So, I finally have located enough parts to complete, I think, my personal Rivett 608, so it makes sense to get back to working on that when I have time. The bed needs to be scraped, wear, some corrosion, etc.
The question is about the headstock contact area. That area of the bed, and the corresponding part of the headstock, are presumably totally un-worn, and represent the original factory scraping and alignment. The side surface would be the same in the same area.
I hate to throw away that reference, but I am not sure it is even usable.
The bed is worn, to the extent of maybe a few thou on the top, but considerably more on the side dovetail.
If I scrape the entire thing, I probably need to use the headstock as a gauge, and then possibly touch it up as well. That would lose all the original references, for what that is worth.
But, I am not sure how I could use the original surface under the headstock anyway, except as a known reference when checking vs a test bar held in it.
Because of the design of this bed, there are 10 surfaces to keep in alignment, the back, top surface 1, side surface 1 of the V , side 2 of the V, top surface 2, side surface 1, dovetail surface 1 side surface 2, dovetail surface 2, side surface 3.
Here is the end view, with the top of the right-hand vertical surface being the "back", and proceeding counter-clockwise from there.
All 10 surfaces must be held in tight alignment, since they are all carriage contact surfaces. The carriage may need to be built up with one of the various means, likely turcite, but perhaps that won't be needed.
If I leave the headstock area alone, I can build-up the headstock with the parts I have obtained, and have another large section done. But getting the rest of the bed aligned with it looks like a problem. It would need to be aligned, but offset a few thou.
If I scrape the entire top, then I must leave the headstock bare, since it will need to be scraped as well. But the entire bed top would be aligned with itself. The question is whether it is aligned with the sides, especially the carriage dovetail. It could be pretty easy to get the alignment "off" enough to require a lot of scraping on the side, messing up the dovetail, leadscrew, and feed rod (the leadscrew and feed rod are set into the bed, with no bracket, in the recesses at left).
The idea is to do as good a job as possible, given that I obviously have no access to the factory master jigs. To me it looks as though regardless of original reference surfaces, scraping the entire top at once is the best.
I don't know how I could use the original surfaces as a practical assistance, other than scraping a jig to them, and using that as a reference for re-scraping the entire top. That jig would presumably be either the headstock (used as-is), or the tailstock (scraped to fit the H/S area) or both.
Any obvious advantage one way or the other?
The question is about the headstock contact area. That area of the bed, and the corresponding part of the headstock, are presumably totally un-worn, and represent the original factory scraping and alignment. The side surface would be the same in the same area.
I hate to throw away that reference, but I am not sure it is even usable.
The bed is worn, to the extent of maybe a few thou on the top, but considerably more on the side dovetail.
If I scrape the entire thing, I probably need to use the headstock as a gauge, and then possibly touch it up as well. That would lose all the original references, for what that is worth.
But, I am not sure how I could use the original surface under the headstock anyway, except as a known reference when checking vs a test bar held in it.
Because of the design of this bed, there are 10 surfaces to keep in alignment, the back, top surface 1, side surface 1 of the V , side 2 of the V, top surface 2, side surface 1, dovetail surface 1 side surface 2, dovetail surface 2, side surface 3.
Here is the end view, with the top of the right-hand vertical surface being the "back", and proceeding counter-clockwise from there.
All 10 surfaces must be held in tight alignment, since they are all carriage contact surfaces. The carriage may need to be built up with one of the various means, likely turcite, but perhaps that won't be needed.
If I leave the headstock area alone, I can build-up the headstock with the parts I have obtained, and have another large section done. But getting the rest of the bed aligned with it looks like a problem. It would need to be aligned, but offset a few thou.
If I scrape the entire top, then I must leave the headstock bare, since it will need to be scraped as well. But the entire bed top would be aligned with itself. The question is whether it is aligned with the sides, especially the carriage dovetail. It could be pretty easy to get the alignment "off" enough to require a lot of scraping on the side, messing up the dovetail, leadscrew, and feed rod (the leadscrew and feed rod are set into the bed, with no bracket, in the recesses at left).
The idea is to do as good a job as possible, given that I obviously have no access to the factory master jigs. To me it looks as though regardless of original reference surfaces, scraping the entire top at once is the best.
I don't know how I could use the original surfaces as a practical assistance, other than scraping a jig to them, and using that as a reference for re-scraping the entire top. That jig would presumably be either the headstock (used as-is), or the tailstock (scraped to fit the H/S area) or both.
Any obvious advantage one way or the other?