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It's just as easy as regular threading. It is a 3B class thread, which is the most difficult part of cutting (close tolerances). Keep your compound spindle handy and test the fit after every cut once you get close.
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South Bend 9 Compound Condition & "weld up" fixes?
- Thread starter graham-xrf
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It's just as easy as regular threading. It is a 3B class thread, which is the most difficult part of cutting (close tolerances). Keep your compound spindle handy and test the fit after every cut once you get close.
Only when someone catches you!
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Definitely not going there! Kitchen is to have planned makeover anyway, but even so ..
Serendipity ??
I happen to have 2 x 7kg butane gas cylinders + regulator left over from when old chez caravan, purchased as already 2nd-hand in 1998 finally reached a condition where it had to be disposed of in 2018. One cylinder is full, the other about half-full. It seems natural to have them be useful again. Then I compare the cost of a eBay gas hob to the cost of variously, a ACME tap, a replacement nut, some fire bricks, etc.
Looky here!!
So I clicked "Buy it now". The HM collection of rabbit-holes has now led me into (partial) heat treating. This gas hob, with some ad-hoc modification on top to contain and connect to the compound, becomes a major resource not subject to censure for sneaking time on the kitchen cooker. Also, it is acquired at the price of doing single point ACME threading (sans tap) learning curve.
I will probably expend a good deal more than that practicing both the weld, and making ACME threads.
Now also, I am bounced into reading Machinery's Handbook to discover what are class 3B threads, because it begged the question..
"What other classes are there"? Must so stop with the distractions!
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There are 6 classes of threads - three for external (1A, 2A and 3A) and three for internal (1B, 2B and 3B). Class 1 threads are the loosest fit, Class 2 are a little tighter and Class 3 threads are the tightest fit. They are just really tolerance classes.
Just my take. Delrin and the high end plastics will work pretty good for cross-slide nuts. It’s usually done as a delrin insert inside the bronze housings of said worn out bronze nuts. And the advantage is less backslash.
But, this thread is about a broken t-slot. That’s a totally different animal in my opinion. J-b weld will never hold those forces.
Personally, I’d try bronze braze for that repair. But that’s not an easy repair because after you braze it then it needs to be milled perfectly squared, otherwise the tool post ends up being cocked.
I’ve tried it and I never really got it perfect.
now, in my defense.... that was when I first started in this hobby. I didn’t even have a mill...so I had to file it with a hand file. Filing a t-nut perfectly isn’t easy. Damned tool post always wanted to rock a little.
But, this thread is about a broken t-slot. That’s a totally different animal in my opinion. J-b weld will never hold those forces.
Personally, I’d try bronze braze for that repair. But that’s not an easy repair because after you braze it then it needs to be milled perfectly squared, otherwise the tool post ends up being cocked.
I’ve tried it and I never really got it perfect.
now, in my defense.... that was when I first started in this hobby. I didn’t even have a mill...so I had to file it with a hand file. Filing a t-nut perfectly isn’t easy. Damned tool post always wanted to rock a little.
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Oops - please don't misunderstand.
I started out wanting to weld the T-nut, because the remains of the slot, while able to hold the tool post, will be considerably weakened. The original lantern post had been replaced by a square rotatable, and then lately, by a quick-change tool post, which are larger. The edge of the T-nut is partly over the break.
It's a weld repair and a Acme nut replace
I noted the backlash was a bit much, but when I took it apart, to clean up for the weld, there I discovered the less than wonderful Acme nut. It turns into two operations to fix. It seems wrong to put such a wrecked Acme nut back in a repaired compound. I guess mentioning the messed up stuff in the compound, additional to the weld repair is "off topic", but I am contemplating doing stuff to my compound generally considered serious, and risky. The commentary so far has been extremely valuable. Such a lot of stuff I needed to know, plus a lot of alternative options. I am still getting up the nerve to actually hurt metal, but it is going to happen. I fully appreciate that things could go badly wrong, and that some choices may be unwise for my level of skill. Nobody need say "I told you so"!
Re: Filing stuff to a controlled flat surface.
Some guys have a muscle memory that works almost as linear as a shaper, but we are not made of unyielding slides. If the file is going to inevitably "rock", then one solution is to have the work rock with it. The same trick sword sharpeners use. Make a little plywood base with brackets to mount a rod to pivot on. Fix a nail onto each the ends of the (wooden) rod, and hang it between V cuts in plywood stands. Clamp the work to the plywood one-axis gimbal. Now, as you file, it does not matter if the file tilts, because the work rocks to follow it. It's especially effective for draw filing.
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Do you have access to a surface grinder, or shaper, or even a mill? One of these could easily flatten the top surface. I would say that using a vertical mill to flatten the underside of the weld would make things really simple
In a pinch, you could file the weld down to flush by hand, then smooth things up with some emory paper. It really is doable.
I’m sure you can get it flat. Trust me. When I was hacking my 618 cracked compound... I really knew nothing. And I got it good enough to use the lathe for a few months. But when I saw one at a really good price... I snatched it up on EBay.
So you’re going to be able to fix yours in my opinion. On the Acme nut... there’s tons of ways to get it better. FWIW, I’ve read many descriptions of fixes of nuts with Delrin and JB. In the end, I just purchased a brass nut from one of the EBay sellers who makes replacements. Not as good as a bronze OE nut, but much cheaper. New nut and a new screw and problem fixed. I still have some backlash. But that’s the nature of the beast. We’re never going to eliminate all of the backlash.
So you’re going to be able to fix yours in my opinion. On the Acme nut... there’s tons of ways to get it better. FWIW, I’ve read many descriptions of fixes of nuts with Delrin and JB. In the end, I just purchased a brass nut from one of the EBay sellers who makes replacements. Not as good as a bronze OE nut, but much cheaper. New nut and a new screw and problem fixed. I still have some backlash. But that’s the nature of the beast. We’re never going to eliminate all of the backlash.
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I do have the brand new Cormak mill drill, and vise, and clamps, parallels, and a MT3 chuck with ER32 collet set, and even a DRO kit.
BUT..
It's still in it's crate, under the welder
From what you say, I think I have to agree. Fooling about with files and hand-held grinders when the mill resource is right there to finish it properly is just not sensible. Building operations or not, I will have to force some space to set it up temporarily, and get the right milling cutter to do T-slots.
I have been grinding on it!
One thing I have to watch out for. The present situation of UK for imports is suddenly strange, I think because UK is now no longer in the European Customs Union. eBay stuff from China on "Free Postage" suddenly attract substantial charges before delivery, which is VAT and customs duty. I am very glad I got the mill purchased just before all this happened.
Perhaps a 6mm wide cutter, about 20mm diameter might do. So now I am checking out milling cutters. I am not sure about what is best used on the top face. There will be weld sticking up. Does it need a face mill, or a fly cutter? That is a bit one can reasonable get flat with a file.