Reconditioning a Relmac lathe

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Originally Posted by Kip

I was thinking of a bar of plaster in the tailstock ready shaped and then pushed up to the headstock...Did that make sense?

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Not really, although i can see where you're coming from. The challenge is that the tailstock is MT1, spindle is 1.25" diameter. You'd have to embed an MT1 arbour into the plaster when casting it in a 1.25"ID tube and how would you ensure its dead central and in line? Seems a lot of hassle to me...

Also a 1.25" reamer is about £70 which is way more than its going to cost to have the spindle reground...

I had a quote from a 'mobile line-boring' company who normally do much bigger jobs but it was silly money. If I had another working lathe and a milling machine I suppose I could make up a line-boring jig using 2 bearings supported on the cross-slide to hold a boring spindle with a small pulley to be driven from my 3phase VFD'd motor and using the tailstock centre to align it... but then if I had another lathe I could take a fine cut off the spindle, although getting an accuracy of 4 - 5thou over a 12" length would probably be tricky.

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Originally Posted by Kip

Here's me thinking everyone has lots of reamers and a working lathe ;) (mine was out of action for 2 days waiting on belts and I was beside myself) My previous one made the rivets for the Titanic.....I sure don't miss it :D Although I discovered that a LH thread requires modification to my 1992 Warco! Oh well it's all fun....Or savage amusement lol

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Well when I get this one up and running a LH thread will be easy.... :) can do either, in imperial or metric....

The spindle is going in to be reground tomorrow AM early and I hope to get it back next week. They reckon it'll be 2h work inc setup as they'll need to make a MT3 arbour to hold the nose end and chamber the inside of the tail end to hold it on the grinder centres - they do all precision grinding between centres.

So this weekend I'll turn my attention to the Gamages lathe and get that set up on a board so I can try it out. At least the motor is running!

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Originally Posted by irving2008

Well when I get this one up and running a LH thread will be easy.... :) can do either, in imperial or metric....

The spindle is going in to be reground tomorrow AM early and I hope to get it back next week. They reckon it'll be 2h work inc setup as they'll need to make a MT3 arbour to hold the nose end and chamber the inside of the tail end to hold it on the grinder centres - they do all precision grinding between centres.

So this weekend I'll turn my attention to the Gamages lathe and get that set up on a board so I can try it out. At least the motor is running!

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Any joy with the Gamages lathe ? how did the regrind go ?

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Originally Posted by CheekieMonkies

Any joy with the Gamages lathe ? how did the regrind go ?

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Should get the spindle back on Wednesday....

The Gamages started out well and went downhill.... :(

http://www.kisolutionz.com/ttforum/l...MG_2956_1k.JPG

http://www.kisolutionz.com/ttforum/l...MG_2957_1k.JPG

Working on a strap to repair it... to save repeating myself, look here: [ame]http://www.practicalmachinist.com/vb/showthread.php?t=160002[/ame]

Got my spindle back :)

http://www.kisolutionz.com/ttforum/l...MG_2963_1k.JPG

Cost much less than expected cos they did it as a 'homer' for cash as a favour and not through the books. All nice and shiney and smooooooooth :) and good within .0002 thou (well much tighter than I can measure anyway)

So weather permitting its 'pouring time' again this weekend!

BTW, anyone got a mill :rolleyes: I could get access to, as I'm not likely to get a milling setip working any time soon (apart from the lack of space!)

What about one of these:
http://www.mycncuk.com/forums/photop...1_DSC04561.JPG

B'n'Q sell one like it for around £50, this one i use and it seems to be the best i have seen for that price range, or do you need a proper "Mill" ?

The spindle looks sweet mate, cant wait to see what this weekend has to offer !

A proper mill - something that'll take a couple of cubic inches out of a casting in a relatively short space of time...

It could wait till I get the 'big' lathe running...

Didnt think B&Q sold milling machines, nothing on their website and cant say I've ever seen them. I've got a cheap pillar drill from B&Q - bought in the sale a couple of years back, reduced from £75 to £15 last one and with a damaged box but its not exactly a solid bit of engineering, struggles with 6mm into cast iron or 8mm into steel.... but hey, the drill bits cost more than the drill!

