Shopsmith Forums

The first thing I notice different on my '04 Headrest (sample size of 1) is that the big setscrew is inverted compared to a '91 that works as I think it should. The hollow socket is on the top on the '04 so the head, rather than the tip, is providing the landing for the tie bar. While it is much easier to adjust or install this way, it does not seem correct.

Note - This Headrest is not installed, so I can't easily test/compare how it holds. When I was using Headrests I normally set the lock pretty tight because that is how I interpret the manual. Basically I tighten until I can't move the way tube assembly while locked. So it's normal to me that the lock takes a bit of force to fully engage and to disengage.

- David

DLB wrote: ↑Tue Feb 16, 2021 2:49 pm The first thing I notice different on my '04 Headrest (sample size of 1) is that the big setscrew is inverted compared to a '91 that works as I think it should. The hollow socket is on the top on the '04 so the head, rather than the tip, is providing the landing for the tie bar. While it is much easier to adjust or install this way, it does not seem correct.

Note - This Headrest is not installed, so I can't easily test/compare how it holds. When I was using Headrests I normally set the lock pretty tight because that is how I interpret the manual. Basically I tighten until I can't move the way tube assembly while locked. So it's normal to me that the lock takes a bit of force to fully engage and to disengage.

- David

+1

Can someone post a picture of either the newer headrest/tie bar or the older ones? I would like to see what is different on those for attachment of the tie bar clamp compared to mine. I have mine tightened all the way to where if I go any tighter then I can't lift the waytubes when loosened, so I would like to understand how there is less play in the earlier/later designs.

Can someone post a picture of either the newer headrest/tie bar or the older ones? I would like to see what is different on those for attachment of the tie bar clamp compared to mine. I have mine tightened all the way to where if I go any tighter then I can't lift the waytubes when loosened, so I would like to understand how there is less play in the earlier/later designs.
[/quote]

Do these help?

RFGuy wrote: ↑Wed Feb 17, 2021 3:13 pm

Thanks Dusty. In comparing your pics to my headrest and tie bar clamp, I don't see any differences so I am confused. I thought David mentioned that the design was different on my model year Mark V. I am trying to understand what is different here (see David's comments below). I am in the middle of a project at the moment and unfortunately using my Mark V table as a catch-all for it. As soon as I can, I'll try to snap some pics of mine to compare, but I think they are identical to the pics you shared...

DLB wrote: ↑Tue Feb 16, 2021 2:49 pm The first thing I notice different on my '04 Headrest (sample size of 1) is that the big setscrew is inverted compared to a '91 that works as I think it should. The hollow socket is on the top on the '04 so the head, rather than the tip, is providing the landing for the tie bar. While it is much easier to adjust or install this way, it does not seem correct.

- David

I got really busy doing emergency plumbing yesterday. Nowhere near done, I'm just capping leaks (4 so far) rather than making repairs. Still below freezing here, but considerably warmer than it was.

Clarification - I don't know that the 'new' Headrest casting has anything to do with this, just think it's something to consider. The 520 Scott used in the video was Golden Anniversary, so logically the same version. It is only visibly distinguishable to me by the asymmetry at the SPT lock, nothing to do with the Headrest lock. As I said, I did not see anything relating to the Headrest lock except the inverted big setscrew. And I don't have this version mounted to a Mark V so I can't test it. I have a '91 in my shop for unrelated rehab, it locks up solid.

The setscrew inversion would have been procedural during assembly or done by a PO. You can easily 'correct' it to see if it makes a difference if yours is that way. I'm not saying this is the problem, but it is easily changed for evaluation.

If there are any measurements I can make on either that will help just let me know. I can assemble the '04 Headrest into a Mark V at some point but it will be at least a few more days before that's possible for me.

- David

RFGuy wrote: ↑Thu Feb 18, 2021 10:03 am Thanks Dusty. In comparing your pics to my headrest and tie bar clamp, I don't see any differences so I am confused. I thought David mentioned that the design was different on my model year Mark V. I am trying to understand what is different here (see David's comments below). I am in the middle of a project at the moment and unfortunately using my Mark V table as a catch-all for it. As soon as I can, I'll try to snap some pics of mine to compare, but I think they are identical to the pics you shared...

