Pin to bushing clearance?

[Steve in MT]

I used 1" x 3/8" wall DOM tubing when I built the pin on style quick attach for the loader on my tractor. I had to take a die grinder with a burr bit to clearance the tubing to get a 1" pin to slide through it. Obviously this is not a precision way to do this although it did work. I have been looking for a hand reamer to do this and the closest one that I could find is a 1-1/16". This reamer would make the pin to bushing clearance 0.0156. My feeble mind tells me that this is too large and that the clearance should be closer to 0.006.
Does anyone know what a good clearance fit between a pin and bushing should be? And more importantly, where in the Sam Hill do I find a hand reamer ? I'm toying around with the idea to build my own backhoe and it sure would be nice to have a faster and more precision way to ream a bunch of bushings. Thanks for your time.
Steve


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[Buty]

I think if the holes line up correctly .010 would be a good clearance.

 

[joshuabardwell]

.10 should be plenty. Consider getting an adjustable reamer and then you can take it out little by little until it's exactly where you need it.

 

[yomax4]

I did nearly the same thing but I took the tube to the local machine shop and they bored it to accept 1" pins. Charged me $20.00. Another option besides a carbide burr would be a 1" cartridge roll at about 36 grit on a long mandrel. Or even a 1 1/4 flap wheel. Takes a little lomnger than a burr but you wont get the internal dings that a burr causes. Nice job by the way..

 

[joshuabardwell]

Likewise on the machine shop, but lots of people prefer to weld, then ream, since welding distorts the tube slightly,

 

[jmc]

I think 1/16 would wear and rattle.

Misc. thoughts:

Can you measure the pin precisely, ie mics or calipers?

Try inserting a feeler gauge along one side of a factory hole/pin assembly to get an idea of proper clearance.

Could your tubing be slightly oval?

25mm bar would be .985". Might work with your existing tubing and be easier to find than a reamer.

Some company must make off the shelf bushings like this for all the manufacturers.

Lastly, find a hobby machinist or vocational school and have them tweak the bushing ID in a lathe. An expensive machine shop would be overkill for such a simple job.

 

[rankrank1]

My method for non-critical fitments:
a) Carbide burr in die-grinder for roughing in. (Use the biggest diameter burr tool that I can for hole size as it helps keep it round when free-handing).
b) Sand roll in die-grinder for finishing or minimum material removal. (again use biggest diameter roll that I can for the hole to help keep round).
c) If you want to get super critical then you can use a cheapo brake cylinder hone in a drill for the final few thousands of finishing.

Obviously critical tolerance fitments should be done in the machine shop realm which I do not have.

 

[Willl]

c) If you want to get super critical then you can use a cheapo brake cylinder hone in a drill for the final few thousands of finishing.

I'm lacking a reamer in my shop and this is what I ended up using. Slow but got the job done.

 

[dkhntr04]

Ask about "repair sleeve" at your local steel supplier. I do not know the specifics on the steel alloy or brand name, but it is a much harder/tougher steel than A36 but it machines and welds nicely. It comes in over/under sizes, so if you wanted a 1" ID and 1.5" OD the repair sleeve would be something around 1.010" ID and 1.490" OD give or take. I have not mic'd it. You can weld on the tube and for the most part a nominally sized pin will still fit even with distortion. I have used it to rebush an entire FEL on a row-crop tractor, and on a multitude of other projects.

If it is an existing unit you are working on, I second the adjustable reamer.

 

[mrmikey]

If you get a 1" reamer, 1"Ø cold rolled or stress proof will fit as it's done to a more precise size usually nothing over and only a few tho under.....Mike

 

[Steve in MT]

Some good answers guys. One thing that I didnt think of was the tubing being oval and the distortions during welding. There would be 3 pieces of DOM per pivot, one about 3 to 4in long plus 2 on the outside roughly 3/4in long with one of those drilled for the pin retainer. Its pretty tough to align all three up with each other during welding. The thought was to weld up one complete pivot section and then run a reamer through all 3 pieces. It would be nice to have a reamer thats a bit bigger then 1in that has a entry taper for the first inch to start it with the rest of it being the finish side. I have a bunch of pins that mic to exactly 1in but the DOM is a tiny bit smaller. I see some adjustable reamers on ebay so might pick one up to try. So, is there such a thing as a flap wheel that a person can run inside of pipe/DOM? I'll have to investigate that as well. Thanks for the answers.
Steve

 

[joshuabardwell]

An option is to weld a single piece of tubing in place of the opposing bushings, the cut out the middle. Guarantees alignment between the two sides.

 

[jmc]

If I understand your project, you don't need to "line-ream" all three bushings simultaneously. If you get the two outside bushings coaxial, the inside component will fit unless it has almost no width clearance.

Reamers tend to follow the hole. (as opposed to boring bars that cut in the direction you point them.). Nobody every tries to line-ream an engine. They always line-bore it. So in your case, the reamer direction is established by the first outside bushing and most certainly will be off axis with the other outside bushing after traveling 4 inches.

What has worked for me on getting the two outside bushings somewhat coaxial was to hold the two outside bushings in place, pre-weld, with the eventual pin and the thickest shim stock I could wrap completely around the pin, and still assemble with the outside bushings. This keeps the two bushings more or less concentric with the pin while you weld them in place. In my case, everything fit together smoothly before welding but I had to hammer the pin out after welding. Still, upon reassembly without the temporary shim stock, everything assembled nicely. So whatever distortion occurred while welding was less than the shim stock thickness.

 

[the old grind]

Steel shop guy tells me 'stress-proof' is all the rage these days for pins. Supposedly, forming imparts a surface hardness that extends wear life. It definitely tools well on the lathe, could be turned down a few thou for clearance IF .. bushings are aligned right to begin with. Don't remove too much stock from bushings. High spots caused by distortion will wear down first once you er .. tap things together. (Gotta be some room for grease to flow evenly till 'broke in.')

btw: IIRC, my supplier says 'stress-proof' doesn't weld nearly as well as it machines. Dunno. I make lotsa chips in the shop, but I'm too old & shaky to weld.

 

[Steve in MT]

Ah, some more answers, bring them on. I have a leftover piece of DOM that I just measured. Turns out that its actually 0.995in on the inside and the pins are dead on 1.000in. I think that JMC is correct that I really dont need to ream through 3 pieces at once, just the outside ones. The idea of the shim stock and/or welding a length of bushing/DOM and then cutting out the center section are 2 more conciderations. Now about the "stress-proof" pin stock? I haven't heard of that before and will have to check around on that. I do have a old Sears (Atlas) 12x24 lathe to make pins with if need be. I found an interesting reamer today that measures 1.004in and is used for Ford king pins. The reamer section of it is pretty much in the center with with a nice straight section on both sides of it. Im waiting for a responce from him with more info. I'll let you guys know what I found out.
steve

 

[the old grind]

You could ream to whatever size tool you have after welding and turn down a larger round on the Atlas to achieve your preferred clearance, er .. depending on how that 'alignment thingie' works out. (ream by hand. also, welding heat may harden bushing mat'l, and unevenly...) Your clearance will allow for a smidge of misalignment, and not much, but I wouldn't necessarily count on a 1 pc bushing to hold perfect alignment at both ends after welding and cutting the center out, either. Span, the weld, and bushing thickness may 'make or break' that worry. btw: that piloted reamer sounds like a sweetie-pie.

 

[David Devuono]

I have built a loader and a backhoe. I go to my local hydraulics place and buy their Pins and Cross tubes. One inch pins fit fine. It might be a little more expensive then just a piece of DOM tubing but by the time you buy a reamer you will not be further ahead. If buying DOM tubing is the route you want to take, why not buy much larger and add brass bushing. Here is a picture of a bucket I am making. I used one inch cross tubes cut down as needed.

 

[David Devuono]

I will also add that I have never noticed the effects of tube warpage and they glow red when I am welding them. Pins continue to slide easily. Just remember to have a pin handy so that everything is lined up before welding.

 

[David Devuono]

Note, 4.5 inch long, 1 inch ID cross tube cost $7.99 so I used less then $16 on my bucket, so you will not be saving much using DOM tubing and reaming it.

 

[Steve in MT]

David, you have my attention. Can you tell me what the wall thickness is on the cross tubes? Looking at your bucket, they appear to be about 1/4" which is about the size on a factory bucket. Sorry, but I have not heard of "Cross tubes" before. What are they and what were they designed for? When you built your backhoe, were you able to use these in the center pivot position as well? I dont recall that DOM was cheap to buy but thats what I was able to come up with at the time that I built my quick attach. Inquiring minds need to know (and I'm sure that I'm not the only one)
Steve