It's time to replace the end mill, but the holder isn't cooperating.

I've already watched the instruction video, and tried it their way.  

The best I can get is to slightly twist the end mill in the holder, but there's no vertical movement.  I tried propane, then map-pro (assuming the propane was taking long enough for the end mill to heat up and expand), but no difference.  I've tried from the medium high heat they recommend, to glowing, but same results.

Anyone have experience with this?  I have a good supply of end mills, but don't want to drop another $45 for the tool in the holder.

Thanks.

Try freezing it .  Heat and cold make things expand and contract.

Soak it In 5W30

Shoot it with .375H&H as a last resort

Good thinking!  That's an excellent reason to get a 375 H&H!

Like you need a reason to get a 375 h&h

But, I need a budget for a 375 h&h.

When I changed out the end mill I just just heated the tool holder, pulled the old bit and dropped in the new bit. It went easy peezy. Sorry I can't offer anything else.

Edit: I just used a propane torch and heated until the holder until it glowed pretty bright.

Welp, freezing didn't do it, so after it came back to room temp, I hit it with both the propane and map-pro, testing every minute or so for movement.

The old end mill finally popped out when the holder was past orange hot, which is far hotter than I wanted to get the piece.  (I don't know much about metallurgy, but I do know that heating steel like that removes any tempering it might have had).  

Now to hit the holder with a scouring pad until it fits again.

Check & see if you have any runout with a dial indicator before turning the router on. If there is no runout, you should be good to go; also take your first cuts easy to make sure the tool holder has not lost any strength after the heat treatment.

I remember some where that you can use a magnet to see if your router bit holding tool has lost its temper. If the magnet sticks, the temper is fine, if it won't stick, then you have lost the temper in the metal.

I've always heated with map gas and popped it out with pliers.

After scouring the piece, I checked for run out by manually turning the tool first in the router, then with the router adapter on.  I don't have a dial indicator, but I put a length of spring metal under tension, against the holder, and watched for fluctuations (ghetto, I know). It did pass the magnet test, so I should be relatively good to go.

When I replaced mine, I just heated it up with a propane torch until it was slightly orange, put a pair of locking pliers on the bit and worked it out. It went easier than expected.

OP - how many lowers did you get through with your end mill?

I broke my first end mill on my first lower.  Broke my 2nd after a couple.  Replaced it with a radiused end mill and it's survived 10 or so, even with some mistakes bouncing it around.

If you let it bounce or get sideways they tend to chip out, that's how I broke the first two.  My radiused end mill has survived a few mistakes like that without braking.

I've completed four 80% lowers using the original Modulus Arms jig set with their end mill.  Worked fine, though my lowers showed upon close inspection that they were done by someone who was not experienced.    All still fully functional.

I recently bought a new 5D Pro jig and end mill from them and it's night-and-day better, easier and faster.  I still use the same DWP611 router - but used the new end mill I got with my 5D kit.  I've done 2 lowers and they look substantially better and other than being in-the-white, they look almost OEM.  Already tested fit with a LPK to sure safety lines up and moves easily without play and also the trigger pin holes.  Also test fit uppers to ensure the rear pocket and takedown pin fit.  All good.  I have 4 more I need to do and haven't noticed any degradation of the end mill.  Was just wondering how likely it is that the end mill will last through 4 more lowers (6 in total).  I use dark cutting fluid in the pocket and on the end mill tip between each notch adjustment.

I was on my 5th.  

I read a suggestion to drill your holes before milling so the hole's would be smoother / rounder.  The endmill caught a tooth as the hole was exposed and did the jitterbug.  One of the end teeth got knocked off.

In other words, OP messed around, and found out.

I've done my last few that way. Drilled the selector holes to 1/2" deep. FCG holes to 3/8" deep. I go slow (especially around the outside), and take very shallow passes, usually 1/3 of what the jig has. It takes a few hours to finish a lower, but I've been happy with the results. The holes for the FCG came out perfect on the inside. Selector may or may not need a little cleanup inside. I would recommend getting a foot switch for the router, and making very sure the mill is centered in the pilot hole before stepping on the switch. That way you can hold on with both hands as it spins up.

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I also use a foot switch to turn the router on and off.