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View Full Version : New Jacobs chuck collar same as my old 633C chuck?



skaye
11-24-2009, 06:38 AM
Hi folks,

The chuck below is a Jacobson 633C 0-1/2" and is the original that came with my 1950's Craftsman drill press pictured (model # 103.23570).

This chuck has the threaded collar which binds it more tightly to the press spindle, allowing side-thrust applications (e.g. sanding drum) w/out fear of the chuck falling off.

The metal lip that holds the collar to the chuck has broken off on this old chuck and I am interested in buying a new Jacobs replacement chuck. The one model I have found with the collar is the 34-33C ("C" for "Collar") in the catalogue screenshot at bottom. Note that the new collar is spec'd as 1-1/16"-20 thread.

My question is whether the collar threading on the new 34-33C should match the threading on the old 633C ?

Thanks!


http://img.skitch.com/20091122-mgexeguu6qhuw9cp4uia14tupx.jpg

http://img.skitch.com/20091122-6b4bh4knq3fifd3cemdj7get1.jpg

http://img.skitch.com/20091124-dj7cwia9u4ifx45277qepqhf4w.jpg

skaye
11-24-2009, 09:21 AM
Should have done this first, but maybe others will find the info useful.

Spoke with Jacobs technical support and the current 34-33C chuck was designed 25 years ago specifically to replace the original 633C that came with Craftsman DP's. Also, the 34-33C is the only chuck Jacobs makes with the threaded collar.

DR
11-24-2009, 09:57 AM
.......................................

.................................................. ....

the 34-33C is the only chuck Jacobs makes with the threaded collar.

The locking collar chucks get a fair bit of discussion on the various forums.

Apparently, Rohm is another manufacturer making a chuck with the locking collar although I can't find a listing for it.

Back in the day Supreme also made a locking collar chuck.

Kenwc
11-24-2009, 03:11 PM
Should have done this first, but maybe others will find the info useful.

Spoke with Jacobs technical support and the current 34-33C chuck was designed 25 years ago specifically to replace the original 633C that came with Craftsman DP's. Also, the 34-33C is the only chuck Jacobs makes with the threaded collar.

I have the 34-33C on an Atlas Model 73 DP that originally had the 633C and it works fine.

atomicjoe23
05-01-2012, 12:01 AM
I know this is an older thread, but I find myself in a similar situation.

Looking at the page that was posted it looks like the largest capacity for a 33JT chuck (at least from Jacob's) is 1/2". . .do any of you know if there is a 33 JT mounted chuck with greater than 1/2" capacity.

It may be cheaper for me to machine a 1/2" shank holder for the stuff I want to hold that has a larger diameter shank than 1/2".

Thanks for any and all help!

DR
05-01-2012, 12:47 AM
There's a very good reason those chucks only have 1/2" capacity. It's because the drill presses like the Craftsman and other quality dp's from back in the day only had a 1/2" capacity in mild steel.

It';s very common to see drills with shanks reduced to 1/2" so you can put a larger than 1/2" drill into the machine We've all done it, but the machines aren't rated for it.

I have several old 1940's-50's Atlas/Craftsman dp's. I consider them one of the best of the older dp's. Recently my son brought over some steel plates for structural bracing on a construction project. He used one of my dp's to drill 5/8" holes in them. Standing a distance away as he drilled I could see the table flexing down under the pressure he needed to push the 5/8" drill through the 3/8" material. I've done the same drilling a number of times, it was a real eye opener to actually see the flexing due to exceeding the machine's capacity. The flexing is something you're not aware of when you're doing the drilling yourself.

atomicjoe23
05-01-2012, 08:37 AM
Standing a distance away as he drilled I could see the table flexing down under the pressure he needed to push the 5/8" drill through the 3/8" material. I've done the same drilling a number of times, it was a real eye opener to actually see the flexing due to exceeding the machine's capacity. The flexing is something you're not aware of when you're doing the drilling yourself.

If you have a properly sharpened drill and you step drill you shouldn't see this should you?

I know that if I step drill I can feed the drill with practically no perceptible resistance to the drill at all. . .

. . .just thinking out loud and wondering if my thinking is correct?

DR
05-01-2012, 11:15 AM
If you have a properly sharpened drill and you step drill you shouldn't see this should you?

I know that if I step drill I can feed the drill with practically no perceptible resistance to the drill at all. . .

. . .just thinking out loud and wondering if my thinking is correct?


Yes, your thinking is correct. By step drilling you reduce the forces needed to push the drill through.

Another issue related to drill press capacity is how low the lowest speed is. Once you start stepping up in size the peripheral speed of the cutting edge of the drill can exceed recommended speeds for dry drilling of mild steels. The result is a burned up cutting edge of the drill.

