Threading Innies & Outties

[Tinkerer]

I have an indexer with a 1.375 x 8tpi and a small chuck off the little 109 with a .5 x 24tpi back plate. So I needed a adapter... dug up some 2" round and made one up. First I trued up the bar and clocked it in in the four jaw till it was dead nutz on... bored the hole. Heated and bent a blank of HSS to form a single point tool. Ran it upside-down on the back side to cut the 8tpi threads. Next remove flipped it round and re clocked to nutz and cut the .5 stub and then threaded to with 24tpi.

Here's some pixs

http://img.photobucket.com/albums/v665/A-Tinkerer/000_0762.jpg

http://img.photobucket.com/albums/v665/A-Tinkerer/000_0764.jpg

http://img.photobucket.com/albums/v665/A-Tinkerer/000_0763.jpg

http://img.photobucket.com/albums/v665/A-Tinkerer/000_0766.jpg

Have some other things I've whittled this week and will post up some pixs when I get them resized.

[rockrat]

Nice job. What will your first project for it be?

I always get stoked when I make a tool that helps me out. Made a little puller for my grinder the other day to remove the interchangeable arbors. What a time saver.

[Tinkerer]

Thanks rockrat... Here's a couple things. Top one a replacement part for the banjo adjuster bracket bolt on my atlas... got tried of fumbling around with that friggin' nut hidden behind it every time I wanted to change gears. With this it's a straight forward op and much quicker. Milled the 3/4" inboard nut. Second is a swivel handle for another tool I'm making.

http://img.photobucket.com/albums/v665/A-Tinkerer/000_0768.jpg

[Alistair Hosie]

Nice job tinkerer well done Alistair p.s have fun

[lynnl]

" ....Heated and bent a blank of HSS to form a single point tool. ..."

Well I'll be golly! I would've thought that would destroy the hardness of the tool.
Not so...??

[oldtiffie]

" ....Heated and bent a blank of HSS to form a single point tool. ..."

Well I'll be golly! I would've thought that would destroy the hardness of the tool.
Not so...??

This "forging of tool-bits" has been going on since the year "dot".

Use heat and move it around as you like and let it cool slowly.

Earlier carbon steel tools needed subsequent hardening and in some cases - tempering.

Not so any more with HSS.

I've seen a few reports that this is so - including the newer tungsten (?)-rich varieties of HSS.

Further HSS is much "stiffer" and more rigid that any combination of tools, tool-holders and the like and will therefore be less likely to resonate ("sing") than just about anything else.

Use the "fish" aka "Thread form and setting guage" - referred to elsewhere on this thread - to grind the tool and set it - on the job or on the tail-stock quill.

It is essential to"
- reduce the total cutting surface at any time;
- hone all cutting edges and faces to a dead fine edge and finish;
- use adequate correct cutting fluid/lubricant;
- tighten all cross and top-slide gibs as far as is practical;
- have the top face of the tool "tilted" so that it is at right angles to the helix of the thread - add back rake (say 10 -15 deg to suit);
- check that the chuck is not "bell-mouthed" and is "true";
- check that chuck-backing plate bolts are tight;
- check that backing-plate to lathe mounting face are tight and if on a spindle thread, make sure it is tight.
- "feel" the chuck, head-stock, tool-post, and cross-slide for vibrations that can cause or worsen vibration caused by resonance;
- just putting your hand on things can not only better detect the source of vibration, it can actually act as a "dampener".

Turning tools when used on very fine cuts (and the reduced load and vibration) are "scrapers" and work in much the same way as the blade in a wood-working hand/bench plane - so treat the lathe tool with the same due diligence and care regarding "keeping the edge" as you would for a plane.

And take it slowly. "Crashing" half-nuts on a lathe is worse that crashing gears in a "crash-box" - in fact if you lean on the engagement lever it will rub on the lead-screw (steel) which in turn has a shearing/cutting/wearing action on the softer nuts (bronze) - not unlike poking something down onto the spiral in a meat mincer.

I have dealt with this in some depth on another recent thread in this forum but can't remember where or what it is.

[Tinkerer]

" ....Heated and bent a blank of HSS to form a single point tool. ..."

Well I'll be golly! I would've thought that would destroy the hardness of the tool.
Not so...??
lynn... Here is a photo of the tool I used to cut with. The first thing I did was to grind the inside relief. First attempt I tried to bend it at a cooler temp and cracked it. The next one I heated the blank to a cherry/orange red and bent it then dashed it in a can of sand to cool. Then ground the out side of the bit honed and cut. Worked well for me.

http://img.photobucket.com/albums/v665/A-Tinkerer/bentbits.jpg

You'll notice I used the inside bend to create that side of the 60º profile. And yes I agree everyone needs a thread pitch gauge. They'll allow you to square the bit to the work and confirm you have a 60º grind.

[pntrbl]

Just had a "light bulb" moment. The little notches in the side of the fish are meant to be used right up against the work to align the bit? Duh. I never knew.

I've been using the big notch for accurate bit grinding but that's all.

I got a feeling as soon as I stop slapping myself in the head my threading is about to get a whole lot more predictable. :D

SP

[lynnl]

Ok, now here's where it appears to me there's some inconsistency. Several years ago I took a few machining classes at the local vo-tech college, and there, as well as numerous other places, I've seen the warning "when grinding a tool bit don't let it heat up to the point where the bit becomes discolored".

If heating to an orange-red for bending doesn't weaken the tool bit, how's come a little blue at the tip is such a grievous sin? ...or is it?

Yeah, I'm aware that in olden days when cutting tools were mostly just high carbon steel, that were forged to shape. But they also didn't hold up to high speed cutting as well as HSS.

[speedy]

A bit of colour when grinding the toolbit for machining is Ok ( and if your fingers can handle it ) but when you are near to finished you do not want colour on the cutting edges. Don`t forget to hone a sharp cutting edge.
Use plenty of coolant.