, it probably is no longer sharp and you risk breakage.  Keep the set screw at 90 degrees to the key and make them all the same to they will be interchangeable.  Spot face a flat for the lock-nut that is on the setscrew.   When installing on the axle, temporarily tighten the new screw enough to mark the axle, then remove and grind or file a flat in the axle for the set screw, that way it holds better and doesn't raise up material  that makes disassembly difficult.

[Marv 943]

I agree with all the above. Some hubs are thicker than others in the area you will be tapping new threads. I suggest you go slow tapping and be careful how much pressure you exert on the tap. The thicker hub can be especially tough.

Marv

[pfrederi 17,887]

The hubs have a slight taper to them.  WH machined a flat surface around the hole .  You will not have that.  So be very cautious about cinching down the lock nut.  it will put sideways stress on the set screw and it may snap off.  Do not ask how i know this.  Some poor dumb SOB will get an electro 12 some day and i hope he never has to remove the hub.

[953 nut 55,845]

Note to self;   DO NOT BUY Paul's Electro!                         

[ebinmaine 68,446]

Remind me Never to buy an Electro 12....

 

 

HAHAHAHAHHAHAHAHA !!!!!

 

I was typing out nearly the same note when you were

[953 nut 55,845]

1 minute ago, ebinmaine said:

I was typing out nearly the same note when you were

                 Deranged minds seem to work alike!          

[ebinmaine 68,446]

13 minutes ago, 953 nut said:

                 Deranged minds seem to work alike!          

Dick, I'm not sure if that's good news for you.

[953 nut 55,845]

1 minute ago, ebinmaine said:

not sure if that's good news for you.

Not proud of it,    just stating the obvious fact!     

[ebinmaine 68,446]

2 hours ago, 953 nut said:

If you will be drilling that many hubs I would suggest making a gig to hold the hub upright and steady while drilling. A piece of 4 X 4 with a "V" notch cut in it attached to a piece of plywood so you can clamp it to the drill press would probably do the trick.

The other thing that would help out would be to find a small socket wrench to fit the tap or weld a tap wrench to an old socket extension so you can use a ratchet to tap the threads. Sliding that little handle back and forth on the tap wrench would get old real fast.

 

It occurred to me when I saw your diagram above that I have a vise that sits with the drill press. Experimented with it a bit tonight. Pretty happy with the results and ease of drilling.

 

 

 

[953 nut 55,845]

1 hour ago, pfrederi said:

WH machined a flat surface around the hole .  You will not have that. 

If you use a larger drill bit than the nut, probably 5/8" prior to tapping your threads you could probably create a recess that is perpendicular to the set screw. Probably have to sneak up on it using several slightly larger bits.

Could also grind a slight taper on a washer under the nut.

[kasey54 305]

If you don't have it, you should obtain a tap/drill chart and get the correct size drill for the size set screw you select. I have done a half dozen or so and went to the next size bigger set screw than the original .

 I felt there was no way I could make a flat spot on the hub for the locking nut that would truely be perpendicular to the hole I drilled. Instead I bought set screws with the cup type point designed to dig into the shaft, you tighten and loosen 3 times. It won't loosen. My background is electrical apparatus repair, and work with lots of pulleys, fans, and locking set screw pillow blocks that encounter way more vibration and such than the wheelhorse axles ever do. Also if you are new to tapping new threads you want a tapered tap, not a bottoming tap. Also you turn your tap in about a half turn then back out a half. then go in a full turn, back out a half, and continue. This breaks and frees the material your cutting as to not jam up the tap. Some cutting oil is of great help as well. I've found any oil is way better than none. I use the next size bigger set screws because the next size tap is much stronger and less likely to break. Likewise the bigger set screw can be more forcefully tightened. you definately want flats on the shaft where the set screw digs in to aid in future removal. a considerable burr will be raised.

 Go for it!

[edgro 677]

You could also use red locktite on the set screw rather than a lock nut

[pacer 3,174]

I would add to all the above (all good advice) that you find a top grade tap, the hardware store or big boxes are likely not to be this. A good grade HSS tap, and a comparable drill bit, will make a lot of difference - especially doing multiple holes. If like most of us you have one of HF's little angle grinders it will do a nice job of getting a flat spot on the hub, and the axle - it can be difficult to keep the drill bit from "skittering?" in trying to get it started otherwise.

 

Ive have added 2 extra set screws on several on mine!

[Sarge 3,463]

All good points above - but of course, I have some things to add to this. 

 

3/8"-16 thread, the common size for the set screw/bolts for the hubs uses a .3453" pilot hole as it's optimum size. 11/32" drill bit is close enough to work and on cast iron will hold the threads just fine for this application with a good, sharp tap. To create a flat, I use a socket head piloted counterbore bit that cuts a recess - using the 5/16" size cap screw counterbore with a pilot size of 11/32" is a way to "cheat" a bit and create a nice flat for the locking nut to sit against. Outside bore diameter on this size counterbore is only 1/2", the nut will require that area to be enlarged but it's easy to do that with a grinder or a good file in short order.

 

http://www.victornet.com/subdepartments/Solid-Counterbores-and-Step-Drills/2129.html

 

Now, you don't need to go out and buy an expensive bit, I grab good quality name brand used one off the auction site - have several for this type of purpose as well as their intended use for countersunk cap screws. I do have one much larger bit made for a 5/8" socket head cap screw, with the pilot ground down to fit the pilot hole size for 3/8" bolts (11/32). Cast iron cuts pretty easily, but it can also easily dull taps and other cutting tools due to it's properties/ingredients - use a lot of tapping oil here. For cast iron, I use either TD Foamy (available from Fastenal) or PB Blaster air tool oil. Be sure to start your initial hole with a smaller bit down around 3/16", then enlarge up to the 11/32" pilot size to help hold your centerline point.

