Re: 795, 895 (etc) DC motors
On Wed, Sep 4, 2024 at 02:01 AM, Keith S. Angus wrote:
... Here's one I drew earlier ...
Thanks very much Keith for your advice and taking the time to work this out, and (once again) for your previous ideas. It's all very useful and much appreciated.
?
Aaagh! Another project (I love it of course really...)
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Re: 795, 895 (etc) DC motors
Pi times radius squared is the formula for area.? Pi times
diameter is the formula for circumference.
Chuck Daldry
On 9/3/24 19:02, Richard Burrows wrote:
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I don't believe that is correct, the cutting speed would be
dependent on the circumference of the part being turned.
Circumference is calculated as??¦°°ù2
(Pi times the radius squared).
?
To calculate the actual cutting speed? at a
specific RPM the formula would be:
?
?¦°°ù2*RPM
?
?For an object 3" in diameter at 1000 RPM the
calculation would be:
?
3" diameter divided by 2 = 1.5" radius
?
1.5"*1.5"*¦°*1000
= 7068.6 Inches Per Minute
?
If you want to calculate the RPM needed to meet a
specific cutting speed the calculation would be:
?
1/(¦°°ù2*/Cutting
Speed) = RPM
?
The RPM required for an object 3" in diameter
with a cutting speed of 7068.6 inches per minute would be:
?
1/(1.5"*1.5"*¦°/7068.6)?
= 1000
?
==============================================================================
?
Cutting speed nomenclature is dependent on what linear
measurement and rotational speed you use.
?
If you do the calculation using the diameter/radius
measured in inches you get inches out.
If you do the calculation using the diameter/radius
measured in millimeters you millimeters out.
If you do the calculation using the diameter/radius
measured in furlongs you get furlongs out.
?
If you do the calculation using revolutions per minute you
get distance per minute in out.
If you do the calculation using revolutions per second you
get distance per second in? out.
If you do the calculation using revolutions per fortnight
you get distance per fortnight in out.
?
?Be aware; as the diameter is reduced the cutting speed is
reduced, as you reduce the diameter of an object you may need to
increase the RPM to maintain the desired cutting speed.
?
Richard
?
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Re: 795, 895 (etc) DC motors
Hi Peter:
We thread
milled production parts at work. I have several of the cutters.
They look similar to your Woodruff cutter, but with 60¡ã teeth.
Carl.
On 9/3/2024 9:01 PM, Keith S. Angus
wrote:
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On Tue, Sep 3, 2024 at 06:55 PM, Peter Brooks wrote:
I think the spindle would have to be inclined
slightly to cut the thread at the correct angle?? These angles
would change from item to item depending on the pitch.
I think that if the cutting tool is small diameter compared
to the thread being cut there will not be a problem. I can't get
my brain around the multiple angles and helices and so on, but
there will be a cut-off point where the cutter spoils the thread
form - but by how much, and does it matter - is another
question. A quick calculation shows the helix angle of an M3
thread is 3¡ã. The helix angle of metric thread becomes less as
the size goes up, so M3 is a good starting point. Your large
diameter threads will be much less - I don't think there will be
a problem
?
How on earth would you make a cutter? ?I guess you would
start with the (for instance) 55 degree triangle profile at
the end, then mill alongways to create individual teeth? ?How
many 'teeth'? ?Apart from the U3 lathe I have the milling
attachment (with fine feed), and the indexing / dividing
attachment, so I guess there is no excuse!
?
Here is a Woodruff cutter :
?
?
?
Now imagine the teeth formed with a 55¡ã (or whatever) angle
on them. The width of the teeth would determine the coarsest
pitch it could cut - your 12 tpi is only 2.12 mm pitch. If you
reduce the number of teeth it is possible to cut them out with a
mill.
?
Here's one I drew earlier :
?
?
?
This is for 12 tpi. Overall diameter is 15 mm, shaft is 7 mm
(to fit an ER11 collet). Tooth width is 2.5 mm, cutting angle is
55¡ã. The notches are cut with zero rake, for cutting brass, but
by taking them in a bit further you can get 7¡ã for steel. If you
want to go to 20¡ã for aluminium you will only get five notches.
Harden and temper it, then a very light touch with a fine hone
to sharpen up the edges, maybe giving slight clearances behind
the cutting edge. I can draw up similar cutters for other
pitches if you like. I think once you've made a couple you'll
get the idea. You might need opposite handed ones for internal
and external cutting, but probably not.
