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Old 08-17-2002, 12:54 PM   #1
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Default A few lathe questions

I am the proud new owner of a Xipp super lathe, and I have some questions about the comm cutting process.

1. I am using a 4cell 3000H pack and a stock motor set to zero timing to power the lathe. On some of my older comms that really needed a cut, (all stock) the battery dumps and I have to recharge it. Is this normal?

2. Is it smarter to buy many carbide bits or a diamond bit?

3. Do I always have to use new brushes after I cut the comm?

4. What should I be using for lubrication? I am currently using a sharpie on the comm and trinity royal oil for where the arm shaft and the carbide V-blocks meet.

5. How quickly should I be moving the bit across the comm? I have been doing it very slowly, maybe it's an answer to question #1.

Thank you all!
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Old 08-17-2002, 01:18 PM   #2
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1) Yes, packs seem to dump very quickly when cutting comms. I would advise you to purchase a 12volt wound motor for lathes and either power it from a power supply, charger, or 12v automotive battery. I know badly chewed up comms take several passes, and the pack you are using isnt going to give you a long enough run time on one comm, much less two.

2) Buy a few carbides first to get the hang of cutting correctly, then make that expensive purchase when you feel you can cut well enough to make that $80 bit last forever.

3)That depends, you dont have to use new brushes every time, AS LONG AS the SERRATED area is not fully worn away, If it is you will either have to re-serrate them, or replace them. The new Integy Brush station makes perfect cuts, and not a bad price either!

4) Your doing it right! Black sharpie is the best.

5)It should take atleast 1 minute, no less, to make one forward pass. Making a reverse cut is another story, some say it dulls the bit, and is not necessary to get a mirror finish, while others say a mirror finish is a must. Personally I do not make reverse cuts since the second you give the motor juice it destroys the mirror finish anyway.

Hope this helps!
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Old 08-17-2002, 02:27 PM   #3
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In response to Hobbipro...

1) Disagree - you should get plenty of life out of a four-cell pack - certainly more than a couple of cuts - it's only spinning a motor with a very light load (assuming you're making shallow cuts and not plunging the cutting bit deep into the comm) - it may just be that the pack is past it's best.

2) Disagree - may as well take the plunge with the diamond bit straight away if you can afford it - not only does it last longet, it should give a better cut as well

3) Disagree - serrations are only there to help bed a brush in - you can run a worn brush on a freshly cut comm, just give it plenty of time to break in (running in on the 4 cells) - but brushes don't cost much, so you may as well make the most of the power boost a cut gives.

4) I don't know what a sharpie is

5) Disagree - if you can spend a minute doing a single cut, you must have the slowest and steadiest hand known to man - just a gentle constant motion across will get a good shiny cut - taking about 10secs say - and I cut both ways as well.
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Old 08-17-2002, 03:03 PM   #4
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Here is my take on your questions

1. I can cut several comms with my 4 cell 2400 pack before it needs recharged. You are either taking too much time, cutting too deep, or the pack it bad.

2. I just bought a diamond bit, the only difference I can tell with it is that it cuts easier, with my carbide bit I could hear the slave motor loose RPMs when cutting, with the diamond it stays constant but overall the cut is the same.

3. No but serations will help seat the brush faster and they give you a little more RPM

4. I have heard that a sharpie is enough lubrication, I don't see how it lubricates at all. Personally I don't use anything. The sharpie does help show if you have a clean cut or not. There is another thread about cutting lubrication.

5. I make a pass one way in about 10 to 15 seconds.
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Old 08-17-2002, 03:57 PM   #5
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For almost a couple months after i got my lathe i used a 4 cell 2000 pack to cut the comms, and i would generally get at least 3 cuts off the pack before i dumped. This was with a Hudy lathe, Hudy Motor.

I currently run it off a T-35 at 2V.

I started out with a diamond bit, and am glad i did. Yes, you do need to "learn how to cut", but it's not that hard, at least it was not for me after watching people cut mine for all the time before that.

I just cut a comm a couple minutes ago, and for the sake of this thread i took a stopwatch with me. 29.56 Seconds to cut in, and return it back to the outside.
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Old 08-17-2002, 05:05 PM   #6
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Thanks everybody. Looks like I'll be saving up for a diamond bit.
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Old 08-17-2002, 05:44 PM   #7
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Beware!!!