An easy to remember rule of thumb I use to determine cutting speeds in mild steel is, 3/8" diameter drill should run at no more than 1000 rpm. Likewise turning a 3/8" diameter piece in the lathe 1000 rpm or less. So, if you were step drilling up to 3/4", can your dp speed be reduced to 500 rpm ?

Rosco-P
05-01-2012, 11:21 AM
If you want to drill big holes, you really want (need) one of these: http://www.beautifuliron.com/gs_drills_camelback.htm Spindles typically accommodate MT3, 4 or larger shank drills, most have power down-feed and a speed range to match larger sized drills.

atomicjoe23
05-01-2012, 12:08 PM
Yes, your thinking is correct. By step drilling you reduce the forces needed to push the drill through.

Another issue related to drill press capacity is how low the lowest speed is. Once you start stepping up in size the peripheral speed of the cutting edge of the drill can exceed recommended speeds for dry drilling of mild steels. The result is a burned up cutting edge of the drill.

An easy to remember rule of thumb I use to determine cutting speeds in mild steel is, 3/8" diameter drill should run at no more than 1000 rpm. Likewise turning a 3/8" diameter piece in the lathe 1000 rpm or less. So, if you were step drilling up to 3/4", can your dp speed be reduced to 500 rpm ?

Use the formula below to determine your RPM:

RPM = SFPM x 4/Diameter

Off, the top of my head I believe the recommended SFPM for drilling MS is 80 SFPM. . .therefore. . .

RPM = (80 x 4)/0.75 = ~425 RPM, but in my experience that is a bit on the fast side. . .once I hit 1/2" I'm usually down around 300 RPM, I would be around 120-150 RPM for 3/4".

uncle pete
05-01-2012, 02:15 PM
Actualy on any standard home type drill press, That table deflection is always going to be a huge problem even with step drilling. Don't believe me? Set up a dial indicator off the DP's rear coloum with the indicator probe towards the outside of the table, Then just use your thumb to add increasing pressure to the table. After about 10-20 lbs of pressure, You'll soon see that even the varying weight on the items being drilled will greatly affect just how much the table deflects no matter what the size of the drill bits, Or how well you've trammed the table to the DP spindle. If your needing real close to dead straight holes, Your not going to get it without adding a secondary outer support to the table.

Those built in design problems can be worked around if you take a lot of time to do so and your need is great enough. It's not easy or fast though. I drilled a 10 1/2" deep 3/4" diameter blind hole into 2" diameter stainless. Checking it after the hole was completed, I ended up with the bottom of the hole just over
.060 off of being concentric with the O.D. But it took almost 3 hours to set the job up with clamped on table supports, Aigning the shaft central and verticly straight to the DP spindle with a dial indicator, etc,etc. Then as the hole got deeper, Reset and realign everything again. The whole thing looked like a porkupine with all the bars and clamps sticking out in every direction you can think of. Yes that was a job that should have been done in a lathe, But at that time I didn't have a large enough lathe to do so. Normal hobbiest type drill presses are a very flexable piece of equipment and pretty inaccurate if you want a 90 degree hole. For anyone that does take the time to check that table deflection? I'll apologise for ruining your day when you see the results. The over hung design supporting the DP table is in reality a very poor design. Trying to redesign it to get proper support with very little table deflection is more than a bit tough for anything I've considered so far.

Pete

lynnl
05-01-2012, 05:01 PM
This is new/unfamiliar to me. Is that threaded collar threading onto external threads on the spindle itself?

That of course suggests they're only for certain drill presses designed to accomodate such.

Learn something every day I guess.

atomicjoe23
05-01-2012, 06:10 PM
Actualy on any standard home type drill press, That table deflection is always going to be a huge problem even with step drilling. Don't believe me? Set up a dial indicator off the DP's rear coloum with the indicator probe towards the outside of the table, Then just use your thumb to add increasing pressure to the table. After about 10-20 lbs of pressure, You'll soon see that even the varying weight on the items being drilled will greatly affect just how much the table deflects no matter what the size of the drill bits, Or how well you've trammed the table to the DP spindle. If your needing real close to dead straight holes, Your not going to get it without adding a secondary outer support to the table.

Those built in design problems can be worked around if you take a lot of time to do so and your need is great enough. It's not easy or fast though. I drilled a 10 1/2" deep 3/4" diameter blind hole into 2" diameter stainless. Checking it after the hole was completed, I ended up with the bottom of the hole just over
.060 off of being concentric with the O.D. But it took almost 3 hours to set the job up with clamped on table supports, Aigning the shaft central and verticly straight to the DP spindle with a dial indicator, etc,etc. Then as the hole got deeper, Reset and realign everything again. The whole thing looked like a porkupine with all the bars and clamps sticking out in every direction you can think of. Yes that was a job that should have been done in a lathe, But at that time I didn't have a large enough lathe to do so. Normal hobbiest type drill presses are a very flexable piece of equipment and pretty inaccurate if you want a 90 degree hole. For anyone that does take the time to check that table deflection? I'll apologise for ruining your day when you see the results. The over hung design supporting the DP table is in reality a very poor design. Trying to redesign it to get proper support with very little table deflection is more than a bit tough for anything I've considered so far.

