Needs Pictures: 0
Results 1 to 15 of 21
Thread: Thread chart, help needed.
-
23rd Dec 2020, 05:40 PM #1
Thread chart, help needed.
Pitches and feeds chart on the Hercus 260 now has me baffled.
Last week I cut a M~14 x2 thread single point with no hassle. According to the chart #4 is engaged with B lever in position. Stud gear 18 was left on as I interpreted the chart that it can be either ~18 or 45.
See the chart.
Attachment 390189
20201223_161432.jpg
Beautiful thread that mates perfectly with a corresponding M~14 x2 internal cut with an M~14x2 tap.
20201216_122023.jpg
Today I tried to cut a ~1.5 thread in a brass sleeve. I checked my settings made a scratch pass. To my surprise, the scratch didn't confirm ~1.5 but ~ 0.8!
So I changed the stud gear to the 45 and got a scratch pass done that confirmed ~1.5 on my gauge.
So I proceeded to cut the thread. Being a little fine on brass it was difficult to see but as I proceeded it seems the peaks were cut as the valleys were broadened. It seems that each pass cut in the same pattern but not in the same position. I hasten to add this happened on my first attempt to single point a thread as I had the compound set at 30° so my advancement of the compound cut off the thread in the same way as this shows on each pass. Since then I have learned to set the compound angle to 60°
20201223_161415.jpg
So my questions are 2.
1. Why did the first scratch pass not conform to ~1.5 until I changed the stud gear from 18 to 45.
2. What am I missing to result in my thread being eaten?
Thanks for any help.
-
23rd Dec 2020, 07:05 PM #2Most Valued Member
- Join Date
- Jun 2007
- Location
- sydney ( st marys )
- Age
- 64
- Posts
- 4,890
From what I can see with your first 2 mm thread at those settings it should cut .75mm pitch.
From what I calculate 1.5mm with 45 stud should be pos B hole 6.
1.5 mm with 18 stud pos A hole 4.
2mm with 45 stud pos B hole 3.
2 mm with 18 stud pos A hole 1.
Not sure how you got 2mm pitch with your first set up.
What gear is on the screw?
-
23rd Dec 2020, 07:50 PM #3
-
23rd Dec 2020, 08:47 PM #4Most Valued Member
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 3,228
I've always believed the line between the 18 and 45 is in the wrong place, because there's no way you could get the same thread pitch with two different gears and with the levers in the same positions. I reckon that line should be in line with the line below the "B".
Chris
-
23rd Dec 2020, 08:53 PM #5Most Valued Member
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 3,228
You had your compound set on the 30 degree mark, which on the Hercus is actually 60 degrees off perpendicular. So when you advanced the compound you were getting too much movement to the left (Z axis). Hence you were removing more metal than you should have been with each pass.
Chris
-
23rd Dec 2020, 09:12 PM #6
Hi Guys,
Whilst I understand the reasons for angling the compound, for fine threads I just set the compound to zero and go straight in it makes virtually no difference to the thread being cut. I also use threading inserts and I believe that they are not intended to be used in an angled condition. All the pictures/illustrations in manufactures literature show them being used by going straight in.Best Regards:
Baron J.
-
24th Dec 2020, 02:22 AM #7Most Valued Member
- Join Date
- Jun 2007
- Location
- sydney ( st marys )
- Age
- 64
- Posts
- 4,890
Generally makes no difference with inserts if plunging or offset for vee threads.
-
24th Dec 2020, 07:20 AM #8Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
- Posts
- 6,561
-
24th Dec 2020, 09:20 AM #9
-
24th Dec 2020, 09:28 AM #10
-
24th Dec 2020, 10:07 AM #11Most Valued Member
- Join Date
- Jun 2007
- Location
- sydney ( st marys )
- Age
- 64
- Posts
- 4,890
What method were you using to cut the thread?
-
24th Dec 2020, 10:33 AM #12
The same method I use before. Set the cross slide at zero and advanced the compound. I didn't need to use the thread dial. Something else went on that I didn't notice...
In fact I've made a 1.5 a year ago in aluminum and it was fine. Looking back on my photos at the time I can reconstruct some of the details.
20200121_193204.jpg
Here I can see I chose lever 4 and pos A
20200121_192158.jpg
I even made a threaded sleeve nut for the outside sleeve. It was for an oversized fishing rod reel seat.
I should have checked my past records before I cut the thread. But I'm still no wiser why. I'm going to try again after Christmas and recheck my settings and execution. I could just have over looked something simple that I didn't notice. "Measure twice and cut once!"
-
24th Dec 2020, 11:16 AM #13Most Valued Member
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 3,228
OK, well it's not that then. You are correct about not requiring the threading dial, so it's not that either.
The thread on the brass looks a bit like a buttress thread. Did you have the thread cutting tool set at the correct angle to the workpiece? I.e. the centreline of the tool perpendicular to the surface you are going to thread? I can't think what else would cause a thread to look like that.Chris
-
24th Dec 2020, 11:38 AM #14Most Valued Member
- Join Date
- Jun 2007
- Location
- sydney ( st marys )
- Age
- 64
- Posts
- 4,890
So you left the half nuts engaged and reversed the spindle?
-
24th Dec 2020, 11:51 AM #15
no, I disengaged the the half nuts at the shoulder, withdrew the cross slide, moved the carriage back, returned the cross slide to zero, then if needed moved the compound, or a spring pass which meant I left the compound in it's position. I proceeded to cut another pass by engaging the half nuts, etc
Similar Threads
-
Imperial and Metric Bolt Thread and Torque Chart
By moorebrm in forum METALWORK GENERALReplies: 5Last Post: 31st May 2016, 01:48 AM -
Printable imperial-metric-bolt-thread-torque-chart
By moorebrm in forum CONVERSIONS & CALCULATIONSReplies: 0Last Post: 16th May 2016, 09:03 PM -
Gas Thread info needed
By ericg in forum METALWORK GENERALReplies: 5Last Post: 12th Jan 2015, 01:31 PM -
ACME thread chart
By morrisman in forum METALWORK GENERALReplies: 1Last Post: 7th Aug 2012, 09:48 PM -
AL-340A Thread Chart Misprint
By matthew_g in forum METALWORK GENERALReplies: 1Last Post: 12th Jul 2010, 08:32 AM