MK2 Metric Thread dial gears.

[o0norton0o]

A 28 tooth gear with an o.d. of 19 mm would have a modulus of .633. OTOH, 28 tooth gear with an o.d. of .748" (19 mm) would have a diametral pitch of 40.05. I suspect that the lathe has Imperial gears. If the lathe were offered with an option for a metric lead screw rather than a standard Imperial lead screw. I would suspect the latter is the case.

Regarding CAD generation of gears, they are not necessarily true to form. I know that is the true for my 2012 version of SolidWorks. There is a third party add on which will generate a geometrically accurate gear but it is somewhat cumbersome to use as it requires parametric equations .

From what I have seen, McMaster Carr's 3D gears are geometrically accurate and my approach is to download the model and modify it to meet my needs. Another way to create accurate gear models is to download them from SDP/SI's site and modify them to my need.

So,... it took me a bunch of days reading and researching to figure out what most of this meant. I re-measured the single existing gear that I do have for my thread dial and the module turns out to be closer to .631 with more precise measuring. Since the lead screw isn't "purely metric" because of it's odd diameter size for the given lead screw pitch, there isn't much in the way of preformed gears or cutting tools that I can buy, with the exception of a single tooth slitting cutter.

I thought about making a hob style cutter out of metric trapezoidal rod, but the 2mm pitch rod isn't made in a 12.57mm diameter. If I want to make a spiral hob to cut plastic gears, I have to first make the hob myself. If I make a circular hob then I have to make the complex rotational index for all three different sized gears I want to produce.

I did go to the websites suggested to design the gears, and saved the spec read out. I really didn't want to bother my CAD friend and have him code and print the gears, but I'm curious what they will be like printed versus cut. Needless to say cutting them myself is a elaborate process given that I have to make the cutters to cut the gears.

Thankfully, I had previously done the work to enable reverse chuck rotation on my lathe, so I can always leave the half nuts engaged to keep my place when threading and power back and forth to the start of any threads I make. It sure would be nice to use the half nuts as well,.. but it's a challenge at my experience level to make a hob for the lathe. As a cabinet maker, I feel like I could make a jig for the table saw to cut the gears with the only question being grinding a blade to the tooth profile.

Thanks again for all the comments. It took me a while to learn what some of the issues are with this project. If I get some worthy result, I report back the method and the result...

 

[WobblyHand]

Who originally manufactured the lathe? If they are not available to purchase from them, can you get the drawings? That might help a lot.

 

[francist]

Nice floor...

 

[o0norton0o]

Who originally manufactured the lathe? If they are not available to purchase from them, can you get the drawings? That might help a lot.

I called Clausing and they are no longer produced, with zero in stock..... but I did not ask for drawings..... because I didn't think of that.. but that's brilliant because it saves me from any math errors if I have the spec's. Great idea, I'll make the call and see...

Nice floor...

thanks, I was 25 years old when I did that job. My associate actually got the job and realized it was a big math puzzle, so he hired me. On day one the draftsman had drawn the whole pattern on the floor without a grid for reference. When I showed up and began measuring his pattern, it was all over the place. I announced that the whole thing had to be erased, and the whole floor needed to be gridded so the pattern could be exactly regular or else every cut would be and individual measurement rather than a repetitive part of the puzzle exactly the same size. Day 2 all the concerned people were there to see what my problem was with the job, (customer, designer, architect, draftsman, my friend who hired me and me) I told them why the pattern had to conform to a grid for the pattern to be cut quickly and accurately. After I finished my explanation they all looked at the draftsman who said...... "He's right!" and they all went off into a huddle without me while I assembled the 26' straight edge I made the afternoon before to begin the work drawing the grid. They finally broke the huddle, came over and said, "Ok, do it!" In two weeks, the floor pattern was routed and all the parts were cut and ready to be glued in...

 

[o0norton0o]

So,... I got the drawings from Clausing for the thread dial gears... Wow, are they generic images as far as actual visual drawings go, but all the specs are there. RJ was right. The gears are Imperial with a diametrical pitch is 40. I am continuing to persevere.

The more I read, the more I can see how complex gear manufacturing is. As a fabricator, I think I could make a hob style cutter and a jig to cut teeth into circular blanks, but because of the helical angle on the gear and the complex geometry of the teeth, I don't give my friend, who is a CAD designer, much chance to print these gears correctly. I can see how involved gear design is from the software side now. It's much like my own profession where certain parts of the profession are specialist categories and the best results come from those who do that specialty... I'm still going to contact him because I'm curious about printing. I'll report back on his result,... or lack there of...

again, thanks to all for the help!

 

[o0norton0o]

I'm almost there. I found an online 3D gear design program, and an online 3D file viewer. I entered the parameters of each of the gears I wanted in the design website, then downloaded the files. Then I uploaded them to inspect them on the online file viewer site. The gears all were correct,.. so I went over to the Shapeways website and uploaded all 3 gear files to get a quote on them printed in nylon. Each gear came out to roughly $7. each, so I ordered 2 sets of gears.... a lifetime's supply and I am spared the trouble of making any sort of jig for a hob style set up....

After doing a mountain of research learning about helical gears, it actually only took 30 minutes to design the gears, view them, and order them from Shapeways....

Granted that I am getting away easy because thread dial gears don't have a load on them. There was a list of different prices for these gears in different materials and made with different methods. The gold plated, brass version of one of these gears was $10,450. which is a long way off from $7. each...

 

[o0norton0o]

My gears will arrive on monday. I was curious as to the kind of fit that the thread dial gear and shaft employs. From my research it was claimed to be just an interference fit. I took a drift and drove the existing metal gear off the thread dial shaft today to inspect the gear and the shaft. There's a light spline pattern on the shaft where the gear mounts but no spline teeth on the gear. I assume this is a way to make the shaft and the hole in the gear the same size, but still get some purchase on the pattern's high spots when the gear is driven onto the shaft.

I'm going to try the same fit technique with one set (I bought 2 sets) of my nylon replacement gears and see how that goes. I really didn't want to change anything about the dial. I just want the 2 gears that I was missing to work with the dial I have without having to rework the whole thing. I think the spline pattern will work fine with the nylon gears if I get the size of the hole "just right", although I know that plastic creeps over time so maybe at some point a nylon gear will just drop off. I have to measure the dial shaft at the knurled and the un-knurled shaft and try to get the hole just right!

I'm open to other suggestions if someone sees a more obvious solution. I'm thinking of buying a second, used thread dial off ebay, just to maintain the integrity of the one that I have, and then I can mess around with mounting the nylon gears on the extra thread dial. This way I won't risk the original thread dial I have... Suggestions?? thanks

 

[o0norton0o]

The gears look good, I thought I would post an image or two just so people can get an idea of what the final result was... The original metal gear doesn't have the helical angle on it unlike the gears I had printed to complete my the thread dial gear set for my MK2 metric 10200 model lathe. I only had a small hole made in the printed gear because I wasn't sure about how I was going to mount them. (splined, squared, or something else) I'll figure that out once I do some more homework and figure out WTF I need to do without guessing....