What size drill chuck?

[fireguyfire]

I have a bench top milling machine from the 1980’s, and it’s actually a pretty decent machine for what I need it for. What I don’t have is a drilling chuck for it, so I’m looking to buy one.
I’ve got a lot to learn regarding sizing lingo, so I thought I would just post up my question here so that I don’t buy the wrong chuck.
My mill has a long drawbar from the top and the threading on the drawbar is 3/8” 16.
What size or designation of chuck do I need for my mill? I see the collets are MT3 size but I’m not sure if that’s the drill chuck size I need to source?

So I guess my first question is, does a drill chuck for a bench top milling machine use the drawbar to hold in the drilling chuck like a collet?

 

[PeterT]

A drill chuck requires an arbor. So drawbar > arbor > chuck. The drawbar threads (like 3/8-16) must match arbor threads and arbor must match the spindle taper (like MT3 or R8 or...). The other end of arbor has a different taper (like JT#) to engage the chuck body so must match the socket taper of the chuck. Some chucks come with arbor essentially hard mated on, sometimes called integrated chucks. This can be good in that potentially better runout specs, assuming the factory did it right. Downside is more permanent if you want to remove chuck. My preference is integrated because it eliminates the middleman, but in all cases try & establish TIR specs. If they dont list it, its kind of you get what you get. If they say 0.001" and yours is 0.005" you have some recourse to exchange refund. Its a bit of crap shoot but there are many good offshore chucks on the market for substantially lower cost than years ago. Read the purchase comments or do a search here. Although no guarantee that Brand ABC 3 years ago is better or worse than today.

 

[ChazzC]

3/8-16 drawbar is typically for an MT3 spindle taper.

 

[fireguyfire]

I’m not having much luck finding an MT3 integral draw bar chuck on the internet.
Any suggestions on a specific supplier to look at?

 

[Susquatch]

I’m not having much luck finding an MT3 integral draw bar chuck on the internet.
Any suggestions on a specific supplier to look at?

A quick look on my part didn't turn one up either. Your key difficulty is the word integral.

Integral may be hard to find. But it isn't necessary for a drill chuck. Most of mine are not integral. In fact even my top of the line Albrecht chucks are not integral. You can find lots of MT3 to JT3 arbours that will fit damn near any style of chuck you want. In fact, I'd bet that many integral arbours are really JT3.

https://a.co/d/08qUGnOo

Have fun!

 

[fireguyfire]

Thanks for the advice Susquatch; I’ll order one of those up.

Which leads to 1 more question, is there a good recommended brand name on a JT3 chuck? I’m definitely looking for a good quality one.

 

[PeterT]

Ya I think my reply was a bit too generalized or too R8-orientated. Left Pic = arbor only. Right = integrated arbor + chuck. Sometimes its not obvious that they are integrated or use a different name for that configuaration. I think (but not 100%) integrated also means 'well stuck together'. But looks like for MT3, integrated is not as common at all, so you are likely going the seperate arbor + chuck path. MT3 may also dictate the nose taper size which may then dicate the chuck options, so you'll just have to peruse catalogs. Keyed vs Keyless chuck usually gets lively opinions, I prefer keyless myself.

 

[fireguyfire]

Looking closer at the Arbour it’s a 1/2” drawbar size. I’ll need a 3/8” 16 MT3 to JT3

 

[PeterT]

https://a.co/d/08qUGnOo

Have fun!

and this example is what you need to verify. MT3 but different drawbar thread

 

[Susquatch]

Looking closer at the Arbour it’s a 1/2” drawbar size. I’ll need a 3/8” 16 MT3 to JT3

Ya, sorry. I didn't even look at that. Just wanted to show the way to go.

Which leads to 1 more question, is there a good recommended brand name on a JT3 chuck? I’m definitely looking for a good quality one.

Well, if you can afford it, get an Albrecht. Ya, even used is pricey! Even so, they are worth the coin and are easily rebuilt. MC sells rebuild kits.

Best to get the drill chuck and the arbour at the same time to make sure they both use the same adapter taper.

Other good makes are Genuine Jacobs with a bearing, Goose, Rohm, South Bend, Gerardi, to name just a few. I'm sure I've missed more than a few makes. Those are just the ones that came to mind.

Before you spend a small fortune on a top of the line chuck, it might pay to make sure you really need one. Often times an inexpensive chuck is more than adequate and sometimes an ER collet set (or some other collet system) makes more sense on a mill.

 

[trlvn]

I may be complicating the issue, but...

Keyed or keyless. Keyless = convenient. Most of the time. Until it jams. Or slips. I use my keyed chucks a lot. If I only had one, it would be keyed.

Min/max shank size. You may want more than one chuck. Many chucks max out at 1/2" diameter shanks but 5/8" is very little extra money. If you do any small work, check the min size the chuck can hold. I use a 0 to 1/4" keyless chuck for very small drills. The small chuck also consumes less Z height. That matters more often than you might think.

Consider straight shank rather than MT3. If you have a good 1/2" MT3 collet, use a 1/2" straight shank on the drill chuck so you have a chance to use the same collet for preceding or following operations. If you have an electronic edge finder with a 3/4" shank, maybe get a 3/4" shank for the drill chuck. Etc. Some days in the shop, it feels like all I have done is swap collets! 😉

Finally, drilling is a roughing operation. Drills often cut oversize, wander, leave egg-shaped holes and do other nasty tricks. Don't overspend to get "precision". Frequently, you can get a tray lot of drill chucks from an online auction for a fraction of the price of a new one.

FWIW,

Craig