Shoptask 1720

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Keyair
Posts: 90
Joined: Wed Aug 03, 2016 6:09 pm

Re: Shoptask 1720

Post by Keyair » Mon Sep 05, 2016 3:00 pm

Used the lathe to clean up the 1" diameter Beadroller shafts, with emery cloth.
I will be using the mill to slot a couple of holes in the beadroller frame, and drill some additional holes.
Its amazing how liberated I feel to be able to do these things!
This week, I will be starting my build on a radius turning attachment. I measure about 6" from the cross slide to the lathe center.
This one looks like what I think will work...
http://bedair.org/9x20camlock/Bob.html

Keyair
Posts: 90
Joined: Wed Aug 03, 2016 6:09 pm

Re: Shoptask 1720

Post by Keyair » Thu Sep 08, 2016 10:14 am

Did not get a chuck key for the mill head chuck.
I have a 1/2 key, but it is too small...
What is the next size up?

spro
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Re: Shoptask 1720

Post by spro » Thu Sep 08, 2016 5:05 pm

The next size up is collets, if you want to mill anything. For a Jacobs style chuck (which isn't a Jacobs) there are those 4 ended things. One is for smaller and another for larger sizes of Asian drill chucks. These days one can take the chuck to a hardware store and see if it fits.

spro
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Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Shoptask 1720

Post by spro » Fri Sep 09, 2016 4:28 am

I see what you were saying. The key for a Jacobs 3 or 3A doesn't quite fit an Asian "World 13mm" chuck. That is pretty old now but may still apply. I would go right to Grizzly for that key for drilling.
There is no question that collets will actually serve for milling. You may be very unsatisfied with the performance using a chuck as this. Mine is R8 arbor with a heavier machine and the drill chuck flat sucks for milling. It extends too far and that multiplies the other extensions, resulting in a bad experience. AND if you hang up an end mill with that chuck, it can re-orient the head and cause some damage.

pete
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Re: Shoptask 1720

Post by pete » Mon Sep 12, 2016 11:50 am

And a drill chuck can't come close to the grip a collet can. You have three jaws in the chuck that give almost a line contact at those 3 points on a tool shank. A proper collet has far more gripping surface and you can't even come close to gettting a drill chuck tight enough. I don't even want to think about a razor sharp end mill getting pulled out of a drill chuck and then bouncing all over the shop and maybe you. At most you can get away with it while plunge cutting something like a counter bore if your careful. But if the drill chuck isn't an integral shank, or held ion to the arbor with a machine screw any side cutting will cause the taper to release the chuck off of the arbor.But they still can't hold any tools used while milling and there not designed to do that. I tried it just once and filed that idea away as a non starter.

Keyair
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Joined: Wed Aug 03, 2016 6:09 pm

Re: Shoptask 1720

Post by Keyair » Mon Sep 12, 2016 12:05 pm

Agreed.
I will figure out and order a collet system this week.
One of the issues I see is when I use a collet, the head maybe to high to reach the workpiece...
Need to buy a thick block of steel to bolt stuff to.

pete
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Joined: Tue Feb 10, 2009 6:04 am

Re: Shoptask 1720

Post by pete » Mon Sep 12, 2016 1:07 pm

Rare to not be able to reach a work piece, but there's an option for that. You can use an ER collet chuck and collets. Order the shank in whatever taper and drawbar thread you have. Something like an ER 32 size ends up a couple of inches below the spindles face so that might do it for you. But the collets get snapped into the collet nut first and the nut is then threaded onto the chuck body. Changing collets is just the reverse. Closing torque numbers are fairly high. About 100 ft lbs for the 32 size and over 120 for the 40 size. But ER sizes in something we'd need start out at the 20 or 25 as well.And go as small as the ER 8. For your machine I'd be looking at the 25 or 32 depending on how large a tool shank you might use now or in the future. It's a good system but not quite as rigid as directly fitting collets into the spindles taper. The closer you are to the spindle bearings the more rigid things are. But the ER's will work fine.

