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Member postings for Andy Carlson

Here is a list of all the postings Andy Carlson has made in our forums. Click on a thread name to jump to the thread.

Thread: Using a Graver
02/08/2020 20:48:16

These two videos are a good intro to graver honing and their use

https://www.youtube.com/watch?v=gK-5s5jAg0c

https://www.youtube.com/watch?v=gCb_ZHGb9ws

Thread: Can a small lathe handle a tail stock die holder?
01/08/2020 23:51:49

Maybe there is more than one type of tailstock die holder but the ones for my Cowells work well for smaller threads. They use the outside diameter of the tailstock barrel for guidance and slide along it as the thread is cut. A tommy bar provides the torque.

I cant recall whether I had the lathe running under power or used the nut that I made for the mandrel to drive it by hand, most likely handraulic to start off but maybe with some slow speed power once things were underway.

Not sure how the Sherline is for low speed torque but even if you do the job completely without power the die holder still has the advantage of holding everything in the correct alignment.

I was cutting an M6 thread though - a 3/8 thread involves shifting a good deal more metal and therefore maybe double the required torque so that may be pushing things.

My 3/8 BSW die is 1 5/16 diameter so it wont fit on the Cowells. The (hand) die holder for this size has much longer and thicker handles than the little tommy bar for the tailstock holder too, so 3/8 may be too much for a little lathe.

Thread: Starting Small Holes
30/07/2020 23:06:56

I've had plenty of success using a No 0 centre drill and conventional tailstock drilling to start small holes (down to 0.3mm). You don't need to go very deep at all, but you do need to make sure that the centre drill has not cut a 'donut'.

Sometimes I find that the centre drill can start with a 'donut' and will then 'find' the centre and make a proper dimple.

If you are working with an over-long piece of bar and the centre drill hole gets too big, you can always face some metal off after you have drilled your small hole.

That's what works for me anyway.

Thread: Silly issue with HBM parting blade
24/07/2020 18:14:47

An update... it works a lot better when the blade is the right way up

22mm to 1 inch of EN1A. Setup was very careful, using a square (again) to check the blade was vertical and perpendicular.

Ran into some chatter about half way through. Tried increasing speed from 253 to 456 RPM but that made it unbearable. Went back to 253 and stuffed the tool in harder... chatter gone.

It came out very well, no obvious sign of doming when inspecting the finished cut but for some reason the blade looked like it was veering off to the right during the cut - must have been an optical illusion brought on by numerous prior failures I guess.

p1070553.jpgp1070554.jpg

Thread: Faircut lathe tidy up
22/07/2020 08:28:56

I like the thing with the spanner - I've never thought of abusing my toys in that way.

On my lathe the tailstock dovetail locking nut is drilled and tapped for a simple lever made from round bar that screws in - same diameter as the lever in the barrel clamp. I've freed mine up so that I can take the lever out when I want to otherwise I cant take the tailstock off the bed without removing the leadscrew handwheel. You may find a threaded hole in one of the flats on your nut (or maybe not if it has been swapped).

I always keep a 3/8 Whitworth ring spanner handy (pre-war size so almost exactly 18mm A/F) - that size crops up all over the place on my lathe.

Thread: My Faircut Lathe
22/07/2020 08:12:25
Posted by Jacob Leonidou on 22/07/2020 07:59:55:

Im assuming by the right change gear you mean one with an even number of teeth?

Depends what you need for the job really - a gear with a number of teeth that is a multiple of the number of divisions that you need for the job.

Using the gears to lock the spindle is pretty quick if everything is to hand - just taking one nut off the banjo, adding a washer and then putting it back on. Cleaning the oil off the mandrel gear and chalking it in the right places takes a bit longer.

I wouldnt use this method (or the backgears) to lock the spindle for anything involving shock loads though.

Thread: Faircut lathe tidy up
21/07/2020 13:59:14

Hi Jake,

Have you tried grinding and using HSS cutting tools? I very rarely use carbide insert tooling and when I do they behave very differently from HSS. The usual advice is that carbide is for modern, fast, rigid machines. I use it only when trying to cut something difficult like cast iron or when I want to use my very long, thin boring tool.

