newbee ?-- plz define trepan

[rmatel]

NM

[Spin Doctor]

Are you refering to trepaning tools? If so you can basically think of them as grooving tools that feed axially rather than radially. Clearance it extremely important. Try SPI(Swiss Precision Instruments). Their catalog has good pictures of high speed ones. Or is this about primitive brain surgery?

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[SGW]

A hole saw, for instance. Cutting out a slug of material to make a large hole instead of boring it out as chips.

On a lathe, you can do it with a suitably ground lathe bit with the work mounted on a faceplate. As S.D. says, toolbit clearance can get to be an issue.

[Thrud]

There are very goods trepaning tools available from distributors to cut larger holes in materials. They are rather specialized and very expensive. A poorly designed one is very dangerous to use - as such all commercial versions are a balanced designed (two cutters, dynamic balancing).

Annular cutters are a better choice and safer to use. They do require a special shank to hold the cutter. High quality milling tools.

Automatic Boring heads can be used to cut large holes as well - big money.

[Al Messer]

What sort of job are you wanting to do?

[rmatel]

Thanx for the replies. I saw the word in a procedure and didn't understand. So, its basically parting axially?
Bob

P.S. To all grammarians: please excuse that last comment.

[Al Messer]

Yep.

[Don Clement]

See:
http://www.aucegypt.edu/faculty/gaaf...Trepanning.doc
for a definition of trepanning.

I have been looking into the best way of making 2” diameter holes in ½” 6061-T6 aluminum plate on my mill. Trepanning appears to be one solution. Looking at SPI Type 2000 trepanning tool for the mill. I have an SPI Val-Cut trepanning tool for the lathe that uses a 6mm cutter bit that works well. I have been using a 1 15/16” piloted annular cutter with the mill, (Technically this is trepanning.) followed by using a boring head to finish the hole to size. I think that the SPI 2000 trepanning tool will allow cutting a hole closer to the desired 2” diameter so only a finish cut with the boring tool will be needed.

Don Clement
Running Springs, California
Owner: Clement Focuser

[Thrud]

Don

A 2" annular cutter will be dead on, as long as the arbor is not bent. I have seen them to 6" diameter and 4" deep. A diamond core drill will also work in Aluminum very well and provides a finely finished surface if done at high speed. Carbide drills are ideal for Aluminum. APT has spade drills that are reasonably cheap (HSS, coated HSS, & Carbide blades) and produce accurate holes.

[This message has been edited by Thrud (edited 12-08-2002).]

[Don Clement]

I should measure the accuracy of the 1 15/16” diameter hole made with the annular cutter. The hole needs to be 2.000” –0.000" + 0.004”. So if the annular cutter proves accurate, then a 2” annular will work. Finish cut with a single pass of the boring head. The annular cutters are one piece HSS with a ¾” diameter shank. If the annular cutter works, it would be much less expensive than an SPI 2000 trepanning tool with a 5mm bit that would cut through ½” plate. KBC has the Polish made HSS annular cutters on sale for $53. SPI 2000 trepanning tool with a 5mm bit is about $180. Diamond would work with aluminum but the big problem that I have found with aluminum is getting the chips out of the annular slot. Do diamond cutters have good chip clearance?

Don Clement
Running Springs, California
Owner: Clement Focuser