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Old 04-10-2010, 01:42 AM   #1
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Default Starting Mini-Lathe Mods

The adventure begins. I'm starting on a George Carlson quick change toolpost. It uses a 1" diameter round post to support the tool holders. A tangential clamping screw holds the toolholder in position on the post. This is a link to some pictures of this QCTP.

http://homepage.mac.com/bhagenbuch/m...es/freeby.html

I chose this design because it's takes up little real estate on the cross slide and is pretty simple to make tool holders for. I've removed the compound from my lathe because I don't use it very often. By attaching the toolpost directly to the cross slide, I will have greater rigidity and fewer places for things to move where I don't want them to. Anyway, it just removes a lot of clutter from a pretty small space.

Here's the beginning. I turned it from a 3" long, 2" diameter steel rod. I offset the column from the center of the base so there would be room for the screws that attach it to the cross slide.





Chuck



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Old 04-10-2010, 07:34 AM   #2
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Default Re: Starting Mini-Lathe Mods

That's a neat looking project Chuck.

Removing the compound does take a ton of slop out of that machine.

If you feel up to it I'd recommend lapping the slides on the compound and cross slide, check the straightness of the gibs and toss those silly carriage retainer system and replace the ridiculous jack screws in those plate with shims.

That will take nearly all of the slop out of the carriage.

Also, it's important you get a good carriage lock.

I did the above carriage mods to my 7x lathe and it made a huge difference. Night and day. I'd be happy to detail how at some point if you'd like.



Lastly. Make sure the carriage is sitting flat on the ways.



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Old 04-10-2010, 09:19 AM   #3
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Default Re: Starting Mini-Lathe Mods

Chuck,

I don't know how you feel about doing surgery to your lathe, but I did a large rescue to a really poorly one.

http://madmodder.net/index.php?topic=627.0

Yours should be nowhere near as bad as that, but I would thoroughly recommend doing the tapered gib mod, it totally transforms the running and rigidity of the machine.

Also, a little further into the post,

http://madmodder.net/index.php?topic...sg5085#msg5085

it shows how I did a quickie saddle clamp using just a brass ended bolt. The way they come from retailers who market such things, they are a rather bad design, and will still allow a little movement under heavy cutting. The way I designed mine, it locks it up solid and doesn't get in the way of anything.

It might be worth a little troll thru to see if it gives you a few pointers.

Bogs

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Old 04-10-2010, 08:17 PM   #4
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Default Re: Starting Mini-Lathe Mods

John, (With apologies to Chuck for a small hijack)

I found your post on Mad Modder about fixing Darren's lathe. What a terrific job. I was fortunate that the work I did to my old 7x took just about all the slop out. If I had a bigger mill I'd have gone about that as you did. Nice work!

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Old 04-11-2010, 12:24 AM   #5
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Default Re: Starting Mini-Lathe Mods

Mike, thanks for the comments and the suggestions.

John, I had seen the thread on MadModder where you had rebuilt Darren's 7 x 12. I'm not at all afraid of surgery and will be doing a few things as time permits. First thing is a decent tool post. I've also discovered a problem with High / Low range lever. It doesn't shift complete into high gear and will pop out of gear under the slightest load. I will also be doing some work on the carriage. It's a little tight right now and I like the idea of the taper gibs, although anything involving tapers tends to make me break out in a cold sweat.

I plan to use this lathe mostly for small, precision work. A lot of operations will involve drilling from the tailstock so that will no doubt require some attention and tuning. I also need to find a good drill chuck and short MT2. I like the keyless chucks, but they tend to be kind of long so I might go with a 1/4 or 3/8 Jacobs.

I also want to make an ER collet chuck for the spindle. I have an ER40 set so I may go with that. Or something smaller if that turns out to be too big.

