Reconditioning drills

[smoggyrich]

Hi everyone.

I'm new to the forum and I am hoping to pick your brains for a minute.

My problem is, is the ammount of drills we are going through.

We are using Guhring tin plated drills to machine forged steel.

We have a drill grinding machine, but the reground drills are obviously not lasting anywhere near as long as the new drills, as we have no way of recoating the tip of the drill after regrinding.

What methods are available to us for recoating drills? Is there any specialist equipment available to anable us to recoat drills in-house?

Thank's for any help/tips.

 

[saberblue]

Before I got involved in re coating my own drills I would make sure that the regrind operation was running a well as possible. Over the years I have chased numerous tool grinding problems and often found that the tool geometry was not similar and that the tools had been "burned" or other wise damaged during the regrind process.

Also look at when you are pulling the drills -- some times pulling them before they are totally "dead" will make a big difference in the regrind process.

good luck and happy grinding.

 

[Compositepro]

I agree with saberblue. Geometry and finish are more important than coatings. Also, The coating that is missing from the sharpened surface is on the back side of the cutting edge where there should be minimal wear.

 

[MikeHalloran]

Not to be excessively pedantic, but the coating on the drills is not elemental tin, but TiN, or titanium nitride.

You might ask Guhring for hints about optimizing drill life.
They will ask you for such things as:
workpiece material
coolant
drill diameter
feedrate
drill rpm

You might also get more help here, given that same essential information.





Mike Halloran
Pembroke Pines, FL, USA

 

[BrianE22]

There are companies that will strip coatings on tools and recoat them. I doubt you'd be able to do it cheaply in-house. Must be big drills to make this effort worthwhile?

 

[unclesyd]

We us ed 100's of Guhring drills for drilling of PH SS where hole count was relatively low so we had Guhring resharpen the. If my recall is working we usually got the same number of holes as the new drill. Again if recall is working we would get three cycles from a drill.

http://www.guhring.com/PS/Reconditioning.htm

 

[smoggyrich]

Thanks for the replies. Some helpfull ideas there.

here's a bit more info that may help...


we are using 10 and 12mmm dia TiN coated drills.

we are peck drilling forged chromium steel (46Cr2n) using coolant. Drill depth is upto 100mm deep.

we are running at 650rpm and 0.2mm/rev feed rate.

I've attached some photo's of a worn drill. Sorry the quality isn't good they were taken on my phone. hopefully you can make out the area of wear. The drills tend to wear out at the corners then rub and wear along the shaft.

I am still interested in the coating process if anyone can help?

Thank's again.

 

[unclesyd]

On your deeper holes the L/D is approaching 10. Drilling a tough material the ration it is very hard to maintain drill geometry.
It might not be the answer but here are a few things to try.

First of there is no panacea for your problem. I Would get with a Guring Applications Engineer to discuss you problem.

As mentioned above checkout the geometry of available drills.

Test different coolants. This can make a lot of difference in a hurry. When they took Trichlorethylene + oil out of shop it took almost a year to find a coolant that would work,though not as good as Triclean and oil.

Make sure you are clearing the chips. A chip will push the bit sideways and cause excessive wear real quick.

Our peck is used on smaller drills than yours and we use a lower RPM and feed rate.

Checkout different coatings like those offered by Impreglon.

How many holes are you talking about?

Required quality of the hole?

Have you considered EDM or Carbide drills?

http://impreglonpvd.us/surface-coatings/front_content.php?idcat=107&changelang=3

 

[saberblue]

I have spent more than 30 years working in the MWF field and know from both labratory testing and field experience that fluid selection and application can make a major difference in drilling holes. We are still short a lot of the information that would make a specific recomendation better I can tell you that what you should be looking for is a fluid which will go down the hole easilly and rapidly either a heavy duty sulfur chlorinated soluble oil or a low viscosity less than 150 SUS with active sulfur and chlorine. If you can go to coolant thru drills with sufficent volume to clear the chips you might do very well.

 

[unclesyd]

I would try a Relton Groo-V drill bit. These bits are inexpensive and can work quite well. I've have drilled some extremely hard cast iron with no problem.
Also you may want to try this type of drill bit from BA manufacturing.

http://www.technologylk.com/3-8-x-4...celain-multi-purpose-drill-bit-lk-GRT6-4.html

http://www.technologylk.com/1-2-x-6...celain-multi-purpose-drill-bit-lk-GRT8-6.html

http://www.bamanufacturing.com/page_30b.htm