Thread: A silly thing for me to offer really

Originally Posted by Greg Q

I'll see what Mike G ( the Lilydale Mike G who helped with the granite) needs for his machines. I know he has two and a half Rivett 608s (glutton that he is) and several missing change gears. One of the lathes would be an ideal metric conversion given that the usual wear items all need replacing. I'm guessing that would mean a completely different set of change gears. I'll email him this thread for his input. If you are of a mind to rent out those cutters PDW I think I could make use of them for a week or so sometime down the road.

GQ, groggy from a lunch of black truffle & dead pig dumplings in Hong Kong.

See what he needs and I could bring the cutters over on my trip north, pick them up when I come south. I think I'm missing 1 or 2 of the 16DP set but I definitely have the ends of the range. Ditto for 12DP. I've rack cutters in 9 & 10DP and a few other 10DP cutters. Mick Moyle generally has the cutters at around $60 each.

As for slippage, I've cut a lot of gears with plain bores & never had one slip. I'd be looking at the arbour I mounted them on if I was getting any slippage. As Phil said, a fine thread and a decent sized lock nut shouldn't allow movement. The cutting force is along the arbour after all, no radial component.

I bought a 20DP 127T gear 20+ years ago so I could use it as an indexing wheel. So far I never have. Cutting a bunch of these in any convenient size as indexing plates would be a useful service IMO. Gashing the slots with a 3/16" slitting saw would be one way to go.

PDW

PDW-
Yes, I do, in essence, have 2 Rivett 608 lathes and some extra stuff. Actually, if I had another bed, I would cobble together #3.
One is an older model 4NS collet headstock change gear lathe. One is a 5c model with gear box, but has not been assembled yet.
A previous owner of the change gear model had a few of the missing gears cut of brass, but they were not cut properly (don't mesh right).
The older change gear 4NS model gears are 14.5 PA and 24 DP. I need the following: 45T, 36T, 25T for the gear change range, and 22T for the tumble reverse, all 14.5/24. Of particular interest is the 22T tumble reverse. I already have a fully functioning tumble reverse, but I want to try to make up a dog clutch for this lathe (Rivett 608 lathes didn't have that feature - only the early pre-war 1020, of which only 4 or 5 are known, had that feature) and that is the essential gear.

For a brief history of Rivett:
http://neme-s.org/Shaper%20Books/Riv...0Rivett%20.PDF
For more info, see the Rivett 608 Group site:
Rivett-608 : The Rivett-608 Group
For an article on making a dog clutch:
Screwcutting Simplified | Model Engineer
For a video clip on how a dog clutch can work in thread cutting (on a pre war 1020 Rivett):
[ame=http://www.youtube.com/watch?v=pNuDqv-Ompc]threading on 1942 Rivett 1020 lathe - YouTube[/ame]

Hope this is of interest...,
Michael

Hi Michael,

Interesting that you should mention the 1020, Alan, who's on backsaw.net just posted that he just bought one a Rivett 1020F a few days ago.. (ex Hershey )

New tool for machining parts...Rivett 1020F - Saw Discussion Forums

I wonder if Alan's is a pre-war one with that feature?

Regards
Ray

Ray,

Attached an image of one of the VERY rare pre-war 1020's. Four? known....
That's the one with the dog clutch.
I don't believe that the later 1020's had that feature.
I would dearly love to turn one of those early ones up in some shed, but I would not like the chances here in Australia. I don't think any Rivett lathes made it here with the Yanks.

Alan's is a post war model.

Regards,
Michael

Let me try that upload again....

Originally Posted by mmgarwood

The older change gear 4NS model gears are 14.5 PA and 24 DP. I need the following: 45T, 36T, 25T for the gear change range, and 22T for the tumble reverse, all 14.5/24. Of particular interest is the 22T tumble reverse. I already have a fully functioning tumble reverse, but I want to try to make up a dog clutch for this lathe (Rivett 608 lathes didn't have that feature - only the early pre-war 1020, of which only 4 or 5 are known, had that feature) and that is the essential gear.

