Cutting a coarse left hand thread.

[Boringgeoff]

Thanks for your vote of confidence Chambezio. It's just lucky that the grandson (who's as old as we are) had the foresight to rescue it before the farm was sold, it's just a pity that he couldn't find the whole machine.
Soundman, I think it did work because of the way all the wear points between wood and metal are so flogged out. Hard to see from the photos I've posted, but where the vise grips are which is where the crank handle was connected, a hard wood bearing has been inserted, possibly in later times, due to excessive wear. My hope is to get this up and running to where I can actually bore a post. I'll keep you posted.
I guess it will be a "Boring post boring post"
Cheers,
Geoff

[Boringgeoff]

While we're on the subject I may as well ask for opinions on the drive cogs used on this tool.
The larger of the two has 26 teeth and has 106 (or 901) cast into it and is about 5 1/2" (140 mm) diameter and 1 3/8" (35 mm) thick.
The smaller, 10 teeth, is 2 9/16" (65 mm) wide and 2 3/4" (70 mm) thick. It has the number 1797 cast on it.
I put an enquiry about them in The Old Machinery Magazine a couple of months ago and got no response whatsoever. For authenticity I need to get as close as possible to the original and to that end I've looked at a lot of old machinery but if someone recognises what machine they're from would narrow the search down a lot.
Cheers,
Geoff.

[franco]

Geoff,

Your gears appear to be 5DP (diametral pitch) gears, assuming the diameter of the teeth on the smaller gear is 2 3/8", since the flange appears to be slightly larger than the distance across opposite teeth. Pressure angle of the teeth would most likely be 14 1/2 degrees on gears of this age.

I have no idea what machine they might have come from originally, but realistically any two gears of somewhere near the same ratio (11:5, very roughly 2:1) and similar sizes would do the job. Maybe a pair of old engine camshaft drive gears about the right size would work? Do you particularly want to preserve the remains of the original machine in its present state, or could you use the existing gears on the replica/rebuild?

If you really want to stick to the original sized gears, it would not be difficult to duplicate the bigger gear if you could find someone who already has a set of 5DP gear cutters. 14 1/2 degree 5DP cutters are still available at a price:
http://www.victornet.com/subdepartme...ters/1660.html
but to buy the two cutters required specifically for the job would make it very expensive.

The smaller gear with the end flanges, which are probably necessary to reinforce the teeth on a gear with such a small tooth count might be more of a challenge to make though.

Alternatively, one of the several American firms who carry stocks of common sized gears might be able to provide a pair off the shelf cheaper than they could be made individually - still not cheap though.

Frank.

[BRADFORD]

They look like gears from an old harvester or seeder.
I've got a ton of very similar gears out in my junk pile.
The gears you have look to be in serviceable condition for that application, certainly the ones I have are no better.

[PDW]

They're cast gears and I wouldn't bet on them being any particular DP. The smaller one in particular has less teeth than recommended for an involute gear - my cutters and references list 12 teeth as minimum. The big one looks more like peg teeth than involute or cycloidal profile but the picture is too poor to be sure.

The small gear in particular, as configured, is damn near impossible to mill, it'd have to be cast as per the original. My experience with foundries is, they'll do it (my local one certainly would) but you won't like the cost of a single gear.

PDW

[Boringgeoff]

Thanks Frank and PDW,

There are any number of old machines laying around on farm junk heaps as Bradford mentions, that will have suitable gears, it's just identifying the correct machine that's the difficult part.
I want to try and keep what's left of the original boring machine in one piece, with perhaps a "before and after" type of set up. Through the club I belong to, The Hand Tool Preservation Society of WA, we attend various country shows and fairs with exhibits of old hand tools and this sort of thing always gets a lot of interest.
Eventually it would be nice to have the whole lot end up in a museum or the like somewhere near where it originated from.

Geoff.

[Michael G]

Geoff let the cat out of the bag here, but I quietly volunteered to help him out with his boring machine parts. After the variety of opinions on how easy it was or alternately how close to impossible I was just going to try a few things and see how I went.
Today I got some to time to have a go. I didn't start well - cutting the stock off my last bandsaw blade broke and I'm bingo for gas at the moment so it was either parting in the lathe or hacksaw - oh, and the carbide holder crashed a little while ago so it would be parting with HSS...

Any, that behind me I started by bringing the stock down to the diameter for the 3/4" thread. The bar was around 450mm long so maximum speed was 164rpm because of chatter. One pass was around 20 minutes. (DOC was limited because of deflection too). Then I single pointed the 3/4 thread. That length of thread (300mm) took some time too, although a pass was quicker than the plain turning. I smeared the thread with Trefolex while I was cutting and while the can is quite emphatic that it should be used for hand operations only, I can say that it works a treat for long slow thread cutting.
P1020666 (Medium).JPG
I was asked about the set up for spiral milling - this is it. The really large gear is just there as an idler as otherwise the gears wouldn't mesh. It's 127 teeth - I made it when thinking about inch to metric conversions before realising that it probably would not be needed. The train had such inertia in it that the high spots on the gears were enough to stop the feed.
Basically the dividing head is just acting as a right angle reduction gear box. Feed from the leadscrew is geared up to feed the head at the appropriate rate.
P1020669 (Medium).JPG
Here is the dummy pass, the final pass to depth and a close up of the cut (complete with swarf)
P1020668 (Medium).JPG P1020670 (Medium).JPG P1020671 (Medium).JPG

Michael

[Steamwhisperer]

As usual Michael, beautifully done.
Can I ask why you didn't use a traveling steady while cutting the 3/4" spiral?

