Simple Auto Retract Thread Cutting

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Mar 3, 2021, 07:47 AM
olderdan

4 Attachment(s)

Simple Auto Retract Thread Cutting

Needing to make new frame to engine studs for my latest motorcycle build (it came with all thread) it is important to me that the threads only go through the fastening and not the parts being fastened. This involves accurate run out when screw cutting without an undercut. I have got pretty good at manual manipulation of the controls over the years but that means threading at much slower speeds than are ideal. To speed things up and to be able to single point thread at at least 350 rpm with no undercut I needed some help so came up with this idea which gives plenty of time to drop the half nuts. I already had a plate along the rear of the bed originally for copy turning from templates, this plate clocks true in both axis to the bed and has two precision ground riser blocks to take a ½ inch round bar or plate templates (It mostly gets used for a DTI) mag base. So with a ground bar and a simple 45 deg collar I have a way for the tool to retract the at the right moment, the slide is disconnected from the feed screw and retracts by the needle roller follower meeting the collar. At the moment thumb pressure on the cross slide is used and works well enough for me and is very fast to use, I have a means for spring pressure or air ram to be used but so far not needed. Depth of cut is by the flank method from the top slide. Obviously when threading to a shoulder I have to resort to the traditional method. I can imagine some chuckles from the CNC guys but this cost me nothing to make.
Attachment 38675
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Mar 3, 2021, 06:34 PM
dagrizz

Ask the CNC guys how long it would take to program the threading into the machine, then we'll see who's laughing. BTW, great use of available resources.
Mar 3, 2021, 09:07 PM
mdhatter3

That is a truly neat idea. Nice. Very nice !!!👍👍👍👍
Mar 4, 2021, 01:32 AM
tonyfoale

Alan,

Very impressive.
Why do you avoid an under cut? As you can imagine I have made many such studs and I always have an undercut.
Mar 4, 2021, 01:42 AM
tonyfoale

Quote:

Originally Posted by dagrizz

Ask the CNC guys how long it would take to program the threading into the machine, then we'll see who's laughing. BTW, great use of available resources.

Actually it would not take long at all. There are pre-defined Gcodes for threading but most users would use a wizard with very few inputs needed.
Mar 4, 2021, 03:55 AM
olderdan

1 Attachment(s)

Quote:

Originally Posted by tonyfoale

Alan,

Very impressive.
Why do you avoid an under cut? As you can imagine I have made many such studs and I always have an undercut.

Tony, I understand that a bolt or stud is only as strong as the thread root dia, if I use undercuts I use a radius tool. The reason for not is for originality, I am restoring a 1919 V twin AJS so I am making parts as close to OEM as possible. I bought this machine from an oil worker who brought it back from India and it was in poor shape although mostly complete having been used as a daily hack, the way these people keep things going is incredible. PIC.
Attachment 38716
Got my work cut out this time!.
Mar 4, 2021, 05:17 AM
DIYer


Thanks olderdan! We've added your Auto Retracting Thread Cutting Tool to our Tapping and Threading category,
as well as to your builder page: olderdan's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/homemade-auto-retracting-thread-cutting-tool"> <img src="/uploads/247862/homemade-auto-retracting-thread-cutting-tool.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/homemade-auto-retracting-thread-cutting-tool">Auto Retracting Thread Cutting Tool</a> <span> by <a href="https://www.homemadetools.net/builder/olderdan">olderdan</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/lathe'>lathe</a>, <a href='https://www.homemadetools.net/tag/threading'>threading</a> </div> </div> </div> </div>
Mar 4, 2021, 07:28 AM
tonyfoale

Alan,
Originality, yes I understand that. It has never been part of my own outlook but I understand its importance for tasks such as your current project, which looks to be a huge amount of work. My kids and friends would think that I was ill if I started worrying about originality. Keep us informed as things progress.
Mar 4, 2021, 11:11 AM
slasher102

i would like to see a YouTube video of tis in action Well done love it
Mar 4, 2021, 03:58 PM
wizard69

Quote:

Originally Posted by slasher102

i would like to see a YouTube video of tis in action Well done love it

I have to second this! Your description is great and I do understand how it works but videos just make me chuckle. That is a good laugh or smile at a well done project.
Mar 4, 2021, 04:13 PM
Canyonman44

I would like to follow the motorcycle restoration! Ken
Mar 7, 2021, 08:08 PM
Toolmaker51

I dislike under cuts also, radiused is first choice. Issue; as depth increases, hitting the 'center' gets trickier. So, when needed, I use a cut-off tool with edges radiused instead.
Your manual kick-out is a creative answer. Can't imagine thinking of that solution, though did like pneumatic version operating the half nut lever here [hmt.net] awhile back.
Some lathes kick feed out, can't think of any doing that for threading.
Reasoned out why! Yours not actually kicking out, it's more a taper attachment. Kick-out would require retraction as well, unlike feeding to a shoulder.
Mar 8, 2021, 12:50 AM
tonyfoale

Quote:

Originally Posted by Toolmaker51

I dislike under cuts also, radiused is first choice.

