PDA

View Full Version : Today's project.... Rivett crosslide screw, ...done except for some decisions.



J Tiers
02-09-2014, 12:32 AM
The old crosslide screw on the Rivett project was so worn that parts of it look like a worn Whitworth thread and not acme.

So I decided a considerable while ago to replace it. There has been talk of making new screws on the Rivett group, but I decided to have a go at it myself.

The screw is fairly long, has an integral 13 tooth pinion cut in it, a 10 tpi LH acme thread, and some slots, flats, and odd holes in it. The diameters of the bearing areas need to be within about a half thou or the dial, handle, and general fit will be sloppy.

Then also, there are screws in the ends.... one, the dial lock screw, has a 3/16-20 thread, while at the other end, the screw for the bearing bushing, is 5/32-40. not your common everyday hardware store thread.

Anyhow, I roughed the thing out, then cut the gear, put in the slots and flats and "lock foot" hole, and polished the bearings to size. I still need to cut the handle end to length, and put in the screw holes with their odd threads.

I have not decided exactly what to do about the screws.... If I change the threads, I have to make new screws, and I don't have knurls for the lock foot screw that will look right. If I use the old screws, I have to make taps, since I don't think I want to buy taps of those sizes....

No pics of the roughing process...

http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/Rivettnewcrossfeed1_zps9afa5867.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/Rivettnewcrossfeed1_zps9afa5867.jpg.html)

http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/Rivettnewcrossfeed2_zps6a44834b.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/Rivettnewcrossfeed2_zps6a44834b.jpg.html)

http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/Rivettnewcrossfeed3_zps04a2e0b7.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/Rivettnewcrossfeed3_zps04a2e0b7.jpg.html)

J Tiers
02-09-2014, 12:32 AM
And the finished part.

http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/Rivettnewcrossfeed4_zps7dde0d05.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/Rivettnewcrossfeed4_zps7dde0d05.jpg.html)

some of the odd extra holes, and flats
http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/rivettnewcrossfeed5_zps12ebbe2a.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/rivettnewcrossfeed5_zps12ebbe2a.jpg.html)

The stub tooth gear the pinion fits with (crossfeed drive)
http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/Rivettnewcrossfeed6_zpsc564576a.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/Rivettnewcrossfeed6_zpsc564576a.jpg.html)

The parts assemblage, complete with the extra part that I still need to cut off. The dial lock screw goes in teh end, once I figure out what I want to do about it.
http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/Rivettnewcrossfeed7_zps70f4aecf.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/Rivettnewcrossfeed7_zps70f4aecf.jpg.html)

Tony Ennis
02-09-2014, 12:58 AM
That's a very fine looking piece of work.

Sun God
02-09-2014, 01:43 AM
Beautiful work for a beautiful lathe. :cool:

doctor demo
02-09-2014, 01:49 AM
Then also, there are screws in the ends.... one, the dial lock screw, has a 3/16-20 thread, while at the other end, the screw for the bearing bushing, is 5/32-40. not your common everyday hardware store thread.

I have not decided exactly what to do about the screws.... If I change the threads, I have to make new screws, and I don't have knurls for the lock foot screw that will look right. If I use the old screws, I have to make taps, since I don't think I want to buy taps of those sizes....


Well, You "stumped the band" on those two sizes.
I went to my odd stuff and came up with taps of : 5/32-32 and a 3/16-24, I have another box of weird stuff but I don't think it has anything that small in it. I'll look through it tomorrow.

Steve

Richard P Wilson
02-09-2014, 03:52 AM
5/32x40 is available in the UK, as part of the ME (Model Engineer) series of threads. Taps and dies are stocked by, amongst others Tracy Tools, who have a website. Admittedly, these will be 55 degree threads, and presumably the Rivett used 60 degree threads, but in that size, I seriously doubt that anyone could tell the difference.

Richard

Arthur.Marks
02-09-2014, 10:24 AM
I have not decided exactly what to do about the screws.... If I change the threads, I have to make new screws, and I don't have knurls for the lock foot screw that will look right. If I use the old screws, I have to make taps, since I don't think I want to buy taps of those sizes.
Got a picture of the original screw's knurl? Is it weird somehow or just a different pitch from what you've got?

Tony Ennis
02-09-2014, 10:48 AM
How difficult would it be to make a matching knurler?

J Tiers
02-09-2014, 11:14 AM
It's just a different pitch knurl. And I don't generally do anything other than a straight knurl, and very few of them, so I have holders for single knurls, but not double. I should make a scissors knurl holder.

It's really more that I'd like to use the original construction for once, in this case, using the old screw.

duckman
02-09-2014, 11:53 AM
I personally favor a straight knurl rather than a diamond for a knob.

JCHannum
02-09-2014, 12:45 PM
Victor carries both 5/32"-40 and 3/16"-24 in HSS taps at reasonable prices.

http://www.victornet.com/subdepartments/Special-Pitch-Taps-up-to-1/2-inch/1260.html

Edit to add, I checked my stash and have one of each. I will offer on loan. PM me your address and I will drop them in the mail tomorrow.

