Nice threading jig. *LINK*

Re: Nice threading jig.

Dick Coers

Something isn't right when he backs off the lid to deepen the thread. It just gets a touch in a couple of places. I suspect some play in his jig. At 9:08 in the video.

Re: Nice threading jig.

john lucas

Actually that problem shows up when using the jigs. The problem isn't the jig itself it's the inaccuracy of our lathes and some wood movement. I had this problem when using my Baxter jig. Since I live close to them I went over to their shop and Vic checked out my jig using a Dial indicator that had millions of an inch. My Threader was acccurate to 3 ten thousandths so it wasn't the threader. Vic said he had seen that problem before and argued that is was the lathes but but people think their lathes are perfect. In reality the lathes we use don't have machinist tolerances. Then you add in a tiny bit of wood movement, it doesn't take much for cutter not to touch the wood all the way around. Mine have on occasion been off as much as .015" which is almost half of a 16tpi thread. Doesn't really cause a problem with the threading because you have to leave the threads loose enough to allow for seasonal wood movement anyway. I just cut until the lid fits good with a little slop to allow for this movement.

What I thought could be a problem with this style of jig is not having the jig perfectly aligned with the bed. I mean your aligning it by eye. I have one of the Chefware jigs which works like this one. In theory it would produce a tapered thread but since your only cutting a thread 1/4 long it really doesn't show up as a problem.

Re: Nice threading jig.

John K Jordan

I suspect there is also a bit of play in the jig from unlocking the thread depth advance lever each time he backs off the jig. That could help explain why the cutter just touches in a couple of places.

I wondered if the way this jig is lined up on the lathe axis by lining up the chuck body by sight. I suspect with the short threaded lengths typical in wood threads any slight misalignment would not be a problem.

From the video the jig certainly looks well made.

JKJ

I agree John

Dick Coers

You can see that there is play in the jig. The fixture is also too short, so just a slight play is very easily transferred from the cranking motion into the wood. Watch where the contact is made, it definitely relates to the crank and when he releases the lock.

Re: Nice threading jig.

robo hippy

I haven't looked at threading jigs up close for a while, and still have my Bonnie Klein jig. The pivoting ones are new to me, but the problem of not having the cutter almost perfectly in line with the headstock is huge to me. Probably just as big as not having the male and female parts almost perfectly parallel to the bed. Saw one turner who claimed that it didn't matter because the cutter would even things out, but when finished, the lids would still slip down over a few threads before engaging. I guess you could lay a straight edge up against the chuck to give a longer 'stick' to sight with....

robo hippy

Re: Nice threading jig.

john lucas

I used to think that also but after using the chefware jig quite a bit I threaded a lot of boxes and ornaments with it without any problems. There are other problems with the Chefware that I don't like and this new one seems to answer them.

I think any slop in the system could be taken up by those two adjusting screws but I'm not sure I like the idea of just using brass to push against the threads.

It's hard to beat the Baxter threader. It is a precision piece of gear.

Re: Why multiple cuts?

Dave Paine

I have done a good amount of single point threading on my metal lathe, where multiple cuts is normal. I am aware of max and min diameters for a given thread.

I have not tried threading on the wood lathe. With the double bevel cutter, multiple flutes, the speed it is rotating and the shallow depth of the thread, why are multiple cuts required for wood?

I agree with John Lucas, the brass tipped screw to lock the threads is not the best design.

Re: Why multiple cuts?

john lucas

Wood simply tears out too easily. The cutters are really scrapers as well. The multi flutes I think are mostly because those are metal cutting cutters that are easy to buy. There was a single flute cutter sold by one company out of Austrailia or New Zealand that went along with their threader. I think multi flutes are better. Your only running at 3000 rpm which is really too slow for a single cutter that is about 1/4" in diameter.

I have my threader rigged up with a router so my cutter runs at 23000 rpm. It leaves cleaner threads but not as much as you might think. It also burns wood like Cherry and Osage if you slow down your feed rate even a tiny bit.

Multiple cuts also helps a lot to get clean threads in wood. I usually will make 2 fairly deep cuts and then the final 1 or 2 sneak up on the fit cuts are shallower and that's when I will apply the CA glue on soft woods.

On hand chasing threads I've been trying to emulate metal thread cutting. If you push the cutter too fast you are cutting into the next thread. If you get the speed just right you are cutting down the face of the first thread similar to what you do on a metal lathe. I think it leaves cleaner threads but it's so hard to get that "feel".

Re: Why multiple cuts?

robo hippy

Like John said, wood does want to tear and chip more than metal does. There are only a few woods that are well suited to hand chasing of threads, maybe a couple more that can be made to work okay, and the rest are seemingly impossible. I haven't done any boxes in a while, but when getting close to the final cut for the threads, I would chase the threads with walnut oil to lubricate the thread. Chasing them with thin CA glue does work but I am too messy for that one to work well for me.

I didn't need the tilt away for boxes to test for fitting, and having to leave enough room to back off away from the cutter to check. I used pencil register marks on the boxes where the grain on both pieces line up. I rotate till the mark is straight up/on top on the male piece. Then slide the jig up to the cutter and use the ruler from a try square (1/16 thick or so) to keep an exact and repeatable starting point for threading. Same with the female piece. I found out with 16 tpi cutter, on the female piece, if I backed it off about 1/8 of a turn, the pieces would come out with the pencil marks almost in line every time, requiring minimal 'adjusting' of the shoulder to get a perfect line up. Huge time saver, and no more having to adjust almost a full 1/16 inch down. Also if you go down too far and have to cut some more threads, it is simple to exactly reposition the piece for cutting.

robo hippy

aligning grain/figure

John K Jordan

>>Then slide the jig up to the cutter and use the ruler from a try square (1/16

>>thick or so) to keep an exact and repeatable starting point for threading.

I'm trying to understand this. Do you use the metal ruler as a thickness gauge to position the center of the cutter the same distance from the mating surfaces? Or something else?

The next time you do this could you possibly take a couple of photos or make a little diagram for some of us getting elderly and feeble minded?

JKJ

Re: aligning grain/figure

robo hippy

I need to do a short video of it, and boxes are not high on the priority list. Think of it as a stop block on the chop saw or table saw, or a spacer block on the arm of your Wolverine system. You can exactly position the piece you are cutting for exact duplicate cuts, and a spacer block puts it in the exact same position every time. So, slide the jig with the mounted piece up to the cutter, grain registration mark on top, insert spacer block, push up to blade and lock down the jig. Hope that makes more sense. Bonnie told me it was impossible.....

robo hippy

Re: aligning grain/figure

john lucas

That sounds somewhat like what Bestwoodtools is doing with the Baxter jig now. You have a plate that you bolt down to the bed of the lathe before you start cutting the threads. Then you can slide the entire unit away from the cutter while you check the fit of the lid. Then slide it back to that block and it will repeat the thread exactly. Make a slight adjustment, cut more thread and then repeat the process until you have the fit you want.

Re: aligning grain/figure

robo hippy

I couldn't find any pictures of it, but it does sound like it does the same thing. My version is probably cheaper, but it makes the process repeatable as long as your pencil mark is in the same place. Hmm, do I need a Baxter jig.....?? Now, if there was a way to time the threads (machinist talk for lining up the grain) exactly every time instead of just getting it close....

robo hippy