Phil

[chambezio]

As has been said before.....its not necessarily the finished part that gives satisfaction, its usually the journey of how you do it that gives the satisfaction. The set up on the mill is quite an ingenious contraption!!! Could this be the method the original blacksmith used to make the part in the first place???

[franco]

Michael,

Nice work.

If you still have to make the other one, it would probably save quite a bit of time and irritation cutting the unsupported 3/4 thread if you made it in two pieces, plain 3/4" round and 3/4" threaded rod. I did this for the leadscrew on my Blanchard lathe. The leadscrew is 1030 long, with the threaded portion 730 long. I drilled the plain portion 9 mm diameter and 30 deep, then turned an approximately 9 mm spigot 30 long to be a firm push fit in the drilled hole, and put a generous 45 degree bevel on both pieces while still in the lathe. I then set them up in vee blocks and tacked welded the joint in four places, then welded right round, then cleaned up the weld to 3/4" in the lathe.

Probably by pure dumb luck the maximum TIR is 0.003", which was better than I hoped for, and would certainly be plenty good enough for the OP's purpose.

Regards,

Frank.

[Michael G]

Can I ask why you didn't use a traveling steady while cutting the 3/4" spiral?

I'm a rebel and live life on the edge?

I did think about using travelling steady when doing the 3/4 UNC but normally when I cut a thread there is a small burr thrown up on the sides of the thread (none of this setting compounds over for me) and I was not sure whether that would push the bar away from the steady. This was the first thread I've cut where the tool was sharpened on the SG and it did not seem to do that so I may try that next time.

Having said that, I cut it pretty much as I would any other thread so the lack of a steady did not slow me down any.

(If you were talking about the mill, I did think about blocking it up but it did not deflect noticably so did not bother)

Michael

[Michael G]

The (near) finished article


P1020673 (Medium).JPG P1020672 (Medium).JPG

Franco, the two piece solution might work except that the straight piece tapers down from 5/8" at the boss to 1/2" at the base of the thread. From solid is not a bad thing (although time consuming)

Chambezio, it is possible that this is how the original was made, as helical milling has been around for some time (Pre-dates CNC I'm told...). Whether this was the technology used is another matter as in rural WA I'm not sure how much access to a mill capable of doing this there would have been. Those that would have known are not able to say.

Michael

[Boringgeoff]

That's amazing Michael, well done, and thank you very much. I'm completely blown away by the skill and knowledge available and freely given on this forum. The technical language in regard to the equipment used to do the job, one term I was familiar with leapt out at me "hacksaw" yep I definitely know how a hacksaw works!
Bradford came out for a visit yesterday and we had an enjoyable hour or so looking at and discussing the machine. He brought a couple of cogs with him from his resources depot (junk heap) not exactly the same but a starting point nonetheless.
I'd been looking at it from the point of view of a table mounted machine that bores the post prior to being put in the ground, but Bradford raised the possibility of it being a portable tool that could be attached, by some means, to the posts to bore them after they were planted. From what I can gather, although the original owner only had one arm, he was a big powerful fellow so may well have been quite capable of lugging this machine from post to post. The crank being positioned off centre lends itself to this hypothesis, if it was standing on its end would put the crank 900 - 1000mm above ground level which is a reasonably comfortable height.
I've spoken to a lot of old timers about fencing methods and at least 80% will say that it is preferable to bore your post after they're in the ground and in a lot of cases being sceptical about pre-boring them. On the other hand I've spoken to a number of people who have pre-bored them.
Thanks everyone for your input.
Geoff.

[PDW]

I've spoken to a lot of old timers about fencing methods and at least 80% will say that it is preferable to bore your post after they're in the ground and in a lot of cases being sceptical about pre-boring them. On the other hand I've spoken to a number of people who have pre-bored them.
Thanks everyone for your input.
Geoff.

Having done far more fencing than I like to think about, I'd go with the bore after planting group too. Reason is, variable ground, rocks etc means posts get dropped into holes of varying depths. Easy to trim off the top with a chainsaw then drill the holes.

Michael has done a nice job, about how I would have tackled it except I'd have used my B/port and a set of sprockets/chains to get the table drive to the indexing head.

PDW

[RayG]

I've spoken to a lot of old timers about fencing methods and at least 80% will say that it is preferable to bore your post after they're in the ground and in a lot of cases being sceptical about pre-boring them. On the other hand I've spoken to a number of people who have pre-bored them.

That's the way it's generally done around here as well, excepting the droppers of course are pretty much always predrilled.

I would have used a CNC mill with a 4th axis.... that is, if I had mine finished....

Ray