?
And I've realised I have a couple of those smaller fully
cased motors that started this enquiry. The bodies are just
about 2" diameter. I'm trying to get around to setting one up as
a grinder with? 50 mm diamond wheel. I've already satisfied
myself that this will be a good alternative to a normal bench
grinder, giving very sharp toolbits, with a nearly polished
finish, but at a moderate speed so that you can control how much
metal it takes off. Also not much noise, no sparks, no smell of
burning and no grit spread all over the place. Ideal for working
on the kitchen table.
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Re: 795, 895 (etc) DC motors
On Tue, Sep 3, 2024 at 06:06 PM, NapierDeltic wrote:
Here is my 2003 bench drill press with a 220W motor. Meanwhile the specs for motors were shifted from continuous to 3x power( W/kW) intermitent. Just paper work for advertising.
The chuck on that is just the same as the one on my old drill, the motor power of 220 W is not very much more then my 160 W, and the speeds shown are much the same too. Given that my motor is an old fashioned one, I suspect it can handle a significant overload for the time it takes to drill one hole. If I was drilling all day it might get a bit hot, but last time I was doing batch work on it the holes were all 1 mm.
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Re: 795, 895 (etc) DC motors
I don't believe that is correct, the cutting speed would be dependent on the circumference of the part being turned.
Circumference is calculated as??¦°°ù2 (Pi times the radius squared).
?
To calculate the actual cutting speed? at a specific RPM the formula would be:
?
?¦°°ù2*RPM
?
?For an object 3" in diameter at 1000 RPM the calculation would be:
?
3" diameter divided by 2 = 1.5" radius
?
1.5"*1.5"*¦°*1000 = 7068.6 Inches Per Minute
?
If you want to calculate the RPM needed to meet a specific cutting speed the calculation would be:
?
1/(¦°°ù2*/Cutting Speed) = RPM
?
The RPM required for an object 3" in diameter with a cutting speed of 7068.6 inches per minute would be:
?
1/(1.5"*1.5"*¦°/7068.6)? = 1000
?
==============================================================================
?
Cutting speed nomenclature is dependent on what linear measurement and rotational speed you use.
?
If you do the calculation using the diameter/radius measured in inches you get inches out.
If you do the calculation using the diameter/radius measured in millimeters you millimeters out.
If you do the calculation using the diameter/radius measured in furlongs you get furlongs out.
?
If you do the calculation using revolutions per minute you get distance per minute in out.
If you do the calculation using revolutions per second you get distance per second in? out.
If you do the calculation using revolutions per fortnight you get distance per fortnight in out.
?
?Be aware; as the diameter is reduced the cutting speed is reduced, as you reduce the diameter of an object you may need to increase the RPM to maintain the desired cutting speed.
?
Richard
?
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Re: 795, 895 (etc) DC motors
On Tue, Sep 3, 2024 at 06:55 PM, Peter Brooks wrote:
I think the spindle would have to be inclined slightly to cut the thread at the correct angle?? These angles would change from item to item depending on the pitch.
I think that if the cutting tool is small diameter compared to the thread being cut there will not be a problem. I can't get my brain around the multiple angles and helices and so on, but there will be a cut-off point where the cutter spoils the thread form - but by how much, and does it matter - is another question. A quick calculation shows the helix angle of an M3 thread is 3¡ã. The helix angle of metric thread becomes less as the size goes up, so M3 is a good starting point. Your large diameter threads will be much less - I don't think there will be a problem
?
How on earth would you make a cutter? ?I guess you would start with the (for instance) 55 degree triangle profile at the end, then mill alongways to create individual teeth? ?How many 'teeth'? ?Apart from the U3 lathe I have the milling attachment (with fine feed), and the indexing / dividing attachment, so I guess there is no excuse!
?
Here is a Woodruff cutter :
?
?
?
Now imagine the teeth formed with a 55¡ã (or whatever) angle on them. The width of the teeth would determine the coarsest pitch it could cut - your 12 tpi is only 2.12 mm pitch. If you reduce the number of teeth it is possible to cut them out with a mill.
?
Here's one I drew earlier :
?
?
?