DLB wrote: ↑Tue Feb 16, 2021 2:49 pm The first thing I notice different on my '04 Headrest (sample size of 1) is that the big setscrew is inverted compared to a '91 that works as I think it should. The hollow socket is on the top on the '04 so the head, rather than the tip, is providing the landing for the tie bar. While it is much easier to adjust or install this way, it does not seem correct.

- David

Might this have anything to do with Way Tube length and/or insertion depth of those tubes into the casting? Just a thought in passing.

The locking principle is one of applied tension and friction. Technology is not at play.

My exposed Way Tubes measure 48" plus a little bit. (not enough to measure)

There are several differences on the Greenie version of the Headrest lock:
1) The screw has a larger head, about 1-1/8" at max diameter.
2) A bushing is used rather than the tightly coiled part of the spring on the newer ones. The bushing has a 3/8" I.D. and 5/8" O.D. and is 1-1/2" long. It eliminates most of the slop where the screw can move around in the Headrest. Appears to me that it is made of two sleeves pressed together.
3) The spring is shorter but otherwise similar to the portion of the new one that performs a spring function.

Just from inspecting these, I feel like the bushing would provide significant improvement. I have no clue when this was changed, right now I put it anywhere from 1957 to 1991. Most of the Headrest locks I see on EBay today have the bushing. I'm not suggesting this is the cause of the movement experienced by Scott and RFGuy, just that I think it would reduce the movement.

(I also inspected another of the newer Headrests, a 2001. This also had the inverted, to my way of thinking, big setscrew. So sample size of 2 now, but 2 out of 2.)

- David

DLB wrote: ↑Thu Feb 18, 2021 4:53 pm There are several differences on the Greenie version of the Headrest lock:
1) The screw has a larger head, about 1-1/8" at max diameter.
2) A bushing is used rather than the tightly coiled part of the spring on the newer ones. The bushing has a 3/8" I.D. and 5/8" O.D. and is 1-1/2" long. It eliminates most of the slop where the screw can move around in the Headrest. Appears to me that it is made of two sleeves pressed together.
3) The spring is shorter but otherwise similar to the portion of the new one that performs a spring function.

Just from inspecting these, I feel like the bushing would provide significant improvement. I have no clue when this was changed, right now I put it anywhere from 1957 to 1991. Most of the Headrest locks I see on EBay today have the bushing. I'm not suggesting this is the cause of the movement experienced by Scott and RFGuy, just that I think it would reduce the movement.

(I also inspected another of the newer Headrests, a 2001. This also had the inverted, to my way of thinking, big setscrew. So sample size of 2 now, but 2 out of 2.)

- David

If you see this as an issue is there any reason you can not just "invert it" again. Can the allen wrench be inserted upward from the under side?

DLB wrote: ↑Thu Feb 18, 2021 4:53 pm There are several differences on the Greenie version of the Headrest lock:
1) The screw has a larger head, about 1-1/8" at max diameter.
2) A bushing is used rather than the tightly coiled part of the spring on the newer ones. The bushing has a 3/8" I.D. and 5/8" O.D. and is 1-1/2" long. It eliminates most of the slop where the screw can move around in the Headrest. Appears to me that it is made of two sleeves pressed together.
3) The spring is shorter but otherwise similar to the portion of the new one that performs a spring function.

Just from inspecting these, I feel like the bushing would provide significant improvement. I have no clue when this was changed, right now I put it anywhere from 1957 to 1991. Most of the Headrest locks I see on EBay today have the bushing. I'm not suggesting this is the cause of the movement experienced by Scott and RFGuy, just that I think it would reduce the movement.

(I also inspected another of the newer Headrests, a 2001. This also had the inverted, to my way of thinking, big setscrew. So sample size of 2 now, but 2 out of 2.)

- David

Are these differences significant factors?