Scraping the 608 bed. Where to start?

The CI gib discussion was good and timely for me since there is a similar gib on the Rivett 608 I am restoring. I am definitely no pro at this, but it will be the 4th machine I have scraped-in, so I have some credit hours in the school of hard knocks.

I noted the side discussion about the Schaublin bed, which is typical of jeweler's lathes, and some Rivett machines.

The Schaublin comments were, however, not encouraging..... The 608 has the same situation of bed cross-section, on the carriage where the slide rest fits. I will eventually need to probably align the crosslide by working on that interface, unless I find I can scrape the seating surfaces of the "carriage angle" part and align that way.

And, the bed also has a similar situation...

I already have the slide rest assembly done, other than final fitting the bottom of the crosslide to the carriage. They lock together and the actual slide is the top surface of the part that fits on the carriage. You can see the slide dovetail, and the three under- surfaces that fit to the top of the carriage angle.



The green lines in the picture below show the surfaces that the headstock and tailstock contact. I will have to work on them, because the bed needs scraped, due to wear.

The red lines are even more interesting, because they show the surfaces that the carriage contacts. Apparently it contacts ALL of these simultaneously, although the top of the bed is contacted by the separate "carriage angle", which allows some scraping of flat surfaces between it and the carriage to align it. The gib is at the top of the dovetail.



The carriage angle is a part that fits on the actual carriage.... here it is shown in approximately correct position on the carriage. the generally flat part is the "carriage" and the angle is the rounded part that fits against the carriage and sticks out to the left. If the picture looks odd, it is actuually upsy down so as to show the parts as they fit on the bed.... I set them together upside down to get the photo.



Here's the carriage angle by itself. You can see the surfaces that bolt up to the carriage.



I haven't figured out exactly where to start on this, and felt like a dummy... but now I don't feel quite so bad about it..... But I still don't know where to start.

My inclination was to start on the top surface, and get the headstock and tailstock alined, then make the rest fit.

The "make the rest fit" would presumably be to first get the dovetail area set up straight and aligned with the top, then get the carriage scraped to fit it.

Last bit to get the "carriage angle" to fit the bed, possibly with Turcite to fill in the gap I expect to find after scraping.

Maybe also Turcite to raise the carriage up to align with the feed rod and lead screw. Clearly they are not moving relative to the bed..... and I expect the carriage to shift down too much to ignore.

More pictures to show construction

The carriage together and on the bed, in "barn fresh" condition.



The carriage and "carriage angle" as set together on the bench, after cleanup of the grime and some disassembly



Bed near headstock

I just drove 10 hours and am opposite side of MO..Joplin.....anyway I can help you figure it out when I get a good nights sleep. Can you take a pic of the whole machine. There is another Gentleman in your area that is a respected rebuilder and forum contributor who scrapes. I am not sure if he is on here...but his nickname is J Tears on the other popular forum. Also over in Alton Ill is Abbott Machinery who uses gallons of Moglice. Bob and Rich Abbott are super nice guys and if you give them a call they might give you a tour. Rich

Thanks for the info.

But I'm here to tell you that guy you mentioned as being from around this area is a prize turkey! I know him pretty well and he hasn't been any help at all. He has nothing original to contribute that I didn't already think of.

As far as a pic of the whole thing, not really, as it has been taken apart.... I'm going through the entire machine piece by piece, repairing or making new parts where needed. I never took an overall pic of it before I started, but it's a pretty standard late model (1946) 608PV on the underdrive steel "kneehole" cabinet stand. It was being abused by a dragster builder when I bought it for a song.

pretty much just like the picture here
http://www.lathes.co.uk/rivett/img12.gif

JST said:

But I'm here to tell you that guy you mentioned as being from around this area is a prize turkey! I know him pretty well and he hasn't been any help at all. He has nothing original to contribute that I didn't already think of.

Click to expand...

I'd tell the guy what you said next time I talk with him but I'm sure he'll have heard before I get to him.

Very funny.

May I chip in here-a little off topic,I know but about Rivetts. Can anyone tell me the purpose of the front slide arrangement,yet the saddle still goes over the top of the bed? Back on topic now-that's quite a fitting exercise there! Ted

Near as I know, it was "the way Rivetts were made".... they had their pet good idea, and they kept on with it.

It does give a huge contact area, the 8" swing Rivett 608 has something like 75 square inches of contact between bed and carriage. That's equivalent to an area a foot long by 6" wide, an area you don't generally find on V-way beds until considerably larger machines.

