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JCDammeyer's 42 projects

whydontu said:
Forgive me for this question, but why not just buy a chunk of 3” XXH pipe? 3.5” nominal O.D., 2.3” nominal I.D., only made in seamless material so no weld bead.
Click to expand...
No idea where to get that. I need about 3".

Its assembled like this. The bearings go onto the spindle. I do have material to make that.
1726102597462.png

Then the spindle goes into the piece that I was planning on casting.
1726102629029.png

The other side I have material for too but this next piece will likely be another casting.
1726102717805.png
 
whydontu said:
What material? Steel, stainless, aluminum?
Click to expand...
6061 I think is more than adequate for this robot arm.

I'm really tempted to print the core box and core. I have one other project ready to cast that has T-Slots as sand cores. I use fine silica sand along with flour and molasses water to make the cores. It's baked in a table top oven until it's hard enough to not fall apart. Same technique used for the tailstock hole in the Gingery Lathe project.

The core approach requires the least amount of post machining but the most work to get there. The pipe blank (with the 3 degree taper for ease of pulling it out of the green sand) just requires making more chips.

The big advantage to casting is if I screw up the machining I'm not out any money other than maybe $1 worth of Natural Gas for the foundry and WD-40 for machining lubricant.

I'll be looking for advice on machining this too. The bearing races should just be a friction fit and line up the bearings for the spindle. But there's that should in between.
 
jcdammeyer said:
Well aside from one broken 2.5mm drill bit and one broken 3mm tap and accidentally changing the X=0.000 location the result is passable but really a piece of crap.
After all is said and done and some file work it's usable but I'm not happy.
View attachment 51501
The backlash and positioning really didn't make for the greatest cut. A depth of 0.1" per pass and 5 IPM with a 1/4" two flute end mill. I likely should have left 0.010" and then done a single pass around with a 1/4" four flute end mill.

I may have to restart project #42 and add ball screws to the mill. The backlash is killing me.
Click to expand...
Well rats. The 5 replacement M3 taps and 10 each of 2.5mm, 3.0mm, 3.2mm and 3.5mm arrived today except the 2.5mm drill bits were actually 2.0mm. That's of course the one I broke drilling the holes in this plate.

I've asked for either replacements or I'll just order 10 of the correct ones. It's not a lot of money. Just the delay.
 
Fortunately the next group of holes to drill are 5mm for 6mm tapping. And lots of lathe and mill work.
I do have a question though...
The yellow section is made from 3 separate parts. Inside the thicker one are two tapered bearings. The thinner piece clamps onto the body of the planetary reduction drive which is driven by that stepper motor.

1726789575360.png


This is the spindle which has to be concentric with the outer part that goes into the bearings and the inner part that slides over the planetary gear shaft.
1726789842435.png


Needless to say the outer bearing race holes in the thick part and the planetary gear clamp must also line up perfectly.

For the spindle starting with 2" diameter shaft and drilling and boring until the 14mm shaft size is reached seams the best way to go. Then the outer part. Once that's done flip it end for end in the lathe and bore out to the key clearance diameter so the broach can make it through. As far as I can see that should make this much better than the 0.002" concentric tolerance.
1726790175911.png



But that yellow section. How to line up the holes so they are concentric and parallel to the base? In the old days maybe assemble it after rough machining each hole. The clamp it to the lathe carriage and use a between centers boring bar to cut the holes.

The issue is the outer bearing races have to line up and there's that shoulder inside that the outer races press against.
1726790581956.png


So how to make this hole and so it lines up with the planetary gear clamp piece?
 
I wonder if anyone has used their lathe as a line bore machine? Use an appropriate size bar with a cutter attached mounted between the head and tailstock with the part mounted to the carriage. Not going to be quick or easy but I think it could be done.
 
YotaBota said:
I wonder if anyone has used their lathe as a line bore machine? Use an appropriate size bar with a cutter attached mounted between the head and tailstock with the part mounted to the carriage. Not going to be quick or easy but I think it could be done.
Click to expand...
I have. Indirectly. Back when I made my Gingery lathe the headstock was set up to move along the ways push/pulled by the lead screw. A boring bar was set up between a bracket with the drive pulley and a dead center at the other end.

I can't find any photos of that setup but here's a before shot.

1726801963822.png



Edit. From the Gingery Lathe book. Wasn't done between centers.
1726802399225.png
 
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YotaBota said:
I wonder if anyone has used their lathe as a line bore machine? Use an appropriate size bar with a cutter attached mounted between the head and tailstock with the part mounted to the carriage. Not going to be quick or easy but I think it could be done.
Click to expand...
The older machines were built with that in mind. They had tee slots on the wings of the carriage........ Myfords have a pretty good cross slide for it as well. I bought a tee slotted cross slide casting from Metal Lathe Accessories for my South Bend 10k with that idea in mind.
 