I'm puzzled why you are having issues with your drills not going where you want them. If the centre drill is working OK then the point of your bigger drill should not be playing any part until you are a few mm deep... by which point the full width of the drill should be engaged so there should be no opportunity for it to wander.

Are you using a big enough centre drill? Another option is to step the drill size up gradually - the load on the drill is a function of cross sectional area so drilling, say, 7mm and then 10mm would share the work equally between the two drills. Don't pay too much attention to YouTube videos of bigger lathes that can dive straight in with a 1 inch drill.

Thread: My Faircut Lathe
21/07/2020 13:58:40

I didn't lock the spindle for that job because I wanted to turn it by hand as part of the operation. I do disconnect the power because at some point I WILL hit the lathe start button by mistake when intending to switch on the milling spindle.

I did lock the headstock spindle when using the milling spindle when cutting the flutes on the tap. Unfortunately there is no straightforward way provided by the lathe. The drive belt/pulleys dont help because the play in the bull gear peg or backgear means that the spindle can still rock a little. My answer is to use the change gears. I add an extra (bigger diameter) washer outside the gear on the first banjo stud and then put the usual washer and nut back on. This prevents the gear from rotating. The collar on the tail end of the spindle also needs to be tight to prevent any movement there otherwise the gear can rock a little bit on the locating pin. Select the right tooth count, add some chalk marks on the relevant teeth and you have a headstock dividing setup.

When done I disengage all of the locked drive train before plugging the power back in.

Thread: Silly issue with HBM parting blade
20/07/2020 20:17:23
Posted by Andy Stopford on 20/07/2020 20:05:16:

These are good, and don't break the bank:

https://www.chronos.ltd.uk/product/new-3-8-sq-shank-clamp-type-parting-tool-with-4-1-2-m-35-hss-chipbreaker-blade/

I think you probably need to get the dedicated holder for them to locate properly. No need to grind the top face of course, which makes life easier.

I recently bought one of these:

https://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Lathe-Accessories/Tool-Posts/Model-000-Parting-Tool-Holder-Horizontal

If you already have, or are thinking of getting, the appropriate QCTP, then I'd thoroughly recommend getting one to go with it.

Thanks Andy. I've loked at these but I dont think they will fit my toolpost as is... I have more of an SCTP than a QCTP. I need to unclamp the tool even if I just want to change the angle on the toolpost.

20/07/2020 20:14:27

Thanks. I have been quite careful with the parting tool, even getting a decent sized square out to check that it was perpendicular to the axis. I just didn't twig that the writing needed to be upside down. If I'd looked really closely at the blade I would have noticed but I didn't (until yesterday).

So hopefully my parting will improve but if it still fails to perform then I shall check out the insert tool - at a fist look it does seem like the 12mm 'standard type' one will be just the job. At the moment I've moved several jobs over to the vice for hacksawing but if things improve I might even consider making some washers which I would not contemplate just now.

20/07/2020 13:58:16

Yes, the acute angle of the parallelogram needs to be the one doing the cutting and it needs to be the fat edge, not the thin one. Having had another play with it I think there is only one correct orientation - writing visible and upside down.

Hopefully my next parting job will go better but it sounds like others have produced domed parting cuts even with this the correct way up.

I'd be quite happy to consider an alternative to the RDG blade and holder. Price (within reason) is not a big issue but so far I haven't found much else that will suit.

I don't have a rear toolpost on the Faircut at the moment and really need milling on the lathe to be going rather more smoothly before tackling a big lump of metal like that so for the time being I will persevere with the conventional toolpost.

The advantage of the RDG holder is that it does actually fit my lathe - the only part of the holder that needs to be below the 'shelf' is at the front end. In my case the 'shelf' is the top surface of the compound because the toolpost is open at the bottom. There is about 12mm between the compound top and centre height.

Edited By Andy Carlson on 20/07/2020 13:58:37

20/07/2020 08:52:32

Bought this from RDG at the Midlands show last October

p1070543.jpg

I've used it several times and have not so far had good results, usually ending up with a slightly domed end to either the job or the remaining bar. I've trawled the threads on here and tried all sorts of ways to improve matters.

I was thinking about buying another blade so last night I fetched the blade and holder out to measure it...

... and found that the thick edge of the blade was at the bottom.

So with mine the writing on the blade needs to be upside down. I havent tried it again but I'm hoping for better results when I do.

