What I learned this week about end mills and sights

[cking]

First one was, all of sudden I couldn't hit $hit at my plate match or the IPSC match. So I used a couple of the paper targets to check my zero, seemed I was shooting a little high and to the right. But then on next target it wasn't?????

Finally found it, my Bomar windage retaining nut had come loose from it stake point on the adjuster screw. So my sight was floating around when it came to windage. Restaked the adjuster screw and back in business.

Next was I needed an end mill to make Brazos style holes in my slide. Wow do they make a lot of styles of end mills. 2,3,4 flutes, center cut, material, coatings, length of cut. So after talking and reading I found out I needed something that would plunge cut, which all 2 flutes will but some 3 and 4 flutes can be cut to plunge also. Since most slides are fairly hard a carbide with TiaLN coating. Thanks to Internet all things know can be found in less than hour!

Just had to share.

[BrianH]

Just a little tip but TiaLN coated carbide is way overkill. Get uncoated carbide and you'll be fine.

[robomanusa]

Let me know what size you need, I probably have one laying around.

[Carlos]

Let me know what size you need, I probably have one laying around.

CKing - Now THAT is quite an offer from roboman! Couple of hints: the holes require removal of a LOT of steel. Mills are very expensive while drill bits are dirt cheap. You may consider locating each hole, locking and undersized a drill bit USING A COLLET (not the drill chuck) and the use the drill to remove most of the steel, followed by the mill to final dia. This also removes the distinction between center cutting & non-center cutting end mills, since you will have removed the center of the cut with the bit. Use a stub length drill bit - sometimes called a screw machine bit.

Edited September 11, 2007 by Carlos

[robomanusa]

I dont know if I have any small stub drills or not, I dont recommend using a drill, even if spotted, to much of a risk for walking and boogering up the hole...

Measure twice, cut once, you dont wanna have to weld it up and go back into it, LOL

[John Dunn]

Carlos,

If you were drilling an oblique hole like the Brazos style, wouldn't you need to mill a flat spot before drilling? I've heard that drilling on an angled surface can deflect the drill and cause generalized badness.

[Dan Sierpina]

Carlos,

If you were drilling an oblique hole like the Brazos style, wouldn't you need to mill a flat spot before drilling? I've heard that drilling on an angled surface can deflect the drill and cause generalized badness.

John,

If you centerdrill it first, so the full drill diameter is within the angle of the centerdrilled hole, it will be okay. Better to use an undersize endmill before the finish one, besides the centerdrilling.

[10es&]

I am far from being a master of any trade, but I have been a journeyman toolmaker for 10+ years.

That being said based on past experiences I would do the following to my gun and feel confident in getting great results.

After being certain of all of my measurements! I would set the slide to the desired angle and use a new #3 center drill followed by a cobalt .250-diameter drill (new or freshly sharpened). The reason for the cobalt drill is three-fold #1 it is much harder than regular highspeed (HSS) steel drills #2 it is less prone to walking or flexing than HSS and #3 it is not as brittle as carbide.

With out getting into an long boring speech about carbide, the Readers’ Digest version is carbide is very very brittle, in the particular application of drilling on an angle only one flute of the drill will enviably engage the slide for the first couple of revolutions. Carbide is very unforgiving with vibration as well as intermitted cuts and will likely shatter and even worse if this does happen the possibility of a small piece of carbide may embed itself in your work-piece. When this happens it is nearly impossible to remove the carbide chip from your work-piece with out some collateral damage.

Next I would follow the .250 drill with two more undersized drills (cobalt) and finish the hole with a good cobalt endmill.

Hope this at least helps out in your planning.

[robomanusa]

I may have a carbide one with radiused edges instead of sharp, depends on the size he needs....HSS should work though, slides by all rights arent really that hard, the hardest ones Ive seen were the ones on the norico 1911's, most i'd say are between 28-34Rc

edited to add....does the slide have hardchrome? hard chrome is just that...about 70-80Rc.....still in a machinable range but hard, LOL.

Edited September 12, 2007 by robomanusa

[cking]

RoboMan

Thank you for the offer, but I already purchase a endmill, about $35.00 with shipping.

As far as technique, I will leave that up to guy who owns the mill. Although I will print all these and bring them along to hear his opinion.

Wish me luck

Again Thanks

//ck

[robomanusa]

If you need another one, just let me know, I have many laying around.....16 years in the machining business you tend to gather all kinds of shit...LOL