Chuck

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Old 04-11-2010, 12:29 AM   #6
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Default Re: Starting Mini-Lathe Mods

Got my first tool holder made for the new tool post. It's a tangential cutter which uses a 1/4" bit. It started out as a 2" long piece of 1 1/2" x 1" cold rolled steel. The front is milled to a 12 degree angle, then the 1/4" wide slot is milled at a 12 degree angle to the side. The tool bit is ground at a 30 degree angle as measured diagonally across opposite corners. The bit needs further sharpening, but it cuts brass real good as it is.









I need to add a height adjustment stud and nut which will reference against the top of the post, like the Aloris style.

Chuck

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Old 04-11-2010, 02:14 AM   #7
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Default Re: Starting Mini-Lathe Mods

Chuck,

I wasn't implying you go that heavy route, just trying to maybe help a little.

With regards to the tapered gibs. Reading between the lines on a few sites and write ups about them, it seems that a few people have just gone ahead with the mod, without first checking the main casting out, and they are still getting the same sorts of problems they were having before doing it. So it isn't the cure all that everyone thinks. It needs to be a combination of things to be checked and done.

So if you did want to go that route, make sure you check out the main casting first, as I did.

I have done a couple of main bed true ups since doing that Darren post, one was only out by about 0.0015" and didn't really need doing, but he insisted I got it as good as humanly possible, so I machined it up, the other one did need it, it was about 0.006" difference in thicknesses along the bed, so really, it seems that it is pot luck as to whether you have a good enough casting or not to do the tapered gib mod, without first machining the bed to a good degree of accuracy.

As you may have noticed in that post, I showed a very easy way to get perfectly matching tapers, and I can assure you, it really is nothing to sweat over. Once you have the basic one cut, all others just drop into place using the basic one as a template and guide for machining.

I know exactly what you mean about the length of keyless chucks, and I can imagine it could cause a bit of a problem on a smaller machine, but now having gone over almost completely to keyless now (only my tapping stand has a 1/4" Jacobs keyed one, plus some of my air tools), I find them very robust and accurate.

But what would the world be like if we all used exactly the same tooling and methods, very boring.

Everyone to his own.

I have been pondering over whether to make one of those 'diamond' cutters for a while now, and seeing as to how you have made such a good job of yours, I might ponder it over a little more, for when I have some time on my hands.

John

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Old 04-11-2010, 02:55 AM   #8
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Default Re: Starting Mini-Lathe Mods

Thanks for the info, John. I will be approaching all upgrades and tuning cautiously and as needed. I also want to take of items which might become problematic soon and/or accelerate wear. I've read that the socket head cap screws used to hold the carriage clamps in place should be replaced with studs and nuts since the screws don't thread in very far and tend to wear quickly.

I really need to look over the lathe pretty well and get familiar with all it's little vagaries.

Chuck

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Old 04-11-2010, 03:03 AM   #9
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Default Re: Starting Mini-Lathe Mods

IMHO a cover for the apron gears is a must. just about any material will work. Plexiglas, poly carbonate. ,aluminum or steel. I used aluminum. I keep wanting to do a cam lock for the tail stock but have not yet another is the saddle lock .
Tin

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Old 04-12-2010, 06:33 PM   #10
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Default Re: Starting Mini-Lathe Mods

Lots of cool mods can be done to lathes. I like your QCTP, Chuck!

Let us know how that tangential holder works out for you too.

Bogs, I had missed your tapered gib conversion and enjoyed going back to see it. I would think it would be straightforward to add a very convenient saddle lock to such an arrangement. My RF-45 mill has tapered gibs and the locks work by applying additional pressure to the side of the gib. Seems like you could come in from the front of the apron and do a very nice job of that.

Long ago in a galaxy far away I started to make a lock that never got finished:

http://www.cnccookbook.com/MTLatheSaddleLock.htm

It had considerable holding force due to the combined leverage of a screw and the lever lock itself. I just needed to bolt it to the carriage, but ultimately lost interest. That's a less intrusive way to go. In retrospect, I should have completed it as I have reached for Ye Olde Wrenche many times before parting.

Cheers,

BW



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