Maybe just a question of language but are not those the same. When I first mentioned undercutting it never occurred to me that anyone would consider one that was not radiused.
Mar 8, 2021, 02:55 AM
olderdan

Quote:

Originally Posted by Canyonman44

I would like to follow the motorcycle restoration! Ken

I will post progress on the build but it will be a while as I have more work to do on my workshop. Tiling the floor, benches, wiring etc. Thanks for the interest.
Mar 8, 2021, 03:08 AM
olderdan

Thanks for your input Toolmaker51, The main objective in making this was to enable single point threading at increased mandrel speed up to 400 RPM to get a better finish. It would also help in as you say hitting the centre point of a radiused undercut. The thread shown is a 26 TPI cycle thread only .0205 depth so a clean thread is important.
Mar 8, 2021, 05:19 AM
tonyfoale

Quote:

Originally Posted by olderdan

The thread shown is a 26 TPI cycle thread only .0205 depth so a clean thread is important.

It seems that all the old brit bikes used 26 tpi. I always knew it as Brass thread, only later did I learn that it was Cycle thread. There seems to be a difference in the angle though. 55 deg for brass and 60 deg for cycle. I still have a bunch of brass thread dies that I used in the 1960s, little realising that the studs that I was making were wrong. I had never heard of cycle thread at that time.
Mar 8, 2021, 05:53 AM
olderdan

I also made that early assumption thinking that being british it would be the same as BSF and WHITWORTH form, metric is so much easier.
Mar 8, 2021, 10:34 AM
Toolmaker51

Quote:

Originally Posted by tonyfoale

Maybe just a question of language but are not those the same. When I first mentioned undercutting it never occurred to me that anyone would consider one that was not radiused.

When I'm asked what drew me into operating machine tools or machinist [US phrase], or engineering [per the Continent]; our ability to convey an entire part verbally is what most impressed me, and that continues. Certainly beyond vocabulary of laymen or daily conversation, it IS widespread clearly among practitioners. Compare that how one particular phrase is argued incessantly......"shall not be infringed".

For the three concerned; have we not mislabeled [or mixed continental meanings] that kind of design feature?

For remaining audience, proper description hereabouts is "thread relief". Some are less than root depth, others just under pitch diameter. Intent preserves strength of a fastener calculated in square units, helps mating nut not jam on incomplete threads, reduces stray bits of material tear off and foul a mechanism. Despite that, we confer corner radii are part of a properly completed transition from thread to fastener body.
An "undercut" defines a different feature; often to create 'square' corner, between a diameter with adjacent face. A proper turning tool is radiused at leading edge, that could interfere with a tight fitting mate, though a chamfer on the mate can accomplish same thing. In contrast, a relief is somewhat an O-ring groove, undercut more like a snap ring groove.

Here is a side note. Does not a large diameter meeting a wide flange introduce a tool dilemma? That's easily conquered. With compound at 45°, use carriage and cross slide to 'walk' a narrow bit into contact with both sides that 90° corner. Zero the compound dial, and back off. Spin part by hand and lay in Dykem or felt-tip marking. Proceed with cut, just a couple thousandths beyond corner insures a clear mating surface with least possible reduction of material.
Reasons to use one or combinations of, enter into part design, materials, and workmanship; but I think most intertwined in tooling available/ processes of manufacture.
Sep 30, 2023, 05:26 AM
meyer77

This might not be related to the above post, but I think anyone who had used a lathe will enjoy this story.
Back in August I started working part time (I am retired) for a gun dealer, my job was to log in all of the guns bought at auction and consignments, get all of the info SN caliber etc.
The owner is wanting to get out of buying and selling firearms and gen into more restoring work. He currently has about 4 guys working refinishing.
They did a Luger for me a while ago I was very happy with.
He has a pretty well equipped shop with a small mill, bluing and parkerizing tanks but no lathe.
About a month ago the owner told me he had bought a lathe, but it was on backorder.
On Tuesday we got a call saying the lathe was going to be delivered the next day.
When the driver showed up he was driving a box truck with a lift gate, the caller the day before said a forklift was needed to get it off the truck ( It was 14"x40" Grizzly gunsmith lathe and weighed 1500#)
Well there was no forklift on site so the driver used the lift gate and got it on the pavement.
The wooden box the lathe was in was 3'x 6'x 5' tall!
The only thing on site was a pallet jack, and when trying to get off the lift gate it almost fell over a quick call out from me and fast response from the driver(who was on the control of the pallet jack) avoided it falling.
After getting the box off I could see why it was so tall the lathe and base were on a pallet that was almost 8" tall.
After getting it inside, I said to the owner the lathe needed to be lifted up to get pallet out from under.
I had been reading the manual that came with the lathe and it said there were two openings at each end of the lathe that would take a 1 1/4"x44" bar and would provide the lifting points.
The owner was going to rent an engine hoist to to the job.
I called him in the morning and told him I get the two bars as there is a welding supply near me, that sells steel of different sizes. It would save him a 60 mile round trip.
After getting the two bars I went to the shop. When I got there the lathe was on its back near the floor and the rear electrical panel was crushed, and oil all over the floor!
They had a chain around the ways, trying to upright it!
Luckily I brought some nylon lifting straps (3,000# rated).
After about an hour and a half we got it upright The good thing? is when it fell over it hit a work bench which slowed its fall some what.
I left shortly after getting it upright. one of the shop guys had taken apart the electrical panel box and was in the process of getting back into shape.
As far as I see only one of the relays in the box was crushed, the rest looked ok.
When I checked the Grizzly parts web site that relay was discontinued, and its replacement look a lot larger!