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Thread: solid carbide 90°end mill, HOW??

  1. #1
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    solid carbide 90°end mill, HOW??

    Last night I used a solid carbide 90° to mill a slot into the top of a large octagonal BAT 'M' action. I want to be able to remove the scope base and desired a solid keyed locking surface...... I wanted a 1/4Wx1/8D slot in which to epoxy a key..... I used a 1/4" drill bit for the key. I tried small ball endmills and flat end mills.... In the end I milled the slot using a 1/2" diameter solid carbide tool with a wicked sharp 90° tip. It's designated as MCH-4D.

    And of course it knocked the tip off.

    My question is, is there a bit, a grind that will cut a decent 1/4x1/4 slot? I'm picturing a bit like a 3/16" center drill with side-cutting capability

    I have keyway stuff, I'm looking for ease of setup

  2. #2
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    Al, Rough slot first 3/16 then finish with a 1/4 I would go with straight flute carbide key seat cutters..what rpm are you running at

  3. #3
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    Thanks George but I'm trying to get away with just clamping a flat-sided receiver in the vise and milling a slot with a Bridgeport..... I'm looking for a quick easy way to make a take-off system for picatinny rails. Stiller's TAC and Predator actions and the Kelbly steel actions have nicely fitted pin systems and they work perfectly, but are an absolute time buster for me to make on my silly ancient equipment.

    I have keyway cutters but jigging the receiver up to cut a key slot in the "side" is such a pita that I'll never do it that way. I'll drill and ream holes for pins easier.

    So specifically I'm looking for a 3/16'ish milling bit with a 3/8 inch shank and only a short cutting bit. I have a lot of 1/8-3/16-1/4 inch endmills but they hang down so far they flex unmercifully when milling a slot.

  4. #4
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    You could also clamp straight to table against pins and use a milling cutter on arbor at 90* try the straight flute cutters they are made in stub length the helixed cutters have a higher shear angle for finish
    Last edited by geo.ulrich; 01-12-2020 at 08:41 PM.

  5. #5
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    If you want a .250 wide slot, use the 3/16 EM and make it 1/4" wide. Never use an EM the same size you want to make the slot. It will blow it oversize and give you a crappy finish on the slot walls. Carbide likes high RPM. Rough slot with a hog mill and finish with 4 Flute. Both 3/16.

  6. #6
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    Funny they have been finishing slots with on size end mills for years. look at electric motor shafts or printing rolls ....unless it NEEDS to be press fit cutting both sides just wastes time. and in mach. shop time is money...

  7. #7
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    Quote Originally Posted by geo.ulrich View Post
    Funny they have been finishing slots with on size end mills for years. look at electric motor shafts or printing rolls ....unless it NEEDS to be press fit cutting both sides just wastes time. and in mach. shop time is money...
    On size end mills for slotting have to be 2-flute. A 4-flute will flex and make an oversize slot every time unless the material is very soft. This is less of a problem with a short carbide end mill, but HSS is bad about it. Even if you use a 2-flute, the climb cutting side of the slot will be smooth compared to the other side which will be conventional milled.

    RWO

  8. #8
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    Hence the reason for the 2 flute straight flute key seat cutters no felix less torquing

  9. #9
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    OK, so this last little bit is worth a lot to me. I have a bunch of 2-flute endmills and didn't know that they would be OK for SS. I've been using them only for aluminum.

    I will try them

  10. #10
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    Al, again STRAIGHT FLUTE CARBIDE key seat cutters not helixed. actions are hard but not real bad just take it easy over the base holes thats where corners will get chipped

  11. #11
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    Quote Originally Posted by geo.ulrich View Post
    Al, again STRAIGHT FLUTE CARBIDE key seat cutters not helixed. actions are hard but not real bad just take it easy over the base holes thats where corners will get chipped
    YES..... thank you. I have two straight flute carbide endmills that I've never fired up. They came from an estate. I just took one look back when I opened the boxes and said "I'll just knock the edges right off of those"


    Now, I be crank UP the RPM's and crank DOWN the feed..... and I be try 'em!

  12. #12
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  13. #13
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    them is the ones....

  14. #14
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    Al, keep in mind, you need to run carbide end mills fast with a lighter feed. How fast are you turning the mill?

    The Bat Actions are made from 17-4 at around 36 RC hardness. You really should not have any problems running a 1/4 inch carbide end mill to cut a slot.

    It won’t hurt to use some sulphurized cutting oil on the mill as well.

  15. #15
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    Quote Originally Posted by jackie schmidt View Post
    Al, keep in mind, you need to run carbide end mills fast with a lighter feed. How fast are you turning the mill?

    The Bat Actions are made from 17-4 at around 36 RC hardness. You really should not have any problems running a 1/4 inch carbide end mill to cut a slot.

    It won’t hurt to use some sulphurized cutting oil on the mill as well.
    I've got an old Bridgeport with the step pulleys instead of the vari-speed drive. I put a VFD on it and I _think_ my high speed is around 3300RPMs

    I normally run it around 2500-ish (guessing) with Carbide but these little bits I might just run 'er up to maximum, try for 3000+

    I have several sulphurized cutting oils like Rigid but for something like this I use Vipers Venom or Do-Drill

    I think my problem was that I was using a 3/16 cutter with a 3/8 shank and the cutting tip is too long, I got 'er all cleaned up but that stainless is sticky stuff and I was fighting both deflection and (I think) work hardening.

    This BAT is on my Heavy LR gun, a 300WSM pushing big bullets hard. She Bucks.... HARD.... The flat-topped BAT has only 4 8-40 holes to hold the flat-bottomed base down. March 8-80 is a heavy scope...... I think it was moving as the gun just hasn't been crisp. And when I remove the picatinny rail after gluing it down it always comes off easy. I've been fighting it for a year, swapping scopes etc. Now she's keyed and glued.


    We gonna' find out! She's all rebuilt, just got 'er put back together. Time to shoot.

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