Kevin Groenke @ PersonMakeObject
Indispensable. I bought dozens for the student shop I managed for years. Eventually I discovered that the Clockwise branded ones are without a doubt the best value. If you use cheap ones and get frustrated with dead batteries, creeping zeros, and hinky movement, do yourself a favor and get the best cheap digital caliper available. I just wish they made a 4" one.? 
|
Re: Off Topic measuring units
Aaron, ? “Good” standards should be constant and be able to be reproduced wherever one may need it.? Celsius degrees are the same size as the earlier centigrade degrees and are not arbitrary.? A decent glass blower can make a thermometer anywhere in the world, set zero to the freezing point of water and 100 to the boiling point of water and go from there.? The difference between degrees Celsius and degrees centigrade is that the Celsius numbering begins at absolute zero, which is the exact temperature at which all molecular motion stops and just happens to be approximately 273 degrees below the freezing point of water.?? ?If the basis for units appears arbitrary, it is because the definitions have changed over the years so they may be reproduced WITHOUT having to have a physical standard like a 1 kilogram mass or a bar of Platinum-Iridium alloy on which are scribed two lines 1 meter apart. ?Even the second has been redefined so that with the proper equipment it can be reproduced anywhere in the universe. ? Jerry F. ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Aaron Woods
Sent: Saturday, September 16, 2023 6:46 AM
To: OldToolmaker; [email protected]
Subject: Re: [Unimat] Off Topic measuring units? The core imperial / standard units really are not that weird. Sure not as neat and tidy as metric with its base 10, but really not hard to work with.
Most of the really out there units are very industry specific, hogsheads, bushels, ffurlongs etc, and they are only weird out of context. If you were a 19th century winemaker then Horseheads would seem perfectly reasonable.
Metric is less flexible resulting in its own need to adapt non-metric units in specific cases such as the French system for medical catheters or gauge system for needles.
Don't even get me started on Celsius which in no way follows the rule of 10 of the metric system and is just as arbitrary as ferenheit only using other numbers.
|
Re: Headstock spindle spring
Hello
David:
My 1973
Unimat came with one, and it was the first thing I took off.
It is nice to have the spring return, but with the spring
there is only 19mm of stroke available. Take it off and you
have 25mm of stroke.
Just
use the quill lever to lift the spindle up and lock it there.
Carl.
On 9/16/2023 8:24 PM, David James via
groups.io wrote:
toggle quoted message
Show quoted text
I saw a headstock spindle spring for sale on ebay. My old cast
iron unimat did not have one when I got it and my manual does not
show one either. Were they only on later models and are they a
worthwhile addition?
I suppose they are good when using it as a drill press.
|
I saw a headstock spindle spring for sale on ebay. My old cast iron unimat did not have one when I got it and my manual does not show one either. Were they only on later models and are they a worthwhile addition? I suppose they are good when using it as a drill press. 
|
Re: Tips on machining pulley grooves
This what i was thinking Peter 
|
Re: Tips on machining pulley grooves
I took a machine shop class in high school, finished the class and graduated from high school right around 50 years ago. A bit over 15 years ago, I bought my first lathe. One of the Chinese Mini-lathes, a Harbor Freight 7x10, model 93212. That was around August 2008, IIRC. From then until December of 2014 I had the devil's own time trying to get that lathe to do what I wanted it to do. Got a lot of great help from this and other boards over at Yahoo groups, before they crashed and burned. Still wasn't doing all that good with my life. My wife got tired of my griping about it, and told me to take another class! So I did. Started in February 2015, and I finally completed it in May of 2022. That's 7 years and 3 month, to the day. It was supposed to be an 8 or 9 month class if you attended full time. And I started full time, but was also working full time, and I'm not a teenager anymore. ;)
I think I made it through the first couple of months, but after that, it was two nights a week, 3 hours per night. One of the things I learned in that class was that I had completely forgotten (assuming I had ever learned) how to measure parts accurately. The class taught me that, and a bit of practice with their equipment, including a set of Johannsen blocks to practice on, fixed that in a couple of days. I searched messages for your first questions here. And that was not a whole lot over a year ago. It took me 7 years to figure out I was failing abjectly, and 7 more to do a lot better. I should be a better machinist than you are. But I would be willing to make a small wager that if I am, it won't be for long! You've made tremendous progress in just over a year! I'd have to be blind and stupid to not recognize that! I will admit to being crazy, but I try not to be stupid! ;)
Oh, and there wasn't a single thing wrong with my first lathe that a bit of skill wouldn't have been able to overcome. All the problems were the "Stick Actuator" as we Air Force folks call it. :)
Bill in OKC
William R. Meyers, MSgt, USAF(Ret.)
