Why I didn't start a new engine today

[Sshire]

This looked like a good day to start a new engine.
Had a collection of plans on the bench and plenty of stock.
Then for some reason I was thinking that I hadn't even tried single point threading on my new (and first) lathe. The manual from Grizzly isn't bad; I've seen worse. After decoding the change gear chart and figuring out where the 2 gears went, I replaced "gear A." that wasn't bad. A little Kroil and some swearing to get the gear off but not bad.
Now "gear B"
More Kroil, lots more swearing, various wedges, prying things, hammers, heat gun and it's off.
Now, put the selected gear on the same shaft. Not with a 20 ton press (if I could have hung it off the gearbox) would that gear go on. ?????
Inside mike. Measure the hole in the gear. Outside mike. Measure the shaft. The shaft is 5 thou bigger than the opening in the gear. Much more swearing follows.
I will call Grizzly on this issue after I measure the rest of the gears, but I wanted to try threading.
Put the gear on the mill. Center it with the Blake.
Test of the reducing collar I made for the Criterion boring head. Worked well. Bored out the gear about 8 thou. Test fit a bit tight. Back to the mill. Bore another 3 thou. Nice sliding fit on the shaft now.
No engine parts today. No threading either.

Best
Stan

 

[wheeltapper]

I had much the same thing with my chester comet.
no way would the changewheels come off without a fight.

then the others wouldn't go on.

turned out all the keyways were too narrow.

half an hour with a file and they all fit now.

Roy

 

[Sshire]

Roy
The keyways were my first thought. I measured them and they were close but OK.
I didn't understand why most people said that the Chinese machinery was fine once you disassembled them, filed burrs, lapped the gibs, etc.
Now I understand perfectly. I'm not at the stage where I could get an old Southbend or Clausing or Hardinge and rebuild it. I suspect that you need a working lathe to rebuild the older lathe.
The new lathe is fine but does need a bit more "tuning" than I had expected.
Best
Stan

 

[pete]

Suprisingly the concept of interchangeable parts is far more than 100 years old. In todays world of CNC manufactering, Then those gears should have never have left the factory like that. Bad dimensioned or steps missed during machining does happen even with the worlds best manufacter's. At least you had the skills,equipment and knowledge to fix what the factory should have done before they got shipped in the first place. Sadly, Problems like these for someone with little experience turns them completely away from machining as a hobby.

Pete

 

[Sshire]

Absolutely agree. While the threading practice was not essential, it was aggravating to fix this issue. Of course, I could center and bore any others in the set that were incorrect, but I'm going to insist that Grizzly send a replacement set and that they are sure that these have the correct bore. The gear set is not a "semi-finished kit. They are a part of the lathe package and as such should be correct.
There are a few other issues that are minor, but annoying. I'm aware that an $1100.00 Chinese lathe is not going to work like a restored SB or similar, but it will work for me once I work through the few ( I hope) issues.
Best
Stan

 

[///]

I got my 7x14 about 5 years ago, and this was an issue then.... so nothing has changed :big:

 

[prof65]

We like to built small engines. But we also like dismounting, cleaning, repairing, modifying, upgrading our machines. Chinese people knows it. They are able to make parts within .0001 mm tolerance, but they work hard for make mistakes that we can proudly repair... ;D

 

[90LX_Notch]

Stan,

You are assuming that the gears are out of tolerance and not the shaft(s). You might want to consider a little deeper investigation with more measuring of the various components involved.

-Bob

 

[Sshire]

Bob
That was a possibility that I had considered. If I had the prints for the lathe it would be easy to determine.
Two choices were:
Disassemble the headstock to remove the shafts and turn them down. But I don't have a second lathe.
Bore the offending gears (BTW there are three that have a small bore)

As usual, I went with the easier choice, and in this case, my only choice. Ten minutes per gear to center and bore on the mill.

I'm checking with a few guys who have the G0602 lathe to see if they can mike the two shafts for comparison.

Thanks
Stan

 

[90LX_Notch]

Stan,

I only mentioned it because it would stink if you have to mount one of the bored out gears on the other shaft in order to cut a different screw pitch and you have too much clearance. (The opposite of what you have now.) As long as you bored the three offending gears to the same id as the other gears in the set you'll be alright.

Bob

 

[Sshire]

Bob
Thanks. I appreciate that.
Stan