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Working on my South Bend 9C
- Thread starter Golem Pens
- Start date
Golem Pens
Michael
I don't even have to leave the house for that!
(I meant more holistically for my bigger workflow, but ask an obvious question... Hah)
I think it actually looks damn good. Just a few problems.
The thread root suffers from random release. Either make a threading relief at the root and stop each pass in the relief, or finish each thread pass by turning the chuck manually till you reach the same point each time. When I turn the chuck, I just stick a chuck wrench into any jaw and turn the chuck by hand cranking with the key. You can put a pen or marker mark on the work so you always know where to stop.
One side of the thread looks different from the other. When I zoom in on your threading tool, I see an arc on the left side while the right side is straight. Crisp flat edges on both sides are required.
The tops of each thread are flat. That is good - they should be like that. Ideally, they would be round but flat is fine. On the other hand, the roots are pointed. They should be rounded or flat too. Many guys leave them sharp. For most threads, that's ok. But ideally they would be rounded or flat. You can accomplish that by advancing the compound and backing off on the cross-slide the to get the same Z amount. Basically the cutter moves sideways without increasing the depth of cut.
Overall, I think it's great!
Looking good. When you get a nice thread you are happy with, try something close to the same size on your pen blank material so its apple to apples. I can think of a number of reasons why the blank may be less forgiving. High resin content & hardness should be similar results, but if you have interesting things in the mixture, it might actually tend to tear it out of the matrix & yield a rougher finish. I could see that happening in wood blanks too even though they are resin infused.
Golem Pens
Michael
Right, I was basically ignoring that on this go around. I'll primarily be threading, if not TO a shoulder, then limited BY the shoulder and tool colliding. For training purposes a relief is fine but in practice that is a design element I do not want in my pens (some makes do it, I don't care for the look). Running a collet chuck still so no jaws, but I'll figure out something to manually finish it. The 5-6mm threaded tenons are going to be interesting to figure out...
Ah thank you! I will straighten up that left side before my next attempts.
Lucky me, I just didn't want to cut too far!
Interesting! I also read about recommendations to include a very small flat at the tip of the tool. Is that to achieve the same effect, or for something else?
Other thoughts on the go:
- Considering transposing gears, my brain much prefers metric. I guess I could move my entire design spec over to imperial dimensions but it feels so....
- Need to get my head around target minor diameters for given pitches.
- Will need to figure out how to grind an internal tool too.
Golem Pens
Michael
Absolutely. I was going to do some more practice with the delrin because it's quite easy to work with before jumping over to my other materials. I had a few notes on my commonly used materials over here too https://canadianhobbymetalworkers.com/threads/tool-grinding-question-back-rake.20563/post-249181
See earlier notes. Turn the chuck by hand using a key to finish the thread and make a mark so you stop exactly in the same spot each time. I made a special key for the purpose that is eaaier to hold and use. Dont need a T handle to turn chucks.
Yes, I have seen others do that. I don't personally like it. At a minimum, it turns your multi-pitch tool into a tool that only cuts a very limited range of pitches. If you are going to go to that trouble, I'd make it a proper root radius instead. Myself, I prefer to shift the tool the required amount instead.
I prefer imperial. But I can do metric when I need to. It is my view that hobby machinists need to be comfortable doing both. Don't be tempted to lock yourself into one or the other. Do what the job dictates.
This info is in the charts. But you can also calculate it. One advantage of single point threading is that you can do custom diameters if you want to.
Yes, you will. I usually cheat. I have ground many inside tools over the years but it's a lot of grinding. So I usually buy blanks already ground into the right basic shape and then tune them for what I want.
Golem Pens
Michael
If I had my druthers I'd have found a metric machine, but so be it! For this, it may we worth re-speccing my designs to imperial at least for this phase so I don't have to keep converting on the fly. Having transposing gears on hand would certainly be a nice-to-have for versatility.
I have a few hand me down bits and I may see if any of them can be re-ground to serve the purpose. I also grabbed some 1/4" round blanks. I've got pretty small I.D.s at ~12.5mm and 9.2mm so a decently skinny tool is needed.
I will burn that bridge when I come to it! And many others too of course. While I am moderately emboldened by my progress so far I am not delusional enough to think I understand a fraction of the skills needed yet.
Golem Pens
Michael
Just occurred to me that I can grind my threading tool off-center to get closer to the shoulder. Will try that.
Gotta do a facing/shoulder cutter as well, then I'll have my external bits mostly in hand...
Gotta do a facing/shoulder cutter as well, then I'll have my external bits mostly in hand...
Yup, exactly! In fact, you can even grind it right to the pitch width from the edge.
Feels good, doesn't it!
Golem Pens
Michael
I'll start with the mostly left aligned one for now, but I'm sure I'll dig into more refinements later.
In the meantime with my unadjusted first tool, I've threaded to decently fit an off the shelf 7/16x14tpi nut!
Next.... Finish both sides of this threading tool and then I guess I have to dig into the internal tools since these are destined for custom diameter pieces?
In the meantime with my unadjusted first tool, I've threaded to decently fit an off the shelf 7/16x14tpi nut!
Next.... Finish both sides of this threading tool and then I guess I have to dig into the internal tools since these are destined for custom diameter pieces?
I could be wrong, but I think he is just using what he has.
But I'm with you. Smaller is much easier.
i think he was carving that tip out of 3/8" wide cutter blank.
Golem Pens
Michael
Yep, using what I had on hand. Will presumably buy more of a range of stuff once I know more of what I'm doing.
Golem Pens
Michael
I've got some 1/4" arriving soon already.