Aphorisms to live by: Good judgement comes from experience. Experience comes from bad judgement.? SEMPER GUMBY!
Expect in one hand, expectorate in the other. See which one gets full first.
On Saturday, September 16, 2023 at 05:54:06 PM CDT, Julius Henry Marx <sawbona@...> wrote:
On Sat, Sep 16, 2023 at 07:19 PM, Bill in OKC too wrote:
... well done! Congratulations!
Thank you, appreciate your saying so. 8^) Best, JHM
|
Re: Tips on machining pulley grooves
What about forming a valley in the centre of the 5mm form tool. Sort of back rake on the front and sides. I've seen this on some parting tools
On Sun, 17 Sept 2023, 7:20 am Peter Brooks, < peter@...> wrote: Thanks both, good advice and sounds like a mix of steps would be the way forward. Roughing out, followed by left / right cuts before a final, slightly deeper forming cut.
I appreciate that the U3 probably isn’t quite up to the task.? I’m making the motor pulley first and am hoping I can use the more powerful DC motor to make the other two.
(Night here in the UK now, more tomorrow no doubt).
|
Re: Tips on machining pulley grooves
Hello Bill:
toggle quoted message
Show quoted text
On Sat, Sep 16, 2023 at 07:19 PM, Bill in OKC too wrote:
... well done! Congratulations!
Thank you, appreciate your saying so. 8^) Best, JHM
|
Re: Tips on machining pulley grooves
Oh, so very well done! Congratulations!
Bill in OKC
William R. Meyers, MSgt, USAF(Ret.)
Aphorisms to live by: Good judgement comes from experience. Experience comes from bad judgement.? SEMPER GUMBY!
Expect in one hand, expectorate in the other. See which one gets full first.
On Saturday, September 16, 2023 at 04:28:48 PM CDT, Julius Henry Marx <sawbona@...> wrote:
On Sat, Sep 16, 2023 at 06:20 PM, Peter Brooks wrote:
... the U3 probably isn’t quite up to the task.
There's a more than one way to skin a cat, just that sometimes you have to push the envelope a bit more than would otherwise be comfortable. I was in the exact same spot, did not want to spend absurd money on something I was (reasonably) sure I could make myself but only had my Unimat 3 to work with. Check [url=https://www.model-engineer.co.uk/forums/postings.asp?th=187100]this[/url]thread at ME. Best, JHM
|
Re: Mensuration, was Re: [Unimat] What is the 'BEST' Unimat ?
My experience was otherwise, on the loading of cassette tapes, and my friend that used my TRS-80 to get a job at the local Tandy Computer Center said that they were a great deal faster and more reliable than paper tape, which was about the only other option at the time for amateurs. Once floppy drives became available, you would be correct. However, IIRC, the first 10mb hard drive cost way more than my computer when they came out. That computer was a Level 1, Model 1, TRS-80, with 4k of ram. For $600. That was somewhat less than two months of my pay at the time. Seems to me that the 10mb hd was several thousands of dollars. Just downloaded the March 1980 issue of Kilobaud Microcomputing. A Perscom 40-track floppy system with 1 drive was only $400. A Northstar Horizon System with an 18mb hard drive, and two floppies was $9329, and an additional 18mb HD was another $5000.
I was able to get by just fine with my cassette driver for several more years. ;)
Now, I'm using my SIL's former game machine, with a 200+gb SSD, and a 4TB hard disk... But I don't program anymore. Was never all that good at it, but did put myself online with an H-89 with CP/M, two floppies & a 300 baud modem on a TurboPascal terminal program in 1988 or 89. Fun times!
Pretty sure for what I spent on those, I could have bought a decent small lathe. Looked at an EMCO 5" lathe in 1984, in a department store in Wiesbaden, Germany. It was about $350, but I was TDY for medical purposes and couldn't cash a check large enough to get the Deutsch Marks to buy it. Pretty sure it would have fit in my suitcase! Saw it again (or one very like it) when I was stationed there in 1991, but by then it would have cost about $1000 due to the declining value of the US dollar... SWMBO had two of our 3 kids there, so no lathes for me.?
