|Robin Graham||13/06/2021 01:23:46|
|865 forum posts|
Title is a bit vague - how long is a piece of string (longer than you think!), so I'll give a particular case.
A while back I was approached by a woodworker who had who had acquired a Kity table saw which he was thinking of scrapping because the moulded handwheel which controls the rise/fall and tilt of the blade had failed:
It's a bad design because the nylon (I think) gear meshes with with a steel rack cut in the pressed steel housing of the machine, with a predicable result.
I made a replacement in steel which involved measuring up the original, drawing it out (in my primary school way):
and making a new one in steel:
It's straightforward enough lathe work, but I have no realistic idea of how long it took because I am quite disorganised.
I suspect that I am slow - perhaps it took me 2 or 6 hours from start to finish. Maybe more!
I'd be interested to know how long this would take others using manual machinery. In my head it was "Half an hour mate, stick a lump of 3 1/2 inch in the chuck, twiddle some handles, bung it on the mill, drill and tap a few holes, job done." But of course it isn't really like that.
Edited By Robin Graham on 13/06/2021 01:27:33
Edited By Robin Graham on 13/06/2021 01:44:04
2224 forum posts
Me about a week. Then it would be wrong & have to do it again.
|pgk pgk||13/06/2021 04:54:00|
|2293 forum posts|
It’s the 'thinking about it', finally getting around to drawing it then deciding how/where to source material and then cleaning up afterwards and inevitably buying 2 blanks of steel to allow for a bog-up and not making allowances for tool wear, oils and abrasives. Reality on that piece is that there's very few critical dimensions - just the bore for the spur gear but obstinacy could make one fiddle for exact sizing of the rest.
|Howard Lewis||13/06/2021 05:27:42|
|5228 forum posts|
As long as it takes, but some things take much longer that expected! One job always spawns at least one other.
You have a long piece of Ali angle to machine, so you clamp it to a steel bar with a Toolmakers clamp at each end, and the mill vice to hold it in the middle. Then you need to find suitable parallels to set it all at the right height in the mill vice.
As you tighten the clamps, one breaks.
So the immediate job is to make a new jaw for the toolmaker's clamp! Once you have found what threads are; and found the Taps and the correct size drill.
You don't reckon much to one of the clamp screw threads, so now you have a turning job involving cutting the thread with a Die, and knurling `the end. The finished article looks so much better than the other, so you make a second one to match.
Then the cutter doesn't give as good a finish as you'd hope, so you set to work to give that a regrind.
But it is an inserted tooth cutter.
So out with the cutter grinder and sharpen each tooth.
Then you need a fixture to set the teeth at the same level.
And so it goes on.
Originally, all you wanted to do was to skim ten thou off the face of a piece Ali angle and two days later, you still are barely set up to do the job!
Draining the swamp and Alligators come to mind!
Hopefully, there is no deadline on the job, otherwise you have to start cutting corners, with the risks of making even more work, rectifying the accidents!
Worst of all is, almost at the end of a project, you can't find the "safe place" in which you placed the special pivot bolt that was the first part that you made.
Son in Law's chop saw lost a rivet out of the linkage that lowers and raises the guard over the blade. Make new rivet, fiddly but done. Drop one of the special pivot screws.
CAN'T find it, so make a new one! Different head, but hidden, and it does what is required.
Several months later, find the missing screw, and put on one side, ready to refit.
But you can't be messed about stripping the thing down to put it back, in place of your home made special!
|not done it yet||13/06/2021 07:02:02|
|6270 forum posts|
Extra time if you made the spur gear instead of buying it in! Same with the handle.
|776 forum posts|
If time is money then not as long as if it isn’t.
Make in multiple parts to reduce machine time, could be made completely with bought parts fitted together. Cost versus time.
|Chris Evans 6||13/06/2021 08:12:37|
1950 forum posts
I reverse engineer a lot of parts for old motorcycles. As much time goes into measuring and sorting out how to make the item as the machining time. Sifting through the metal stock for something suitable can add a while. As for the part from the OP I would be happy with a day in the workshop.
|Martin Connelly||13/06/2021 08:12:39|
1848 forum posts
4.84 times whatever you thought it was going to be. This is based on the rule of thumb we used at work, "Work out how long it will take to do something, then double that, then add 10% for good measure then double it again and add another 10% and cross your fingers hoping it is about right".