I can't remember if the blade was already in the holder when I bought it but if yours isn't performing then it might be worth a quick look.

I guess one could argue that in an inverted toolpost the writing would be the right way up. I'm not sure I'd be thinking like that even if I was using an inverted holder.

Thread: Inserted cross slide feed nuts
19/07/2020 09:20:23

Well that went fairly badly.

I've made a tap, all bar the square on the back end anyway.

Two issues... Firstly both corners chipped off the thread cutting tool - one after about 10 thou of cut and the other towards the end. I cut a bit deeper which should hopefully put the untidy part of the profile in a place where it will do no harm.

p1070525.jpg

The bigger and more puzzling issue is that my 0.0406 thou tool managed to cut wider grooves somehow. The threads measure a tad under 1mm rather than a tad over. I'm not sure why so that does not bode well for being able to correct the problem.

p1070523.jpg

In spite of the issues I decided to finish off the tap and cut the flutes using a 3mm ball end mill in the Potts Spindle. There was a 40T gear on the lathe spindle so I decided that four flutes seemed like a good number. The square for the tap wrench is still to do because the poor little Unimat motor was getting rather warm.

p1070531.jpg

The tap almost certainly won't work for an unworn feed screw but hopefully I will at least be able to find out if the tap approach can produce a cross slide that actually works, albeit still with a worn feed screw.

18/07/2020 13:12:51

@Hopper: yes, hole measuring... tricky. The nut goes in for about 3mm easily so the fat end is somewhere around 507 thou. I have resolved to make another plug to measure the thin end but right now there is a nut in the way and the lathe occupied by a rather blank looking tap. 'All over the place'... not so sure. Assuming for a moment a parallel hole at the 'fat diameter' and the nut goes fully to one side of the taper then that's 1.5 thou in 14mm (nice mixed units there) which I work out as 1 in 367. There is of course an unknown amount of distortion and a bit of material being scraped off so the pressing is definitely still on the suspect list.

TBH after trying an approach involving doing all of the accurate work in the lathe chuck and finding that it didn't work out too well I'm becoming more convinced that I need to do things in a similar way to the way that Faircut did them... and given the eccentricity in the original nut it seems that 'in situ' was definitely how it was done.

@Nigel: I've struggled to find much concrete info about square threads (as opposde to Acme or modified square). The stuff I've found is fairly vague and hand wavy and says that the screw should be made to size and the nut should have about a thou of clearance. I've gone to plus two thou on the major and minor diameter because it should make no difference to the backlash but your post is the first time I've seen 10 thou quoted. The major diameter is not a big issue - it's just a matter of leaving enough meat in the surrounding nut. 10 thou on the minor seems like a lot - that's a quarter of the depth of the thread.

18/07/2020 11:13:39

The nut was based on measurements of the original one that came out. That was a bit uneven but has a taper from 511 thou at the fat end to 506 at the thin end. The lower measurements at the fat end are 509 thou so I was cautious and made the new nut to 509 thou tapering to 506.

To be honest though the clearance is not the big issue - that could be solved by changing the tolerances when I make the nut. The alignment issue is the big problem and I think that for this I need to do the finishing cuts on the nut thread in situ... which will hopefully also mean that I have control over the final major and minor diameter too.

Whether the alignment issue is coming from the pressing operation or the hole is not clear but I did press it out and back in again after turning through 180 degrees. That made it worse, but still to the same side... so I removed it again and put it back how it was originally. I think this makes it pretty certain that the error is not coming from the nut.

17/07/2020 23:13:36

A little update on the cross slide nuts...

I've made a short section of male thread from some 3/8 steel bar so that I have an unworn example to test with. This did not turn out perfectly. Practice nut No 2 went most of the way on with a healthy degree of drag but is quite tight on the last half inch. As far as I can tell this is the result of pitch error. I noticed when tidying up the point where I stopped threading that the tool did not pick up the thread correctly at that end even though the screw cutting train had not been disengaged and the backlash was going the correct way. I can only conclude that the tool was pulling itself ahead of the leadscrew and into the backlash a little.

For practice nut number 3 I made another threading tool from the 3mm HSS mills to 1 thou over the nominal groove width. I was expecting the usual struggle and fettling when I finished cutting but the test thread screwed in at the first attempt. I foolishly allowed myself to start thinking that I was getting the hang of it and moved on...

