Help Tramming a Table With a Fly Cutter

Most of the work I do is smallish stuff that sits in the vice mounted on the table. I recently started doing multiple parts the span most of the table and was finding parts were coming in slightly thinner or fatter. Since it is thin, long pieces of metal stock that can only be supported at the ends I thought it might be from the metal warping at various degrees and might be just one of those things where I'd have a certain amount of waste parts because of factors outside my control, but on the second run I noticed the parts followed a similar pattern depending on where they were on the table.

I put my DI all over the table and turns out the table is out of the spec in a couple places, as much as .020" differential from highest to lowest. The table isn't the actual table... it is a an aluminum 6" riser that is mounted to the actual table. It has been on there forever and has never been trammed since it was installed and precision ground.

Now I'm not doing super precision stuff, +/-.005" on any given part makes me happy. I would normally just throw an EM on there and program it to make the nice skim cut to get it in spec but the problem is the edges/corners are well beyond the range of travel. To be able to hit the further parts out of reach from the spindle (corners/edges) it requires a 5" radius tool to reach out there. I don't have any fly cutters close to 10" in diameter so what I did was make one using a stout carbide tipped boring bar by making an adapter that it could be mounted in at an angle of around 20 degrees or so.

It works fine except the finish is not great, maybe akin to vinyl record. I know the carbide is probably not ideal but I didn't have a HSS boring bar in that size. I feel like the carbide drags/gouges a bit more than it cuts trying to flycut aluminum. In general I never seem to get very smooth results from fly cutting even when I turn the feed super slow with a generous RPM and more than one pass, but a rarely ever have needed to fly cut anything so it could be the nature of things or something I'm doing.

What I'm wondering, does anyone have any suggestions on the best approach for this? Maybe make a different tool that holds a HSS lathe bit and put a certain profile on it? I suppose the being mostly pointed tip profile from the boring bar isn't helping. IIRC a lot of fly cutters have kind of a swooping profile where it hooks upwards a bit so it takes a wider cut?

In all reality I'm sure the results as they are now are better than before but hoping to get a finer finish. Just from the differences in the cutting actions I doubt I can cut as good as finish as with an EM but hoping to at least get it to where I can't distinctly feel the finish like I can now.

Thanks!

If you're asking about variance in part thickness you haven't mentioned what difference you're getting. You also haven't mentioned the mill you're using or the distances per axis traveled. If it's a knee mill I wouldn't expect the variance to be less than .002 as a general rule. The condition of the mill makes a large difference as it may have more wear in the middle of the travel for each axis and very little wear out at the ends of travel. That means the machine table can "dip" slightly in the middle of travel and be raised back up to where it was when brand new (unless it's a cheap Chi-Wan machine). There's also the tram of the head-to-table for perpendicular that affects the difference from front to back of table for part thickness as well as middle of table to sides of table. How close you're trammed in translates directly to part accuracy/consistency and you haven't mentioned whether you trammed to the table or how close. While we're at it, the thread title is what led me here. Tramming the table is about setting the machine head to be perpendicular to the table, it has nothing to do with a fly cutter or any other cutting tool. You've been a member here for almost 3 years, you should do some reading about some basic things like nomenclature, expectations for machine accuracy, and tooling geometry. I don't know everything either and I do still ask questions now and then I also try to help myself. The questions you're asking were things I learned my first year in the machine shop, that was before the internet age. I certainly don't mind answering questions, I'm supposed to pass my knowledge along to the next generation, I have greater respect for the man (woman) that does the homework BEFORE asking basic questions. If you're running these parts as a job for your own business then I would think it even more important for you to ensure the success of your company by investing in your knowledge rather than relying on the collective here as a "human resource" to be tapped when needed.

OBTW, carbide in a fly cutter sucks even for aluminum. I've used it but try not to for several reasons. Yes HSS does tend to work better because of the ability to grind a particular geometry on it but that's just one of the reasons and you should know the others. If you're working the aluminum dry then that's part of the finish problem as well and I have some suggestions for that. I'm not trying to be a jerk, I'm trying to get you to be able to try to help yourself. I don't think you know how to do that yet.