Bill in OKC
William R. Meyers, MSgt, USAF(Ret.)
Aphorisms to live by: Good judgement comes from experience. Experience comes from bad judgement.? SEMPER GUMBY!
Expect in one hand, expectorate in the other. See which one gets full first.
On Saturday, September 16, 2023 at 04:02:46 PM CDT, Bruce C <bruce@...> wrote:
[Even more off topic] My recollection of loading from a cassette is that it often took several
attempts, and even when successful, the programmes (using the archaic British spelling) did
very little of any practical value.
Bruce
On 14 Sep 2023 at 17:43, Andrei wrote:
>
> Damn, Bill. we had similar computers.
>
> My first PC was the Sinclair Z80, some 43 years ago. Has a whole 16kb
> of memory and had to load programs from a cassette tape.?
>
> https://en.wikipedia.org/wiki/ZX80
>
>
>
> ZX80 - Wikipedia
>
> en.wikipedia.org
>
>
>
>
>
>
>
>
>
> via groups.io <wmrmeyers@...> Sent: Thursday,
> Subject: Mensuration, was Re: [Unimat] What is the 'BEST' Unimat ? ?
> Nope. Half an inch is 12.7mm. That two tenths of a millimeter is
> important! Sometimes! ;) I can use either system, but I'm
> math-challenged despite decades of study, so I use a calculator
> regardless. And the only time I needed to deal with 1/128" was back
> when I got my first Vernier caliper. What I hate is things that mix
> the two systems. Chevrolet vehicles, for example. BASTARDS! :) Had to
> change out the starter on my mini-van this week. Most everything on it
> is metric except the starter bolts.?
>
> Once upon a time, digital calculators were expensive. My first was a
> TI SR-51-II, and I paid $100 for it. That was about a third of my
> monthly paycheck then. When my teaching career ended, a bit over a
> decade ago, I could get a MUCH more powerful calculator for $1, with
> more scientific functions. And the TI-86 graphing calculator was going
> for about $100, then. It used a processor based on the Z-80 chip that
> ran my first appliance computer, the TRS-80 Model 1, and had the same
> graphics capability. Unlike the TRS-80, the TI-86 fit in the palm of
> my hand. Now I have a cheap Android phone, a MOTO G7 Supra. It has
> 32gigabytes of storage, and 2gigabytes of program memory. MUCH better
> graphics capability, too. I have a .5tb or 500gb micro-usb card in it
> for additional storage. And a scientific calculator app that will
> about everything BUT graphing. Including all the normal conversions.
> And another app that will display dwg files.?
>
> THERE IS NO EXCUSE FOR SUCH LACK OF PRECISION!? ;)
>
> Going through a set of drawings and trying to convert every dimension
> would be tough, though. Which means we need a means of converting on
> the fly. Digital calipers, anyone? ;)?
>
> Actually, I'll bet that if there is a method that can be used, someone
> is using it. I actually prefer to use the Imperial system, as modified
> in the USA, but can get along fine in Metric. Lived for a tad over 5
> years in Germany, and 3 in Turkey. I have bought gasoline in litres,
> and assorted foods in kilograms & grams, so I can get by.?
>
> Bill in OKC
> ?
> William R. Meyers, MSgt, USAF(Ret.)
>
> Aphorisms to live by:
> Good judgement comes from experience. Experience comes from bad
> judgement.?
> SEMPER GUMBY!
> Improvise, Adapt, and Overcome. Physics doesn't care about your
> schedule. The only reason I know anything is because I've done it
> wrong enough times to START to know better. Expect in one hand,
> expectorate in the other. See which one gets full first.
>
>
>
> On Thursday, September 14, 2023 at 09:14:11 AM CDT, Andrei
> <calciu1@...> wrote:
>
>
> I was too lazy to calculate so i just threw in the closest numbers:
> 9/16 is greater than half inch. Half inch is 12.5mm so the conclusion
> was that it is bigger than those two numbers the lazy way out Andrei
>
??
|
Re: Tips on machining pulley grooves
Hello
Peter:
You are
right, taking cuts from different angles will help a lot. Just
because a big lathe could form cut this pulley in one plunge,
doesn't mean you must. Lots of lighter cuts are OK.