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Originally Posted by irving2008

BTW, anyone got a mill :rolleyes: I could get access to, as I'm not likely to get a milling setip working any time soon (apart from the lack of space!)

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Rather depends on where you are.

I'm due south of London, stop just before it gets wet.

About ten miles west of Brighton.

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Originally Posted by Kip

Anywhere near Yorkshire?

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Brighton's a lot nearer... :)

Any advancments ?

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Originally Posted by CheekieMonkies

Any advancments ?

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Not so far, family things got in the way yesterday :( and its too windy outside today to do a pour.. cant even keep the burner alight! And i dont want to do it indoors there's nowhere to run if it goes wrong! So I'm installing the 3phase motor and tidying up wiring...

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Originally Posted by irving2008

A proper mill - something that'll take a couple of cubic inches out of a casting in a relatively short space of time...

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Hi I’ve got a mill and travel from north down to Kent fairly regularly M6, M1, M25, A2M2

Would you be interested in me doing some machining?

Kevin

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Originally Posted by keebo

Hi I’ve got a mill and travel from north down to Kent fairly regularly M6, M1, M25, A2M2

Would you be interested in me doing some machining?

Kevin

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Kevin, Thanks for the offer. I'm going to look at a short term fix first but will come back to the milling out option if that proves unsatisfactory.

Nice mill btw...

regards,
Irving...

Well despite my best endeavours nothing got done the last 2 weekends mainly cos of family things but the weekend before last was just too windy.

Anyway, was going to do it this weekend. Got it all set up and then decided to DTI the spindle from the slide and see how parallel to the ways it was. The end result was it was 0.15mm out in 80mm, but I couldnt decide if that was the tailstock being out or something else. As you will recall from a previous post i am holding the chuck end of the spindle in place using an MT3 deadcentre located in the centre hole of a JT6/MT1 arbor held in the tailstock. But the tailstock wouldnt normally be at that end of the bed so i cant tell if the error is due to the tailstock, the centres or something else...

So I decided to order an MT3-MT1 sleeve and an MT1 parallel test bar. The plan is to hold that in the spindle and locate the far end on an MT1 centre in the tailstock. That way the bar will better show the true direction of the spindle over a 300mm length and will allow me to DTI it from the slide more accurately.

The runout on the reground spindle is impressive. It doesnt even move the needle on the DTI so better than 0.0025mm!

Hopefully next weekend!

Well i ordered the taper sleeve and test bar from RDG on Sunday eve, shipped out to me Monday, arrived this morning. Test bar wasn't as long as I expected, 100mm not 300mm :( Anyway, I fitted it all up for a trial and with relatively little adjustment was able to get 0.02mm across an 80mm traverse with .01mm runout on the taper sleeve. Quite pleased with that (<0.01degrees taper), so no more than 0.1mm out (4thou) over the full bed traverse. So will set it all up tomorrow night (and try to remember to take some pics) to give it time to dry for the weekend...

well sods law prevailed... I decided before I finally did the pour that it might be a good idea to check the tailstock to spindle relationship when the lathe was actually bolted down and level... well suffice to say the relationship was far from level in the horizontal plane and when the lathe was bolted down and the spindle actually level the good parallel I'd measured went out the window. Eventially after much measuring and cursing I discovered that the lathe bed is twisted and needed packing about 3mm on two opposite corners when I bolted it down. This means I will have to pour the bearing with the lathe bolted in place to the bench. Once bolted down and leveled I then found the saddle would stick badly at a couple of points so I removed all that and cleaned it up, refitted and readjusted the horizontal and vertical gib strips. I also tightened up the leadscrew preload to give 4thou clearance and discovered a hitherto unknown screw that tighens the clasp-nut onto the leadscrew, which allows a modicum of backlash removal. Now it all runs much smoother than before if somewhat slightly stiffer than I would like... taper now measures 0.04mm in 80mm but its more consistent and doesnt vary with saddle travel direction. I also discovered that the tailstock has an adjustment underneath so I'll take the final taper out once the lathe is up and running.

