Hillbilly tapping drive

[dusty]

Tried 2 drill chucks on one of my machines and they both fit on but they want to go on too far and contact the plate. Didn't try to tighten them but perhaps the design was such that they didn't want people to use that shaft for anything but a power take off??

Ed

I was wondering the same thing. I noticed that the coupling hub on my idler shaft was quite short, and the end was closed, so it can’t go on too far.

My idler shaft is in pristine condition, and the inner race of a bearing appeared to be mounted on that same diameter. Which says to me that the shaft-diameter tolerance should be well under 0.001”.

My Mark V is a 2005 vintage machine, and I seem to recall that yours are somewhat older, so I have a hunch that Shopsmith changed the shaft diameter to 16 mm (.630”) at some point. I’ll measure the OD with a micrometer tomorrow. Does anyone else with a newer machine know if your chucks and arbors will fit onto your idler shaft?

If the shaft diameter was changed would there not have to be different versions of hubs to accommodate that change?

[rjent]

What a great idea and great ingenuity Dennis! Nothing like Farmer (hillbilly) engineering!

[BuckeyeDennis]

I was wondering the same thing. I noticed that the coupling hub on my idler shaft was quite short, and the end was closed, so it can’t go on too far.

My idler shaft is in pristine condition, and the inner race of a bearing appeared to be mounted on that same diameter. Which says to me that the shaft-diameter tolerance should be well under 0.001”.

My Mark V is a 2005 vintage machine, and I seem to recall that yours are somewhat older, so I have a hunch that Shopsmith changed the shaft diameter to 16 mm (.630”) at some point. I’ll measure the OD with a micrometer tomorrow. Does anyone else with a newer machine know if your chucks and arbors will fit onto your idler shaft?

If the shaft diameter was changed would there not have to be different versions of hubs to accommodate that change?

That's a good question, Dusty. My auxiliary-shaft coupler clearly has a somewhat larger ID than my collets & arbors, as it will fit onto that apparently-oversized idler shaft. But a coupler doesn't really need tight tolerances. If it fits on a spindle loosely, the set screw will draw it over to one side and lock it down. That will cause runout, but those long plastic couplers can tolerate a lot of runout, so it probably isn't a problem.

I just put your question to the test, by trying out several couplers on that idler shaft. The aux-spindle coupler from the same Mark V did not fit onto the idler shaft. But I tried four or five couplers from other machines, and the rest of them did fit. So then I inspected the coupler that came installed on the idler shaft, and discovered that it has apparently been modified. As you can see in the pic below, the ID was re-bored after the coupler had been black-oxide coated. That was not the case with any of my other couplers. So now I'm suspecting that Shopsmith got in a batch of oversize idler shafts at some point, and simply modified the couplers to fit.

Modified coupler.JPG (354.72 KiB) Viewed 18148 times

Out of curiosity, and also to further qualify my micrometers, I measured the OD's of all the Shopsmith spindles in my shop:

* Mark V main spindle: 0.6240"
* Mark V aux. spindle: 0.6241"
* Power station main spindle: 0.6236"
* Power station aux. spindle: 0.6237"
* Speed reducer: 0.6235"
* 10ER SN 85493: 0.6248"
* 10 SN 1750: 0.6245"

And I just looked up standard tolerances for a "Class IV Transitional Fit (Snug)" for mating shafts and bores. This class is specified for speeds over 600 RPM, but where the parts can still be assembled by hand. For a 5/8" nominal shaft, the permissible size ranges are:
* Shaft OD: 0.6242" ... 0.6248"
* Bore ID: 0.6250" ... 0.6259"
Interestingly, only my 10E and 10ER spindles meet that standard.

However, "Class III Medium Fit" dimensions are a bit more relaxed:
* Shaft OD: 0.6235" ... 0.6244"
* Bore ID: 0.6250" ... 0.6259"
All of my other spindles meet that standard.

Given that you and Ed can fit chucks onto your idler shafts, it appears to me that mine is simply oversized. I'd bet that Shopsmith got in a batch of these, and just made them work instead of scrapping them.

[JPG]

I think SS 'corrected' the wrong part.

'Somebody' took the easy way out rather than the correct way.

Ya it was cheaper, but still wrong. It did not correct the problem!

If that was my idler shaft, it would get reduced by wrapping abrasive (crocus cloth) around the shaft while rotating until the od is 'correct'. JMHO

[dusty]

I would put the question to Shopsmith Engineering. I have two idler shafts that I bought new from Shopsmith. It was months ago but one measures .5875" and the other .5835". An older third shaft measures .5890".

Bearings 6903RZ (made in China) on the two newer ones. When you check the specs on these it just adds to the puzzlement (17 x 30 x7).

Can you date the suspect shaft? Does the plastic coupler fit on the idler shaft?

I did not measure the hubs; I tested them only by fitting them onto operational equipment that has been in the shop for a long time.

[BuckeyeDennis]

I think SS 'corrected' the wrong part.

'Somebody' took the easy way out rather than the correct way.

Ya it was cheaper, but still wrong. It did not correct the problem!

If that was my idler shaft, it would get reduced by wrapping abrasive (crocus cloth) around the shaft while rotating until the od is 'correct'. JMHO

I might just do that, if I ever really need mount anything other than the coupler hub. My larger concern is that either Shopsmith or their supplier may have pressed on a bearing with much too heavy of an interference fit. But it’s had no problems so far, and a whole new idler assembly only costs about 40 bucks. So I’m not going to lose any sleep over it.

[JPG]

I think SS 'corrected' the wrong part.

'Somebody' took the easy way out rather than the correct way.

Ya it was cheaper, but still wrong. It did not correct the problem!

If that was my idler shaft, it would get reduced by wrapping abrasive (crocus cloth) around the shaft while rotating until the od is 'correct'. JMHO

I might just do that, if I ever really need mount anything other than the coupler hub. My larger concern is that either Shopsmith or their supplier may have pressed on a bearing with much too heavy of an interference fit. But it’s had no problems so far, and a whole new idler assembly only costs about 40 bucks. So I’m not going to lose any sleep over it.

I have been assuming that was a water pump shaft/bearing, not the newer version shaft with two bearings.

[BuckeyeDennis]

I would put the question to Shopsmith Engineering. I have two idler shafts that I bought new from Shopsmith. It was months ago but one measures .5875" and the other .5835". An older third shaft measures .5890".

Bearings 6903RZ (made in China) on the two newer ones. When you check the specs on these it just adds to the puzzlement (17 x 30 x7).

Can you date the suspect shaft? Does the plastic coupler fit on the idler shaft?

I did not measure the hubs; I tested them only by fitting them onto operational equipment that has been in the shop for a long time.

Dusty, my Mark V has a 2005 date code. I acquired it in 2012, and as far as I know it still has all-original headstock innards. The drill chuck that came with it is the only component that didn’t look new. I suspect that original went missing, and so the eBay dealer substituted an older one to make up a complete 520 package.

My plastic couplers fit fine on the idler-shaft drive hub. That’s the one that appears to have been bored out to fit the oversized idler shaft.

As for contacting Shopsmith engineering, I figure they already have plenty work on their plate, without worrying about what manufacturing variances may or may not have occurred back in 2005. I’d much rather have them work on getting their PowerPro service act together.

[BuckeyeDennis]

I have been assuming that was a water pump shaft/bearing, not the newer version shaft with two bearings.

Beats me. Do you know they changed over?

[JPG]

I have been assuming that was a water pump shaft/bearing, not the newer version shaft with two bearings.

Beats me. Do you know they changed over?

No, but yours 'appears' to be the water pump type. Check out the end of the shaft.