Getting bad cut from lathe
08-24-2006, 07:37 PM
#16
Originally Posted by geeunit1014
easy way is to coat the comm with a sharpie before you cut it. once all the sharpie is gone, the comm is round
NOT TRUE AT ALL!!!
If the lathe is cutting at and angle that is deeper at the inside vs the outside. The sharpie would be gone but the Comm. would be tapered.
If you cut it deep enough all of the Sharpie will be gone anyway...
Last edited by imprsme; 08-24-2006 at 07:48 PM.
08-25-2006, 04:15 AM
#17
Tech Regular
Originally Posted by Tek Nickal
Thanks, that helped a lot. Now, the comm is smooth but, its not as shiny as it was before. I think its time for a new bit...does anyone know which carbide bit fits the integy auto lathe? Also, where can I get it pretty cheap?
08-25-2006, 08:19 AM
#18
Originally Posted by James35
Tek Nickal,
Big Jim has been the authority on brushed motors, but even I was a little skeptical with I read Big Jim's post saying that even new carbide bits need to be sharpened!
So I followed his advice, paid $25 for a diamond hand file (220 grit) and learned how to sharpen the carbide bits. Here is how:
http://www.rccars.com/forums/attachment.php?postid=6980
Well, I used an 8X power eye magnifying glass to see what I was doing, and I got pretty good at it. Man what a difference! After sharpening the bit, the cuts look like a copper mirror. It's so easy and fast to sharpen the bits, that I do it ever as soon as 5-8 passes!
After I become proficient at it, I started putting brand new carbide bits up against my hand sharpened bits, and wouldn't you know it, Big Jim was right. The new bits definately have room for improvement and the powerful eye magnifying glass will makes it apparent.
Big Jim has been the authority on brushed motors, but even I was a little skeptical with I read Big Jim's post saying that even new carbide bits need to be sharpened!
So I followed his advice, paid $25 for a diamond hand file (220 grit) and learned how to sharpen the carbide bits. Here is how:
http://www.rccars.com/forums/attachment.php?postid=6980
Well, I used an 8X power eye magnifying glass to see what I was doing, and I got pretty good at it. Man what a difference! After sharpening the bit, the cuts look like a copper mirror. It's so easy and fast to sharpen the bits, that I do it ever as soon as 5-8 passes!
After I become proficient at it, I started putting brand new carbide bits up against my hand sharpened bits, and wouldn't you know it, Big Jim was right. The new bits definately have room for improvement and the powerful eye magnifying glass will makes it apparent.
08-25-2006, 09:14 AM
#19
Well, the great news is, the diamond file does not take a lot off. The cheap carbide bits can be sharpened over and over. To the touch and the naked eye, a worn bit is still pretty sharp looking and feeling to your fingers. But when you use a 8x power (or more) jeweller's loupe or photography magnifying glass, you can easily see the difference.
Last edited by James35; 08-25-2006 at 10:05 AM.
08-25-2006, 09:32 AM
#20
Originally Posted by imprsme
NOT TRUE AT ALL!!!
If the lathe is cutting at and angle that is deeper at the inside vs the outside. The sharpie would be gone but the Comm. would be tapered.
If you cut it deep enough all of the Sharpie will be gone anyway...
If the lathe is cutting at and angle that is deeper at the inside vs the outside. The sharpie would be gone but the Comm. would be tapered.
If you cut it deep enough all of the Sharpie will be gone anyway...
ACtually if you made to pass one left to right with sharpie then one right to left with sharpie you could confirm out of round cuts. With very very small depth of cut... My diamond bit hudy cuts both ways... not sure if that was every its intent but for 5+years i cut both ways
08-25-2006, 11:03 AM
#21
Originally Posted by drew85
Is there anyway to tell if its not cutting round? I was thinkg just go in a bit and make a pass without cutting but moving in a bit at a time intill it hits a high spot..just wanted to see if there was a standered way of doing it.
Thanks
Thanks
08-25-2006, 01:30 PM
#22
OK thats a great idea, im going to try it this weekend.
08-25-2006, 02:09 PM
#23
Originally Posted by imprsme
NOT TRUE AT ALL!!!
If the lathe is cutting at and angle that is deeper at the inside vs the outside. The sharpie would be gone but the Comm. would be tapered.
If you cut it deep enough all of the Sharpie will be gone anyway...
If the lathe is cutting at and angle that is deeper at the inside vs the outside. The sharpie would be gone but the Comm. would be tapered.
If you cut it deep enough all of the Sharpie will be gone anyway...
I don't think it really matters if you have a little bit of taper in the comm. I know my lathe cuts with a small ammount. You can see if if you look at the brushes after like 30 seconds of run. After that its unnoticable. Maybe it works better that way, cause you have more surface contact.