Pete

Good points. . .the drill press was never designed to do mill work.

Fortunately the material I'm drilling into is only 1" thick and I'm going to be welding afterwards so I don't have to worry about these things at the moment. . .I simply need to remove old material (that has broken) in order to replace it with new material (was broken when I bought it and I'm fixing it).

uncle pete
05-01-2012, 07:35 PM
Atomicjoe,
Nope I wasn't implying any drill press would come close to a good mill. But DR posted about that table deflection that he hadn't really noticed till he was watching the operation off to one side. Too many automaticly think "It's a drill press so it's got to be pretty accurate", They tram the table to the spindle and then think everything is great. It wasn't till the first time I tested my DP that I finally understood just how flexable they really are. Today I don't even use my DP other than for items around the home. Precision gets done in my Bridgeport clone. But even it has a certain amount of flex in the head mounting. A 90 degree straight drilled hole is far tougher to achieve than a lot would think.

Pete

atomicjoe23
05-01-2012, 08:12 PM
Atomicjoe,
Nope I wasn't implying any drill press would come close to a good mill. But DR posted about that table deflection that he hadn't really noticed till he was watching the operation off to one side. Too many automaticly think "It's a drill press so it's got to be pretty accurate", They tram the table to the spindle and then think everything is great. It wasn't till the first time I tested my DP that I finally understood just how flexable they really are. Today I don't even use my DP other than for items around the home. Precision gets done in my Bridgeport clone. But even it has a certain amount of flex in the head mounting. A 90 degree straight drilled hole is far tougher to achieve than a lot would think.

Pete

Funny how such a seemingly simple task is so difficult to achieve. . .

. . .and I wasn't trying to imply that's what you were implying either. It was very good information to pass on. Can't wait to a Bridgeport mill here in my homeshop!

sasquatch
05-01-2012, 08:25 PM
Not to get too far O/T here, but the subject that has popped up about drill press table deflection is very real.

Years back i only had a little 10inch drill press and needed to drill a bunch of 1/2 inch holes in about a 16x20 1/2 inch plate.

The plate was not only heavy enough that i thought it could break the table off, but overhung badly.

I took some carefull measurements and cut up some 2x4's to jam upright under the table to support the weight.

I then got the 1/2 inch holes drilled, but that poor little press was moaning.:eek:

uncle pete
05-01-2012, 08:40 PM
Joe,
Funny enough the more you learn, The more you begin to test for, The more you find just how inaccurate the world is. While mine isn't a true Bridgeport, It's a Taiwan built clone. I'd never want to be without it now, But there is and are far more accurate and rigid types of mills. The overall design is really vesitile though.

It took me a long time to start to appreciate the fact that solid metal is very much a lot like rubber on a microscopic scale.

LOL, And I won't bother getting into just how inaccurate drill bits actualy drill a hole.

Sasquatch,
You posted while I was still one finger typeing mine. LOL, A very descriptive post and I can't say I haven't done the same. If some of our tools were animals, The SPCA would arrest us.

Pete

atomicjoe23
05-01-2012, 09:04 PM
I won't bother getting into just how inaccurate drill bits actualy drill a hole.

Pete

What's that saying. . .

Drill to remove material, ream for size, and bore for location. . .

. . .I'm a toolmaker apprentice so we get to learn all about the inaccuracy of what we do!

uncle pete
05-01-2012, 09:12 PM
Just a slight modification. Drill for material removal, Bore to get it round and straight, Then ream for size. Pretty well the same thing though.

You'll be a long ways ahead of us for information being a Toolmaker Apprentice though. A tough and demanding apprenticeship.

Pete

atomicjoe23
05-01-2012, 09:44 PM
A tough and demanding apprenticeship.

Pete


I'm in my second year and I LOVE IT!!! The most rewarding job I've ever had and WAY more interesting than my other jobs.

As it turns out my Rockwell doesn't have a 2MT in the spindle. . .at least I'm pretty sure it doesn't. There is no drift slot in the spindle so I'm guess I'm gonna stick with the 33 JT chuck that's in there now; there's nothing wrong with the chuck other than capacity and I'll just work around it. . .that's one of the great things about this hobby. If it isn't available figure out how to make it/do it yourself the way you need to.