Unfortunately the smallest cutters I have are 16DP so I can't assist in this. If you wanted to buy the cutters, I'm pretty sure Mick Moyle would have them, around $60 each the last time I got one. There are plenty of us who would cut you the gears with the correct cutters in hand.

PDW

This thread at PM is about the pre war 1020 and shows a few views of the inside of the gear box. Phew!!!

Rivett 1020

Hi Michael,

Thanks for the Rivett info, beautiful machines, The gearbox on the pre-war one you linked to on PM would qualify as artwork..

Here's another PM thread.. this is the 1020F that I mentioned earlier it's a 1963 model evidently, Alan has a thread on PM with more pictures and details 1963 Rivett 1020F

Regards
Ray

I managed to get some dividing head work done on the mill today, among the jobs I had queued up was machining down those blasted Whitworth bolt heads so that I could use a normal spanner, putting flats on a morse taper so that it would self-eject and then something that I've been wanting to do for ages - cutting some helical gears.
In the first post I commented on the time it takes to set up for gear cutting. This is the mill changed from it's normal vertical guise to how it was set up this afternoon. (The lights are the video lights that I was talking about in another post. They really make a difference)

Attachment 206513 Attachment 206514

I discovered the hard way that when swapping from a RH helix to a LH helix, the direction of the gear train from the table needs to be reversed (add or take a gear from the train). All the gears in the set I have were made in previous sessions and took literally weeks to do. Fortunately the gears I was making today were just from PE that I had lying around. Some of the fabled machining wax may be better for try outs as PE gets really stringy, so you have to spend time later deburring and cleaning.
I also have the issue that I have a metric mill and am cutting imperial system gears (DP) so at some stage I'm going to have to look at a 127:100 compound gear to get the helix angle right.
Part of the issue with cutting spirals is that standard cutters are not used in the normal way. A 22t gear would normally be a no. 5 cutter, but with spirals the number of teeth is divided by the cube of the helix angle and then the cutter for that number is used - as a result these gears were cut with a no. 2 cutter. I need to look into that a bit as the teeth look a little thin to my eye, as a gear does if the cut is too deep. I used a standard value for d+f, so there may be a factor that I've missed, or it could be that the error in the helix angle was enough to cut the tooth space wider than it should have been
Anyway - the end result before deburring (3/4" high, 1.5" OD)-
Attachment 206515

Michael

Whooee! Noice. I have a modul 1.5 hobb...could you use it with your universal?

Greg

Too cool. Are they for a project Michael?

Thanks Guys.
I don't know whether a hob would give me any advantage over the cutter I have. There are various things people call hobs too - are you thinking of one with a series of profiles or one with a spiral profile? The first type would probably produce a similar result as the cutters I'm using; (my understanding of) the second type is that they use the spiral to pull their way around the gear, so that would not work in this application. However, the mill did come with the European mandrels that I was told are typically used for running horizontal cutters there (22 and 27mm) so to cut module gears I may have to work out what gear cutters are called in metric Europe*.

The project was to experiment on how to cut a helical gear. At some stage I want to make a bolt on head for the mill that will let me cut racks along the bed of the mill. Currently all I could do would be a short length - say 150mm - before I run out of space. If I make up a set of skew gears I should be able to use either the vertical or horizontal spindle to mount a cutter to do that. A skew gear seems a nice way of turning through 90 degrees and if I can get my profile problems sorted, easier to make than bevel/ mitre gears, especially if a speed change is incorporated.

This is all tied up with some of my volunteer work (Technical Aid to the Disabled), where occasionally small gear boxes are desirable and they can be pricey off the shelf

Michael

* My previous employer dealt with a company supplying German engines. In Australia to start a diesel engine on a cold day you use a cold start system. The German name was Flammenwurfl - I'm told literally "Flame start". I never would have guessed that.