This is for 12 tpi. Overall diameter is 15 mm, shaft is 7 mm (to fit an ER11 collet). Tooth width is 2.5 mm, cutting angle is 55¡ã. The notches are cut with zero rake, for cutting brass, but by taking them in a bit further you can get 7¡ã for steel. If you want to go to 20¡ã for aluminium you will only get five notches. Harden and temper it, then a very light touch with a fine hone to sharpen up the edges, maybe giving slight clearances behind the cutting edge. I can draw up similar cutters for other pitches if you like. I think once you've made a couple you'll get the idea. You might need opposite handed ones for internal and external cutting, but probably not.
?
And I've realised I have a couple of those smaller fully cased motors that started this enquiry. The bodies are just about 2" diameter. I'm trying to get around to setting one up as a grinder with? 50 mm diamond wheel. I've already satisfied myself that this will be a good alternative to a normal bench grinder, giving very sharp toolbits, with a nearly polished finish, but at a moderate speed so that you can control how much metal it takes off. Also not much noise, no sparks, no smell of burning and no grit spread all over the place. Ideal for working on the kitchen table.
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Re: 795, 895 (etc) DC motors
Cutting speed refers to cutting speed of materials. For example the cutting speed of cast iron as shown in Machinery¡¯s hand book is 50 feet per minute.?
A complete list of cutting speeds of materials is listed in Machinery¡¯s Hand Book.?
Most experienced machinists use this method to establish a starting point of RPM. As machinists gain experience these parameters become second nature and we estimate the speed in rpm.
Dick
http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
?LARGE TURRET TOOL POST PLANS
?MINI-LATHE CARRIAGE LOCK PLANS
?SMALL QC TOOL POST PLANS?
?QUICK CHANGE LATHE TURRET
?MINI LATHE COMPOUND PIVOT MODIFICATION
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Re: 795, 895 (etc) DC motors
tomstechniques.com, which appears to be offline today published a chart with the formula that¡¯s being discussed.? This is the chart and rule of thumb formula that I believe the original poster had intended
to express.
?
Scott
?
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From: [email protected] <[email protected]>
On Behalf Of Elliot Nesterman
Sent: Tuesday, September 3, 2024 2:07 PM
To: [email protected]; johnd@...
Subject: Re: [Unimat] 795, 895 (etc) DC motors
?
I imagine it's: CuttingSpeed = (RPM*4) / Diameter
But what measure to use for diameter, Imperial or metric?
1000RPM * 4 / 2" = 2000 inches/minute (166 ft/min)
1000RPM * 4 / 50mm = 80 mm/min (3.15 in/min)
1000RPM * 4 / 5cm = 800 cm/min (315 in/min 26.25 ft/min)
My guess is imperial inches, but who knows?
On 9/3/24 3:10 PM, John Dammeyer wrote:
CuttingSpeed = (CuttingSpeed * 4)/Diameter??? Missing a parameter here?
*From:*[email protected] [mailto:[email protected]] *On Behalf Of
*OldToolmaker via groups.io
*Sent:* September 3, 2024 4:55 AM
*To:* Keith S. Angus; [email protected]
*Subject:* Re: [Unimat] 795, 895 (etc) DC motors
Keith,
The formula for calculating cutting speed is four times cutting speed
divided by the diameter.
This has served me for over 50 years and never fails. I learned it in
trade school.
Dick
--
?OFF-SET-tailstock-center-65965#post105972
<>?SMALL TURRET TOOL POST PLANS
<>?LARGE TURRET TOOL POST PLANS
<>?MINI-LATHE CARRIAGE LOCK PLANS
<>?SMALL QC TOOL POST PLANS
<>?QUICK CHANGE LATHE TURRET
<>?MINI LATHE COMPOUND
PIVOT MODIFICATION
--
Elliot Nesterman
elliot@...
"The finest jewel cannot disguise a flawed character."
|
Re: 795, 895 (etc) DC motors
I imagine it's: CuttingSpeed = (RPM*4) / Diameter
But what measure to use for diameter, Imperial or metric?
1000RPM * 4 / 2" = 2000 inches/minute (166 ft/min)
1000RPM * 4 / 50mm = 80 mm/min (3.15 in/min)
1000RPM * 4 / 5cm = 800 cm/min (315 in/min 26.25 ft/min)
My guess is imperial inches, but who knows?
toggle quoted message
Show quoted text
On 9/3/24 3:10 PM, John Dammeyer wrote: CuttingSpeed = (CuttingSpeed * 4)/Diameter??? Missing a parameter here?
