Here is a list of all the postings Andrew Tinsley has made in our forums. Click on a thread name to jump to the thread.
|Thread: Martin Cleeve's Dog Clutch|
I have been reading Martin Cleeve's book on screw cutting. I was very taken with his dog clutch fitted to a Myford.
In the fullness of time I would like to make a similar unit. Does anyone know if drawings were ever made available?
|Thread: Knurling question|
When I was a lad, I was a BMC car enthusiast, my friends laughed at me because the Ford cross flow engine was so much better!
However I later learned that the Ford engineering of their engines was far inferior to the BMC A and B series engines. The BMC heads had proper pressed in guides that could be replaced. The Fords had holes bored into the cast iron cylinder head, no guides. When this wore oversize the only option was a new head or internal knurling of the hole to reduce its diameter. Needless to say, this didn't last too long!
|Thread: How do you put new headstock bearings in an ML7 lathe|
I am still unsure of how do this job. Do I simply put in the new white metal bearings, then put the mandrel back and shim the headstock top retainers, until I get a smooth turning of the mandrel, without it binding up?
Does one then use engineers blue and scrape the bearings in?
I have seen that people sometimes use a flat block and reduce the bearing half diameter to get a good fit. Seems odd to me as this will make the bearings none round and hence they probably will need scraping.
I have one mandrel that is in visual good condition (i.e. no scoring marks). This doesn't mean that it has not worn undersize. Does anyone know what size the mandrel bearing surfaces are? I also have brand new white metal bearings. These are as rare as hen's teeth, so I do not want to make a mess of this job!
So anyone that can make some helpful suggestions would be very welcome. Maybe this is a straightforward job for those that know, but I am a scientist and really not into the ins and outs of practical bearing fitting!!
Edited By Andrew Tinsley on 29/03/2017 12:17:41
Thanks for the link. Not quite as helpful as I hoped. I have the old unhardened mandrel and a brand new set of white metal bearings. With this combination, I expect to have to do some scraping, also I have this awful feeling that the finished combination will probably have a different centre height to specification!
The title just about says most things. The lathe mandrel appears to be in excellent condition and I have a new set of white metal bearings.
My scraping abilities were learnt off full size locomotive axle boxes and to say the least are not good for small size bearings! So hopefully any scraping can be kept to a minimum.
|Thread: Piston Ring|
I stick by what I have said about piston rings. I am not going to get involved in discussions that usually lead nowhere. I have made enough piston rings t learn the hard way what works and what doesn't.
If the rings are not pressing against the cylinder wall then, you will have blow by and the pressure on the outer face of the ring will be marginally higher than behind the ring (dynamic set up, not static as many people seem to get confused with).
I know nothing about the work of Sir Harry Riccardo, so I am unable to comment. It doesn't seem to be appropriate to quote 1915/16 work, as I am sure things have developed since then!
I would not disagree with Tubal Cain, I have not seen his articles that you mention. But too much radial spring, increases friction and promotes wear. My final step is to anneal the ring and then to use diamond paste to lap the ring. Amazing what you can see in the way of high spots as the lapping process continues. The finished product shows excellent fitting of the ring. However it SHOULD exert some positive pressure on the cylinder. Don't forget we are talking of compression ratios of 1 : 10 or so for these engines. Diesels are a different kettle of fish having far higher compression ratios. I do not have any experience of rings for such engines, so I am hardly in a position to give advice.
My main interest these days is in vintage spark ignition engines intended for speed.
The idea of "pressure" behind the ring expands it, is totally flawed and can easily be shown to be untrue. I had to learn the hard way.
Dykes rings on the other hand ARE designed to expand under pressure, They are L shaped and have been used from time to time in model aircraft engines. They show almost zero compression when flicked by hand. I have obtained several Dykes ring engines for next to nothing, because the seller thought they were "clapped out"!
Rings should have plenty of spring in them and they should push against the cylinder wall. I will not go into the proper way to make rings as this is getting off topic.
The ring should be a relatively loose fit in the groove, otherwise they are likely to stick and then compression is compromised.
|Thread: Drummond 4" roundbed changewheel pins.|
You don't need to cut a template for the shaper tool. All that is needed is a plain old HSS tool ground to whatever pressure angle you are using, plus the "bottom edge" ground off at the appropriate width that one would use for the bottom width of the gap, in an equivalent rack gear. I hope that makes sense!
If you rig up the shaper as discussed in a prior post, then that is all that one needs to do, in terms of making the shaper tool. The beauty of this system is that it will cut perfect involute gears. NO expensive cutters to buy or make and don't forget, a cutter is only accurate for one size of tooth. Using the shaper method, described previously, you get accurate gears cut for any DP.
If you have a shape,r then make up the required rotational jig (not difficult) and make perfect involute gears for any size you may want.
I have been on my back for the last couple (?) of days with acute sciatica. Now moving again thanks to some potent pain killer, that makes my normal morphine seem like aspirin. So NO workshop for me, this stuff is NOT compatible with moving machinery!
I now have Ivan Law's book on gear cutting, but no mention there of how to derive "d" (the bottom width of the "tooth" gap).
