Question On How To Make An Mt3 Socket?

[kizmit99]

Hi All - question for you...
I have piece of O1 drill rod that I need to cut an MT3 "socket" into. I have a set of roughing and finishing MT3 reamers (cheap set from ebay):



The drill rod is basically 1.5"diameter 4 inches long. I need the MT3 socket on-center - here is a rough sketch of what I'm trying to do:


So... how should I go about prepping the part for using the reamers on it?

I'm thinking mount it in a 4-jaw chuck on my lathe (G0602), indicate the rod to be sure it's centered up good. Center-drill, then step drill up to approx 3/4" drill, then bore out to about .800, then start with the roughing reamer, finish with finish reamer... The small-end of the reamers is just under .800 dia, the large end is about .950. Would that be asking too much of the roughing reamer?

The only other option I can see would be to approximate the MT3 taper (undersized obviously) using a boring bar and the compound. I don't think I have 4" of travel on my compound though, but since it doesn't need to be perfect I may be able to do it in two passes? This would seem to require less metal removal by the roughing reamer - but I'm concerned it may also not allow the reamer to "find its center" as well and maybe I'll end up with socket that isn't straight and centered in my part?

Looking for suggestions - thanks in advance!

 

[Bob Korves]

I am pretty sure you need to use the compound and get pretty close to save wear and tear on the reamers. What I do not know, and am interested to find out, is how to best plan the job to maximize concentricity and correct taper at the same time. I am guessing that the roughing reamer should contact true surfaces close to full depth initially to help the reamer find the center. The tailstock center can keep the large diameter end running true. I have never done this, and am listening as well.

 

[Chipper5783]

Deffinately bore it, whether stepped or tapered (doesn't really matter). When you drill, you cannot be sure it is on center (a drill is a roughing tool) - there are a few things that can go wrong with drill, including wandering. The reamer will simply follow the existing hole (if the hole is off center or off axis, then the reamer will be too). Start with a piece quite a bit longer than needed (the extra length is what you hang onto for machining). Bore the ID, cut the OD in the same set up (that will give you the best concentricity).

Let us know how it works out.

 

[TomS]

I agree with Bob in his post above. Doing it the way he suggests will save your reamers and you will be more likely to maintain concentricity between the tapered bore and the material OD.

If you are concerned about concentricity why not finish ream your internal taper, then make a tapered stub mandrel, install your finish reamed part, then finish machine the OD.

Tom S.

 

[Bob Korves]

It is probably well worth making sure your tailstock center is as perfectly in line with the spindle axis as you can get it, too.

 

[Bob Korves]

The finish reamer should only remove a few thou. I would not want the roughing reamer to remove more than about .020" at the most. Get the axial accuracy from the boring and the finish and taper angle accuracy from the reamers.

 

[joshua43214]

You should rough the outside before drilling. The rod will likely change shape after being drilled, you want to give it as much chance to relax as possible.

Are you going to be making these for a living? If not, you can just drill, bore, and ream with the finish reamer and sell the rougher. Boring at the approximate angle is not a bad idea just to speed things up a bit. You can put a center between centers and sweep it to set the compound angle.
Some gunsmiths routinely ream chambers from nothing more than a barrel to finish size with a finisher. The claim is that you get a smoother finish that is more concentric by not roughing. I'm not a gunsmith, they say you get 10-20 chambers per reamer. In my mind, there is no reason to use a roughing reamer when you can bore to rough size and finish ream.

 

[kizmit99]

Are you going to be making these for a living?

That would be a no... unless the project I'm working on turns out to be so popular that everyone just must have one (which I suspect is less likely than I would hope ... but there's always PowerBall tonight! )

Some gunsmiths routinely ream chambers from nothing more than a barrel to finish size with a finisher. The claim is that you get a smoother finish that is more concentric by not roughing. I'm not a gunsmith, they say you get 10-20 chambers per reamer. In my mind, there is no reason to use a roughing reamer when you can bore to rough size and finish ream.

The difference in size between these reamers and chamber reamers is pretty significant (unless you're chambering a 20mm cannon)... Thus far I've only chambered one barrel (but I did make the reamer) - hopefully more in the future though...

The finish reamer should only remove a few thou. I would not want the roughing reamer to remove more than about .020" at the most.

That seems like a reasonable goal. I'll see how close I can get to the correct taper angle with the compound, but I doubt it's going to be very close. If I just did a straight bore it's looking like I'd be asking the roughing reamer to take about .075 off the large end of the socket... which does seem a bit much to be asking of it.

 

[Bob Korves]

(snip)I'll see how close I can get to the correct taper angle with the compound, but I doubt it's going to be very close.(snip)

Find a MT3 shank (drill bit?) you can chuck up and indicate it while moving the compound. Or use gage blocks and a sine bar to set the compound. Either of those would be well more than close enough and pretty easily done. I'm sure there are plenty of other ideas as well.

 

[Jimsehr]

I am so lazy I would buy a # 3 taper drill socket
from Enco for less then $2o dollars that already
has a # 3 taper in the inside . Then I would turn a
#3 taper on the od of a piece of stock in the lathe
so it is dead true. Then tap the store bought
socket on the turned taper and then machine the
turned od to the print. I did that to make a tapered
sleeve for my Logan lathe . I was too cheap
to buy the reamers to do the id taper .
jimsehr