What type of drill bits for lathe?

[James04]

I just purchased this set of drillshttp://www.mscdirect.com/IWCatProduc...3010&Keyword=Y for my lathe. They are 118 degree jober lenth HSS. Only when I attempt to use them as soon as I make contact with the work piece it wonders of center and then it chatters the whole time Im cutting with it. I was drilling a piece of 1/2 dia. aluminum that was being spun in my lathe chuck and the drill was in the tailstock. I was using a very slow feed (by hand) and I had made a centering hole before I attempted to drill. Are these the wrong type of drill bits? Is it the low quality of the bits. Or am I doing something wrong?

James

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[cncadmin]

You have to use a center 1st, to locate the center of the work piece and than you can drill it out. Run the piece at a high speed when using the center bit.

[James04]

Read my post again. This was done. I also faced it before centering operation.

[cncadmin]

What type of "centering hole" if their was a counter bore, the drill bit should not have walked.

[Klox]

James,
I have info to answer your question.
I'll try to attach a zipfile of 9 pages.

Klox

[Klox]

James,
It seems the zipfile is to BIG.
I'll e-mail you the info.

Klox:

[James04]

Klox,

I had Email option turned off. I have now emabled it. Please send the Zip file. I can use all the help I can get at this point.

James

[Klox]

James,
I havent forgot you. I'm struggling to get the files down to a manageble size. I'm working on it, Cadcam offered me help.
We'll find a way to get it to you....

Sorry for the inconvenience.

Klox

[cadcam]

klox if you get me a file today I can at least make a link from my server to get at least a view or a direct download.

[cadcam]

James are you using a drill chuck in the center to hold the drill ? if so are you sure this chuck is straght are you cneter drilling first. 118 drill are a normal but there can be few reasions I have found for it to wonder.

[James04]

Cadcam,

I don't know what you mean when you say "in the center". I am using a chuck in the tailstock. It is a taper mount jt33 (enco precision 13mm cap.). I just got it. Could be defective! I'll have to check it for runout. Yes I am center drilling first. I found that my tailstock setscrew (on the underside of the ram) was loose. This did improve things a bit and I also made an adjustment to get the ram Parallel with the ways. It was off by .0005. This Lathe isnt all that precise and you can move the ram when fully extended by .001 or more depending on how hard you push. However when staring to drill the ram is fully retracted and it relativly sturdy in that position. Im looking into truing the Lathe chuck jaws but I need to wiat till I get some drill rod to do some checking.

Thanks,
James

[cadcam]

James I am putting links togeather that contains the info From Klox. most likly bu Wed being tommorow.

Time for some sleep sorry all.

[barry]

You might want to try screw machine length drills. They are shorter in length and have I believe a 135 degree point. Also check your rpm speed you don't say what size bit you are using but with cutting aluminum say using a 1/8 bit you would want to be somewhere around 250 SFM which would put you 7639 RPM. Good Luck

[boxwood]

Hi

1 First check to see the material is running true place an indicator on stationary part of lathe ie ways,cross slide and put the neddle on your work piece and turn the chuck by hand this will let you know if the part is way off or not
2 also you can check your tailstock alignment by placing magnetic base indicator on face of chuck and the needle on the tailstock quill takes a little positioning and rotate the chuck slowly by hand there sould be adjustment screws on the base if it is off
3 those are some cheap drills I have had some that where actually sharpened backwards maybe try anothe drill and see
4 last but not least make sure the chuck is turning the right way
no offense I have made this mistake so i mentioned it.

Hope this helps good luck

[HuFlungDung]

James, you didn't say how far you are trying to drill before the bit starts to wander off center. It is practically "normal" for some wander to occur, let's say if you drill a hole that is deeper than 4 to 6 times the drill diameter. Hence the need to drill, then bore the hole to straighten it up.

You said you had faced the end before drilling, which is good, as I would have said that a drill bit approach that is not perpendicular to the surface will always wander on entry.

However, practically all other machine adjustments have little to do with wander during drilling, that is, if the start of the hole is good, but the exit side is out of center.

If your tailstock is misaligned, you will notice the drill bit jumps over immediately when touching the spot hole, because the drill must gravitate to the rotating axis of the part, if it is sharpened equally on both lips.

Do not move the part between the spotting operation and the drilling operation if you can help it. 3 jaw lathe chucks are seldom accurate enough to put the spotting hole back on center if you move the part. On a long part, use a steady rest to support the part for both the spotting and drilling operation, so you don't have to move the part.

When drilling holes that are too small to bore easily, what I sometimes do is drill a smaller hole to start, then use an endmill as a drill to true up the hole for as far as it will reach, then switch back to a drill bit the same size as the endmill, and attempt to bore out the eccentricity of the deeper part of the hole. This is like using the front of the hole as a guide bushing to help guide the drill.

Don't feed your drills too lightly, nor too heavily. Too light of a feed will make them squeal, as there is too much rubbing going on. Keep the cutting lips under the chip.

[Durkee]

HuFlungDung pretty much has it nailed with that last post I think. A little more info from you James may make it easier for us to help out.

What size drill are you using and at what RPM's are you turning your workpiece? Sometimes a small CNC spot drill with a flatter point on it than the point on your drill will work better than a drill/countersink.

In non-ferrous mat'l, a lot of guys make the mistake of not using enough feed on the tooling which will cause chatter. Feed is more important than speed, and that could be important, as most lathes will not turn the high RPM's required for small hole drilling or turning.