By the time I'd done that on Saturday there wasnt time to do much else and today was a washout (literally and metaphorically) as family things got in the way again...

Hopefully next weekend...

Well a weekend came and went... but today I managed to get the day to myself, as SWMBO went shopping with daughter...

So rechecked everything, was still as I'd left it 2 weekends ago. I'd already decided that the main problem before, primarily, was not enough heat in the bearing housing so the metal set too quickly. So I wrapped the whole lot in loft insulation and pointed my 500W heat gun into the centre and left it to cook for 30min. That got it nice and hot. Unfortunately I didnt take any pics cos my camera battery was flat and I couldn't find one of the kids. Anyway, melted the metal, skimmed the slag off the top (using a bit of wood, not metal apparently is good practice) and proceeded to pour. Now being on my own (which prabably wasnt a good idea) I was trying to hold the heat gun in one hand and the ladle in the other so as to keep it all hot as it went in... this worked but it was impossible to pour slowly as I had intended and some 'missed' the hole and ended up on the drip tray. But the two vents seemed to work and hot metal bubbled up all three holes at the same time...

Left it to cool, by which time son was home and found me his camera. So banged the spindle out with a rubber mallet... its a tight fit.. i found a quick reheat helped to release it...

took the first 'dam' off...

http://www.kisolutionz.com/ttforum/l...SCN1787_1K.JPG

Well that was looking good... but wait a mo, whats that down in the RH corner... took the other dam off.... :(

http://www.kisolutionz.com/ttforum/l...scn1788_1k.jpg

bu***r, almost got it right... oh well set up for another go...

http://www.kisolutionz.com/ttforum/l...scn1790_1k.jpg

Dont' know if that problem was lack of heat down there, or an airlock. So for next time (tomorrow hopefully) I'll put a couple of additional air vents down there... like this... note I'm only using the firecement to form the vents. Standard bathroom silicone selaer is all thats needed to fix the aluminium sheet 'dams'... it stands 380degC no problem...

http://www.kisolutionz.com/ttforum/l...scn1791_1k.jpg

http://www.kisolutionz.com/ttforum/l...scn1792_1k.jpg

more to come tomorrow hopefully...

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Originally Posted by Kip

Looks like a partial fill Irving :(

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Thanks Keith for that deep insight :D...

Ok, so the story continues...

Here's some pics of the heating arrangements...hot air gun and some rockwool...

http://www.kisolutionz.com/ttforum/l...scn1793_1k.jpg

http://www.kisolutionz.com/ttforum/l...scn1795_1k.jpg

Note the cute funnel (made out of ally) to try and avoid spillage. Oh and did I show you my VFD install on the wall behind (RH side pic 2)

So... heat it all for 30min (till it all too hot to touch) while melting the metal in the ladle and pour slowly using both hands this time...

and leave to cool....

http://www.kisolutionz.com/ttforum/l...scn1796_1k.jpg

Well it clearly filled to the top on both sides and in the centre... and a probe with a scriber in the smaller vents shows there's metal in the bottom of the upper vent... but nothing in the lower :( ... oh well nothing to do but remove the dams and have a look...

http://www.kisolutionz.com/ttforum/l...scn1797_1k.jpg

this side looks OK, note the slot caused by a shim in the bearing housing slot... that worked well and made it much easier to get the spindle out... nice clean bearing surface from this side...

but OMG once again a failure from the other....

http://www.kisolutionz.com/ttforum/l...scn1799_1k.jpg

it can't have been an airlock so I can only assume it wasnt hot enough and the metal solidified too soon - you can see there is a nice curved flow edge. Also note the nice clean edge to what would have been the 'slot'.

Clearly I need to find a way to get the lower half of the cavity hotter, but I'm getting closer and I can see this will work eventually...

just takes a good hour to chop it all out again and another 2 or 3 to line it all up and prepare it and then 24h to leave it to dry (even with a 10min blast from the heat gun)... so next attempt will be next weekend as I wont have time during the week.... :(

What can I say? Nemo repente sapit, your perseverence is amazing :D

The problem may be asking the metal to go all the way around and then rise to fill in below the slot. Perhaps is you added a channel on the ends so it could go around the slot ends so everything flowed downhill, or, up ended it and put a fat sprue over the slot with a diametrically opposed vent?

