Chamfer a Shaped Bar

[cunninghamkl]

I am investigating a method for chamfering the end of a shaped bar (See attachment). The major dia. is around 3". These bars would be around 12' in length. I am needing a 0.400/0.500 X 30 degree chamfer on the ends.

What are some economical ways about achieving this? Most chamfering machines that I've seen on the market are for round material. Thanks for the help.

Kevin

 

[mrainey]

I don't know of any way other than to profile around it with a milling cutter on a CNC machining center. Even then, the 12' length could be a problem.


Software For Metalworking

http://closetolerancesoftware.com

 

[MikeHalloran]

You might be able to modify a bar pointing machine to do what you want.



Mike Halloran
Pembroke Pines, FL, USA

 

[TJOrlowski]

What is the purpose of the chamfer? What is the tolerance on the 30 degrees?

-TJ Orlowski

 

[cunninghamkl]

We provide the shaped bar stock to a customer who has asked if we can provide the chamfer for them. The purpose has something to do with them loading the bars into a screw machine. The 30 degrees would probably have a fairly liberal tolerance; +/- 5 degrees or so. Thanks for the help.

 

[unclesyd]

I think the CNC approach as posted above is the best option. You have too many tight radius's on a small diameter. Even with milling you are going to have to give up some of your radius profile.

I've look at catalogues for bevelers and bar chamfering machines and I find nothing, even with modifications' that could do the job

Is this a one-off or quantity job?

 

[cunninghamkl]

There would be about 40 pieces in the average week.

 

[TJOrlowski]

Find someone with a CNC HMC with either:

A) A very long table that could hold the whole part
or
B) A machine that has a side door or panel that could be opened or removed and the piece could be loaded through the side, and supported on the worktable and the outside during the cutting operation.

The bulk of the time on each piece would be loading/centering and unloading. I'm not sure how cost effective it will be.

-TJ Orlowski

 

[BrianE22]

Are you sure they need the chamafer on the whole profile? If it is just to help get the part started in a bushing then maybe a chamfer on the outer periphery is all that is needed.

 

[saberblue]

As this chamfer is to make the bar easily loaded into the bar machine collet your customer is probably already doing the job one way or another talk to the people on their shop floor who are actually doing the job now they will have lots of ideas.

Depending on the volume you could build an angle fixture on an angle grinder and do the job free hand

 

[looslib]

I was going to suggest the same as BrianE22.
If all they need is a guide chamfer to feed into a screw machine, just do a chamfer on the 'outer diameter' since that is what will be guiding the bar in.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[ornerynorsk]

Ditto what looslib said. Also, a bar pointer should do the trick, as your profile is essentially symmetrically round, for practical purposes.

 

[MRSSPOCK]

Another idea would be to machine them on a 3 axis CNC machine with an indexer on the table. Machine them between centres with just an A axis and Z axis series of movements.

 

[williedawg]

"The purpose has something to do with them loading the bars into a screw machine. The 30 degrees would probably have a fairly liberal tolerance; +/- 5 degrees or so"

If the screw machine only needs this feature for loading the bars, why not make a chamfered & hardened lead-in bushing on the screw machine itself? That way, the bars don't need to be pre-machined.
If it is needed inside the machine near the chuck or business end, then the other suggestions re CNC profiling should work.

BTW, is it understood that the entire profile needs chamfering or tapering at 30deg?........as unclesyd mentions, some of the profile may be reduced to whatever cutter can effectively get inside the inner radii.

 

[unclesyd]

I think your best bet would be to modify the work holding device to accommodate the part. I would look at something like a hex collet if they come in the required size. Another possibility is to use a self centering chuck similar to the ones made by J-Lok.

I looked through my profile sander brochures over the weekend and could fine nothing that might be worth considering.

You could contact someone like Skill Craft or J-Lok with your requirement.

http://www.skill-craftcompany.com/index.html

http://www.j-loc.com/index.htm

Another possibility is to modify your present work holding device where the sharp edge entry would be self aligning. If practical another possibility would be to add a guide ring to existing work holding device.

 

[racookpe1978]

I'm going to go against other (more experienced!) advice at this point, but why go to all that trouble?

At a "low tolerance" problem on a long piece of bar stock (12 foot) for only 40 per week -just hit the end to be chamfered with a pad grinder. 2 minutes per bar. 40 grit pad. No loading or unloading or aligning into a CNC machine for that long a bar, no mods to the CNC machine.

Not even much of a need to unload the bar from the pallet even.

But - What am I missing or misunderstanding?

Robt

 

[mrainey]

You're probably not missing anything. It looks like one of those problems that could be solved quickly and easily if we had a little better understanding of the customer's needs.

Software For Metalworking

http://closetolerancesoftware.com

 

[gadkinsj]

I have seen one of our local machine shops do something similar to this with what was basically a glorified routing table. guy was hand pushing the stock through guides and was able to get a couple bars an hour. And these were more like 18' bars.