 

Drill presses are a useful tool, but not a milling machine - you must remember that. Sure, you could use an end mill to cut the recess, but only if that is a very heavy, solid and tight industrial model press with a heavy spindle, which almost all of them are not. Otherwise, the operation can be done using a piloted bit to control wandering, which any flat bottom cutter is going to try to do when cutting something that is hitting on only 2 points (outside of a circle). 

 

For drilling into round objects, especially on a drill press, there is a handy indicator tool that makes the job of trying to center the point of cutting much easier -

https://www.amazon.com/HHIP-4401-0027-Drill-Center-Finder/dp/B01LW6N7N9

This tool, when chucked into the press will show the exact top centerline of a circle when the two marks line up. This will help "clock" the part to be bored on the proper plane to hold the hole 90* to the bore in those hubs. Without doing that, you can end up with a hold that is off-center and even possibly break a drill bit when trying to cut the pilot hole. 

 

Just some tips/cheats

 

Sarge

 

[lynnmor 7,354]

2 hours ago, Sarge said:

 

3/8"-16 thread, the common size for the set screw/bolts for the hubs uses a .3453" pilot hole as it's optimum size. 11/32" drill bit is close enough to work and on cast iron will hold the threads just fine for this application with a good, sharp tap.

 

 

The tap drill size for 3/8-16 is 5/16" (.3125"),  using a non rigid machine tool like a drill press or hand drill, or a less than a perfectly ground drill bit, might well cut oversize.  Cast iron is easy to tap so a slightly smaller 7.75mm tap drill would be perfect.  Always drill a smaller hole, then the tap drill, so that the chisel portion of the bit doesn't contribute to any run out.  With cast iron, use a much smaller drill first that leaves plenty of material for the finish size to cut, otherwise in may corkscrew right into the hole.  Do not use cutting oil on cast iron, a cutting fluid like Tap Magic is ideal.

 

The job in question would best be done in a vertical milling machine like a Bridgeport.

[ebinmaine 68,446]

As you can see in the picture above I messed around with this a little bit last night.

I came out this morning and started poking around a little bit more.

 

Took all of your advice in combination and watched a couple videos on YouTube and did some reading.

I didn't even know it but I actually did have a tap drill size chart in with my tap and die set.

 

I discovered that when I wanted to put a flat spot on the first Hub I did, I wished I had made the flat spot before I had done the drilling. So on the next two, the ones for the 657, that is what I did.

You know those times in your life when you find a tool that you never never need and then the one time you want to have it you can't find it? I know I have a couple of grinding Stones around here that have quarter inch shafts on them and I could have mounted them in my drill press but I'll be darned if I could put my hands on them this morning.

It ended up being the easiest for me to make a pencil mark or two on the Hub and carefully line up on my 6 inch grinding wheel by hand and make the flat spot that way.

 

What I ended up drilling ... start with a 3/32 hole. Went to 13/64. Then to the final hole at 5/16.

I then put a chamfer at the top with a half inch diameter drill because one of the videos I saw recommended a chamfer so as to guide the tap into the hole better.

I put the Hub in the little vice on my roll around table and carefully cut the threads in about a quarter turn forward and then 3/8 to 1/2 turn backward and then repeat, repeat, repeat, until I was all the way through.

I have quite a few old cans and bottles of shop supplies from my grandfather's Barn. I found this stuff so I used it.

 

 

 

In consideration that this is the first time I've ever done this and I don't have the most appropriate tools at hand, I'm very satisfied with the results.

 

 

 

 

[midpack 892]

looks good from here!I

 

bet that cutting oil reeked... looks like sulfur based oil

[ebinmaine 68,446]

1 minute ago, midpack said:

looks good from here!I

 

bet that cutting oil reeked... looks like sulfur based oil

 

Didn't smell too bad. That said, my nose is a bit stuffed. Sometimes Allergies have their benefits.

[Sarge 3,463]

20 hours ago, lynnmor said:

 

The tap drill size for 3/8-16 is 5/16" (.3125"),  using a non rigid machine tool like a drill press or hand drill, or a less than a perfectly ground drill bit, might well cut oversize.  Cast iron is easy to tap so a slightly smaller 7.75mm tap drill would be perfect.  Always drill a smaller hole, then the tap drill, so that the chisel portion of the bit doesn't contribute to any run out.  With cast iron, use a much smaller drill first that leaves plenty of material for the finish size to cut, otherwise in may corkscrew right into the hole.  Do not use cutting oil on cast iron, a cutting fluid like Tap Magic is ideal.

 

The job in question would best be done in a vertical milling machine like a Bridgeport.

 

That's why I hate phone apps - wrong application chart again, so I deleted it. The 11/32" pilot seemed odd and I should have caught it, my bad. 11/32" works for the initial counterbore for socket head screws, but not regular cap screws. 

 

Looks good on those hubs, will make a big difference in keeping them tight to the axle shafts.

 

Sarge

[ebinmaine 68,446]

1 minute ago, Sarge said:

Looks good on those hubs, will make a big difference in keeping them tight to the axle shafts.

Thanks Sarge!

 

Second set screw should certainly add a pretty good margin of reliability to all the tractors I'm going to do it on.