Author Topic: Threading by hand  (Read 32927 times)

Offline wongster

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Threading by hand
« on: June 17, 2010, 06:34:28 AM »
Hello,

I'm pretty new to this.  Please go easy with me ok?

I'm in the process of making the brass torch as my first real project.  The main body turned out ok but I am now stuck with the cap.  After getting it ready for threading I find that I'm not able to hold the M10 die square to the shaft.  The 1st pic shows the cap ready to be threaded.  The 2nd shows the failed attempt to put the thread on.

I've not started with the Die Holder.  Thought of getting this over first before I attempt that.  Anyone has a trick or 2 when threading by hand?

Regards,
Wong

Offline colin563

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Re: Threading by hand
« Reply #1 on: June 17, 2010, 06:41:54 AM »

Offline No1_sonuk

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Re: Threading by hand
« Reply #2 on: June 17, 2010, 08:08:30 AM »
Not sure if you can do it with your machine, but I have used the front of the tailstock quill to get dies on squarely.
See attached pic.
In that pic (grabbed from someone else's site), he's using a collet chuck in the tail stock, rather than the front of the quill.  However, the front of the quill should do a good enough job, assuming it's big enough.

WRT the die holder referenced by colin563:
If you can't find one locally, there are plenty of online ideas for making your own.

Offline wheeltapper

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Re: Threading by hand
« Reply #3 on: June 17, 2010, 08:28:57 AM »
if the quill isn't big enough pop the tailstock chuck in and wind the jaws right into the body.

Roy
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lordedmond

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Re: Threading by hand
« Reply #4 on: June 17, 2010, 09:11:39 AM »
Why not screw cut it in the lathe , good practice for future work . finish with a die if you want

then it will be square and the correct tightness

Offline wongster

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Re: Threading by hand
« Reply #5 on: June 17, 2010, 09:13:35 AM »
Maybe I should cut it on my lathe.  I've this threading attachment still in the box. Have to read up on how to install it.  The spindle motor has to be removed for this to work.

Regards,
Wong

Offline wongster

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Re: Threading by hand
« Reply #6 on: June 17, 2010, 09:24:37 AM »
Not sure if you can do it with your machine, but I have used the front of the tailstock quill to get dies on squarely.
See attached pic.
In that pic (grabbed from someone else's site), he's using a collet chuck in the tail stock, rather than the front of the quill.  However, the front of the quill should do a good enough job, assuming it's big enough.

No1_sonuk,
How was the die held in the pic?  Or it is just being pressed onto the stock?  Can't see that from the angle.

Wong

Offline kvom

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Re: Threading by hand
« Reply #7 on: June 17, 2010, 10:09:45 AM »
I also use the tailstock to press on the die/holder, as shown in the above pics. 

Offline wongster

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Re: Threading by hand
« Reply #8 on: June 17, 2010, 11:01:37 AM »
Thanks for clearing this for me.

Appreciate all the responds.  Now looking for step by step pics on how to install the Thread Cutting Attachment.  I'll get the larger diameter steel/aluminum to make a die holder.

Regards,
Wong

Online mklotz

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Re: Threading by hand
« Reply #9 on: June 17, 2010, 12:14:25 PM »
First, are you using the correct side of the die?  If you look closely, you'll see that the die threads on one side of the die are tapered so that they don't take a full bite at first contact with the workpiece.  This helps the die to get started properly.  Using the correct side of the die is important even if you are using a guided die holder.

Second, if your die is adjustable (as most good dies are) open it to its maximum to start the thread.  The shallow thread you cut with this setting will serve as a guide.  On following cuts, close the die until you have the correct depth of thread.

Finally, you can often turn a small section of the workpiece end down to a diameter that just slides into the die.  This will help the die to align and guide the cut.  After the thread is formed, the guide tenon can be cut off.
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Offline Bernd

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Re: Threading by hand
« Reply #10 on: June 17, 2010, 01:22:48 PM »
Finally, you can often turn a small section of the workpiece end down to a diameter that just slides into the die.  This will help the die to align and guide the cut.  After the thread is formed, the guide tenon can be cut off.

Never thought of that. Neat little trick Marv.