Just to
let you know the risk of pushing your motor to the limit, I
pushed my Smithy Granite to mill a welded channel square. Then
there was this funny smell and a bit of smoke came out of the
motor! It isn't dead yet, but I need to plan on a new motor
soon. I'm thinking 3 phase with a variable frequency drive
(VFD) so I can have full torque at lower speeds.
Carl.
On 9/16/2023 5:20 PM, Peter Brooks
wrote:
toggle quoted message
Show quoted text
Thanks both, good advice and sounds like a mix of steps would be
the way forward. Roughing out, followed by left / right cuts
before a final, slightly deeper forming cut.
I appreciate that the U3 probably isn’t quite up to the task. ?I’m
making the motor pulley first and am hoping I can use the more
powerful DC motor to make the other two.
(Night here in the UK now, more tomorrow no doubt).
|
Re: Tips on machining pulley grooves
On Sat, Sep 16, 2023 at 06:20 PM, Peter Brooks wrote:
... the U3 probably isn’t quite up to the task.
There's a more than one way to skin a cat, just that sometimes you have to push the envelope a bit more than would otherwise be comfortable. I was in the exact same spot, did not want to spend absurd money on something I was (reasonably) sure I could make myself but only had my Unimat 3 to work with. Check thread at ME. Best, JHM
|
Re: Tips on machining pulley grooves
Thanks both, good advice and sounds like a mix of steps would be the way forward. Roughing out, followed by left / right cuts before a final, slightly deeper forming cut.
I appreciate that the U3 probably isn’t quite up to the task. ?I’m making the motor pulley first and am hoping I can use the more powerful DC motor to make the other two.
(Night here in the UK now, more tomorrow no doubt).
|
Hello:
toggle quoted message
Show quoted text
On Sat, Sep 16, 2023 at 05:48 PM, Charles Daldry wrote:
... same problem with my Emco Compact 5 ...
Ahh ... I see a pattern becomes visible. Not only Unimat 3s.
... brass I made did not eliminate the play in the carriage, so I filed about about .004" from the part of the gib ...
Yes, that's one way to do it albeit with a huge disadvantage: any further adjustments will always require partly dressing the brass gibs. Dressing the gibs' mating surfaces to the level where they should be is a permanent solution. And if and when further adjustment is needed you just turn over the gibs, evenly dress the whole side evenly or make new set.
... need to acquire the skill first.
Same thing I said till I decided to jump in and be done with it. Just have to remember that Prudence, Patience and Constance will be your best friends while at it.? Best, JHM
|
Re: Mensuration, was Re: [Unimat] What is the 'BEST' Unimat ?
[Even more off topic] My recollection of loading from a cassette is that it often took several
attempts, and even when successful, the programmes (using the archaic British spelling) did
very little of any practical value.
Bruce
On 14 Sep 2023 at 17:43, Andrei wrote:
>
> Damn, Bill. we had similar computers.
>
> My first PC was the Sinclair Z80, some 43 years ago. Has a whole 16kb
> of memory and had to load programs from a cassette tape.?
>
> https://en.wikipedia.org/wiki/ZX80
>
>
>
> ZX80 - Wikipedia
>
> en.wikipedia.org
>
>
>
>
>
>
>
>
>
> via groups.io <wmrmeyers@...> Sent: Thursday,
> Subject: Mensuration, was Re: [Unimat] What is the 'BEST' Unimat ? ?
> Nope. Half an inch is 12.7mm. That two tenths of a millimeter is
> important! Sometimes! ;) I can use either system, but I'm
> math-challenged despite decades of study, so I use a calculator
> regardless. And the only time I needed to deal with 1/128" was back
> when I got my first Vernier caliper. What I hate is things that mix
> the two systems. Chevrolet vehicles, for example. BASTARDS! :) Had to
> change out the starter on my mini-van this week. Most everything on it
> is metric except the starter bolts.?
>
> Once upon a time, digital calculators were expensive. My first was a
> TI SR-51-II, and I paid $100 for it. That was about a third of my
> monthly paycheck then. When my teaching career ended, a bit over a
> decade ago, I could get a MUCH more powerful calculator for $1, with
> more scientific functions. And the TI-86 graphing calculator was going
> for about $100, then. It used a processor based on the Z-80 chip that
> ran my first appliance computer, the TRS-80 Model 1, and had the same
> graphics capability. Unlike the TRS-80, the TI-86 fit in the palm of
> my hand. Now I have a cheap Android phone, a MOTO G7 Supra. It has
> 32gigabytes of storage, and 2gigabytes of program memory. MUCH better
> graphics capability, too. I have a .5tb or 500gb micro-usb card in it
> for additional storage. And a scientific calculator app that will
> about everything BUT graphing. Including all the normal conversions.
