MT3 Collet Drawbar

[Robo_Pi]

I finally finished the collet drawbar.

I wanted a set of collets for my lathe. I would have loved to use 5C collets but my lathe spindle bore isn't large enough. And it's already tapered MT3. I could have gone with ER collets, but I chose to go with MT3 instead. So I bought the following set of 12 collets from 1/8 to 3/4"



But then I needed to make a drawbar so I decided to use a handwheel off an old sewing machine I had laying around.




It turns out to work very well. Some concerns were voiced that this heavy sewing machine handwheel might loosen because of inertia when the lathe starts up or shuts off. But my lathe is sluggish enough on start up and stopping that this is not a concern. But I can see where that might be a problem on a lathe that jumps to life of stops real quick.

This was a pretty big project for me as I am just now tooling up. There were quite a few operations that I needed to learn about and set up for.



I started by cutting the threads for the actual collets. I did this with a standard die by hand. But it was tough to thread. This was made from an old axle of some sort and it seems to be pretty tough stuff. So on the right side I cut that threads using the lathe. That required making a thread-cutting tool bit and learning how to cut threads on the lathe. I posted that operation earlier.

I made the spacer in front of the handwheel again from a large gear axle. I drilled through it and tapped it to thread onto the shaft so that I could then lock it into place with a nut on either end. I had to then cut a shoulder to fit inside my lathe spindle to keep everything well-centered. Then on the handwheel side I turned it down for a press fitting into the handwheel. Unfortunately I got that a tad bit too large and when I pressed it in it cracked the handwheel. It doesn't seem to be a problem though because the outside ring of the handwheel didn't break so it still holds firmly to the shaft. Then on the back side I put a large washer and nut just to be sure the handhwheel can't work loose.

I have some left-over stock on the main shaft that I used when cutting the threads. I was originally going to cut that off and t rim the shaft down close to the nut that holds the handwheel on. But when I was trying it out I found that extra bit of shaft sticking out there a nice place to tap the collet loose so I decided to leave it as is.

It may not look like much, but this was a complicated build for me, and it works. That's the important part. Now I have collets! Yeah.

 

[Shootymacshootface]

Nice job!

 

[bretthl]

That is awesome!

 

[Robo_Pi]

I just came in from the shop. I made another drawbar for another collet set. Not as fancy this time.

This is for ER-20 collets I just bought for the milling head on my lathe/mill combo.

It's a 14 piece set. I'll probably use the 1/2", 3/8", and 1/4" the most for holding end mills. But I also have some fly cutters order that use a 1/2" shaft, so I'll be using this with those fly cutters for sure.


I also bought the ER-20 collet holder in MT3 taper as that's what my milling head takes. But my milling head has a 3/8-16 drawbar. This ER-20 collet holder has an MT12 x 1.75 thread. So I had to make a new drawbar for this. More threading on the lathe. Which is good because I want more experience cutting threads.

Here's the M12 x 1.75 thread I just cut for this collet holder.



It fits!



On the top end I used 3/8-16 because I don't have any M12 nuts.

Here's cutting the threads on the other end:
Making the scratch pass to insure proper set-up.


Finished thread:


I cut this at the lowest speed on my lathe because I was cutting toward the shoulder. I have to keep everything engaged on my lathe when cutting threads, so the only way to stop is to shut the lathe off. Of course, I also retracted the cross slide too. I think I did pretty good cutting right up to this shoulder.

Finished product:



Yeah! Much better than the drill chuck I had been using.

I'm tooling up. Not sure what I'll build next, but at least I'll be prepared.

 

[BROCKWOOD]

Looking good. It's a shame you need 2 different collet types for the same machine. My combo (Grizzly G0773) uses the MT3 for the mill & for the lathe tailstock. So far I use a 4 jaw chuck for the lathe head & do OK.

 

[Robo_Pi]

It's a shame you need 2 different collet types for the same machine. My combo (Grizzly G0773) uses the MT3 for the mill & for the lathe tailstock.

My machine also has MT3 tapers all the way around. I can already use the MT3 collets in the mill if I want to, it already has a 3/8-16 drawbar. I chose to use the ER-20 collets in the milling head for various reasons. And I didn't want to use the ER collets to hold work in the lathe. So I opted for the best of both worlds. The ER-20 collet set was cheap enough.

The ER type collets allow for grabbing onto shafts that aren't the exact dimension as the collet. In short they have a wider range of dependable gripping power. So they can be used to grab onto drill bits that aren't the precise size of the collet. If you try to do that with an MT3 collet things can go horribly wrong. From something as simple as the bit not running true, to the bit actually slipping in the collect which is never good. So the ER collets are better for gripping tool bits. And on the lathe I prefer the less obtrusive MT3 collets to use with standard stock sizes. So for me the two-collet system works good.,

So far I use a 4 jaw chuck for the lathe head & do OK.

That's my next project. I just bought a 6 inch 4-jaw for this machine. But I need to make a backing plate for it. So that project will be coming up soon.

 

[BROCKWOOD]

Actually I misread the part where your machine uses MT3 all around. I had bought the MT3 to ER set & found it used up too much space for my needs. I am much happier with using the direct MT3 collets. Fortunately, the drawbar in mini milling heads like ours amount to long screws. I have a few different thread versions dedicated to the task. Keep up the good work.

 

[Robo_Pi]

It is true that you lose a couple inches using the ER system. In fact, I went with the ER-20 instead of the ER-32 just to keep things a bit smaller. If I need to work on something really large I may need to use the MT3 collet in the milling head. But as I say, I have those too, so I can use either one.

Most of the projects I plan on building are going to be small. So having a milling tool a couple inches lower isn't going to be a problem. And in some ways it's actually better. That's because the milling table is so far below the mill. I had to jack up my vice. I covered that in another thread.

But yeah, holding the tool bit directly in an MT3 collet is the cleanest way to do it. That gets you right up to the very bottom of the quill. That would also be the most rigid and allow you to take the most aggressive cuts. I'm just tooling up with this now and I'm thinking more in terms of having a wide range of versatility. Like I say, most things I plan on building are going to be pretty small lightweight projects. The only time I might end up putting something massive on this mill is if I'm repairing something like a broken tractor or truck part.

I keep dreaming of getting a much larger vertical mill as well. But we'll have to wait and see whether that dream ever comes true.