Keyair
Posts: 90
Joined: Wed Aug 03, 2016 6:09 pm

Re: Shoptask 1720

Post by Keyair » Mon Sep 12, 2016 2:33 pm

To clarify, I think my mill head is MT3.
I thought the drawbar was M12... but in fact it is M8!!!!
Tried to put an M10 bolt down the center and it fits. I will probably convert to M10.
My tailstock is an MT2.

pete
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Re: Shoptask 1720

Post by pete » Sun Sep 18, 2016 7:17 pm

Any mill I've had or have uses imperial threads so I don't know much about the thread sizes used on the metric female thread on MT tooling. There are standards though. And it depends on where you live. If in the U.S. then I'd switch to whatever the thread is on MT 3 shank tooling in imperial threads. Anywhere else check a bunch of tool supplier web sites to find what thread is the most common for MT 3 and use that. Your drawbar thread at the tool end has to match what the tool shanks have. You don't need a great deal of tightening force to retain MT tooling. The taper holds the shank and the draw bar just keeps it from looening and droppong out. Crank up on that draw bar and you'll have to really pound on the end of the draw bar to get the shank to release from the female spindle taper. Doing that will kill your spindle bearings real quick. That's why R8 is a better taper than the MT is. R8 is classed as a self releasing taper and the MT is classed as a self holding taper. It's all about the taper angle that decides what type it is. R8 just takes a light tap. MT takes a lot more if you tighten the draw bar too much.

spro
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Re: Shoptask 1720

Post by spro » Sun Sep 18, 2016 8:50 pm

So the Shoptask 1720 is a BT500 and it has 4" quill travel. It also weighs over 600 lbs and has MT#4 in lathe spindle, MT#3 in M/D spindle and MT#2 in the tail quill. It seems heavy enough for another way to mill upon the table without a riser. If we look at heavy "pillar" or "camelback" DP's, see the spindle drive was at the top and an adjustable quill section was closer to the table. It seems like the lathe spindle has some kind of lock to mill work suspended between the chuck and tailstock.
With this in mind, consider an extension passing through a fixture suspended between the lathe head's chuck and tail stock. This would consist of a replaceable oillite porous bronze bushing/bearing. The shaft will have fine surface and machined for MT#3 at one end, for use with drawbar. The end mill side can be 1/2" precisely drilled hole, with robust Allen lockscew similar to a Weldon, in shape/function.
While seemingly too much work, I'll bet somebody has done the same thing for the same reasons.
The deal is, the 1720 already has a stout fixture between its centers below the milling drive. It doesn't need flat ways on a column to do this. just an idea.

pete
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Re: Shoptask 1720

Post by pete » Sun Sep 18, 2016 9:30 pm

Hi Spro,
I finally took the time to check the Bolton website for this lathe/mill. An odd design to say the least. All you have is the travel on the spindle itself of that roughly 4". I see they do offer a tee slotted riser to lift the work up to somewhere in the range of the head. Something like that should be included in the price of the machine since you'd need it for just about everything. But that riser doesn't look very rigid either. I dunno, if I was trying to make it work I think any time I needed the mill I'd pull the topside and mount a solid tee slotted block directly to the cross slide to get most work up where the tool could reach it. Using that top slide to mount the riser block and/or work just compounds the lack of rigidity. For smaller work it would be faster to just add a milling attachment and use end mill holders or collets in the lathes spindle. But I still can't figure out why they didn't add a way to move the whole milling head up and down and get the tool at the work surface with the spindle retracted to help with getting a bit more rigidity. Selling price would be the only reason they didn't.

But your idea about using the lathe spindle as a lower sub spindle bearing locator would work just like they did on all those old drill presses.

spro
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Joined: Mon Feb 20, 2006 11:04 pm
Location: mid atlantic

Re: Shoptask 1720

Post by spro » Tue Sep 20, 2016 12:19 am

Pete. Since you understand, then being able to lock the spindle is paramount to further investigation. Why not use that vertical head for more than drilling. Locking gears is not enough, it must be locked between centers to consider this. I believe that many bought these machines thinking that they could vertical mill on work in the lathe chuck but there is no travel except Z. The lathe table must be accessed for the axis' and requires an extension. I think the lathe chuck to tail register is good but not the end of it. If it has a steady rest, that would be locked on the sub spindle bearing bar at the tail end. This would allow vertical support at the center height, to mill the shorter work fastened directly to the table.
That was the issue. Otherwise, it appears to be a drill press and milling done by the lathe spindle. Folks been using Atlas, Myford, South bend and others for milling with an attachment. This attachment is a vertical slide with a small vise and attaches to the cross slide.
Why cannot a vertical head with 4" quill travel be fully utilized to mill closer to that slotted table? That is the issue and perhaps we find the solution here.

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