Keith/Robin

Thanks for your comments.

I am not entirely sure I understand your point Keith, I don't think its an airlock issue as there was plenty of room for the air to come out, I am pretty sure its a heating issue, thats the furthest corner from the fill.

You will note in the previous attempt (which didnt have the shim all the way into the spindle) that that side filled OK but the other side failed. I am wondering if the best option is to have two fill points, one through the top and one to the side to fill from the bottom up initially and then from the top.

Keith, your casting experience is far greater than mine and this is clearly a 'casting' problem so I am grateful for your thoughts. I am a little loath to heat the metal a lot more as I have read that overheating causes some of the trace elements such as antimony and bismuth to leach out, but I don't know how hot that means - I cant get anywhere near hot enough to boil it!

I will persevere... it will come right one day...

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Originally Posted by Kip

Irving, My thoughts are that the shim (shown in red) needs the ends trimming to the yellow line to allow a fast and full fill, I think with that modification you will have success.

One uninterrupted pour till metal flows out of the vents (funnels?) maybe use a plumbers mat under the work area to catch the excess metal.

You'll know when you have overheated the metal...Fumes and smoke will start to emanate :)

Keep safe and enjoy the experience matey :beer:

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I think you may be right, but if that was the case why did it work OK at the other end? Maybe something to do with heat distribution... and when I did have the gap in the shim it failed to fill OK on the other side????

Obviously I'm not chanting the right incantations when i do the pour. The main issue with cutting the shim is that it makes the shaft very hard to remove if its solid metal round it. What I might do is taper the shim back towards the outside so that there is a full gap by the shaft and I can get a junior hacksaw blade in the slot to remove the metal where the shim tapers to fully slot the bearing to remove the shaft

I did have one uninterrupted pour... it flowed out four of the 5 vents but not the last one as the pictures show!

Funnily enough I was thinking on the lines of a wooden dam and it would be easier to make into the right shape - what I actually need are two 50mm x 3mm discs with a ~37mm dia x .5mm deep recess and a 32mm central hole with some cutouts for vents... maybe I should make some up...

Cuttlefish bone is clear proof that God does low temperature metal casting. If He didn't why would anything so wonderful exist.

You can sand it flat in a trice, push things in and it takes the shape, doesn't bend, soaks up dross, doesn't melt, doesn't distort when hot, lets trapped air out at the join and has no thermal inertia :D

and where would I buy it???

True, budgies trim their beaks on it, but the big ones go to the goldsmiths. Any problems finding it I can get it off the beach, just have to wait for an onshore wind. We have a thriving cuttlefish population. It weighs nothing :D

It has a thin horny rind on one side, the good stuff is in the middle. Pure white.

Well its been a while but last weekend I finally managed a further 2 attempts at pouring this bearing (getting a dab hand at setting it all up now)...

Anyway, got what I was fairly sure was a good one - I used a digital temperature probe from Maplins (£19.99, also doubles as a cheap multimeter to keep in the garage to save my very expensive one getting damaged) to measure the temperature inside the spindle and heated everything til that was 220degC. But it takes an hour or more to cool down to be able to be touched and I didnt have time to get the spindle out then. But I was working at home today so took an hour or so out this evening to get the spindle out (blowtorch needed to exapnd things a little to free it off) and start the clean up.

I am mightily impressed with the result....

http://www.kisolutionz.com/ttforum/l...scn1801_1k.jpg

http://www.kisolutionz.com/ttforum/l...scn1802_1k.jpg

This is after I cut and tidied up the slot (which makes it easy to get the spindle in and out now) and about 1/2 way filing down the excess on the bearing ends. The bearing is so close that 1/4 of a turn on the pinch bolt goes from 'mildly stiff to turn' to 'locked spindle' and the play is <.0005" on the DTI...

Next job is to clean up the ends and then do a spot of scraping on the bearing surface (although I am hesitant to do too much of that, in fact I am tempted not to do any right now since its so tight and the journal is freshly ground)

Looks like I'll have a working lathe in a few weeks....

