Fly cutting and tramming ?s

[mjarus]

Let me preface this by sayin I am a noob. I have a couple of questions though which relate to my Seig X2.

I was playing with my fly cutter this evening with some 6061. Anywho, I noticed that it was not giving even circles. I was only going about .001 deep (I rest the cutter on the piece til it made a small mark and then locked the z gib). Basically it was scribing to the left and not the right, so I trammed the head. Looked better, but at some points it would not scribe towards the head of the machine (away from me).

So my questions:

1) Could this be explained by a variation in the workpiece? Was I cutting too shallow?
2) How deep are you supposed to cut with a fly cutter?
3) Is there any way to tram the head from front to back on the Seig? I guess .001 (at least) ain't too bad, or is it?!

Any help would be appreciated.

Thanks,

mjarus.

[Mcgyver]

you need tram to the table. your workpiece is not a reference surface. I'm not familair with that mill, but if there is not an adjustment in that direction, its a problem - shims maybe?

Do you have an indicator? The usuall approach is to get the spindle axis square to the table by holding indicator on some sort of extension arm in the mill spindle. When the mill is correctly trammed you will see the cicle of the flycut, the cirlces start overlapping and you get the cross-hatch pattern.

How deep to cut depends, on the mill, material, cutter. what dia is the fly cutter? Since a flycutter is a larger dia cutter, depth of cut is less than for other cutters as this cutter has more leverage on the spindle. at somepoint, the mill runs out of hp but it should handle a lot more than a thou. Also, don't forget to work out your cutting speed.

[NC Cams]

Tramming is most critical variable to look at. Once you do that, try cheking vertical movement/deflection of spindle under axial thrust against part.

WHY? Bearing preload (actually, lack thereof) can also affect finish.

Bearing preload prevents the part being cut from "sucking" or "shoving" the tool into or away from the part as it is being cut. This is why a drill press makes a less than satisfactory mills.

'Presses typically don't use a preloaded bearing in the lower position. Thus, the spindle can float up until it contacts internal thrust washer or down until axial clearance in ball bearing stops motion in that direction.

Keep in mind that the farther you extend the spindle out of the mill head, the less rigid it becomes (more delfection potential).

Also, just because you trammed it in full up position, that doesn't mean it stays trammed all the way thru the travel of the quill.

[MBG]

Your head must be really badly trammed out. What would happen if you take like .050" with that cutter. Cause I konw from my fly cutter if I cut .001" repeatly I would wear out my inserts and that might be what is happening to you.

[ViperTX]

Well....firstly you tram the head.....don't use your workpierce as a reference use your mill table as the reference or some other surface that is guaranteed to be flat and resting on the table surface.....most likely your workpiece is not uniform in thickness.......

[mjarus]

Thanks for all of the replies...

I am going to try tramming it to the worktable this weekend, I have been out of town all week. I appreciate the responses!

I also purchased a few machining books through Amazon, now if that brown truck would just show up

Also, just because you trammed it in full up position, that doesn't mean it stays trammed all the way thru the travel of the quill.

Perhaps a noob question... but could you please elaborate a little bit on this subject?

mjarus.

[NC Cams]

This is easy to demonstrate - hard to explain.

But, in a word, it is clearance,

THe more you extend the quill, the less rigid it becomes. (Look at the length vs dia (l/d) ratio of quill being supported compressed vs full extended).

Also, look at the slop/wobble factor (see l/d above). Unless you lock the quill, it will move which will put it out of tram.

If you have a moveable knee (IE: typical BPT mill), you need to check tram as you move it up/down. Also tram will change if knee is locked vs unlocked.

Each and every thing that can/does/will move has the potential to affect tramming (when you're trying for dead nuts accuracy). Spend some time measuring/tramming.

You'll be surprised at what you'll find/won't find.....

[Zippi]

X2 doesn't have a quill, it's a square column mill, the whole head moves for z.

There are a couple of areas that might cause a problem, along with a couple of fixes.

When you mentioned not scribing away from you, the first thing that comes to my mind is a problem I had with my X2 when I first set it up. My column leaned forward by a few thousandths over a couple inches. I ended up shimming the column mount (three bolts, I shimmed under the front two corners). I shimmed it with aluminum foil until it was true, that's the most sane way to fix the "forward / backward" tram of the column.

At this point, if it's still off after being absolutely perfect in all tramming such that the spindle is true from every direction relative to the table, I'd tighten the preload on the spindle- it's that nut at the top of the spindle with the setscrew. Loosen the setscrew, and tighten the nut with the spanner they shipped with it. Not too tight, but snug. The threading on that nut is "backwards", so tighten by rotating counter-clockwise from the top. After tightening the spindle, re-check the tram all around.

[championp]

After you tram the head in, load your part and run an indicator across it. If the top of the part is not level with the table within .001", you will ony cut one edge of the part. You could also cut deeper with the flycutter, but not a lot deeper.

Theoretically, even if the head is tilted forward, but trammed in to the table, you should still be able to get square and parallel parts. If it is out of tram from left to right, you will get concave parts.


Chris

[mjarus]

Thanks again for the repsonses. I did not have time to fool with it over the weekend as I spent most of my free time messing with the new metal cutting bandsaw. Man, this new hobby does take some time! I am assuming that it is worth the effort on the front to get the set-up right so I wont be pulling my hair out later... but some day I will start making some "real" chips. So far quite a bit of 6061 has been sacrificed checking and re-checking measurements (and just flat out farting around).

I will implement the ideas posted so far and post a reply with my findings.

My machining books from Amazon finally came in too... skimming through them it looks like they will help a lot with my noob questions!

Thanks all,

mjarus.

[BobWarfield]

Originally Posted by mjarus Man, this new hobby does take some time! I am assuming that it is worth the effort on the front to get the set-up right so I wont be pulling my hair out later... but some day I will start making some "real" chips.

mjarus, with practice, you can get pretty quick at tramming. It's not something you do once and forget about. You'll want to recheck it periodically as things can change over time.

I budget a little "machine futzing" time at the end of each project. This is when I check tram, make sure I clean out all the chips, relube, and do all of the other little TLC chores that keep the machine happy, healthy, and spitting out those chips rather than pulling out or graying your hair!

Every now and again you'll read a great thread on this or another board where someone like yourself is getting some advice about how to tune up their machine. Note down those threads and go back to them from time to time and do the tune up steps suggested. Measure your tolerances just for kicks and grins and see if you can improve the state of your machine. It's all part of the fun in this hobby--like adjusting the timing and carb on your hot rod every so often!

Best,

BW

[Mcgyver]

not wanting to get all philosophical on ya, but precision metal working is both complex and a little like a bottomless pit of knowledge - imo that’s what makes it engaging and fun; its challenging and the learning never stops.

what books did you buy? I always suggest a grade 11 or 12 machine shop text - all the basic stuff is presented in a very clear manner (although the shops have more resources than the typical home shop). the next level up is Moltrecht's two vol "machine shop practice", looks at things in more depth.