*From:*[email protected] [mailto:[email protected]] *On Behalf Of
*OldToolmaker via groups.io
*Sent:* September 3, 2024 4:55 AM
*To:* Keith S. Angus; [email protected]
*Subject:* Re: [Unimat] 795, 895 (etc) DC motors
Keith,
The formula for calculating cutting speed is four times cutting speed
divided by the diameter.
This has served me for over 50 years and never fails. I learned it in
trade school.
Dick
--
?OFF-SET-tailstock-center-65965#post105972
<>?SMALL TURRET TOOL POST PLANS
<>?LARGE TURRET TOOL POST PLANS
<>?MINI-LATHE CARRIAGE LOCK PLANS
<>?SMALL QC TOOL POST PLANS
<>?QUICK CHANGE LATHE TURRET
<>?MINI LATHE COMPOUND PIVOT MODIFICATION
--
Elliot Nesterman
elliot@...
www.ajoure.net
"The finest jewel cannot disguise a flawed character."
|
Re: 795, 895 (etc) DC motors
CuttingSpeed = (CuttingSpeed * 4)/Diameter??? Missing a parameter here? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of OldToolmaker via groups.io
Sent: September 3, 2024 4:55 AM
To: Keith S. Angus; [email protected]
Subject: Re: [Unimat] 795, 895 (etc) DC motors? The formula for calculating cutting speed is four times cutting speed divided by the diameter. This has served me for over 50 years and never fails. I learned it in trade school. http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
?LARGE TURRET TOOL POST PLANS
?MINI-LATHE CARRIAGE LOCK PLANS
?SMALL QC TOOL POST PLANS?
?QUICK CHANGE LATHE TURRET
?MINI LATHE COMPOUND PIVOT MODIFICATION
|
Re: 795, 895 (etc) DC motors
3¡± probably won¡¯t work with the standard threading tool. you¡¯d need to raise the headstock to swing that.? Maybe the setup that uses a threaded rod or headless fastener in a chuck to the left of the pulley and a nut arrangement ?fastened to the base? There are several variations of that setup in the files/photos.
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On Sep 3, 2024, at 1:26?PM, Peter Brooks <peter@...> wrote: ? On Mon, Sep 2, 2024 at 10:11 PM, John Entwistle wrote:
What diameter Peter? I was able to cut a .750 x 32 tpi both external and internal on the SL with the threading attachment.
Thanks John - it could be pretty large (by Unimat standards :-)? up to 3", and 12 TPI is pretty chunky.
?
Having said that there will probably be much finer threads as well.
?
Cheers,
Peter
?
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Re: 795, 895 (etc) DC motors
?
this kind of cheap test controller is directly connected with ESC and can adjust on device the speed of motor.
Reverse spinning could be obtained by switching 2 phases between motor and ESC.
Aero RC BLDC motors tend to be open construction, higher torque and lower rev (for propeller efficiency).
Auto RC models are usually closed, slim and high rev. Their characteristic is given as xxx kV which means number of turns per V because the speed is proportional with voltage.
--
NapierDeltic
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Re: 795, 895 (etc) DC motors
On Tue, Sep 3, 2024 at 06:06 PM, NapierDeltic wrote:
...For spindles and even for lathe I would recommend also RC brushless motors...
Many thanks for the suggestion and link!
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Re: 795, 895 (etc) DC motors
On Tue, Sep 3, 2024 at 01:42 AM, Keith S. Angus wrote:
If you are cutting hard brass then you can make cutters from silver steel (drill rod)...
Thanks Keith, there's some great ideas there, and the free-standing motor could be one of the three DC scooter ones I have already.
?
I think the spindle would have to be inclined slightly to cut the thread at the correct angle?? These angles would change from item to item depending on the pitch.
?
How on earth would you make a cutter?? I guess you would start with the (for instance) 55 degree triangle profile at the end, then mill alongways to create individual teeth?? How many 'teeth'?? Apart from the U3 lathe I have the milling attachment (with fine feed), and the indexing / dividing attachment, so I guess there is no excuse!
?
?
|
Re: 795, 895 (etc) DC motors
On Mon, Sep 2, 2024 at 10:11 PM, John Entwistle wrote:
What diameter Peter? I was able to cut a .750 x 32 tpi both external and internal on the SL with the threading attachment.
Thanks John - it could be pretty large (by Unimat standards :-)? up to 3", and 12 TPI is pretty chunky.
