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Way to mount a fly cutter for a longitudinal feed?

jscpm

Titanium
Joined
May 4, 2010
Location
Cambridge, MA
I need to cut a 2" radius cove in a rail and a horizontal mill cannot be used because I cannot easily get a large diameter cutter capable of cutting the radius and it is a short run job so a custom cutter is not feasible.

Therefore, it would seem that the only way to do this will be to mount a fly cutter in an offset arbor, but I cannot find anyone that sells tooling like this. Does anybody know of a tool like this? Note that it does not need to be high power because we can rough out the cove to close to the finish dimension. The fly cutter just needs to do the final pass.
 
Maybe I am missing something, why not use a boring head held in a right angle attachment on your knee mill? If your tolerance is not real close you could set a cutter in a regular fly cutter by measuring the tip to the center line of the spindle.
 
I need to cut a 2" radius cove in a rail and a horizontal mill cannot be used because I cannot easily get a large diameter cutter capable of cutting the radius and it is a short run job so a custom cutter is not feasible.

Therefore, it would seem that the only way to do this will be to mount a fly cutter in an offset arbor, but I cannot find anyone that sells tooling like this. Does anybody know of a tool like this? Note that it does not need to be high power because we can rough out the cove to close to the finish dimension. The fly cutter just needs to do the final pass.

If needing less than 180°, you can use a manual mill and fly cutter set at a given radius. Kick the head to the angle required to give you the radius you need. Then you can use the longitudinal feed.

If you need a full half round or true form, you will need a ball end, or a custom ground endmill.

Or you could make your own flycutter (or 4" face mill) to mount on the horizontal arbor.
Heck, possibly a side cutting slitting saw (with relief ground on the face of the saw) mounted on the arbor.
The above would only be good for finishing. The ruff out would need to be done another way.

Doug
 
Reminds me of when I used to work in auto industry back in the UK.
We installed, in 1975, a new Heller transfer line for cylinder blocks.
I was surprised when I saw the station for roughing out the main bearing bores. It was a head laid over at about 45 degrees "dragging" a face mill through the bores. It certainly wasn't a true semi-circle, but it was an efficient way to rough it out, then finish the bore when the bearing caps were in place.
 
To use a vertical mill I would need some kind of right angle tool gear to use a fly cutter (or boring head) because the rail needs to be fed in the X direction.

I thought of trying to set up the cutter in a right angle tool like an angle grinder, but it did not seem like a safe arrangement to me. I have posted a drawing below to show options:

cove-cutting.jpg

I can't use a ball nose end mill because the radius is an odd dimension.
 
Someone asked earlier about the specs of the curve you are trying to achieve.
One option maybe to get the biggest radius ball end milling cutter you can find.
Then tilt the head a little on each of several passes to "generate" the profile you're looking for.
All depends on the specs of the groove you're trying to achieve.....
Bob
 
Reminds me of when I used to work in auto industry back in the UK.
We installed, in 1975, a new Heller transfer line for cylinder blocks.
I was surprised when I saw the station for roughing out the main bearing bores. It was a head laid over at about 45 degrees "dragging" a face mill through the bores. It certainly wasn't a true semi-circle, but it was an efficient way to rough it out, then finish the bore when the bearing caps were in place.

I have a formula for "faking" a radius using this method, but it depends on the precision required.
 
Gotta answer MrWhoopee's query. Is this a clearance cut? As in clearance so nothing hits this section of the part? If it is, I would just use any old ball mill and step it in with the readouts or dials. If not and you need a precisely shaped and located surface your best bet (depending on size) will be either to use a 90° head and flycutter or send it out to someone with a CNC. You could do it in a planer pretty easily too, but that's time consuming.
 
Rough it out then finish it with a planer or a big shaper? Maybe I overlooked it, but how big of a part is it and how precise does it need to be?

Also - what material? Would probably approach differently if it's something like plastic or aluminum rather than cast iron or steel.