It seems that I will have to stop being lazy and work through the geometry of the involute gear form, to derive the correct formulae for "d" and then calculate from published data.
Mental acuity is definitely not at its best right now and I shall wait until I can leave off taking the medicine!
All the best,
Thanks for the information on the Drummond pins. I do intend to make a full set as I expect the ones that come up on Ebay are probably in the same condition as my existing change wheels.
I now have a shaper, courtesy of one of the advertisers on this forum and will shortly start making the required jig for involute gears, as discussed here on the beginners forum. I think the actual cutting can be accomplished in a few days. One lives in hope that it will work first time!
Edited By Andrew Tinsley on 03/03/2017 17:43:48
I intend to manufacture some changewheels for my old Drummond round bed lathe.
The few changewheels that came with the lathe are pretty battered, especially with the two pin locating holes. I am told that the two holes take tapered locating pins. It is very difficult to check, as at some stage, the holes appear to have been drilled oversize. As I intend to make a new set of wheels , I may as well do this as Drummond intended!
So the queries are,
1/ Do one, or both holes have a taper? If so, is this a standard taper like the usual 1 in 40 taper?
2/ If only one hole has a taper, then what was the original straight pin diameter?
3/ If both holes have a taper, then do they taper in the same or opposite directions?
I appreciate that it isn't too important to get the details correct (except maybe the answer to 3/). But no point in getting them incorrect and then finding that the wheels do not fit on other Drummond lathes!
Thanks for any information, as it does not seem to be readily available here or elsewhere.
|Thread: Gear cutting with a shaper?|
Thanks for giving me the link. I am in some considerable pain at the moment and cannot get my head around the gear blank rotating as the shaper moves across the work. I cannot even see how to mount the blank on my rotary table, which I think is far too big for the job in hand.
I shall take some painkillers and print out the link, that should make it more understandable!!!
I will take a look at the link, somewhat bothered about stepping on sore toes, please accept my apologies for not using the search engine. I really ought to get to grips with the search facility, although I seem to be having a problem, as I always seem to get other topics mixed with what I am looking for.
I will soon have a shaping machine. A small version to replace my huge one which I gave away to a deserving cause.
Now I want to try my hand at gear cutting, I have the Myford kit required to do this on my ML7, when its protracted overhaul is complete.
Meanwhile I would like to try gear cutting on the shaper. I assume that I will need a profiled cutter to replicate the gaps between the teeth! Is this at all possible? Also what is the best method of indexing the blank? Not sure if I can somehow use my rotary table, although I don't know how one would do that!
I am curious to know if a shaper can be used for this task. I am sure that I have read about this, years ago, in an ancient engineering book.
|Thread: Reworking a Hardinge MA99E collet?|
That makes a little more sense to me. Using the Myford collet chuck, if you screw the nose down, then the outer rim of the collet is snug against the nose. At this point, is the bore that stated on the collet? This is before you start to close down the collet. I suppose I really ought to go and measure this dimension, rather than asking here on the forum. Not so easy with the smaller bore collets that I want to modify. The only way I can think of is turning down a rod until it "just" fits.
I understand the comment of using a boring tool instead of drilling and reaming, that makes sense! I know nothing about emergency collets, so I am unaware about packing the slots. Being simple minded on these matters, if you pack the slots and then bore to size, will this give the correct diameter, when used in anger with a rod of the nominal bored size? I can't quite get my head round the problem.
How much packing would be required and would the end results vary with the amount of packing used? I assume that the slots must be closed as viewed from the collet front face, before boring takes place? I am afraid I have a mental blackout when trying to figure this out!
Edited By Andrew Tinsley on 09/02/2017 17:43:54
I am missing a couple of sizes of Hardinge collets, that I would like to have. Not wanting to wait forever, for Ebay to produce them. I thought that maybe I could rework a couple of duplicate collets that I have.
So, simple mind says, put collet into Myford collet chuck, drill out just undersize to diameter required and then ream the hole to size. So what can go wrong? I suppose the steel could be hardened and hence difficult to drill and ream. Maybe the reamed hole could be a bit oversize and then it would not hold the specified diameter?
Is the idea practical or are there any other things that could mean it is a non starter?
Edited By Andrew Tinsley on 09/02/2017 16:27:34
|Thread: Where to get a bed regrind?|
Pretty obvious that hardening should be done before regrinding. But I don't understand the comment that "so he is already undersize". This bed has never been reground, so I expect it could be hardened prior to regrinding, Or is the likely distortion will be so great that the "maximum permitted regrind" will be exceeded?
As a pure matter of interest, is there any figure for the maximum that can be taken off before the bed is scrap? I have seen an ML7 bed that has a large depression due to rusting, although the rest of the bed is rust free. The depression must be around 75 thou at the deepest. The owner is considering recycling it in the near future, seems a pity, but there you go!
I was visiting an old friend the other day. he had just purchased a Myford Super 7, which he wants to overhaul. Bed wear was grim and I suggested he moved it on very quickly!
Despite my suggestion, he wants to get the bed reground and preferably hardened. Since Myford's demise, I would not have a clue where to get such work done and neither has he. So has anyone any suggestions and likely costs involved?
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.