Practice nut 3 has been cleaned up and pressed into recess in the spare saddle. That put an immediate stop to any impression of progress. Even the worn feed screw would not screw in without a major struggle. Clearly the nut had compressed significantly. My plug gauge would not go in. A quick touch with a tapered reamer allowed the plug gauge in and the worn screw went in after cleaning up a slight wear ridge that was making it oversize. This revealed that the screw was not quite parallel to the slides - an error of about 1mm in 90mm.

I've concluded that trying to make a correct concentric nut, press fit it into the saddle and expect it to work is not going to fly. I've now started making a tap which hopefully will be able to finish cut the nut threads in situ and allow the correct alignment for the feed screw. The tap needs over-width threads and underwidth grooves... so another threading tool was made. Including the rejects I think I've made six so far. I'm glad I'm using 3mm HSS - it would take a lot longer to make six of them from 6mm HSS.

Thread: My Faircut Lathe
14/07/2020 19:00:21

By popular damand (well, one person)... I thought up a fairly thin pretext to deploy the milling spindle. I wanted to see if I could use it to Higbee the end threads on the practice cross slide nut. The setup was all done very much by eye, listening to the note of the (not very powerful) Unimat motor and adjusting the angle of the lathe mandrel by hand. The cutter is a 3mm Proxxon one held in an ER16 collet.

p1070520.jpg

Seemed to work, although I chickened out short of going quite as far around the thread as I really should and slightly marked the second thread on t'other end. Hardly a big challenge but it's a start.

p1070522.jpg

13/07/2020 22:43:56
Posted by Jacob Leonidou on 13/07/2020 12:52:09:

haha I need to read more books, period. Well good luck with it all, please keep all fingers clear. Wouldn't mind seeing some action pictures.

Will do when there is something to show. The plan for upcoming jobs has more plot twists than a thriller novel (but rather less excitement) so the milling spindle has been stood down for the time being. It will come out again in due course.

Thread: Faircut lathe tidy up
13/07/2020 22:39:16

Hi Jake,

My tailstock certainly needed alignment when I first got the lathe. IIRC it was aiming low and off to one side.

I think it's pretty impossible to make it perfect in real use because it needs to reach across the cross slide so I usually find that I have quite a lot of the barrel sticking out, which naturally causes it to droop. Several things can help - once the tailstock is adjusted then most come down to maximising rigidity - less barrel sticking out, shorter drill, eliminate the chuck by using drills with integral Morse tapers (not sure how easy these are to buy but I have several from a garage clearance). Doing the barrel clamp up (without actually locking it) can help a bit too.

Probably the best bet is to make things as rigid as poss and then use the biggest possible centre drill to start the hole. If this is rigidly held then it should make a concentric hole even if the tailstock aim is off because it will work like a boring tool... but your description of 'orbiting' does not convey an impression of rigidity.

Bigger drills will be longer so rigidity becomes even more of a challenge so it's essential then to start the hole with something short and rigid.

I don't think I'd go up to a 3/4 drill in the tailstock on my lathe. As a very rough rule of thumb I would not rely on the taper to hold for any drills that are bigger than the opening of the taper itself. So 1/2 inch is the biggest I've used at that end of the lathe.

One more thing springs to mind... it's possible for the headstock alignment on the Faircut to be wrong. The headstock is held down by one bolt underneath in the middle. There is (should be) also a locating pin at the back of the headstock at the right hand end. If the pin is missing (mine is) then the whole headstock can rotate around the single fixing bolt especially when doing stuff that causes sideways force like milling. If the pin is present then the alignment should be constant... either always right or always wrong. You can check the alignment using a DTI (clock gauge) or better by making a test cut and then measuring to see if you made a parallel bar or a taper.

Regards, Andy

Thread: Disposing of a Lathe and (many) related items
10/07/2020 21:16:28

Sounds like you are already very well organised so keep it up.

Figure out what 'belongs' with the lathe and whether there are any other big ticket items that would make sense as a separate sale... other machines, sets of taps and dies for example.

I'm sure if you have any 'what on earth is this?' questions then you can ask them on here without annoying anyone.

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