They had always made their plain turning modelmaker's or clockmaker's lathes with a rectangular bed, and so they had a base of accessories that fit that style. When they made the "8 inch precision" lathe, and added a leadscrew and feed rod, they kept the bed shape, which meant they had to have the carriage on the side. A dovetail was a good way to hold it, I suppose.

Then the 608 was derived from that model. They then made the top of the carriage, the "carriage angle", with the same beveled corner style to fit all the accessories that were already out there. At least I think the size was the same so as to fit them.

The machines were made to do nearly every task that a toolmaker would want... milling, turning, threading, grinding etc., making cutters, you name it. There were accessory devices that would allow making twist drills even.

The kind of accessories that were made for watchmaker's lathes were also available for the Rivetts. They are really almost scaled-up watch lathes, up until the 900 series and the 1020, which were much more modern.

I will start to add a little as I am super busy on a emergency job and can't write it all as I am late for work now and I am pooped at night to read and write.
First of all I would be a detective and document everything. . Stone the bed to knock off and burrs then I would blue up both sides of the bed and set on granite plate A grade or better. Get both ends zero with in .0002" or as close as you can get it. (I can't see how the bed is on the bottom, but set it on parallels or directly on the plate, shimming it or leveling jacks.) Then using a surface gage and .0001" and sharpy write on the bed the low spots and then start a set of documents and record your errors. Then check the squareness of the top and side of the bed, If you look in I believe it's in the Jamboree thread Don Roberts (Bebop) shows in a picture how he checks squareness using a Srarrett Surface gage and granite square. I am assuming you don't have a CMM as that would make measuring it super simple. I would also look in your assortment of angle blocks and straight edges and check them and get them ready.

More later. Riich

Thanks JST. With Rivetts that must be the reason-a way of gaining more working area. I must admit I always thought it was a way of winding the saddle past the tail stock-for whatever reason-until,upon closer scrutiny,I realised part of the saddle straddled the bad. Silly me! Ted

Maybe so. I think it was a combination of factors.

I think they were also sort of locked into a corner by their prior designs. Once they decided to keep the "backward compatibility" with older accessories, they had a real problem. A regular thick carriage on V-ways, plus the thickness of the mounting adapter and a crosslide system would have meant that a given size of lathe might have much less than usual as far as swing over the crosslide.

By moving the carriage locating system (dovetail) to the side, they gained at least the thickness of typical V-ways, plus they could make the carriage portion that had to be on top thinner. I estimate that they "saved" a total of nearly an inch of thickness by doing that.

The machines were primarily for collet usage, this one takes 5C directly in the spindle, and prior models used the now rare 4NS collets. As such, they would not have been totally "defined" by the swing over crosslide, so long as the largest stock in a 5C would clear. But they supplied chucks, and would have needed to be concerned about clearance for larger pieces. I have 3 jaw and 4 jaw DE Whiton chucks that came with the machine, and are stamped "Rivett" as well as Whiton.

Some owners believe that the "carriage angle", that portion of the carriage assembly that goes over the top of the bed, is not intended to actually touch the top, but rather should ride a thou or two clear of actual contact. The theory seems to be that it gives the benefit of support for any large forces that would bend it down, but avoids as much fuss over scraping, and wears slower.

I'm not entirely sure why they think that, it seems to me that any sort of stability requires that extension to actually be in contact (less oil film) with the bed. Rivett obviously didn't give a hoot about the trouble of scraping, and the carriage angle has oiling provisions, as well as way wipers (they go in the grooves you see on the underside).

Also, they seemed to be in the mode of "any expense is OK if it improves the product". So it would not have bothered them to increase costs. They only ever seem to have made around 2100 of the 608 machines of all types, they were not concerned about mass production (mine is from 1946, and the serial is around #1800). I don't know how many of the 8" Precision machines or plain turning lathes they made. They seem to have also made "slide rest assemblies" to fit on other machines of the era, since most accessories seem to also fit "Hjorth" and others.

Mr King.... Yes indeed.... I need to find out if I can again borrow a longer straightedge....my source may be currently using it. And I don't have access to a large enough flat to survey the bed in that manner. I will have to work out other methods. I seem to be a candidate for just buying a longer straightedge. I looked at the Polar tool site, since I get up to St Paul every so often, but saw nothing actually listed. I should inquire. There are a couple local dealers as well, but they run less to straightedges.