Well I was simply asking for a recommendation about the best setup to get a large sweep fine finish flycutting aluminum. I haven't had to flycut something in years and never something where I needed a 10" diameter. I guess I should apologize I used the word "tram" as opposed "level", "true"? I can't believe you took the time out of your day to write up something so unhelpful. Frankly it makes you look like someone who comes here to stroke their ego rather than engage in a meaningful conversation. If that was your goal good on you, and if not you're clearly someone who has a problem with tact so you should probably reconsider what you say/write before you do it. SMH...

Yes, I know carbide isn't ideal, I stated as much, but I figured I would give it a shot since it allowed a quick possible solution. It didn't work as well as I hoped which is why I am asking for a recommendation before I build another tool. And no it is not a knee mill, I am talking about a Kitamura VMC with flood coolant, but this kind of besides the point, I am trying to skim cut what essentially could be considered a part or a waste plate or anything. I was just providing context on why I had to use a 10" diameter cut because that would be impractical unless it was truly necessary.

If you took a moment to think about I solution rather than seeing an opportunity to exert your perceived superiority and give yourself an adda-boy you would realize it is not as elementary as you think. As opposed to me spending time trial and error I figured I would see if someone has done something similar.

A 5" radius adds a lot of leverage, even for a skim cut, and short of adding building a hulking tool it would be easy to induce deflection, particularly if the bit has a larger cutting edge than a simple point let alone with any bite. Short of building it with counter balance it adds more deflection with that much weight trying to get the SFM.

So I guess I'll restate the question in a more direct way with the hopes of getting a specific answer from someone who has something constructive to offer instead of a lecture:

If you were trying to achieve a fine finish that required a 5" radius flycutter how would you profile the cutter and would you build the 5" tool arm (which holds the bit) with a minimum level of stoutness (I was thinking 3/4" square or round bar would be plenty) ?

thebee said:

snip

So I guess I'll restate the question in a more direct way . . .

Click to expand...

Always a good idea.

What kind of spindle do you have? (R8? ZZ collets? 30 or 40 taper?)
Spindle power? Vari-drive? Step Pulley? Back Gear?

If you can provide a little more information to help with completing the picture of what you are working with, I am sure a helpful answer or two will be forthcoming.

I find it hard to believe that the table just suddenly wore .02.

Prolly a bad truck or turcite prolems.

Run over the fixture/ sacrificial table with the fly cutter. don't sweat the finish, IT's flatness you are after.

If you don't like the vinyl record finish, knock the high ridges down with a file. Or scrape to suit.

It's not rocket science, Heck, my mill table has great honkin' tee slots running down the entire length of the table.

But if you replace the sub table, flatten it (blanchard ground) then shim it flat while you mount it to your mill. (also not too difficult)

Don’t know what part of South West Afghanistan you are from but the first thing is to take a name brand flat file to knock off all surface chinks and bugs from the actual machine table. Then with good 8” smooth side oil stone and with oil, stone the surface using figure 8 hone strokes to show the machine table is stone flat. Then you can indicate and mark highs as + and amount from the lowest area. You need know the machine table is flat (with in reason) to mount and re-mount a vise and/or a vise held table. At least to map a small good flat area of the machine table.

A vise is not a very good device to hold a work table so better to find a good area of the table, measure the set location so you might set the fixture in the same place (next time) and hold- down to the table.

To tram set the fixture (on the table or in the vise). Take multiple passes with perhaps a ½ end mill. Hone just a little to take off high ridges then tram to that. Next pass over to just hit high spots to see an even cross hatch. With a nice cross hatch proceed.
Yes a HSS bit will do a very nice job on aluminum.

*But the multiple passes with the ½ end mill will be just as flat as you can get so really no need to fly cut. Mostly the fly cut is for looks with all the lines going across.. but that is not always a flat surface with not seeing an even cross hatch. With not being to tram properly the fly cutter will put in a concave surface with with lead or follow edge that looks beautiful but is not worth the effort.

You could have several problems at work here. Posting machine type, size, and way set up would really help. Is the dip random, or in sections?

