Starting Mini-Lathe Mods

[cfellows]

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/machine/pages/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

 

[Twmaster]

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.

 

[Blogwitch]

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=627.msg5085#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

 

[Twmaster]

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!

 

[cfellows]

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

 

[cfellows]

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

 

[Blogwitch]

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. Rof} Rof} Rof}

John

 

[cfellows]

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

 

[Tin Falcon]

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

 

[BobWarfield]

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

 

[Twmaster]

Chuck,

That post and holder came out very nicely done.

 

[cfellows]

Thx, Tin. The apron gear cover is on the list of things to do.

Thx, Bob. This minilathe is almost like a candy store with the number of mods and improvements that are shared on the WEB. I might spend the rest of my machining career tricking out this minilathe! :big:

Thx, TWMaster. Appreciate the comments.

Here are some pictures of the jig I made for grinding tool bits for the tangential holder. It's made from a hunk of aluminum to help conduct heat away from the tool bit. I use the jig with my 2" x 48" vertical belt sander. Cuts fast and relatively cool.

Chuck

 

[cfellows]

I decided to have a look beneath the covers at my new HF Mini Lathe today. No real surprises. Found where some of the red paint had bled under the carriage where it was riding on the ways and cleaned it off. The good news is that the carriage does fit flat on the ways. However, as Bogs and others have stated, the clamping system leaves a lot to be desired. So, I've decided to go ahead with the tapered gibs modification that was described on mini-lathe.com and also documented by Bogs on Mad Modder.

I plan to use 1/2" x 3/4" x 4" long aluminum for the clamps and 1/4" thick brass for tapered gibs. I'm also going to try this without the taper jig. Positioning the clamp in my milling vise pretty accurately at 1 degree will be pretty easy. Then, I'll used the milled clamp as the jig to taper the gib.

I also ordered a wilton, 5/16" keyless drill chuck with an integrated #2 morse taper shank. I will have to shorten the taper, but this chuck is noticeably shorter than typical keyless chucks and is advertised at .0019" runout, so I think it will work well for this lathe.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=360240116150&ssPageName=STRK:MEWAX:IT

Chuck

 

[itowbig]

i like those tool holders very simple and they work. i made something similar but i like your tool holders better. :bow:

 

[cfellows]

I'm getting along pretty well with my tapered gib upgrade. I'll post the last picture first so you can see what I'm trying to get to.

The clamps are made from 1/2 x 3/4 inch aluminum 4 inches long. The next picture shows me milling out the side where the brass gib will fit. I've lifted one end of the clamp and propped it up with a 1/16" thick piece of aluminum to create the angle. Should be somewhere around 1 degree, although the exact angle isn't critical. Here you see the first pass removing .050".

In the next picture, I've finished the clamp and am using it as a base to hold the brass gib while I mill it. By using the clamp as the base, I am ensuring that the gib taper will exactly match the clamp taper. Note that I've removed the 1/16" piece of aluminum and mounted the clamp in the vise with the base flat.

Despite my initial misgivings, I have to say that so far this project has been a piece of cake.

Chuck

 

[Swarf Rat]

This is an interesting thread. I think it's funny how modifying a Chinese lathe seems so natural while American iron generally seems more sacred.

 

[cfellows]

This is an interesting thread. I think it's funny how modifying a Chinese lathe seems so natural while American iron generally seems more sacred.

Yeah, I think it's been said many times that the chinese equipment represents a diamond in the rough and with a little work, can be made into a pretty respectable machine. The American iron isn't without it's faults since it's usually old, typically well worn, and occasionally abused. I bought an 11" Logan lathe a number of years ago. I had to have the bed reground, replaced the headstock bearings, most of the bushings in the gear train, and several of the gears. Also, the back gears had damaged teeth and I never did get those replaced or adequately repaired. However, having said all that, there's no doubt in my mind that back in 1952, that Logan lathe came from the factory ready to work with no mods or upgrades.

Chuck

 

[Twmaster]

Chuck,

That set of gibs is looking good. Almost seems too easy. I'll be watching.

 

[cfellows]

Thx, TWMaster. Yes, I've been pleasantly surprised at how smoothly this has gone.

Finished up the tapered GIBS today. Here's some pictures of some of the steps.

I liked the rounded cut-out Bogs did for the carriage drive pinion on the front carriage clamp. I didn't have a ball nose mill of the right diameter, so I put the clamp in my milling vise sideways and used a 3/4" end mill to cut the rounded grove from the side. Worked great!

Came time to make the adjusting screws and rather than make them from scratch, I used 6-32 socket head cap screws and pressed a small steel disk on the head of each.

First I chucked up some 3/8" solid rod and bored out a small length on the end about .004" smaller than the SHCS head.

Next I cut of a piece a little longer than the depth of the screw head.

Here I've got the screw mounted on the side of my little palmgren 1 1/2" toolmakers vise. The assembly is ready to go to press, uhhh, my 20 ton hydraulic press. I know 20 ton is a bit excessive, but I don't like to leave things to chance...

Here I've got the pressed-together assembly in the lathe, ready to true it up and trim it back to the right thickness, about .1".

And finally, here are the front and rear, respectively, gibs in place on the lathe carriage. As Bogs would say, it works a treat, very smooth and easy movement with no detectable play at all. I'm very pleased with the way this turned out and, as I said before, how easy it turned out to be.

Chuck

 

[Deanofid]

Looks like a clean and effective setup, Chuck. Well done.

..my 20 ton hydraulic press..

No one will ever accuse you of pussyfooting around. You don't need a 16 lb hammer when you have one of those things.
A man should be decisive! ; )

Dean