A diamond bit is expensive and will chip VERY easy. Once its chipped it is junk. It does give the best quality cut though.
It can be resharpened but you have to find a place that specializes in diamond resharpening.

A carbide bit is much much cheaper and will last a long time with care. Done right, a carbide bit can yield almost equal results to a diamond. The trick is RPM. A 4 cell pack (4.6 volts) spins the come at too high an RPM thus dulling a carbide bit quickly.

If you can get a variable power supply and set it a 2 volts (like TSR6 says) A carbide bit will cut well and last a long time. You can sharpen a carbide bit at any machine shop or Automotive repair shop.

IMO, if your new at this, don't waste your money on a diamond.
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Old 08-17-2002, 07:25 PM   #8
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Agreed, though I don't consider a diamond bit a waste. I do consider it VERY important to get comfortable & consistent in how you cut(just learn to be smooth in everything you do), & then you'll be ready to get a diamond one without worrying about chipping it. (plus, if you already have carbides, keep them with you just in case, if you only have one bit & it chips, then you're out of luck till you can repair or replace it). Now as for quality of cut, I don't see ANY difference between the two, the cuts I get with my diamond bit seem EXACTLY as good as the quality of cut with a carbide, but the nice thing about the diamond one is that I've had mine in the lathe for about 2 1/2 years & have noticed NO difference in the quality of the cut after hundreds of cuts(or even over a THOUSAND, I've been cutting a lot of my friends' comms too). I also agree that a dedicated power supply is not neccessary, but VERY nice(I use a PC power supply's 5 volt leads on a drive motor using a stock arm in a mod can with 0 degrees timing & some mild copper/graphite brushes), there is NEVER a change in motor speed. And for how long to take, I think it depends on the guy doing it,the important thing is to do it as smoothly as possible, regardless of how fast you go, so just concentrate on that & you should be fine(I probably take about 20-30 seconds to make a pass myself). It sounds like you're on the right track, just keep practicing & you'll get good at it...
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Old 08-17-2002, 08:30 PM   #9
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1. Don't know what 'mean' motor you guys are using but I get through at least 10 comms with my 4 cell 1700mah pack! Maybe its the 55T motor I use!

2. If you already have a carbide bit....use it! However, aim to get a diamond bit eventually.

3. Don't know what you're running, but with TC you want torque. Full brush face contact (after the serrations have gone, this gives you more torque!). I use GM03 brushes, serrations are gone after about 3 packs and the car starts to "fly". I get probably around 30 runs with these and cut the comm after about 6-10 packs...1 skim and it is clean (ie. 1 small graduation on the Hudy).

4. I use nothing!

5. If you get a nice cut, then you are fine! I would say I use around 20-30 secs per cut.
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Old 08-18-2002, 01:16 AM   #10
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Default Re: A few lathe questions

Quote:
Originally posted by Joe
I am the proud new owner of a Xipp super lathe, and I have some questions about the comm cutting process.

1. I am using a 4cell 3000H pack and a stock motor set to zero timing to power the lathe. On some of my older comms that really needed a cut, (all stock) the battery dumps and I have to recharge it. Is this normal?
It doesn't sound normal - try charging it at 1Amp. You don't need punch, you need longevity and 1A will take forever to charge it but it will last a long time. Look into purchasing an Integy Dyno. It works great to power your lathe and it is handy for breaking in motors and for kinda benchmarking them.

Quote:
2. Is it smarter to buy many carbide bits or a diamond bit?
You will go through a lot of carbide bits, but if you take care of your diamond bit it will last you forever. Diamonds generally cut better, but if you take REAL good care of your carbide, you can get good cuts out of them.

Quote:
3. Do I always have to use new brushes after I cut the comm?
No. Many say you should. I change my brushes each week just so I start fresh. I can afford it, so I do.

You have to change brushes when the brushes get burned or get used up (too short) - NOT when the serrations are gone, those are only to help break in the brush, NOT every time you cut the comm, although you should definitely clean the brushes with a comm stick if you are going to re-use them or even resurface them with a serrator.