> And another app that will display dwg files.?
>
> THERE IS NO EXCUSE FOR SUCH LACK OF PRECISION!? ;)
>
> Going through a set of drawings and trying to convert every dimension
> would be tough, though. Which means we need a means of converting on
> the fly. Digital calipers, anyone? ;)?
>
> Actually, I'll bet that if there is a method that can be used, someone
> is using it. I actually prefer to use the Imperial system, as modified
> in the USA, but can get along fine in Metric. Lived for a tad over 5
> years in Germany, and 3 in Turkey. I have bought gasoline in litres,
> and assorted foods in kilograms & grams, so I can get by.?
>
> Bill in OKC
> ?
> William R. Meyers, MSgt, USAF(Ret.)
>
> Aphorisms to live by:
> Good judgement comes from experience. Experience comes from bad
> judgement.?
> SEMPER GUMBY!
> Improvise, Adapt, and Overcome. Physics doesn't care about your
> schedule. The only reason I know anything is because I've done it
> wrong enough times to START to know better. Expect in one hand,
> expectorate in the other. See which one gets full first.
>
>
>
> On Thursday, September 14, 2023 at 09:14:11 AM CDT, Andrei
> <calciu1@...> wrote:
>
>
> I was too lazy to calculate so i just threw in the closest numbers:
> 9/16 is greater than half inch. Half inch is 12.5mm so the conclusion
> was that it is bigger than those two numbers the lazy way out Andrei
>
??
|
Re: Tips on machining pulley grooves
All of what you say can be improvements.? The root problem is a lot of cutting surface all at once on a large diameter in a small minimally powered machine.
Going in at two different X positions as you mentioned will help to mitigate this.? And, also, to an extent the chip formations from the left and right sides of the tool will, to some extent, both try to move into the same airspace above the tool bit.? They effectively collide there making things worse.? (The is the reason why single point thread cutting is ideally done at a 29 of 29.5 degree angle so most cutting is only on one edge.? Because for thread cutting this collision of the "left" and "right" chip can be severe.)
You also mentioned what accounts to first roughing the shape.? This can be done with a narrow square end tool (such as a cut off tool because it takes a lot of grinding to make a narrow tool from a standard size tool bit) to make a number of cuts resulting in a stair step shape to approximate the final.? You still have the issue of a large diameter in a too small machine.? But will have the advantage of having a much smaller cross section of the cut.? Then finish with the forming tool.? Or it might even be possible to use a round file that is, or has a region that is, the correct diameter.
Beyond that, it is important to have really sharp tool bits, a slow speed, and a lot of patience.? A cutting fluid for aluminum might help.? But with minimal removal rates, it might not make much difference.? And you probably aren't going to be able to get the part so hot that you have to worry about tool bit temperature.? But you never now.
This is also an example where just because something fits the envelope of a machine, it is not necessarily comfortably within the machine's capability.? There are parts that might need a large swing to clear, but a small diameter is actually being worked on such as boring a hole or machining a smaller diameter feature.? That's different.
Sometimes the easiest solution is to use a larger machine to make the part.? And if you don't have one, find somebody who does.
Charles E. "Chuck" Kinzer
On Saturday, September 16, 2023 at 01:12:27 PM PDT, Peter Brooks <peter@...> wrote:
As part of my 24v re-motoring exercise I’m making new pulleys from aluminium. I’m not finding it easy to machine the groove for the belt and would appreciate any tips (apart from ‘buy them online’ and ‘do it on a bigger lathe’ - I just have the U3).
I use ‘O’ rings for belts, they have a 5mm cross-section diameter. The finished inner diameter at the bottom of the groove will be 38mm. The pulley body is 9mm thick to allow for the flange portions either side of the groove.
For a cutter I first tried a 6mm drill bit cut off at 45 degrees and then milled clean. Blimey a drill bit is hard to saw with a hacksaw. Two blades later… the endmill had no problem however. ?The finished ‘cutter’ didn’t cut very well though.