Might be a good time to invest in that right angle head for the mill.

https://www.ebay.com/sch/i.html?_nk..._odkw=right+angle+adapter+for+milling+machine

Sent from my Western Electric Model 520 Explosion-Proof Telephone using TappityTap.
 
A few possible kludges:

1) On a small horizontal mill, make up a fly cutter to fit the arbor. If the arbor is over, say, 1 3/4" diameter, make up a smaller arbor. This assumes the cross travel is enough to cut the cove in your part.

2) On a regular vertical mill with a tilting head, turn the head 90 degrees and insert an arbor with a fly cutter. You'd have to kludge together and outer bearing suport for your makeshift arbor. This assumes you don't need a very long cut and thus a very long arbor so the workpiece can clear the layed-over head..

3) On a lathe, put an arbor with a fly cutter between the headstock and tailstock. You'd have to have a carriage that could be modified to hold your workpiece (e.g. my old Harrison) and also some method (as simple as parallels?) to adjust the depth of cuts. Steady and follow rests could be used to add rigidity to the arbor if you need a long cut.

4) If the part is aluminum and you're both very patient and courageous -- I've seen molding heads 4" tall for big ass wood shapers. Fitted with simple 2" radius cutters it might be able to slowly nibble its way to depth either on a mill or said big ass shaper.
 
Yes, a right angle head might be an approach. Getting a good one could be pricey though and it is a one off job.

You will use it again and it will be partly paid for. I let one go with the Bridgeport I sold. Sort of wish I still had it but my replacement mills have 30 tapers and the right angle fixture was R8.


In post #9 it was said that you can tilt the head and generate a different radius than the cutter is set to. Trial and error I guess. I can not see how it would work but it has been recommended so many times over the years that it must develop a fairly true radius. You could try it and give us a report.

Post #11 mentions a method probably described in Guy Lautard's booklet. It can develop a very true radius that is composed of a bunch of shallow scallops. a little sanding can smooth them out and give very good results. I have done 3 rifle scope mounts with the method and been happy with the results.
 
Yes, a right angle head might be an approach. Getting a good one could be pricey though and it is a one off job.
Note that I said "invest". You're probably gonna find uses for it in the future, too.

Sent by freight using Tapatalk.
 
Is the part steel?

Have you considered setting this up as a boring operation to skim the last bit?
Your part arranged with long axis of cove set in Z against a block of material so as to not have an interrupted cut.
Depending on what your part is made from that sacrificial block might just be wood to keep the cutter engaged enough.

How long it the cut?
What material?
What machines do you have at your disposal and their travels on each axis?
How many sticks are you making- if four they can be clamped together and skim bored all in one go to save you setting up sacrificial material.

Or is this a cove set into a ten foot stick of material???????
 
Does anyone know the diameter of a right-angle head, seems awfully close to 4 in., perhaps too large for this situation.

In post #9 it was said that you can tilt the head and generate a different radius than the cutter is set to. Trial and error I guess. I can not see how it would work but it has been recommended so many times over the years that it must develop a fairly true radius. You could try it and give us a report.

Here is what Fred taught me for faking a radius. Divide the radius of the cutter by the radius to be cut. This value equals the sine of the angle to tilt the head. The cutter must be smaller than the radius of the cut and the depth must be less than the radius of the cutter. I used this once a very long time ago for a non-critical radius. I've never checked the math on this nor determined how close it comes to a true radius.
 
We used to cut some really close tolerance radii for rubber machines. One of the parts looked like a home plate with the triangle being the radii parts. We made our own boring bars out of flat stock that could be bolted to a face mill holder. You could adjust the length of the bore tool. So you would feed the bar as it swung in the spindle through the part with the Z. You would obviously be away from your finish X and Y dimensions. Worked great. That was back in the day and we were limited by the type of machine we had. That was on horizontals. Crazy shit you had to do...that worked
 








 
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