Here is a list of all the postings Matthew Davenhill has made in our forums. Click on a thread name to jump to the thread.
|Thread: Assessing machine wear|
A straightt forward question I hope! I’m stripping a Bridgeport and it’s seen a shift or two! On each of the machines ways there seems to be what I assume are machined datum surfaces either side of the dove tail. So for the question ! How do I assess the wear and what kit do I need?
Some indication of wear, can see some remnants of scraping on the rear slide, thanks for the advice both.
David- I think I have a copy in pdf format, also have the lion industries book. Don’t really want to scrap it, more because I’m not sure where to start!
I’m in the process of stripping and cleaning a Bridgeport j2, all works but showing a fair amount of wear. Other than scrapping or re scraping the ways, any advice on working with worn machines?
|Thread: Tool grinding|
looking at buying a new grinder, has any one found a better way of doing it that a traditional two wheel grinder? I.e. Something like this. http://www.screwfix.com/p/scheppach-tiger2000s-200mm-whetstone-sharpening-honing-machine-230v/40540
In addition has anyone found a rest that you can set the angle on for sale, I know there are lots of DIY designs out there, or found a bench grinder with a system or the angle already marked?
|Thread: 3 jaw chuck run out after machining|
Tipped tool ,about 3 thou cut an inch from the chuck
This is the reading on the freshly machines surface, any thoughts on the cause? The mounting surfaces are clean.
I'm in the process of commissioning my lathe, when I place a dti on a machined length of bright bar which has been turned in a 3 jaw, I get around 0.02mm run out on the machined surface. Does this sound acceptable?
Edited By Matthew Davenhill on 30/05/2017 19:38:30
|Thread: Accuracy of an old machine|
Thanks for the input, it turns out a gasket I had installed on the saddle was too thick and was removing clearance out of the leadscrew, it was slightly rubbing the lead screw and causing it to lift the saddle and alter the cut
I've checked headstock play in accordance with the Lang manual, initially I put a piece of bar in the chuck and used a length of wood against the ways to lift; however, Lang recommend an end load test of 200lbs from which you determine play with a DTI. I've don't this and it shows 1 thou which is within the tollerence allowed by Lang.
Thanks for the advice thus far, in response to one of the comments, I have the manual from lathes.co.uk. I've done a little more work, unsupported the machine cuts parallel for around 75mm but the suddenly cuts a .05mm taper towards the headstock over the remaining 75mm. (I.e. The dia of the work piece reduces) I did wonder about bed wear but surely it would do the opposite? It has been mentioned that the headstock could be out of alignment, I'm a little sceptical my self. I've put a new gasket between the saddle and the carriage, I did wonder if that could be causing issues. Any thoughts ??
To test for play in the bearings it states the following in the below photo, any idea where I can get a 200lb spring
Some welcome thoughts, its a Lang j6 13" swing. I supect the bearing need adjustment too, I've placed a bar in the chuck and lifted the chuck with a piece of 2x4, there seems to be about .003 play. The bearings have shims in that have to be ground to remove the play. The problem Is i don't have a surface grinder. Also at some point the tool post has been run into the headstock, I'm therefore a little concerned it's shifted the gear head; however I'm a little loathed to start messing with that without concrete evidence it needs adjustment.
I've borrowed a test bar a few weeks ago; however the accuracy of it seemed a little jubious. My next action was going to be to buy a new test bar with a morse taper and stick it in the spindle. This leads on to my next problem, I don't have a reduction sleeve, in the manual it talks of it being a morse taper reducing to mt3; I've tried a 5-3 and it's too small the next size up will be too big. Any advice on where to buy one? I could try to make one on said machine I guess.
I've just turned down a 2" piece en3b, it's showing around 1.5 -2 thou variation over 6" the variation seems to kick in around 3" from the chuck, bed wear I suspect. The material was turned unsupported an thoughts guys? Further to marks comments, How much would It cost to grind the bed and where would undertake such a task? Thanks for the advice guys.
I have a rather sturdy 1960s lathe which I'm in the process of refurbishing. My question is, it's seen a few shifts, what level of accuracy is good enough for general machinhing, say 2 tho over 6-8-12 inches?i get that in an ideal world parallel is the answer; however I don't think that's attainable without some expensive work.
|Thread: Bridgeport and transwave|
I'm a bit new to this, I ve just acquired a transwave static converter for my bridgeport j2b as it was going for the right price. The bridgeport seems to have 5 core SWA where as the transwave receives 4 core. How should this be connected. I will probably get a sparky in however I'm curious. Hope this makes sense.
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