My motors are always fast.
08-25-2006, 03:47 PM
#24
yo pit,i will PM you the way i get my lathe to cut dead nuts straight.i will shoot it over in a bit.
just to clear it up now,this is an involved process that requires expensive equiptment found in a machine shop and i know pit crew has access to this equiptment.
just to clear it up now,this is an involved process that requires expensive equiptment found in a machine shop and i know pit crew has access to this equiptment.
08-25-2006, 04:43 PM
#25
As far as roundness goes you can use another Big Jim trick which is to use a jewelers screwdriver with the wiggly top and run the motor at ~3 volts. If the top hops around then this is where you can show a problem with roundness. This could be indicatine a bent arm shaft in the motor or the lathe needing work. Jim always said that a diamond can give a good looking cut even when it is dull and need relapping, (Carter diamond bits will do this) when it gets dull it can cut out of round. Also if the gibs are too loose it can cause the lathe to cut out of round. A taper is harder to detect. Calipers usually can not see all taper issues unless it is pretty bad. Get some one who builds good stock motors to cut an arm for you. Then cut it using a sharpie and you might be able to tell if you are cutting at a taper by seeing what is left or if you end up gigging the com. Adjusting this to probably 0.0001 will be very hard and you would probably just live with it unless it is bad.
08-27-2006, 05:39 PM
#26
Followup Questions
I have that same lathe and I have had the same problem with the erratic slide movement. I found I can put a little pressure on the thing and get it to cut better so mine has the same issue with needing lube. Can you describe more where the lube goes ?
What voltage should I run it at? 12V nominal (13.2) seems to cut OK and is faster. Running 3-5 Volts is so slow and doesn't seem (by my eye or fingernail on com) to cut much different.
Which way (left or right, looking with bit on top) should I be cutting? I cut both ways (left in towards tabs and back out) - or does it matter?
Two things I have found that helps are (1) I brush away chips as soon as possible (air gun) and (2) I recoat with the sharpie after each pass - I get a much better finish. I even will recut with same depth setting just adding another layer of sharpie and when it cuts that off it smooths out the surface a little better.
I appreciate the postings from folks who have a lot of experience and businesses to run, yet are willing to take time to post help for others....
What voltage should I run it at? 12V nominal (13.2) seems to cut OK and is faster. Running 3-5 Volts is so slow and doesn't seem (by my eye or fingernail on com) to cut much different.
Which way (left or right, looking with bit on top) should I be cutting? I cut both ways (left in towards tabs and back out) - or does it matter?
Two things I have found that helps are (1) I brush away chips as soon as possible (air gun) and (2) I recoat with the sharpie after each pass - I get a much better finish. I even will recut with same depth setting just adding another layer of sharpie and when it cuts that off it smooths out the surface a little better.
I appreciate the postings from folks who have a lot of experience and businesses to run, yet are willing to take time to post help for others....
08-29-2006, 09:23 AM
#27
Correct Autolathe Voltage etc. for better cut
ttt
PS I AM using a diamond bit and my 100x scope says it's still perfect...
PS I AM using a diamond bit and my 100x scope says it's still perfect...
08-29-2006, 10:20 AM
#28
Tech Regular
[QUOTE=swopemike]I have that same lathe and I have had the same problem with the erratic slide movement. I found I can put a little pressure on the thing and get it to cut better so mine has the same issue with needing lube. Can you describe more where the lube goes ?
I had the same problem with mine. I loosened up the set screw to loosen up the depth dial thingy
and had no further problems. I have had it for two years and haven't needed to lube anything.
I had the same problem with mine. I loosened up the set screw to loosen up the depth dial thingy
and had no further problems. I have had it for two years and haven't needed to lube anything.
08-29-2006, 10:37 AM
#29
Detecting taper is easy.....get a harder style brush.....file the faces FLAT....and I mean flat....run the motor at 2 volts for like 10-20 seconds....if it makes contact vertically along the entire brush.....then yer fine....it doesn't, then you more than likely have a taper...you need to make sure the brush is VERY VERY flat for this to work correctly..
Later EddieO
Later EddieO
08-30-2006, 12:02 PM
#30
Stampede, depth dial thingy . . . now which whatchamajig is that doohicky you mean ? 
Anyone know the right Voltage to use to cut the comm?
Where do I lube, just along the bottom where the slide sits in the groove?
Is it OK to cut both ways?
I am a geek and I like reading the instructions. Unfortunately this one didn't come with any (I got it used)
So now I gotta bug somebody to get help
Anyone know the right Voltage to use to cut the comm?
Where do I lube, just along the bottom where the slide sits in the groove?
Is it OK to cut both ways?
I am a geek and I like reading the instructions. Unfortunately this one didn't come with any (I got it used)
So now I gotta bug somebody to get help