Any advances on this mate?

Hi Lee,

Been away on hols, just got back tonight.

Had the lathe up and running but got to sort out some vibration which I think is due to the rear bearing . the new front one is fine and run in now. The other prob I have is that the runout on anything held in the chuck is massive - think a new chuck is needed.

ahh i c, is a new chuck going to be a problem or are they quite generic?

Lee,

The chuck isn't the issue... machining a new backplate may well be because of the non-standard spindle thread (1.25" x 12tpi).... I'll probably need to get it done professionally :(

Why not remachine the existing back plate?

Unless you need to remove a lot of metal to make it suitable for a new chuck, then it should be fine.

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Originally Posted by m_c

Why not remachine the existing back plate?

Unless you need to remove a lot of metal to make it suitable for a new chuck, then it should be fine.

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Because a modern chuck requires a larger boss. Currently it has a 4" chuck with a 3" recess but modern 100mm chucks have an 80mm recess. Also there is possibly a problem with the backplate itself, but until I can clamp it up on a known good machine to measure both axial and radial runout accurately I can't be sure...

i c thabnks for teaching me yet something new i apprecate it. Hope you can get everything sorted out mate.

At the risk of resurrecting this thread, I have been asked if its possible to redo the bearings on another similar lathe. Those who followed the original story will know that this was no mean task and not one I really want to revisit. However I was thinking about how to make it easier. I now know that the original lathes were line bored on a huge jig (see pic) but replicating that isnt going to be easy. I was thinking, maybe it would be possible to make a jig to line-bore the bearing insitu once they had been part filled with white metal around a mandrel smaller than the required bore.

The mandrel would be a piece of steel sheet with a tubular steel core (so as not to require too much heating) approx 1" dia. - this would be clamped to one side of the bearing. The lathe would then be clamped to the end of the workbench with the bed vertical and the bearing recess filled with molten metal. Both bearings would be done at the same time (two mandrels needed).

The question then is how to bore them accurately parallel with the bed? I have a round head mill so swinging the head over is an option, but I'm not sure how I would align everything. Some form of powered spindle (poss the original lathe spindle since it has a MT3 taper and pulleys) clamped to the ways is another and more easy to align but I can't see an easy way to move it through the bore unless I use the existng saddle and I am not sure how rigid that would be... or maybe I'd have to create a new saddle... or a base plate that clamped to the bed with linear bearings? Or that overkill?

Any ideas?

Only a suggestion, a ghastly, unauthentic bodge that may cause you to vomit, but here goes :rofl:

Turn and bore the bearings to size.

File the externals so they can fit perfectly in line

Jig up square and all assembled

Inject Loctite (or metal loaded epoxy if slack), in to wherever you poured the molten metal before

Robin

What you need is a portable boring machine that'll go down to your spindle size (Unfortunately my ancient Buma bar is 2" minimum)

The smaller ones used to be common place in motorcycle and scooter dealers (in the days when you could get your machine re-bored for two shillings and tuppence). Any long established dealers in your area? They may have one you could scrounge?

They're still being made, so there's still a use for them somewhere:

http://www.allstates.com/ShanghaiBoringBar.html

Attachment 1606

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Originally Posted by Robin Hewitt

Only a suggestion, a ghastly, unauthentic bodge that may cause you to vomit, but here goes :rofl:

Turn and bore the bearings to size.

File the externals so they can fit perfectly in line

Jig up square and all assembled

Inject Loctite (or metal loaded epoxy if slack), in to wherever you poured the molten metal before

Robin

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Quote:

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Originally Posted by BillTodd

What you need is a portable boring machine that'll go down to your spindle size (Unfortunately my ancient Buma bar is 2" minimum)
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Robin, I had considered the idea of boring oversize, then fitting bronze bushes which have been lined with white metal and bored to size. But the effort of this outweighs the idea of boring to size since these bearings if done right, will last another 100 years or so.

Bill - interesting but don't see how to get it parallel to ways... these boring machine assume a cylinder block or similar to sit on that is a known perpendicular to the hole to be bored.

