Author Topic: Cross slide feed revamp on my ML7  (Read 12617 times)

Offline arnoldb

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Re: Cross slide feed revamp on my ML7
« Reply #15 on: August 02, 2015, 09:10:05 PM »
Thanks Jo - maybe I should mill a pocket on the top to make sure tools stay there when put down...  Seeing as I've used the front end of the cross slide for keeping drills lying around, I'm sure the flat top will see a lot of use  ;)

Nearly a month without shop time...  At least a bit today.

I had a bit of time to think things though, and decided to use a "Metal Removed" scale, and doing some quick calculations, decided on a 0.05mm scale.  On a 38mm diameter dial - for which I have stock, that leaves divisions that's nicely spaced as well - at about 1.5mm apart for the 80 divisions needed on the dial.  Making a vernier collar to take things down to 0.01mm based on the dial's divisions is also easy; that runs to "100 divisions" at 1.2mm spacing, so also easy to make and see.

First off, the vernier collar - just some 40mm aluminium bar faced and turned down to 38mm OD:


Then I set up the lathe's banjo with a 60 tooth gear on the spindle side, driving a 30 tooth gear coupled to a 50 tooth gear to use as the index, along with the crude detente I made for a similar job at Tel's suggestion a while ago.  The 50 tooth gear even still has the permanent marker markings I made on it  :Lol::


I used a very sharp 60o threading toolbit mounted side-ways to cut the markings about 0.1mm deep.  In theory, only 5 vernier markings is needed for the layout I chose, but I cut 10, with a long marking in the middle for 0.  When I made the scale for my rotary table, I used a similar layout, and have found it extremely useful for working on either an in-feed or out-feed:


Next I bored out a hole in the center - this is to clear all the working bits of the cross slide once mounted to the cross slide bracket.  The engravings also got a tidy-up with a bit of sandpaper and then Scotch-Brite to dull the finish a bit - in use, I don't want the scale to be shiny, as that makes it more difficult to read under the shop lights:


The lot was taken to the mill, mounted on the rotary table (convenient to mount the lathe chuck in my shop), the center of the hole located, and the table rotated to get the zero-line in line with the mill spindle with the X axis at zero and using a small drill to match up to the line.  Just me being lazy to get the workpiece oriented so that the mounting holes would come out fairly square to the zero line on the collar. Mounting holes drilled at 3mm - after this they were counter bored to 6mm to allow room for M3 cap screws to go below the surface:

The vernier collar was then parted off. 

The same bit of stock was then turned down to 38mm to about 6mm away from the chuck, and the rest toward the chuck just skimmed to clean it up.  Then a 40 tooth gear was marked with permanent marker to show the gaps where the 0/1/2/3 mm marks must go (the 0/2 and 1/3 are in the same location) - those have the extra dots on the gear hub, and the 0.5mm spacings are the two without markings on the gear hub.  The 0.1mm markings would come at every second gap in the gear starting from the One markings, and the 0.5mm markings from every second gap starting from the gap just after the One markings:


Actually, it's easier to do than describe - the 40 tooth marked gear was mounted in place of the 50 tooth one shown earlier, the detente adjusted, and the motions followed.  All done here:

The 0.5mm marks are a tad too short  :-[ - that's what one get by just eyeballing things.

The center of the workpiece was bored to 12mm about 15mm deep - this is for space for the pressure spring I want to use- and then drilled right through 6mm to allow for the feedscrew threads.  The index markings was cleaned up, and excess stock sawn off on the bandsaw.  Then it was mounted back on the lathe - this time using the chuck's outside jaws and a bit of aluminium can strip for protection.  There's two reasons I used the outside jaws: 1.  The "curve" on the inside jaws when chucking up like this is bigger than the workpiece, and together with the can strip, it provides good clamping force without damaging the markings.  2.  My three jaw chuck's outside jaws are pretty accurate across the clamping range.  If that wasn't the case, I'd have used the 4-jaw and chucked up the workpiece in that.  The back of the workpiece was then turned down to get rid of the bandsaw markings, and then bored to make a friction surface / locating ring that will match up to the actual handwheel later on:


My scissor knurling tool cannot get close enough to the chuck to use in any of the previous operations, so I mounted the workpiece on a home-made expanding mandrel to get the needed distance and gave it a bit of a knurl with 0.5mm diamond knurls.  I'm well aware that no medals will be won for this job - according to "judging criteria" I've seen, it's too fine a knurl for this size of job, and the tops are not "well-formed and sharp"...  A straight knurl is actually what's required for this application, but I've not gotten around to get a wheel for that, and didn't feel like making one.  I could just have indexed a straight knurl similar to the scale engravings, but that's just too much work for a lazy sod like me.  This fine knurl, only partially done to depth is easy on the fingers in use, but gives a good grip even with oily fingers, so it's practical in use, and completely adequate for my needs:


For today's work, I ended up with this lot - not much, but extremely gratifying:


Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

Offline Don1966

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Re: Cross slide feed revamp on my ML7
« Reply #16 on: August 02, 2015, 09:30:03 PM »
They look great Arnold and it may not look like much but very time consuming I do know that.

