lathe trouble

had to quit my project today…was getting way angry to continue working.

here’s the deal….i had machined most of 5 valvebody’s as i knew i would probably mess one or 2 up…that took me about 3-4 hours to do, which is ok since i had to figure out some stuff as i went along.

came to the external 18mmx1.5mm that goes into the bottle…gearing ratios in the manual is not very precise…for 1.5mm thread….after a bit of googling in found the right ratio’s changed gears and started to cut as i allways do adding .002″ pr cut…..

first cut ran perfectly, with a nice clean cut…i thought it was going to be easy….second cut looked slightly off but i find that sometimes it takes a couple cuts to make it look right….third cut strips the thread…arghhhh…WTF….check threading dail…its as its supposed to…check gears if it can skip or something…all is good

cutting tool is firmly mounted…cant see that doing it…..

im using cutting oil as supposed to….

i tried cutting in some aluminum just to check….and i simply dont get whats going on….

anyone have a clue …..as to what is going on….lathe is one of those minilathe from cummings

mcmike

Participant

September 11, 2007 at 4:07 am

Hello,

I know it’s nice to be able to turn threads but why aren’t you guys not using the tool that is meant to cut threads? (Don’t know the proper english name).
I mean if you are doing lots of valves and need same threads all the time it would be so much easier and you could never make it wrong.

I mean this kind of tool:

shadoh

September 11, 2007 at 2:02 am

Well, its just a name change to one thats already there )

martin777

September 11, 2007 at 1:47 am

quote martin777:

p.s.– We need a topic dedicated to lathes/machining!
Anthony266/Adam in SoCal?–hint-hint

quote Shadoh:

I couldnt agree more.

quote Yellow Ninja:

I third that !!!….

Holy New Topic–Batman!!!
http://talonairgun.com/forum/viewforum.php?f=11

First Class–Good Show!!!

September 11, 2007 at 12:02 am

You need to cut a clearance area where the threads end. The smaller dia. (< or = minor thread dia.)
will provide a relief allowing the tool to gracefully “emerge” at the end of each pass!

Enough relief area will give you room/time to stop the motor and will leave a very nice transition.
💡 You might also cut a 30 Deg. bevel at the end BEFORE u start threading–will make it easier to screw in after your done.

Hang in there— 8)

September 10, 2007 at 11:09 pm

Give me somewhere to post my shop pics…

cygnus-x-d82

September 10, 2007 at 11:05 pm

thanks for the links….there is a bit of chatter…but my cutting die usually fixes this….

the problem is that the tool is not hitting the same place, couple of cuts and it cutting a groove as supposed to…and then suddenly decides to cut the top of the thread, basicly ruining the whole thing

i have tried that cutting at an angle….i messed up and gave up after a couple of try’s

i think i had mine at a 29 degree angle ….but from the wrong angle…i will try that again tomorrow see if helps with the chatter….cant get much worse….

using the numbers…as long as you use the same everytime your fine no matter what….but some threads alow you to just pick one instead of waitng for a particular one to come around…

got the frame threads done on 2 pieces and on one practice piece….then the tip broke off the tool as i got too eager….and the carbide tools i bought where very cheap…its not the first time it happens…luckily i was done and i allready got some bits that i made my self…so im ready for some machining tomorrrow….

the treads going in to the bottle actually came out pretty good i think…after a quick grind with a thread file…they look good…and they screw into the bottle real nice…no wiggle…no slack…just smooth

September 10, 2007 at 10:55 pm

quote :

p.s.– Idea We need a topic dedicated to lathes/machining!

September 10, 2007 at 10:53 pm

😯 You WOULD NOT BELIEVE how well this mod. improves a mini-lathe!!! 😯

http://www.mini-lathe.com/Lapping/mt_lap.htm

p.s.– 💡 We need a topic dedicated to lathes/machining!
Anthony266/Adam in SoCal?–hint-hint

September 10, 2007 at 10:37 pm

Great link, that one goes into my folder for sure. I will check out the others later when I have time.

Thanks for the info.

September 10, 2007 at 10:35 pm

STOP THAT!

September 10, 2007 at 10:34 pm

LOL< you posted the same second I did I guess. I will look at your link though and see if Im right ).

Exactly!!!

September 10, 2007 at 10:33 pm

NM, now that I think about it its not a bad idea. If the angle of your thread is 30 deg then by advancing at a 30 deg angle you would only be using one side of the cutter instead of both sides.

http://www.mini-lathe.org.uk/threading_tool_angle_advance.shtml

September 10, 2007 at 10:18 pm

VERY IMPORTANT!!–Are you set up to advance the COMPOUND ONLY (set at <30 Deg.) or are you plunging the tool straight in with the cross-slide? Plunging the tool straight in is NOT the preferred method but the most commonly used.

You lost me on that one. When you say advance the compound only are you talking about depth of cut? And if your compound is set at 30 deg wont that move your cutting tool sideways as well as deeper into your material? Wouldnt that cut off part of the thread from the previous pass? Im asking because there was nothing about this in the manual that came with my lathe. If there is a better way of doing this or something I need to learn Im all for that.

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