My current plan is to make a saddle out of 1/2" ground plate, approx 8" long which will be bolted to the apron in place of the real saddle and will carrry two braced uprights with oilite bearings in which will run the spare spindle from my breaker lathe and this will be driven by a small, 1/4HP AC motor via two pulleys and a v-belt that I have lying around. This needs a cutter rotating at 400 - 500rpm so gear down 3:1 (1450 -> ~500RPM). I will use my existing MT3 boring bar and draw bar The back end of the saddle will have a gib plate cut at 60deg to match the existing dovetail. I'll fit a handle to the leadscrew at the headstock end in place of the gearwheel to allow the boring assembly to be wound into the headstock...

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interesting but don't see how to get it parallel to ways... these boring machine assume a cylinder block or similar to sit on that is a known perpendicular to the hole to be bored.

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You just need to create a known perpendicular with a couple of right-angle plates, referencing the face and edges of the lathe bed - The boring bar has a built-in three point reference to centre itself in the bore.

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My current plan is to make a saddle out of 1/2" ground plate, approx 8" long which will be bolted to the apron in place of the real saddle and will carrry two braced uprights with oilite bearings

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Ok Sound's like a plan, but seems like a lot of effort - you are, after all, making a complete new spindle boring tool. If you have any kind of removable lathe spindle head (e.g. Southbend type) that could carry a long boring bar, it could save you a lot of work.

Are you going to use the existing lathe to line bore the two new bearing holes in the saddle part? (see attached example) (this would ensure the height and alignment of the boring spindle is correct for the lathe).

Just a thought; What about a couple of self-centring bearing blocks and a length of shaft - i.e. cross drill the shaft at one end to hold a cutting tool. Mount the shaft and bearing between centres while you tighten the bearing blocks to ensure everything is in-line.


BTW How big are these Relmacs?

The pictures show the set-up I used to line bore the bearings for a motorcycle headstock.

The 1" steel bar is held in a collet at one end and a revolving centre at the other. It is cross drilled to hold a cutting tool (broken 6mm carbide end mill).

The second picture shows the use of a DTI to set the cut depth.

You could probably use a similar set-up to bore the bearing holes for you spindle boring tool - that way the new holes would be perfectly aligned with the old spindle.

How about doing it the hill billy way, use the lathe and tail stock, as long as you can get something throgh the tail stock that is. Next you will need a long shaft to go through the head stock and tail stock. Make a bearing through which the bar will go fitted to one side of the head stock then bore out the other side, when done reverse and do the other similar to line reaming car king pin bearings using a piloted reamer.
Peter

Thanks Bill and Peter...

Bill - the Relmac is a 4.5", 16" between centres, the SuperRelm is the same but 20". The headstock is integral to the bed, so we are talking 55kg+ of cast iron to move around! I don't have another headstock of any usefulness available; well I do have the one off the Lorch, but that has no useful taper to attach a boring tool.

Peter... that has given me an idea...

On the back of the headstock is the banjo plus a stud for an intermediate gear. If I was to make something that would bolt to the banjo plus this stud that just cleared the back of the spindle and held a bearing I could pass a 3/4" bar through the spindle with the far end located on the tailstock centre and into the bearing. I could then position the bearing to locate the shaft centrally in the spindle referencing a centre in the tailstock. I can then remove the bar, remove the spindle and replace the bar knowing it was now aligned with the tailstock and therefore with the ways. If the bearing allows the bar to move parallel to the ways then I can use the tailstock ram to push the boring bar into the headstock. All I need is some way to drive the bar round as it moves and to keep it located in the tailstock.. I am wondering about mounting a direct drive motor clamped onto the tailstock ram. I need about 600rpm and if I'm doing a .5mm deep cut at 0.1mm/rev (about 60mm/min, or 30sec to go through the bore), I'll need 80W of cutting power...

Thats a lot less construction effort probably..

My idea was even simpler , just reduce the end that goes through the tail stock to fit an electric drill.
If I was doing it I would also only do one bearing at a time and use the other to hold a bearing block to hold the shaft doing the boring.
Only real problem would be getting the bar straight and long enough but at least you could push the tail stock near to the head.

peter