J Tiers
02-09-2014, 02:05 PM
After adjusting for the damaged threads, and for full form vs truncated form, I have become convinced that I was wrong, and it is really a 10-30 thread. That's pretty available. Victor is much cheaper than MSC, thanks for the kick-start to look at them.

I've pretty much decided to go with the original screws, so I'm going to get a tap for 10-30.... I have one for #9-30, along with a lot of fractionals etc, I'm surprised I didn't have the 10-30. I probably should, I'm pretty certain there are more of them on the unit.

Thanks for the offer.

I like straight knurls too, but these are very visible, and are a fine diamond knurl. Normally I'm not one for super accuracy of appearance, but in this case, I think I'm going that way.

I was able to re-cut the one damaged thread on the lock screw that goes with the crossfeed, so that made the decision easy.

J Tiers
02-09-2014, 11:26 PM
The new screw needed a new bearing bushing. which rides in the end of the crosslide casting to carry the far end of the screw.

I made the new screw a little shorter than the original, and may cut it even more. There were several sizes of the screw extension made, so this is "legit" as far as the "historical accuracy" is concerned.... In any case, I didn't want to cut the original (foreground, with assy number stamped) shorter, so I made another which I can do whatever with.

The new one (rear) also is about 40 thou less in OD of the fat part,. That's the size of the 1144 I had.... I doubt it will matter. Rivett was a little casual about some dimensions, and fussy about others, so...

http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/Rivettnewcrossfeed9_zps05aceb0b.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/Rivettnewcrossfeed9_zps05aceb0b.jpg.html)

jep24601
02-10-2014, 09:09 AM
Are you sure then that the 5/32-40 isn't a 6-40? (Which is fairly common).

J Tiers
02-10-2014, 07:25 PM
Are you sure then that the 5/32-40 isn't a 6-40? (Which is fairly common).

near as I can be.

The limit, from the Federal handbook, of major diameter for #6 is 0.138, but this is a solid 0.154 to 0.155 major diameter. Way bigger than #6, but a little under the minimum for a #8.

Oddly, now that you mention 6-40, I have several #6-36 taps, but no #6-40 unless it is in "back stock" in the drawers.

Gary Paine
02-11-2014, 12:53 AM
No pics of the roughing process...

http://img.photobucket.com/albums/0803/jstanley/Rivett%20608/Rivettnewcrossfeed1_zps9afa5867.jpg (http://smg.photobucket.com/user/jstanley/media/Rivett%20608/Rivettnewcrossfeed1_zps9afa5867.jpg.html)


I know this is a bit off the topic (nice job, by the way), but I wonder about the use of a 3 jaw on the dividing head. I tried mine with an indicator on a chuck mounted ejector pin and I am getting about .006 best TIR at the chuck, more sometimes. That would be mitigated by half with the workpiece halfway between the chuck and the tailstock center on the mandrel, but it still seems too much runout for a gear. Is your chuck extra precision or have you developed a work around to deal with normal chuck runout?

JRouche
02-11-2014, 01:00 AM
I like your machine work. Are you needing a special knurl? I have close to a 1000 knurls. Might be a loaner in the bunch. JR

J Tiers
02-11-2014, 08:37 AM
JR...

Thanks. I cleaned up the threads on the one lock-screw, so there are two now, no need for a knurl right now. I really need to improve knurling capability here, but it's low on the list. I don't do, or need to do, much knurling, and have never bothered to obtain a better setup.

1000? I see someone else is a packrat too!


I know this is a bit off the topic (nice job, by the way), but I wonder about the use of a 3 jaw on the dividing head. I tried mine with an indicator on a chuck mounted ejector pin and I am getting about .006 best TIR at the chuck, more sometimes. That would be mitigated by half with the workpiece halfway between the chuck and the tailstock center on the mandrel, but it still seems too much runout for a gear. Is your chuck extra precision or have you developed a work around to deal with normal chuck runout?

You are correct that most chucks would run out at least a couple thou. It is a small Buck "Adjust-tru" chuck. Adjusts-in like a 4 jaw, except the action is reversed.

There was some "spring" in the workpiece. I'd have liked to put it closer to the support, but needed the space behind it to start the cut. I need to look into reversing the DH so I can run away from it if needed, or reversing the motor. Something blocks the DH when reversed, IIRC it is part of the index plate holder that interferes on the table. Doesn't look like it should, but..... And I ran out of table to put the screw toward the tailstock, the screw was too long.

I have an adapter for 3C collet to B&S 9 , but it has no through-hole. No help there without making more tools.

JRouche
02-12-2014, 02:29 AM
JR...

Thanks. I cleaned up the threads on the one lock-screw, so there are two now, no need for a knurl right now. I really need to improve knurling capability here, but it's low on the list. I don't do, or need to do, much knurling, and have never bothered to obtain a better setup.

1000? I see someone else is a packrat too!

YUP. Packrat. I also dont do or need to do ANY knurling but seem to have over a 1000 of these lil wheels around. Crazy part is 500 of them are "fancy" or "decorative" knurls. 100 of them being original dies. Its like a knurl graveyard over here.

Umm? They are really old but hard as hard goes. A file just skips across them so they are meant for steel.

Odd bunch of knurls I have here... JR