Possible causes:

Machine not level
Column not trammed, yes they can move with jack screws
growth, rust, or alumunum/iron corrosion could lift the subplate(seen here recently as much as .007")
Turcite or trucks worn(are your ways gettting oil?)

Need to put city, state, and country in location. Bosses rules.

michiganbuck said:

Don’t know what part of South West Afghanistan you are from but the first thing is to take a name brand flat file to knock off all surface chinks and bugs from the actual machine table. Then with good 8” smooth side oil stone and with oil, stone the surface using figure 8 hone strokes to show the machine table is stone flat. Then you can indicate and mark highs as + and amount from the lowest area. You need know the machine table is flat (with in reason) to mount and re-mount a vise and/or a vise held table. At least to map a small good flat area of the machine table.

A vise is not a very good device to hold a work table so better to find a good area of the table, measure the set location so you might set the fixture in the same place (next time) and hold- down to the table.

To tram set the fixture (on the table or in the vise). Take multiple passes with perhaps a ½ end mill. Hone just a little to take off high ridges then tram to that. Next pass over to just hit high spots to see an even cross hatch. With a nice cross hatch proceed.
Yes a HSS bit will do a very nice job on aluminum.

*But the multiple passes with the ½ end mill will be just as flat as you can get so really no need to fly cut. Mostly the fly cut is for looks with all the lines going across.. but that is not always a flat surface with not seeing an even cross hatch. With not being to tram properly the fly cutter will put in a concave surface with with lead or follow edge that looks beautiful but is not worth the effort.

Click to expand...

Michiganbuck

Go back and read the second paragraph of the original post. You are addressing issues and topics not related to the post question.

[The table isn't the actual table... it is a an aluminum 6" riser that is mounted to the actual table. It has been on there forever and has never been trammed since it was installed and precision ground.]

Thought I was addressing an out of flat aluminum fixture table that was .020 out of flat.
Start with a flat machine table or find a good place to mount and true up the fixture .. but perhaps I miss read the OP>

[I do is smallish stuff that sits in the vice mounted on the table.
But]
*Oh now I see the vise stuff is different work.

[Since it is thin, long pieces of metal stock that can only be supported at the ends I thought it might be from the metal]

But still the end mill passes are good to make top flat, and the fly cutter method is only good if the machine is tram.

WOW! I can't believe the replies... this is like something one would see on a highschool forum. READ THE GUY'S FRIGGIN O.P. Before you start pontificating

OP - you can make a T bar type flycutter with say a piece of 2"SQ stock 12" long, pop a 1" hole in the middle for a shank and weld a shank in place on both sides. Get a 3/8 hss drill blank or even an old long ctr drill. Drill a hole for it out at one end and hold in place with setscrews. Grind the HSS bit so the tip is a full rad and add about 10 deg back rake from center. You need a nice SHARP cutter with a radius to do whay you are trying to accomplish. The T bar design offsets and hes balance the flycutter. i'd start at about 250 RPM with about a .01 per rev feed . Use WD40 as a coolant and you will have a mirror finished table.

that's the way I would do it anyhow...

Sorry for the bad spelling - Ipad

All good advice but be sure the machine spindle head is square to the table if you want a 5" radius cutter to fly cut something flat. Swing an indicator in a circle on the machine table then tweak spindle head angle in with looking for the cross hatch cut. Fly cutter will give a better finish with having a larger radius or a small flat area (yes with clearance) to the work that equals all or part of the feed per revolution, but yes that will put a little more stress on the fly cutter so less feed rate might help ..Fly cutting aluminum some positive rake angle to the cutting bit top face will help.

[except the finish is not great, maybe akin to vinyl record.] that finish may be Ok or good for the riser table to give a better holding the parts from sliding as long as it is flat and true..

I used a standard boring head with a 3/4" boring bar extended out the side, effectively making a 9" diameter cutter.
IIRC, I used a vnmg style insert made for aluminum.

I programmed a rough, semi-finish, and a finish cut when I originally made my table riser/ sub plate.
The SFM was low, but only b/c the balance (or lack there of) using a boring head, and the feed on the finish path was something like 0.005" IPR.

Since 2006, the plate has been re-skimmed a couple of times. (Usually when we have to remove /remount it)

Doug.