How deep? What size hole?

The hole size is 3/16 the part lenght is 1/2 and I am drilling the length of the part. I used a reamer, but when the drills which I used 2 cut oversize or have a bad finish the reamer will not clean up. I even try using a smaller drill but no luck. It does not happen all the time but need to 100% check the parts. I am thinking its the material but QC said the material check out OK

Garyceng has given you good advice, especially looking at tools!

the 20% failure rate telsme that material iswelding to tool, then sloughing off. then building up. etc. Unstable Build up edge.

BUE does'nt cut on Ti it rubs workhardening and contributing to the bad finish.

Coolant starvation also makes sense.

Nice job garyceng.

milo

Thank you, I will try the turbo flute drills and I have a microscope so I will look at how the drills look before and after. You gave me great advice.

That covers it. The information on tool speeds and feed rates and recommended coolants should be available from the manufacturer of the alloy, but this will only be a good starting point. I've found that with A286 in a Davenport that the feed rates needed to be higher than expected and the coolant really needed to be a low sulfur variety.

There is also the possibility of high pressure coolant or cryogenic cooling of the work area. We were contemplating these but the client was satisfied with the initial results.

We've found it VERY useful to put strain gauges in line with the tool actuators to get an accurate picture of what is happening at the tool edge. You can also tell when a tool is becoming worn without being a master machinist.

In all cases your tool matrial is going to be critical as well, so some experimentation will be necessary.

You get a similar problem with stainless work hardening as you drill it, once the surface hardens it is a real pain to get the drill cutting again.

Keeping the drill sharp obviously helps but also, a flatter point angle seems to keep it cutting better. It may be worth trying this with titanium.

Coolant flow is critical. Have you tried point thinning on the drill.

Thank you, for your advice I did try to thin the point , but it was not easy with carbide but I still had the same problem.

In addition to point thinning, you can grind some extra back clearance on the drill, leaving more space for when the cchips build up. Also, all brands of drill are not created equal. If you contact Kennametal, they will send an applications engineer to your facility with different tools to try, and a lot of info to work with. If the tools don't do the job for you, you don't buy them. They have been a great help to me several times.

If your machine has through spindle coolant I recommend using it for this application. The cost of the drill bit is offset by decreased cycle time and the improved surface finish of the hole. With a fast peck cycle it will be no different than drilling 316 SS. Tooling has come a long way in recent years and I have purchased drills as small as .125 with coolant holes in them. Hope this helps!

The other thing to watch for is vibration or deflection of the drill! Use a short a drill as possible and get as much coolant on the thing as you can! A drill point of 140⁰ may also help! As said above, titanium work hardens very quickly so get the speeds and feed right and don't dwell in the hole!

Larry...send some up sharp drills to the address shown on the link.

http://cyberprep.net/sample_request_form.html

Include a print out of the completed form with your shipment.

First time customer samples are free.

Thanks...Steve