4681 forum posts
If you're old enough you remember when they made stuff like Concorde then you will remember that even unlimited resources made no difference, massive delays, huge cost over runs
Because the first of anything we do is a bespoke item, item 2 gets done in half the time and so on until we spit them out like production parts
So it's always going to be a bit of a plod for a bespoke item, we just learn to plod a bit quicker as we get more experience
|larry phelan 1||13/06/2021 10:04:22|
|1077 forum posts|
With jobs like that, it does,nt really matter how long it takes, what matters is that you CAN do it and can get something working again. I get jobs like that from time to time, and I hate to think how long some of them take.
To be sure, I dont make money from them ! Still, it,s great to see the item up and running again.
|Nicholas Wheeler 1||13/06/2021 10:05:15|
|720 forum posts|
Howard's post above shows why it's useful to have more than one way to do a job! If you break a clamp in the first setup, then move onto another that you rejected for whatever reason, lubricated with plenty of Anglo-Saxon.
Take these jack adaptors
which are about 40mm diameter, 1/4"pins and the radius/taper(which aren't particularly critical) worked out from the distances in CAD. They're one piece just like the original I was given, but that's wasteful in time and material. I should have made the pins separate and loctited them in, which would have been quicker, easier, cheaper and made a stronger part.
|Bob Stevenson||13/06/2021 10:06:13|
|546 forum posts|
I tend to work quite quickly when every thing is to hand with a clear workflow...this is not quite as obvious as it sounds.
At the moment I am getting more than alittle frustrated by my small Chinese lathe, which while a nice enough machine has the problem that chucks are bolted to the spindle with minimal finger clearance for the nuts. This means that I put off these time consuming and frustrating chuck changes and build up three piles of half finished parts and jobs with all those waiting for the 4-jaw, 3-jaw and collet chuck..... This means that it takes forever to finish one part and it's a disjointed process which I hate. When I used a screw on spindle chuck changes were made without any thought and the task of making a particular component could stay in mind until completed. For this reason I think a lathe change might be happening quite soon now!
7473 forum posts
Hofstadter's Law applies. 'Any task you're planning to complete will always take longer than expected, even after Hofstadter's law is taken into account.'
|Chris Evans 6||13/06/2021 11:45:21|
1950 forum posts
|Terry B||13/06/2021 12:00:21|
|13 forum posts|
I used to have the same problem until I turned off the first two or three threads of the studs. This enables me to hang the nuts on and start the nut with my fingertips.
4681 forum posts
Mine would take 5 days and be held together with trademark tack-splodge welds
7473 forum posts
This is a problem, even if you do have small fingers.
I found a home-made tool like this helped:
Just a suitable strip of metal, or Lolly Stick, and a blob of Modelling Clay. Grease works too, though messy. Magnets don't!
The tool let me catch the nut on the thread so it could be spun tighter with my little finger and then spannered. Also helps to make more room by not pushing the chuck fully home on the register until the nuts are on the studs. Then push it on properly and tighten the nuts.
The strip can also be used to direct nuts spun off by one hand into the other. Really annoying when a nut hides in swarf.
I always put a bit of wood across the ways in case the chuck falls off before I get the first nut on. Not happened yet...
Edited By SillyOldDuffer on 13/06/2021 13:58:29
|old mart||13/06/2021 14:52:20|
|3312 forum posts|
I take lots of time to make anything, but it hardly matters unless you are making a living at it.
|Phil Whitley||13/06/2021 17:00:27|
1368 forum posts
It almost always takes longer to set up , than actually machine, odd shapes are especially difficult! When Richard was coming over to make his T-nut last week, I got to the workshop early and put the vice on the mill and clocked it up to the spindle in about 10 minutes, it is probably the fastest I have ever done it!! The milling happened quite quickly, but drilling the hole was a pain, and took maybe an hour to get a 14.5mm hole through a lump of 304 stainless! every drill we picked up needed sharpening, and a couple gave up halfway through. In hindsight we should have drilled it on the mill, and we didnt fasten the vice to the drill table "to save time" LOL!!! The end result was very good, but the pains we went to could have been substantially reduced!
|Howard Lewis||14/06/2021 02:14:27|
|5228 forum posts|
Re confined space for nuts on mini lathes.
DannyM2Z designed and made an extremely simple widget to aid this problem. Appeared in MEW some time ago.
It is just a strip, of banding steel with two cuts and a little filing and bending.. The nuts don't drop when fitting or removing.
Made in minutes with a pair of shears, a file and a pair of pliers. Time well spent, far less frustration and no more searching for dropped nuts.
No reason why it cannot be scaled up for larger lathes.
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