?
Having said that there will probably be much finer threads as well.
?
Cheers,
Peter
?
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I too have always used WD40 and recently I came across another make GT85 with PTFE and this works well too.
?
I would think kerosene would give off a nasty smell I don't know I have not tried it.
?
A few years ago I had to make and cut some very fine 2 1/2D in relief medals on the cnc I made a dam wall of putty around them and flooded it with Johnson's Baby Oil they turned out fantastic finish.
?
Phill
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Re: 795, 895 (etc) DC motors
On Sun, Sep 1, 2024 at 08:43 AM, Paul Allen wrote:
A 160W motor on a drill press with a 1/2" chuck is highly unlikely. Typically they are 8 amp motors at 120v (4 amp at 240v). That would be a 960w motor. You are likely reading the spec plate wrong.
?
Another thing to remember is the 150w 24v motor is being geared down quite a bit in most cases and so it doesn't need the torque of a higher wattage motor. A direct drive spindle motor on the other hand does need the higher wattage in order to be able to maintain speed when using a multi-flute cutter. Plus, you don't have to use it at full power and can control the spindle speed without needing to resort to gear reduction.
?
And these motors are just an example of alternatives to a 775 motor. He could go with a 150w or 300w and probably be ok, depending on what exactly hse wants to do.
?
Paul Allen
On Sat, Aug 31, 2024, 10:28?PM Keith S. Angus via <keithsangus= [email protected]> wrote:
The XD-3420 is available on Ebay UK, item number 314725050514
?
I can't see why you would need a 500 W motor for an auxiliary spindle on a machine that only needs a 150 W main motor. Certainly the power you need depends on just what you want to do, but it's best to keep a sense of proportion. For example my big old pillar drill has a ?" chuck and a 160 W motor, and quite happily pushes a half inch drill through steel - on low speed. But for most jobs the motor hardly slows.
?
I also prefer a fairly well sealed motor for use when cutting metal. It seems the right thing to do.
?
Still looking for something with high power in a small space to replace the motor on my Basic (PC). The standard motor is only 48 mm diameter, and the hole it has to fit in is only slightly bigger. One of those 795, 895 motors would fit and apparently give more power, but I don't like things like a starting current of 10 A - why? I've just touched the terminals of one across a small 12 V battery and there was no big spark when it made contact. I just don't believe it. But it did seem to run quietly - certainly compared to the nosy toothed belts on the Basic.
 ? ?
?
Here is my 2003 bench drill press with a 220W motor. Meanwhile the specs for motors were shifted from continuous to 3x power( W/kW) intermitent. Just paper work for advertising.
?
For spindles and even for lathe I would recommend also RC brushless motors.
?
?
They are relatively cheap and long lived, you can search for apropriate characteristics. There are plenty of tutorials on Youtube so I would not give a specific address...
Ok, here is an example and you could look at entire series related to Proxxon MF 70:
https://www.youtube.com/watch?v=sM5KqNiaeHQ
?
?
NapierDeltic
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I too use WD 40 for aluminium, works well, so well in fact I bought a gallon of it and a spray bottle.
------ Original Message ------
Date 03/09/2024 17:51:37
Subject Re: [Unimat] Cutting Aluminum
Kerosene works great for cutting aluminum, and it is cheaper than WD40, even when you buy it in bulk.
Years ago, maybe here or one of the other groups, someone recommended using WD-40 as a coolant/lube when cutting Aluminum.
I have done so ever since because I have found that I seem to have fewer problems than when using it rather than other stuff.
Just my $0.02 Your mileage might be different!
Dave
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Kerosene works great for cutting aluminum, and it is cheaper than WD40, even when you buy it in bulk.
toggle quoted message
Show quoted text
Years ago, maybe here or one of the other groups, someone recommended using WD-40 as a coolant/lube when cutting Aluminum.
I have done so ever since because I have found that I seem to have fewer problems than when using it rather than other stuff.
Just my $0.02 Your mileage might be different!
Dave
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Years ago, maybe here or one of the other groups, someone recommended using WD-40 as a coolant/lube when cutting Aluminum.
I have done so ever since because I have found that I seem to have fewer problems than when using it rather than other stuff.
Just my $0.02 Your mileage might be different!
Dave
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Carl
OldToolmaker
John Entwistle
NapierDeltic
Dave P.