My mill with fly cutter

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

Moderators: GlennW, Harold_V

User avatar
Harold_V
Posts: 20231
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: My mill with fly cutter

Post by Harold_V »

BadDog wrote: Thu Mar 11, 2021 11:40 am it would seem to me very unlikely that it would develop the dual pattern.
Not true. Unless you can remove the material 100% with the leading edge, and you can't, a cross hatch is very much the thing one should hope to see. Even when grinding, where the pattern may be hard to discern. No cross hatch, the surface isn't flat. Pretty simple.

If nothing else, the tops of the mountains created by the feed rate versus the radius of the cutting tool will get clipped by the trailing edge, creating the same depth valley as was created by the leading edge. That automatically creates a cross hatch.

I am at a loss to understand why it would be important for a cylinder head to not have a cross hatch. What possible reason would could there possibly be? Perhaps someone can enlighten me. Sounds to me more like an old wife's tale than anything. A perfectly flat surface in contact with another perfectly flat surface will provide an excellent seal. Think of the attraction achieved by Hoke blocks.

Assuming it's true that cross hatch is not permissible, it's quite easy to accomplish. The tilt of the head by a half thou will create the condition required, assuming a fine feed and the bearings provide the required thrust, and they should. I've never struggled eliminating cross hatch--but I have struggled getting it to be consistent. A statement about the lack of straightness of the common milling machine bed and table.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
User avatar
BadDog
Posts: 5131
Joined: Wed May 17, 2006 8:21 pm
Location: Phoenix, AZ

Re: My mill with fly cutter

Post by BadDog »

I think I'm not communicating clearly.

To summarize, what I was saying is that ultimately that my larger 2J mill is quite sensitive to accurate head alignment when using a free cutting rigid setup with appropriate depth and feed (depth being only a few thou finishing with a large fly cutter). With larger sweep fly-cutters, any diversion at all from careful alignment quickly looses the second pass tracing traversing in whatever direction is ever so slightly lower. Since typical(?) round column mills are not known to be very carefully aligned (as shown by endless posts of those going to considerable lengths to correct), I'm saying that if all is otherwise good, and the mill is not an unusual case of very good alignment, it's unlikely that he would see the cross hatch going in both directions. However, if it's pushing off the surface due to one or another factors, then it's more likely to get the double pattern even without the head being so closely aligned.

Therefore, since he gets the cross hatch in both directions, it seems more likely that he has a less than ideal configuration than possibility that he has a unicorn round column mill. And, as such, I think it may be worth looking into those other factors, or alternatively confirm that he does have a unicorn mill that is square to within less than a thou or so at the radius swept by his fly-cutter. In fact, what I'm saying is exactly what you describe in your final paragraph, but associated with my expected accuracy of the head actually being VERY square from the factory on a round column mill(-drill).
Russ
Master Floor Sweeper
Post Reply