Don

Offline arnoldb

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Re: Cross slide feed revamp on my ML7
« Reply #17 on: August 09, 2015, 10:59:13 PM »
Thanks Don.  It actually went quicker than I'd thought it would - Indexing off the gear train is a lot quicker than using the dividing head, and there's no need to count turns  :Lol:

A bit more done this weekend.  On Saturday I started off with the handwheel from some 60mm aluminium stock.  The cut end was very carefully faced with extremely light cuts at low speed to "just" get a flat face , as it was sticking out of the chuck quite a bit.  Then center-driled to get support for the tailstock center, and after that I could lay into it and get some turning and knurling done.  The curvy bit was step-turned and smoothed out with a file, and the boss on the face matches up closely with the recess turned into the micrometer collar earlier on:


It was sawn off from the parent stock, chucked in reverse, and faced.  A 16mm diameter recess was bored half-way through it, and the rest was drilled and tapped M6 to match the threads on the feedscrew.  The recess is big enough to allow an M6 nut to be screwed into the recess and tightened with a socket to lock the handwheel to the the feedscrew.  A quick assembly check - the vernier collar isn't mounted yet:


Today I did a bit more - though there's not many photos to show it.  The handwheel was drilled and tapped for a handle and counterweight.  The vernier collar's mounting holes were drilled and tapped.  I scrounged a nice stiff 12mm OD, 7mm ID spring from a "retired" multi-function printer, and shortened that by trial and error to provide a firm-but-easy-to-adjust pressure on the micrometer collar with things assembled.  I still need to finish the crank handle and counterweight, and there's a fair amount of finishing and cosmetic work left to do, but things were finally at a point where I could assemble the lot on the lathe and test it:


 :whoohoo: - Everything works smoothly and feels really good when operated.  I mounted my trusted 0.01mm Mutitoyo dial indicator and checked things out:

Total backlash, without any "fine" adjustment is down to less than 0.05mm - that's good with me.

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

Offline Jo

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Re: Cross slide feed revamp on my ML7
« Reply #18 on: August 10, 2015, 07:19:00 AM »
That looks good  :ThumbsUp:.

I won't be long before the top of the bracket looks the same colour as the rest  :mischief:

Jo
Usus est optimum magister

Offline Ian S C

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Re: Cross slide feed revamp on my ML7
« Reply #19 on: August 10, 2015, 01:27:13 PM »
If you want a fine straight knurling tool, it's easy to make one, it will take 10/15 minutes.  You need to find a disposable lighter, Bic ones seem to have straight grooves, you must make a wee bush to go in the wheel, then get a bit of steel and make a forked end in it, drill it cross ways for a pin, or small bolt, put it on the lathe and get knurling.  I,v got two of them(the gremlins got the first one, so I made another, they bought back the one they borrowed.... you can't win).  Idea borrowed from Stan Bray's book "Introducing the Lathe".
Ian S C

Offline Don1966

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Re: Cross slide feed revamp on my ML7
« Reply #20 on: August 10, 2015, 03:54:41 PM »
Nicely done Arnold and it was enjoyable to follow along. I do enjoy tool making myself. ...... :ThumbsUp:

Don

Offline arnoldb

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Re: Cross slide feed revamp on my ML7
« Reply #21 on: August 16, 2015, 05:12:06 PM »
Thanks Jo, Ian & Don  :)

Ian, I forgot about the lighter wheel knurl - and I have a whole bunch of old Bics lying around...  Actually I must just pull my finger from "in there" and make a proper knurl; I've got loads of silver steel lying around and it shouldn't take too long to make one.

Today I made the cranking handle from some aluminium and the counter weight from stainless steel, as I wanted the counterweight to "stay out of the way" in use:


Next followed some finishing touches.  The front of the bracket was rounded over at the bottom, the feedscrew was trimmed to proper length on both sides, and all corners were generously knocked off with a file.  I stamped numbers on the micrometer dial as well.  Then I took a family photo of all the parts:


Everything was assembled again, and adjusted with a bit more care than last week - backlash is down to 0.01mm which I'm pretty pleased about; the feed nut isn't even split yet for adjustment; I'll do that at a later point when things have loosened up again:


Some turning tests followed, and I'm very pleased with the results.  The direct readings works a charm; I arbitrarily turned a bit of rod down, measured it at 10.27mm with a micrometer, dialled in 0.27mm, turned and measured 10.00mm on the dot with the mic.  The slightly lower feedrate compared to the standard feedscrew works a treat for parting off as well; a couple of parting tests gave a nice "feel" and extremely good results.

Now it's time to clean and service the machines for a change, and pick an engine project - it's a long time since I built an engine...

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!