Next I ground a cutter (my first!) from a 6mm blank. Semi-circular, with a 6 degree angle, and some top relief (as recommended for aluminium I believe). This was moderately successful but it is doing more of a scrape than a cut. It is literally ‘stop start’. It did however produce some beautiful swarf, almost like snowflakes, or frost.
It is making pulleys - but painfully slowly. I have more material to remove and it is not working well at the moment.
I think I should be taking out excess material in smaller chunks first then finishing with the shaped tool, but a plan to do this is puzzling me given the finished shape. It’s taken a long time to get this far from a large chunk of aluminium and I don’t want to ruin anything!
So far I’m going in at one position. I did wonder if alternating cuts between two slightly altered positions (kind of left and right) would be beneficial - the cutter would (or might) only be using 50% of the cutting edge.
I’m making three pulleys in all - one for the motor and one each for the lathe and mill.
As usual I have very little idea what I’m doing so am looking to tap into folks wealth of knowledge and experience. Any tips gratefully received. Thanks!
(Sorry for the overlong post - the quick version would be ‘How would you make a pulley groove?’ :-)
|
I had the same problem with my Emco Compact 5, an overgrown U3.?
I found that the brass I made did not eliminate the play in the
carriage, so I filed about about .004" from the part of the gib
that contacted the carriage. That raised the gib enough to
eliminate the majority of the play.? I should probably finish the
job by marking and scraping the gib to fit better, but I need to
acquire the skill first.
Charles Daldry
On 9/16/23 13:28, Julius Henry Marx
wrote:
toggle quoted message
Show quoted text
Hello:
On Sat, Sep 16, 2023 at 03:42 PM, Peter Brooks wrote:
... thanks for that and for
the link to the post on ME.
You're welcome, hope it was at least it gave you an idea as to
where you stand.
... glad I’m not the only
one to notice ...
Make no mistake: everyone who comes across the problem notices it
as it is a nightmare to try to turn even a small part properly.
What was hard/impossible to find was the actual cause. Easily
traced to the lack of QC + bad design decisions at Emco.
But I digress.
Like I mentioned, I searched all over the web for months looking
to find references/solutions/modifications/etc. which would
address the problem to no avail.
While searching for a solution to making a new set of gibs, a
member of that forum revealed the origin of the problem.
... burring at the bolt
holes and a bit of dressing ...
The problem is actually twofold in origin: on one hand the plastic
glass filled gibs (a contentious issue) and on the other the
excess material present on the mating surface where the gibs sit.
The new set of brass gibs was a start and the iterative process of
dressing/adjusting their mating surfaces to get the right height
made a world of difference.
I was, as you can imagine, scared shitless (cue Stephen
Stills/Woostock/1969) but reasoning it out in detail it quickly
became clear to me that, even with a new set of gibs, if they did
not run at the right height with respect to the guide rails there
was no way I was ever going to be able to get it working
properly. ie: the carriage would always have vertical
movement.
As the U3 carriage is made of Zamak, it has very little mass and
the only way to keep it in place/down is via a properly adjusted
set of gibs.?
Best,
JHM
|
Re: Tips on machining pulley grooves
Use a hacksaw blade to remove some of the material before you use your tool, and that might help. Might also be "Interesting" trying to get just the right depth... ;) perhaps used a hacksaw blade, or piece of hacksaw blade, as a parting tool before cutting to depth with your profile cutter.?
Bill in OKC
William R. Meyers, MSgt, USAF(Ret.)
Aphorisms to live by: Good judgement comes from experience. Experience comes from bad judgement.? SEMPER GUMBY!
Expect in one hand, expectorate in the other. See which one gets full first.
On Saturday, September 16, 2023 at 03:12:26 PM CDT, Peter Brooks <peter@...> wrote:
As part of my 24v re-motoring exercise I’m making new pulleys from aluminium. I’m not finding it easy to machine the groove for the belt and would appreciate any tips (apart from ‘buy them online’ and ‘do it on a bigger lathe’ - I just have the U3).
I use ‘O’ rings for belts, they have a 5mm cross-section diameter. The finished inner diameter at the bottom of the groove will be 38mm. The pulley body is 9mm thick to allow for the flange portions either side of the groove.
For a cutter I first tried a 6mm drill bit cut off at 45 degrees and then milled clean. Blimey a drill bit is hard to saw with a hacksaw. Two blades later… the endmill had no problem however. ?The finished ‘cutter’ didn’t cut very well though.
