Thread: Reconditioning a Relmac lathe
i c thabnks for teaching me yet something new i apprecate it. Hope you can get everything sorted out mate..Me
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?
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
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:
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...
25-01-2010 #77interesting 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
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.
Last edited by BillTodd; 25-01-2010 at 06:24 PM.
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.
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.
By Bodge in forum Lathes, Lathe Rebuilding & ConversionsReplies: 9Last Post: 18-04-2012, 09:45 AM