Quote:
4. What should I be using for lubrication? I am currently using a sharpie on the comm and trinity royal oil for where the arm shaft and the carbide V-blocks meet.
You are perfect! I use a thicker oil on the v-blocks but that's preference.

Quote:
5. How quickly should I be moving the bit across the comm? I have been doing it very slowly, maybe it's an answer to question #1.
Sounds like it. Steady is more important than speed. I saw the Hudy automatic comm lathe and it moves across the comm and back in about 10-12 seconds. I do it in about 10-15 seconds and I make several passes to get it to a brilliant rainbow finish (for some reason I don't like mirror and diamond bits don't cut mirrors). If you're steady it will give a good smooth finish, which is what you want.

Quote:
Thank you all!
You can thank me by giving me one free pass if we ever race (just kidding)
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Old 08-18-2002, 08:06 AM   #11
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1. when i was using battery packs, i wired 2 old 4-cell packs into parallel. this approximately doubled run time. but it would be better to use a stable power source, such as the motor run feature of a turbo35.

2. i recently upgraded to a diamond bit. i went through a couple of carbide bits while learning how to cut properly. the first one dulled quickly and the succeeding ones lasted a bit longer. i suggest that you first practice on a carbide bit because it is more expensive to replace a diamond bit.

3. for racing, it is ideal to replace brushes after cutting the comm. but in my case, i dont usually replace brushes, i just reserrate them after every cut. if they are too short or in bad condition, i replace them.

4. i use comm drops for lubricating the comm while cutting, but once the motor spins, the stuff gets thrown everywhere. i use light oil on the v-grooves.

5. i take about 30+ seconds to make one pass.
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Old 08-18-2002, 01:31 PM   #12
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1. I also have the Xipp lathe, I bought the 55 turn motor with it and it works fine with a 6 cell pack, it also runs for quite a few cuts (I normally use the pack I've just used in the race if it's not flat)

2. i'm getting great cuts with the carbide bit, it cuts as well after a year as when I got it. It works for me and will last ages if used carefully.

3. I just use a comm stick and put the brushes back in, some of my brushes are really old but I've found some good ones and they last for ages and have really good power (the last time i put new brushes in a motor was a couple of months ago) If they're long enough and aren't damaged keep them!

4. Integy matrix cutting oil (makes it nice and shiny)

5. I take longer cutting quite worn comms than slightly used ones. I go really slowly if the comm has a damaged surface.
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Old 08-18-2002, 07:58 PM   #13
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I use a 4 cell 2000mah pack and it lasts for at least 10 motors or more. My lathe motor is a special wound 35 turn in a mod can my buddy had wound for him when he was the Trinity team manager for 3 years.

I like a diamond bit and it will cut the best but if you only afford carbide they cut well when new.

I also use a black sharpie marker to mark my com and then I also use some Cobra cutting fluid on the com. It is just a little precaution and helps the bit last just that little longer.

As for brushes as long as they are not discolored they are still good. You can re-serade them if you have a tool to do. The Team Trinity driver I race with uses the same brushes for a few cuts as long as they are not discolored. He does cut his mod every run but will stay with the brush for 5 to 10 runs. It all depends on how the brush looks.

I guess I'm spoiled as I have a Twister lathe for over 15 years now and it still cuts as good as any lathe on the market today. IT was the 4th one that Twister made as my buddy ran for them for some time before he managed the Trinity race team.

Good luck with you comm cutting. Just take your time and don't be in a hurry.
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Old 08-18-2002, 10:06 PM   #14
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Quote:
Originally posted by wyd
I guess I'm spoiled as I have a Twister lathe for over 15 years now and it still cuts as good as any lathe on the market today.
Oh you lucky dog! That is a sweet lathe! I've owned a Twister (but had to sell it, financial reasons) and then a couple of others and I miss that Twister. . . is yours black or silver?
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Old 08-19-2002, 06:03 AM   #15
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I have an original silver version that I use now but a two years ago I bought a black Twister on Ebay. It was might with a diamond bit. I tokk and and tried it out. It cut like butter. I bought it for only 125 bucks and sold it to my buddy for 200. He was so happy!!!!! He had a guy offer him 400 a few weeks ago for it. He said no way it is never for sale even if I quit this hobby.

I'm very lucky to have it.
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