Next I ground a cutter (my first!) from a 6mm blank. Semi-circular, with a 6 degree angle, and some top relief (as recommended for aluminium I believe). This was moderately successful but it is doing more of a scrape than a cut. It is literally ‘stop start’. It did however produce some beautiful swarf, almost like snowflakes, or frost.
It is making pulleys - but painfully slowly. I have more material to remove and it is not working well at the moment.
I think I should be taking out excess material in smaller chunks first then finishing with the shaped tool, but a plan to do this is puzzling me given the finished shape. It’s taken a long time to get this far from a large chunk of aluminium and I don’t want to ruin anything!
So far I’m going in at one position. I did wonder if alternating cuts between two slightly altered positions (kind of left and right) would be beneficial - the cutter would (or might) only be using 50% of the cutting edge.
I’m making three pulleys in all - one for the motor and one each for the lathe and mill.
As usual I have very little idea what I’m doing so am looking to tap into folks wealth of knowledge and experience. Any tips gratefully received. Thanks!
(Sorry for the overlong post - the quick version would be ‘How would you make a pulley groove?’ :-)
|
Tips on machining pulley grooves
As part of my 24v re-motoring exercise I’m making new pulleys from aluminium. I’m not finding it easy to machine the groove for the belt and would appreciate any tips (apart from ‘buy them online’ and ‘do it on a bigger lathe’ - I just have the U3).
I use ‘O’ rings for belts, they have a 5mm cross-section diameter. The finished inner diameter at the bottom of the groove will be 38mm. The pulley body is 9mm thick to allow for the flange portions either side of the groove.
For a cutter I first tried a 6mm drill bit cut off at 45 degrees and then milled clean. Blimey a drill bit is hard to saw with a hacksaw. Two blades later… the endmill had no problem however. ?The finished ‘cutter’ didn’t cut very well though.
Next I ground a cutter (my first!) from a 6mm blank. Semi-circular, with a 6 degree angle, and some top relief (as recommended for aluminium I believe). This was moderately successful but it is doing more of a scrape than a cut. It is literally ‘stop start’. It did however produce some beautiful swarf, almost like snowflakes, or frost.
It is making pulleys - but painfully slowly. I have more material to remove and it is not working well at the moment.
I think I should be taking out excess material in smaller chunks first then finishing with the shaped tool, but a plan to do this is puzzling me given the finished shape. It’s taken a long time to get this far from a large chunk of aluminium and I don’t want to ruin anything!
So far I’m going in at one position. I did wonder if alternating cuts between two slightly altered positions (kind of left and right) would be beneficial - the cutter would (or might) only be using 50% of the cutting edge.
I’m making three pulleys in all - one for the motor and one each for the lathe and mill.
As usual I have very little idea what I’m doing so am looking to tap into folks wealth of knowledge and experience. Any tips gratefully received. Thanks!
(Sorry for the overlong post - the quick version would be ‘How would you make a pulley groove?’ :-)
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Hello:
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On Sat, Sep 16, 2023 at 03:42 PM, Peter Brooks wrote:
... thanks for that and for the link to the post on ME.
You're welcome, hope it was at least it gave you an idea as to where you stand.
... glad I’m not the only one to notice ...
Make no mistake: everyone who comes across the problem notices it as it is a nightmare to try to turn even a small part properly. What was hard/impossible to find was the actual cause. Easily traced to the lack of QC + bad design decisions at Emco. But I digress. Like I mentioned, I searched all over the web for months looking to find references/solutions/modifications/etc. which would address the problem to no avail. While searching for a solution to making a new set of gibs, a member of that forum revealed the origin of the problem.
... burring at the bolt holes and a bit of dressing ...
The problem is actually twofold in origin: on one hand the plastic glass filled gibs (a contentious issue) and on the other the excess material present on the mating surface where the gibs sit. The new set of brass gibs was a start and the iterative process of dressing/adjusting their mating surfaces to get the right height made a world of difference. I was, as you can imagine, scared shitless (cue Stephen Stills/Woostock/1969) but reasoning it out in detail it quickly became clear to me that, even with a new set of gibs, if they did not run at the right height with respect to the guide rails there was no way I was ever going to be able to get it working properly. ie: the carriage would always have vertical movement. As the U3 carriage is made of Zamak, it has very little mass and the only way to keep it in place/down is via a properly adjusted set of gibs.? Best, JHM
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Carl
David James
Bill in OKC too