Needs Pictures: 0
Picture(s) thanks: 0
Results 1 to 15 of 50
-
19th November 2014, 10:23 AM #1Try not to be late, but never be early.
- Join Date
- Apr 2011
- Location
- Bakers Hill WA
- Age
- 75
- Posts
- 1,077
Cutting a coarse left hand thread.
Hi,
I'm in the throes of making a replica of a multi head fence post boring machine. This machine was made by/for a farmer in the south west of WA after WW1. Part of it consists of two shafts about 18 1/2 inches long, they have a conventional thread on twelve inches of their length which is 3/4 UNC (or Whitworth perhaps?) Cut into this is a counter clockwise thread of extremely coarse pitch of 14 threads per foot.
Multi head drill 001.jpgMulti head drill 002.jpg
My question is: is there anyone here who would be interested at making these for me, preferably from WA?
Cheers,
Geoff.
-
19th November 2014 10:23 AM # ADSGoogle Adsense Advertisement
- Join Date
- Always
- Location
- Advertising world
- Age
- 2010
- Posts
- Many
-
19th November 2014, 12:42 PM #2
Hi Geoff,
Cutting threads that coarse on most lathes can be a problem, the best solution is to find someone with a cnc vertical mill and a 4th axis..
Ray
-
19th November 2014, 02:46 PM #3Intermediate Member
- Join Date
- May 2012
- Location
- melbourne
- Posts
- 43
how critical is the pitch ?
14 tpf(oot) is 1 1/6 tpi, that's an odd size
a 20mm metric thread is about 15 1/4 tpf(oot), is that close enough ?
what are you doing for the corresponding nuts ?
If you need to remake these, then a 20 mm thread should be ok ?
-
19th November 2014, 03:27 PM #4SENIOR MEMBER
- Join Date
- Sep 2011
- Location
- Ballarat
- Age
- 65
- Posts
- 2,659
-
19th November 2014, 05:42 PM #5SENIOR MEMBER
- Join Date
- Jun 2011
- Location
- Australia east coast
- Age
- 71
- Posts
- 1,469
Many people *could* cut those. I certainly have the equipment to do it.
Question is, is this a paying job or a 'slab of beer' deal?
Second question, is there a drawing to work off?
Third question - what about the female threaded part (ie a nut or threaded item the rod screws into)?
You get the idea - more and well detailed information required.
PDW
-
19th November 2014, 06:48 PM #6Philomath in training
- Join Date
- Oct 2011
- Location
- Adelaide
- Age
- 59
- Posts
- 3,149
-
19th November 2014, 07:52 PM #7
This is simply a modified bit similar to a "brace and bit", as used to drill holes in fence posts. I use them a bit but I only have the ordinary type. The device is apparently used to drill multiple holes with multiple bits like this. It would have been used to drill multiple holes in fence posts to pass the wire thru. I don't think anybody puts wires thru the posts like that any more. It is much easier to attach the wire reel to the ute and drive down to the other end of the fence. Staples to attach the wire.
Dean
-
19th November 2014, 08:17 PM #8
On the other hand I may be wrong about this.
Dean
-
19th November 2014, 09:41 PM #9Senior Member
- Join Date
- Mar 2014
- Location
- West Wodonga
- Posts
- 114
Staples are a lazy man's fence. Only good use is on cyclone wire fence.
-
19th November 2014, 09:59 PM #10Philomath in training
- Join Date
- Oct 2011
- Location
- Adelaide
- Age
- 59
- Posts
- 3,149
-
19th November 2014, 10:10 PM #11Philomath in training
- Join Date
- Oct 2011
- Location
- Adelaide
- Age
- 59
- Posts
- 3,149
Looking at the pictures again, I think it misleading to call the coarse pitch groove a thread. It reminds me of a fly press I once saw with a similar arrangement. The fine thread would have a normal nut (or nuts) on it and were probably used as stops. The helical groove would be used for some sort of drive or maybe rapid travel. Because of the groove pitch it could not use a conventional nut. The more likely situation would be a close fitting sleeve with a pin or dog point screw locating in the groove.
Michael
-
19th November 2014, 10:13 PM #12Intermediate Member
- Join Date
- May 2012
- Location
- melbourne
- Posts
- 43
so the coarse thread pitch is not critical, it's just to evacuate the chips
This looks like an easy lathe job, just needs a form tool to cut the coarse thread.
Fine thread can be Whitworth or UNC, it's just to drive the bit forward
But.... what about the cutting edge, bit of tool steel or carbide brazed in perhaps ???
-
19th November 2014, 10:20 PM #13Philomath in training
- Join Date
- Oct 2011
- Location
- Adelaide
- Age
- 59
- Posts
- 3,149
For your average lathe, trying to cut a 1 1/6 tpi will put too much strain on the leadscrew and drive train. An 8tpi leadscrew (common size) probably shouldn't attempt anything under around 4tpi. Not to say it can't but damage could ensue...
Helical milling is probably the less stressful way to go.
Michael
-
19th November 2014, 10:38 PM #14Senior Member
- Join Date
- Sep 2008
- Location
- Riddells Creek
- Posts
- 300
It could be for cutting/forming a thread in to hardwood posts for gate hinges, basically a Tap.
-
20th November 2014, 08:16 AM #15SENIOR MEMBER
- Join Date
- Jun 2011
- Location
- Australia east coast
- Age
- 71
- Posts
- 1,469
There speaks a person who has never cut a coarse thread.
I have a 2.6 tonne Monarch CY lathe with a 7.5HP motor. The coarsest pitch it has in it's gearbox is 2 TPI. Slowest speed is 13 rpm. I've cut 2 TPI LH threads on it. This thread is almost double that *and* on a long, skinny, highly flexible piece of threaded rod so it's going to move and chatter badly. A travelling steady is going to be essential and given the threaded profile, possibly one with a guiding bush.
The sensible way to make this is to use a ball nosed end mill on a milling machine or a lathe with live tooling. This job is a PITA waiting to happen and unless it had to be dead nuts original for a very important piece of industrial restoration for a museum or similar, or it involves a nice collection of folding money, it's best not touched. Especially absent any photos, drawings or other details of what it fits into.
PDW
Similar Threads
-
Thread cutting on the lathe by hand crank
By 19brendan81 in forum METALWORK FORUMReplies: 8Last Post: 10th July 2012, 01:56 PM -
tin snips-left hand or right hand?
By 3 toed sloth in forum METALWORK FORUMReplies: 39Last Post: 18th March 2012, 04:07 PM -
Metric Left Hand Nut - Fine Thread
By electrosteam in forum METALWORK FORUMReplies: 3Last Post: 2nd March 2012, 12:41 PM -
Left Hand Thread
By artme in forum METALWORK FORUMReplies: 17Last Post: 8th June 2008, 08:50 AM