Bernd
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Offline Dean W

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Re: Threading by hand
« Reply #11 on: June 17, 2010, 06:12:18 PM »
Hi Wong;
The instructions for your thread cutting accessory are at this link:
http://www.sherline.com/3100inst.htm

For what you are doing, and obviously the piece is pretty small, using a die in a die stock will get it done well,
and in just a few minutes.  If you can take about an hour to make a die stock to hold your dies, you'll have a
tool you can use for years to come.  It will start dies straight enough for most purposes.

A fellow named Arnold made up a set of them described in this thread:
http://www.homemodelenginemachinist.com/index.php?topic=6368.0
You will only need one at the moment, and if you always buy the same OD dies, that will be all you ever need.

Otherwise, just use a die wrench and push on it from the back side with the tailstock chuck as has already been
described here.  Pay heed to Marv's advice about starting the die from the correct side.

Good luck.

Dean
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Offline wongster

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Re: Threading by hand
« Reply #12 on: June 17, 2010, 09:01:43 PM »
Thanks guys.

Dean, I've the sherline instruction. Someone did post step by step pics and described his "boo-boo" when following the written instruction. Trying to remember the site to avoid the same mistakes.

I'll definitely make a die holder.ore convenient than to setup the thread cutting attachment.

Regards,
Wong

Offline wongster

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Re: Threading by hand
« Reply #13 on: June 18, 2010, 12:34:15 PM »
I managed to install Sherline's Thread Cutting Attachment but encountered a problem right after the first pass (0.25mm).  A little pin on the attachment snapped on the 2nd pass of the same depth.  I was scratching my head thinking what's going on with this threading business.  I found the snapped off pin and measured its diameter to be around 2.5mm.  Found a pin of almost the same size (2.3mm) from the pile of salvaged printer/scanner parts.  Hammered in the pin and trimmed off the excess.  I'm back in business.  The thread was done without further problem and I've my first threaded part!!!

I've taken some pics and posted them here.  The threads are not that nice looking but it threaded into the torch body without problem.

I've bought some 40mm aluminum stock today.  Will try to make the die holder as it is more convenient than having to install the Thread Cutting Attachment and remove the motor to the spindle everytime I need to cut thread.

Thanks for all your help rendered so far.

Regards,
Wong


Offline Dean W

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Re: Threading by hand
« Reply #14 on: June 18, 2010, 11:12:57 PM »
Congratulations, Wong! 
Threading seems to be one of the machinist stepping stones.  You're a step higher!

Dean
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Offline wongster

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Re: Threading by hand
« Reply #15 on: June 19, 2010, 01:38:06 AM »
Thanks Dean. Before I continue with the brass torch, I'm going to make the die holder since I've to make at least 3 pieces to give away. Now I'm boring away from 8mm to 33.25mm for this M10 die of mine.

Wong

Offline John-Som

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Re: Threading by hand
« Reply #16 on: June 19, 2010, 01:40:27 AM »
Wong

That is excellent progress ! The ability to cut screws in that way places you several rungs up the ladder. I know you are new to model engineering but this is quite some achievement so early on.

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Offline wongster

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Re: Threading by hand
« Reply #17 on: June 19, 2010, 04:26:16 AM »
Thanks John. I won't call it an achievement till I finish the torch and die holder. The boring part is taking too long. Need 33.25mm but I'm only at 29.X mm. As the hole gets bigger, the noise level increases. Chips are getting thicker with the same depth of cut. Slow down the spindle without avail. Taking a much shallow cut now (from .25mm to .1mm). Lots of oil (using sewing oil). Still loud with high pitch sound.

Any tips for that?

Wong

Offline Reckless_Engineer

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Re: Threading by hand
« Reply #18 on: June 19, 2010, 06:31:24 AM »
If you are still using the boring bar you started boring from 8mm with your boring bar if far too small. You should always use the biggest boring bar you can get away with,with as little tool sticking out as possible. When boring out tube ect you always get some noise.

What is your finish like inside the bore??

Offline wongster

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Re: Threading by hand
« Reply #19 on: June 19, 2010, 06:55:07 AM »
The finishing on the internal wall looks ok. The bottom is terrible. The loudest noise was produced when I hit the bottom of the hole.

