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View Full Version : Making an arbor for gear blanks....question, ideas



Rif
10-16-2007, 12:07 PM
Hello,

I am in the process of making an arbor, to hold the gear blanks, for my 1893 Pratt & Whitney lathe. Everything was going great until I got to the part where I need to thread the arbor to accept the nut that clamps the blank in place. Yesterday, I got two 7/8-9 nuts to use on the arbor. (In retrospect, I should have gotten 7/8-14 as they would have been easier to thread. Once again, hindsight is 20/20.) So, since I don't have a 7/8-9 die, I figured I would "simply" thread the arbor on my Sherline. After 3 hours (not a typo) I have the threads about 75% complete. :( I was at this from 10:PM until 1:AM last evening.

In the above 3 hours, I also attempted to mount the arbor, in my P&W lathe, and chase the threads by holding the tool bit in a pair of vice grips and supporting it similar to a graver used by watchmakers. This was partially successful in cutting the threads; but, I can see where it would take a lot of practice. (I was chasing the partial threads made by the Sherline.) I also rooted around in some of my dad's stuff and found a 7/8-9 tap...but no die.

Today, I unsuccessfully attempted to find a 7/8-9 die down-town. (Where I work, getting to any place that might have something, other than food, takes about an hour for the round-trip.)

Enco has a round die for $19.54; but, I don't feel like buying one for what is most likely a one-time use. I also don't have anything to hold a round die with, so I would need to buy a wrench as well.

Since the threads are almost complete, I am considering boring the nuts out to work and calling it "finished." Also, since I really don't feel like spending another hour or 2 threading this arbor, does anyone have a better idea?

Thanks,

Brian

tattoomike68
10-16-2007, 12:12 PM
Stop by a machine shop and ask them to chaise the threads?

SGW
10-16-2007, 12:23 PM
You're going to clamp the gear blank between the two nuts, on the threaded section?

If 'twere me I think I'd take a slightly different approach. Turn a stub arbor from 1" dia stock, with a 7/8" section just slightly shorter than the thickness of a gear blank, so the gear blank can slide on with a good fit and butt up against a shoulder. Then drill/tap the end of the arbor some convenient size, like 1/2-13. Slide on a gear blank, and hold it in place with a washer and short bolt threaded into the end.

Rif
10-16-2007, 12:28 PM
Stop by a machine shop and ask them to chaise the threads?

That would work, except that I want to start making the gear blanks tonight. Let me tell you about the closest machine shop that I am aware of. They do great work! I mean, the work is really great....once they do it. The last thing they did for me was the head to an engine. The timing chain tensioner failed, the chain skipped, and the pistons and the valves and a brief, though decisive, meeting. So, I took the head to this machine shop....there was another that I am aware of; but, they went out of business. Anyhow, I knew from past experience that if I am quoted 2 weeks, I'll have it finished in 2 months...maybe. Also, if the price is quoted at $100, it will be $200. I don't have a problem with the price....just the timing. Anyhow, I was quoted 2 weeks so I waited 2 months. Then I called them and was told that they were very busy. So, I told them that I was picking up the head at the end of the week, finished or not, and would pay them for what work they did. I just needed them to do the work. The head was quickly finished.

So, in short, I'll spend another 3 hours threading this arbor...if I have to. :(

Brian

Rif
10-16-2007, 12:34 PM
You're going to clamp the gear blank between the two nuts, on the threaded section?

If 'twere me I think I'd take a slightly different approach. Turn a stub arbor from 1" dia stock, with a 7/8" section just slightly shorter than the thickness of a gear blank, so the gear blank can slide on with a good fit and butt up against a shoulder. Then drill/tap the end of the arbor some convenient size, like 1/2-13. Slide on a gear blank, and hold it in place with a washer and short bolt threaded into the end.

That is similar to what I am doing. I am making an arbor to mount between a rotary table and a tailstock. The arbor will be mounted between centers. About 2 inches from the tailstock end there is a shoulder in which the gear blank is held against. Closer to the tailstock is threaded so that the gear blank can be clamped between the nut/washer and the shoulder on the arbor.

Sorry I wasn't clear. I bought 2 nuts so I would have a spare....Murphy's law, you know. :D I just decided, due to the size of the hole through the gears, that 7/8 would be a better size nut. I think I learned my lesson. :o

Brian

DeereGuy
10-16-2007, 12:40 PM
Riff this is what I made up for making my gears.

http://s2.photobucket.com/albums/y39/Deere_X475guy/Machine%20Shop/?action=view&current=1104061433.jpg

tattoomike68
10-16-2007, 12:40 PM
Thats too bad you dont have a good shop close by. You could call asking to borrow a vice and die for 5 minutes.

At the shop I worked at, I would have ran a die over the threads and sent you on your way in minutes, maybe charged $2 for the beer fund.

Iv done machine work for farmers alot and they loved it when you would fix them up fast so they could get back into the feild.

I guess shop like that are hard to find, kind of like the good old days of service stations where they would pump your gas, check/add oil, check the tires,,,

Rif
10-16-2007, 12:50 PM
Riff this is what I made up for making my gears.

http://s2.photobucket.com/albums/y39/Deere_X475guy/Machine%20Shop/?action=view&current=1104061433.jpg


That is very similar to what I am making. However, I am using a 7/8-9 nut at the right end and I have a flat, at the left end, for clamping a lathe dog. When finished, I can use this arbor in the lathe or mill.

Brian

Rif
10-16-2007, 12:54 PM
Thats too bad you dont have a good shop close by. You could call asking to borrow a vice and die for 5 minutes.

At the shop I worked at, I would have ran a die over the threads and sent you on your way in minutes, maybe charged $2 for the beer fund.

Iv done machine work for farmers alot and they loved it when you would fix them up fast so they could get back into the feild.

I guess shop like that are hard to find, kind of like the good old days of service stations where they would pump your gas, check/add oil, check the tires,,,

Well, there is a good side to the story. Their slowness is what got me interested in machining in the first place. I figured that if it takes them 2 months, with the tools I can slowly and carefully figure out how to do it in 2 days. It has just taken a long time until I could get a place where I can start getting the bigger tools.

Brian

tiptop
10-16-2007, 06:29 PM
Brian, I have a 7/8 X 9 die nut you can borrow. I could put in the mail to you with next day air if you like. Jay:)

lane
10-16-2007, 08:19 PM
What you need is bigger lathe.

lugnut
10-16-2007, 10:55 PM
Bob,(deere_x475guy) thanks for sharing your photos, I learne a BIG bunch from them today.
Mel:)

J Tiers
10-16-2007, 11:11 PM
I have had perfectly acceptable and good results from using a regular arbor of the slightly tapered variety for holding gear blanks for cutting.

When it is pressed hard into a properly sized hole, a regular arbor holds very nicely. No nuts to come loose from vibration either.

If I used a straight arbor (mandrel, really) as I have, I would want a key in it to match the gear's keyway. Then I'd know the nut wasn't going to let me down.

That would be simpler, although you'd need presumably to make that. I have the luxury of picking the right size out of the drawer (unless it is an odd one). You don't so it might be easier to make it as you started to.

I definitely agree on tapping a hole in the end and clamping the blank against a shoulder. Easier, and you probably have everything you need already. Still might let go, but I'd actually trust the screw and thick washer farther than the big nut.

deltap
10-16-2007, 11:14 PM
Make your arbor with a slight taper so the blank fits on by hand at first but becomes a press fit when it reaches the shoulder. No need for a nut to hold it on. Do your machining toward the shoulder. You will need a press to force the arbor into the blank and press it off again.

Rif
10-16-2007, 11:27 PM
Brian, I have a 7/8 X 9 die nut you can borrow. I could put in the mail to you with next day air if you like. Jay:)

Thanks for the offer. Tonight, I ended up turning it down to 0.500 and threading it at 1/2-20. I would have threaded it at 1/2-13; but, the die wasn't cutting. So, once I find some 1/2-20 nuts and make a special washer up...which I wouldn't have needed if I could have gotten the 7/8-9 working...then the arbor will be ready.

Regards,

Brian

Rif
10-16-2007, 11:30 PM
What you need is bigger lathe.


You're right! I need to have some change gears, for the P&W, so that I can thread the arbor, so that I can make some change gears for the P&W. :D

Rif
10-16-2007, 11:35 PM
Make your arbor with a slight taper so the blank fits on by hand at first but becomes a press fit when it reaches the shoulder. No need for a nut to hold it on. Do your machining toward the shoulder. You will need a press to force the arbor into the blank and press it off again.

Hmmm, another problem. :) The P&W doesn't have a compound...so no taper until the taper attachment is completed as I only have some of the parts for the taper attachment. I suppose that I could have offset the tailstock; but, I didn't. Though, it would definately hold better with a taper. I'll do that with the next arbor I make....by then, I'll be threading with the P&W and have a working taper attachment. I might even make a compound for it.

The biggest problem I am running into is that I am using small tools to get bigger tools running.

Regards,

Brian