Running a boring bar between centers on the lathe was a very common practice, not as often done now days. Many small shops did not have any type of milling machine, just a lathe or 2. I believe the older South Bend books/lathe manual had set up in them, and some others also.
In many cases not even a lathe was used to rebore large steam engine cylinders.
 
jcdammeyer said:
Fortunately the next group of holes to drill are 5mm for 6mm tapping. And lots of lathe and mill work.
I do have a question though...
The yellow section is made from 3 separate parts. Inside the thicker one are two tapered bearings. The thinner piece clamps onto the body of the planetary reduction drive which is driven by that stepper motor.

View attachment 51952

This is the spindle which has to be concentric with the outer part that goes into the bearings and the inner part that slides over the planetary gear shaft.
View attachment 51953

Needless to say the outer bearing race holes in the thick part and the planetary gear clamp must also line up perfectly.

For the spindle starting with 2" diameter shaft and drilling and boring until the 14mm shaft size is reached seams the best way to go. Then the outer part. Once that's done flip it end for end in the lathe and bore out to the key clearance diameter so the broach can make it through. As far as I can see that should make this much better than the 0.002" concentric tolerance.
View attachment 51954


But that yellow section. How to line up the holes so they are concentric and parallel to the base? In the old days maybe assemble it after rough machining each hole. The clamp it to the lathe carriage and use a between centers boring bar to cut the holes.

The issue is the outer bearing races have to line up and there's that shoulder inside that the outer races press against.
View attachment 51956

So how to make this hole and so it lines up with the planetary gear clamp piece?
Click to expand...

If there are end plates holding the bearings in, I would fasten the 2 plates together, and bore them both to size. Use a spacer ring between the 2 bearings. Even if boring while fastened to the base plate, in mill or lathe, a spacer ring instead of the shoulder maybe much easier to do. Looks like a casting project, followed by boring.
 
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Bandit said:
If there are end plates holding the bearings in, I would fasten the 2 plates together, and bore them both to size. Use a spacer ring between the 2 bearings. Even if boring while fastened to the base plate, in mill or lathe, a spacer ring instead of the shoulder maybe much easier to do. Looks like a casting project, followed by boring.
Click to expand...
The two bearings are clamped together against that internal spacer by the two moving end plates otherwise you're right. Would have been easier to line everything if the spacer also moved. But that would then rely on a very very tight fit of the bearings.
 
Thanks to a moderator for fixing my mess. Anyway, it was not the bearing endplates, if used, I was (trying to) talk about, but the plates holding the bearings and the planety gear clamp piece/plate. Fasten the plates to to base and bore them. Could be done in a lathe or a milling machine, rough them out with drills/ hole saw etc. follow with light cuts to avoid springing the thinner plate. A spacer may help.
Anyway a few different ways to the end product.
As to the spindle, do all the important machining from the small end, as it appears nothing is attached to the large flange end. Once the small end machining is done and boring to size, including marking fastener bolt circles and possibly hole centers, part off ( length dependent) and flip to face large flange to thickness.
You are likely already there, and of course many things depend on availabile machines and tooling. But an adjustable boring bar is fairly easy to make, for the lathe or the milling machine.
Shiming the bearing end plates can also be done
 
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Bandit said:
Thanks to a moderator for fixing my mess. Anyway, it was not the bearing endplates, if used, I was (trying to) talk about, but the plates holding the bearings and the planety gear clamp piece/plate. Fasten the plates to to base and bore them. Could be done in a lathe or a milling machine, rough them out with drills/ hole saw etc. follow with light cuts to avoid springing the thinner plate. A spacer may help.
Anyway a few different ways to the end product.
As to the spindle, do all the important machining from the small end, as it appears nothing is attached to the large flange end. Once the small end machining is done and boring to size, including marking fastener bolt circles and possibly hole centers, part off ( length dependent) and flip to face large flange to thickness.
You are likely already there, and of course many things depend on availabile machines and tooling. But an adjustable boring bar is fairly easy to make, for the lathe or the milling machine.
Click to expand...
Yes. That's the approach I was going to take for the spindle. The spacer in the middle must be part of the item and it's boring the back side to the right diameter that is the problem. Not if I had a HAAS where finding the center of say the spacer hole is easy when the part is flipped and clamped down again but with my mill back lash more of an issue and there may be issues.

From the assembly manual here's the arm bolted to that spindle.
1726848484428.png


Then the arm side bearing.
1726848526241.png


Now inserted into the housing. You can see that the inner race of the bearing and spindle end line up and extend out of the housing.

1726848782191.png


And next the interesting part. Called the tension ring. Notice how it too is bolted to that spindle.

1726848971308.png


Those 4 smaller holes contain set screws that apply even pressure to the inner race to take out any end play. In the old days on my '64 MGB this was done with shims to set end play but then there was still a nut to hold the works together. Come to think of it the hub likely also had a shoulder so how do they make wheel hubs have concentric bearing holes on either side?
 
That seems to be a hard way to put loading on the bearings. Not sure how you can tell how much preload is applied by each set screw, let alone getting 4 the same.
I never thought about how to machine a wheel hub and get both bearings concentric. Likely machine one side, mount on a linement mandrel while clamping drum/rotor, then machine other side. Finish up by machining drum interior or rotor faces and hub O.D. to suit.
 
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