Offline wongster

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Re: Threading by hand
« Reply #20 on: June 19, 2010, 11:00:16 AM »
I've finally completed the boring job....  Some pics attached.  I was so carried away with it that the bore is almost straight through without the step to hold the die.  The final result turns out to be ok except the hole is a little bigger than the die.  Difference in size is less than .5mm.  Hopefully a couple of set screws will hold it right.  The interior of the hole looks bad.  As I was creeping up to the final size, the cutter suddenly took a deeper cut than the usual .05mm I set.  The smooth finish was destroyed in an instance.  Some sand papers were used (from coarse to fine) to touch up the error.  The workpiece must have moved out of position to cause this.

As I've no success so far in parting off on the lathe, I think I'll likely to turn down the other end from 40mm to maybe 9mm to fit in my 3/8 jacob chuck. If this is not advisable, I'll cut off the back portion using my vertical bandsaw.  This may be tricky as my V-blocks can take only max of 25mm.  Any advice on what I should do?

Regards,
Wong

Offline Reckless_Engineer

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Re: Threading by hand
« Reply #21 on: June 19, 2010, 11:19:05 AM »
Looks like it should do the job and certainly looks the part:thumbup: Grub screws will take up theslack fit of the die and also allow you to adjust the die.

The last cut sounds as if you had push off from the boring bar over the previous cuts and then it bit in on your last cut taking it over size. Next time take a second cut of the same dia. on your 2nd to last cut.

Also is there any reason you held it with the jaws that way around?? You have got alot of material hanging out of the chuck(another cause of the vibration) and the jaws would of been better the other way arond.


Offline Lew_Merrick_PE

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Re: Threading by hand (Off-Topic Alert)
« Reply #22 on: June 19, 2010, 11:43:19 AM »
Why not screw cut it in the lathe , good practice for future work . finish with a die if you want

then it will be square and the correct tightness

Edmond (and All),

If you go to http://www.scribd.com/Lew%20Merrick, you will find a bunch of documents there.  One of them is UN Thread Data Chart.  This contains a lot of information on (inch-based) UN threads that may be useful to you.  One of the columns of information is the threading tool clearance diameter for turning external threads.

The reason I have not done this for metric threads is that there are still five different sets of tolerances and allowances in force for them.  Thus, in order to provide a thorough chart for screw and nut pull-out strengths and equivalent pin diameters, I would have to have 15 entries for each major diameter and pitch class of fit combination.  The ISO metric screwthread specifications are a mess.

Offline wongster

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Re: Threading by hand
« Reply #23 on: June 19, 2010, 11:57:43 AM »
The last cut sounds as if you had push off from the boring bar over the previous cuts and then it bit in on your last cut taking it over size. Next time take a second cut of the same dia. on your 2nd to last cut.

Also is there any reason you held it with the jaws that way around?? You have got alot of material hanging out of the chuck(another cause of the vibration) and the jaws would of been better the other way arond.

Hello Mr Reckless (hope you're not too reckless like me  :D),

Thanks for your reply.

Can you explain a little more on the part "... push off from the boring bar..."?  I don't quite understand being rather new to this.

The max I could hold in the Sherline 4 jaw is 38mm.  I was hoping that the additional 2mm from my round alu stock can fit but it hit the bed...  :scratch: From Sherline's instruction manual, I need to "flip" the jaws around for bigger pieces up to max of 70mm.  I should have turned the rod down to 38mm to be within specs but I was worried that I would have enough left to bore.  Would 4.7mm wall be strong enough for the die holder?  If it is, I'll do up another piece.

Thanks again for your input.

Regards,
Wong


Offline Reckless_Engineer

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Re: Threading by hand
« Reply #24 on: June 19, 2010, 12:24:50 PM »
I see why you had them that way around now lol :doh:

What you have is fine theres no point re-doing it the other way around.

When boring the boring bar has an habbiot of wanting to push off and flex away from the metal instead of cutting it! Hence the reason for using the biggest bar you can fit in the bore. If you put on a thou cut it may not cut at all, then another thou again not cut. It may do this lets say 4 times you measure again seeing a thou needs to come out so you put another thou on and now the bar doesnt push off and takes the thou and the previous 4 thous that didnt cut taking 5 thou off leaving you 4 thou over sized.

Im not the best person in the world at explaining things im sure someone will correct me if i have wrote something wrong but at least you get the idea.

Oh and on the reckless part, I know more than enough to class myself as Dangerous :zap: