# How To Quickly Grind Lathe Bits



## PAturner (Oct 9, 2016)

Hi, 
I'm in the process of grinding the various tool bits I'll need for my lathe, and I'm having trouble doing it efficiently. I have an 8" harbor freight grinder with the stock wheels and it's taking me about an hour to grind one tool! Any tips on how to speed this process up? 


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## Bob Korves (Oct 9, 2016)

I assume you are grinding high speed steel.

Practice!  Beyond that, do not start with a fine grit wheel.  Remove material with a coarse wheel.  Make sure the wheels are well dressed and not dull and clogged up.  It is like sandpaper, it loads up and also gets dull.  With a grinding wheel you can dress that off to expose a fresh, clean, sharp, and square surface.  Don't be afraid to push the tool into the wheel when roughing to shape.  Have a water pot to dip it in so it stays cool enough to hold on to.  Do not worry about "taking the temper out" of the steel when grinding high speed steel.  HSS can go to a dull red heat without losing its temper.  Once it is close to size and shape, switch to a finer wheel and clean it up.  You still do not need to be delicate with the tool.  Finally, hone the cutting edges (I prefer to use a fine grit diamond lap stick) to make them razor sharp.  It takes a while to learn to make the angles close to correct without constantly looking at it to check.  Again, practice, and it will just keep getting better.  Another thing is that none of the angles are critical, so do not get anal about measuring them too much.  Different work requires different angles, and that is learned by study and by experience.  Watch some professional machinists on YouTube to see how they go about grinding a HSS tool bit.


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## P T Schram (Oct 9, 2016)

I foolishly told my machine tool tech instructor that I had signed up for the second semeter solely to learn to grind lathe bits and sharpen drill bits.

Foolish because this meant that I spent the rest of the semester sharpening the lathe bits for all the classes both adult and high school students and sharpening every drill bit that classmates brought in.

It was well worth it because I can sharpen damn near anything and I even am asked to sharpen the knives for the local meat coutner butchers.

That said, once you do get your bits shaped as you want them, surprisingly, a razor sharp point is not necessarily desirable (yeah, I know. I reacted the same way when the instructor told me this). Once you think you're finished, using yur stone or diamond lap, go over the tip and give it the slightest bit of radius. You'll be surprised how much better it cuts.

Counter-intuitive but it has worked for me.

Now that said, I have to admit that I haven't used a hand-sharpened lathe bit in YEARS and have gone almost completely to carbide inserts. This is a change I should have made YEARS ago!


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## rgray (Oct 9, 2016)

It's all in the wheel. Bench grinders come with horrible wheels. That way they last a long time.
A white 46 grit and a diamond point and some kind of jig to hold it to dress the wheel face any time it gets dull or misshapen from use will speed things up x 10.


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## Bob Korves (Oct 9, 2016)

P T Schram said:


> (snip)
> That said, once you do get your bits shaped as you want them, surprisingly, a razor sharp point is not necessarily desirable (yeah, I know. I reacted the same way when the instructor told me this). Once you think you're finished, using yur stone or diamond lap, go over the tip and give it the slightest bit of radius. You'll be surprised how much better it cuts.
> (snip)


Yes, the extra effort of making razor sharp bits is only really useful for cutting certain materials, like soft or gummy metals and plastics.  It is not so good for heavy cuts or harder materials, because the sharp edge can crumble and then leave a worse surface finish when you were looking for a better finish.  Still, I do it most of the time, and I think it generally helps surface finish, keeps the work cooler, and uses less power for the cut, which minimizes deflection.  It is how I learned, and I could be wrong...


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## Tozguy (Oct 9, 2016)

The grey wheels that come with a grinder are terrible for most purposes. 
A soft white wheel in the 40 to 80 grit range will make grinding HSS tools a pleasure.
Something like a 5SG80IVS or 3SG80IVS.


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## 4GSR (Oct 9, 2016)

Try to find some name brand wheels like Norton, Radiac, and others, and try to get the grades like Tozguy mentioned.  Some of the name brands of gray wheels are very good.  I agree, one's that come with a new grinder aren't worth a flip!  Ken


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## Bill Gruby (Oct 9, 2016)

There is only one way to speed the grinding process and that's PRACTICE. Yes, the right wheel will ease the process but it won't take the place of PRACTICE. None of us, and I mean NONE, could grind in the beginning. Don't forget that word. When you think you have it right keep practicing.

 "Billy G"


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## rgray (Oct 9, 2016)

Bill Gruby said:


> There is only one way to speed the grinding process and that's PRACTICE.



Yes but I remember starting out and trying to grind on those bench grinder wheels. Ton of heat and very little stock removed. Just getting a wheel that will cut goes a long way.  And save the original wheel for finish and touch up.


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## mikey (Oct 9, 2016)

I can recall how inept I was when I started grinding tools on a bench grinder. I ground so many facets on my tools that I suspect I could have made a pretty fair jeweler. Burnt fingers, burnt tools, you name it, I did it. BUT I learned, and I think several things can help you beyond the excellent advice already given, namely to buy the right wheels as Tozguy and Ken pointed to and keep it dressed as Bob said.

Using a bench grinder for HSS requires pressure, steady and firm. Its sometimes hard to consistently do that with your hands and arms. It works better when you lock your wrists and arms and use your body to apply the pressure. Move your feet to get the angle you need and then lean into it. This also helps to maintain your tool angles; as long as your feet stay planted your angles won't change. It goes without saying that the grinder must be firmly mounted so nothing moves when you apply pressure.

If you use your body its hard to keep the bit angled properly under that much pressure. The bit wants to turn away from the wheel. To avoid that, use a push block. A 3/4 - 1" wide piece of wood, maybe 6 - 7" long, can be used to back the tool and apply pressure to the tool while your other hand maintains your angle. You will be surprised how much easier it is to grind with this and how much longer you can grind before you have to cool the tool. When you use a block, orient it so as to apply pressure straight into the centerline of the spindle of the grinder. You will find this greatly increases the cutting action of the wheel.

Depending on the angle, it is sometimes easier to pull the tool across the grinding face rather than trying to push and pull. The more pressure you use, the harder it is to push sometimes; so pull. Use the whole face of the wheel to speed things up. 

HSS is already hardened but once you get it to cut, keep going because if it cools its seems to be harder to get the cutting action going again. Learn to watch the tool angle from the top; sight along the top of the tool as it meets the wheel and that tells you how the side you're grinding is aligned. The tool rest angle determines the other angle (relief, rake, etc).
Make a good tool rest. Each face on a turning tool is angled in two planes. One plane is determined by the angle you control with your hands; the other is controlled by the tool rest. A good tool rest is made of steel, is adjustable for height and the angle you need, is ideally resettable to precise angles and is wide enough to completely support the tool bit so you can push down on it instead of hold onto it. The rest must be wide enough to provide support for the bit on both sides of the wheel.
With all due respect, I'm going to go against the common belief that your tool angles don't matter. They in fact do matter and this especially applies to the rake and relief angles. Learn about tool geometry so you know what it is you're grinding. Cutting force reduction comes from the tool grind and this results in reduced deflection, better accuracy, better finishes and longer tool life. The smaller the lathe, the more important tool geometry and cutting force reduction becomes. 

One last thing (I'm cringing in anticipation of the blows I'm about to get) - consider a belt sander to grind your tools. It is so much faster and easier to grind a good tool on it vs a bench grinder.

Hope this helps,

Mike


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## Bill Gruby (Oct 9, 2016)

With all due respect, you failed to quote my whole post. While I agree 100% the right wheel will ease the job it will not make you a great grinder of tool bits. ONLY PRACTICE will accomplish this. FWIW I still grind on the gray wheels with no problem.

 "Billy G"


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## Dan_S (Oct 9, 2016)

Stock grinder wheels are designed for general purpose grinding, think lawnmower blades, mystery metal etc.

Get your self wheels designed for hardened tool steels, like these or something similar.
https://www.amazon.com/Norton-3X-Grinding-Wheel-grit/dp/B0046AFNZM/
https://www.amazon.com/gp/product/B003TFVXO0/

Ideally you want something like a 46 grit on one side to remove the bulk of the material, and then an 80 to 120 grit on the other side to leave a fine finish, that can be quickly be made razor sharp with a hand hone. T be clear I mean the cutting edge, not the tip. Usually you want a small radius on the tip so you get a better surface finish.


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## PAturner (Oct 9, 2016)

Alright, so seems like more time with the grinder and some better wheels. If I'm gonna spend 50 bucks or so on a wheel will a 40ish white wheel be what I need? Or should I go with the blue Norton as suggested by Dan_S?


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## Reeltor (Oct 9, 2016)

Take a look at Oxtool and ABomb79's YouTube video series entitled Chip Control.  Tom and Adam go at it trying to take the biggest cut using HSS hand ground bits, showing how they like to grind their tool bits.  IIRC one of them uses a hand grinder with the bit clamped in a vise to rough in the bit then move to the pedestal grinder.


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## Joncooey (Oct 9, 2016)

I'm relatively new to machining.  I'm a Welder and a Millwright; ('nuff said).  Any way, I like to shape my HSS cutters on the grinder (drill bits too) but often, I like to finish them on the belt sander.  Stationary belt/disc sander, not a hand-held.  Works good to freshen them up too, without removing a lot of material.

  Jon.


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## rgray (Oct 9, 2016)

I've heard a lot of success stories of sharpening HSS on belt sanders. From what I gather the 72" belt style works good. I have one and have never tied using it for HSS...might have to try it.


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## Tozguy (Oct 9, 2016)

PAturner said:


> Alright, so seems like more time with the grinder and some better wheels. If I'm gonna spend 50 bucks or so on a wheel will a 40ish white wheel be what I need? Or should I go with the blue Norton as suggested by Dan_S?
> 
> 
> Sent from my iPhone using Tapatalk



You already have a grinder so wheels it is. Yes,  40ish white wheel will be much better than the original grey wheels.
The idea is to use a soft open wheel for fast cutting. I bought an 80 grit white wheel (2A80H12) which is good for quick roughing of new blanks.
Most of the grinding after that would be touch ups on the same wheel followed up by diamond honing.


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## 4GSR (Oct 9, 2016)

Be sure to keep you a cup of water handy to cool off the tool bit as you grind on it.  Used to use a metal coffee can, can't get them anymore.


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## kd4gij (Oct 9, 2016)

Walmart has coffee in metal cans.


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## Tozguy (Oct 9, 2016)

Cooling the tool in a cup of coffee, keeps the coffee warm.


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## Bill Gruby (Oct 9, 2016)

The can means nothing, it just holds the water. All you are doing is quenching the heat from the tool so you can hold it. You will be hard pressed to take the hardness out of HSS. Burned blue they will still work.

 If you cool the tool in a soup can does that mean you lunch will be warm ?? ROTFLMBO

 "Billy G"


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## stupoty (Oct 10, 2016)

Reeltor said:


> Take a look at Oxtool and ABomb79's YouTube video series entitled Chip Control.  Tom and Adam go at it trying to take the biggest cut using HSS hand ground bits, showing how they like to grind their tool bits.  IIRC one of them uses a hand grinder with the bit clamped in a vise to rough in the bit then move to the pedestal grinder.



I like using an angle grinder to hog away material, i used a 1mm cutting disc to remove two triangles of material last time i ground a threading tool, made it much quicker 

Stuart


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## TakeDeadAim (Oct 10, 2016)

I like to rough my tool bits, for my tangential tool holder, on the belt sander.  I have belts now for my 2x72" and a 36 grit gets them shaped efficiently.  I still like a bit of hollow grind so I finish on a 120 Norton Blue wheel. I seem to have the best luck with a 1/32" radius on the tip. I touch on the wheel makes a bit of a flat and a flat diamond hone finishes them off.

With these tools you just have to put the bit in the jig a touch the top to the wheel and they are ready to go.  I got crazy and roughed in six one day and should have tools that only need touch ups for a while.

I like carbide inserts but man you can't beat the economy or the cut on mild steel with these bits


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## brino (Oct 10, 2016)

PAturner said:


> Any tips on how to speed this process up?



....a belt sander and this site:
http://www.machinistblog.com/grinding-lathe-tools-on-a-belt-sander/

-brino


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## Tozguy (Nov 9, 2016)

This idea came to me from reading this thread and from wondering how to recycle an old 10'' saw blade.
The teeth were turned off the blade on a lathe leaving a 9'' disc. A 9'' peel and stick 80 grit AO disc was added. A smaller 71/4'' blade was used to support the back of the 9'' blade.
This set up ground HSS very quickly and with very little heat. Surface speed varies from 5000 to 11000 fpm depending on where the tool is presented to the disc. 

Angles and corners are crisp.It is very nice to dial in the angles accurately using blade tilt and/or the mitre guide.

It does not grind chip breakers very well but for roughing a new blank or modifying angles on an existing tool it is tops.


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## Christian Poulsen (Nov 9, 2016)

Yes good stuff above...I just "snag grind" to sharpen lathe tooling, drills, even endmils... from tinys up to big 2+ inch drills...yes (as said above), a suitable water "bowl" and practice, practice, practice for on center and angles for what material, yada yada....same for resharpening them on a a tool and cutter grinder or drill sharpener (practice practice practice the set up and grinding)
(When drilling from 64 to 220 .o50 holes through a 2" x 2" square pc of 4130 1" thick in a CNC mill; At 1st just count the # of holes when the drill breaks then change to new drills 1 hole before for the rest of the job (while saving all those used drills for practice practice practice resharpening them on a tool and cutter grinder or drill sharpener for the next job (ifn' then they drill just as many holes as a new drill, you know you're doing something right. (Smiley Face here!)


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## f350ca (Nov 9, 2016)

I use the white wheels in the cabinet shop to grind High Carbon Steel, they're great in the fact that they generate less heat which is important there. But they wear quickly. For the machine shop where its all HSS a good quality grey wheel cuts almost as fast but holds a flat surface longer. As said heat doesn't bother HSS. The wheels that come on the import grinders aren't even worth saving in the drawer. 

Greg


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## Steven Storey (Nov 13, 2016)

After you have rough ground your Tool Bit have a look at the utube vid below on how to finish the grinding process, worth a watch, I've decided to make one myself.


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## kingmt01 (Nov 14, 2016)

I an another that uses a belt sander to get the final shape then hone on a diamond.

Also there is a difference between a sharp edge & a sharp angle. A edge becomes daul from the edge being bent over or chipped. If a edge is rounded then it is hard to do ether to it. A sharp angle makes the edge weak. I like a sharp edge but not so sharp of a angle so the edge is also strong. I hone mine often to keep the edge crisp. This removed the small damaged edge so I rarely have to resharpen unless I do something stupid.


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## Christian Poulsen (Nov 14, 2016)

Yes, some good info. above, also to add: Think microscopic...IE Whatever the cutter material is, whether it's HSS, Carbide, Ceramic, Bonded Diamond....the regrind (final sharpening/machining resulting in edge) also needs to be considered....like the grit of a wheel
Any wear surface will outperform and last longer the better the finish is...
Thinking "microscopic" I mean a "sawtooth" effect along any cutting edge will wear off many times sooner leaving "shiny" (dull)

...also to add; Even "light brown" (using color as a heat indicator) to any hardened steel starts annealing its hardness, blue is worse, then the reds
It's the action of quenching high heat (blue...or yikes! the reds)  immediately that brings the steel back up (but more brittle and not as tough)
...ifn' you, say sharpen a HSS toolbit or drill and get it a dull red then let it cool slowly in room temp. mid air, it can't help but drop in hardness...putting it on a pc of cold steel that acts as a heat sink is better...and again quenching is better yet (but again; consider brittleness and toughness)...

...when talking tool steels, we're mostly talking about the carbon, man!


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## dontrinko (Nov 14, 2016)

I would like to add that tool bits do not have to be pretty to work good.  I would be ashamed to put a photo of some of mine on this site but they work fine. Don


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## Christian Poulsen (Nov 14, 2016)

"PA"; Once you find your wheels and practice; Instead of an hour, it will take you minutes to grind your cutters and less than a minute to resharpen one...
...here's a Google link to various pictures and charts (of angles) of lathe cutters.
...as some have said above: Practice, practice, practice (but also think, read and copy as yoose' practice, practice  )
... add: The "flatter" all the angles on a lathe cutter when appropriate (except like maybe a chip breaker ground in), whatever those angles may be, and better the finish, the better the results...
 (Remembering "rough" ("micro" sawtooth) on the finshed as ground angles that lead to and therefor on any cutting edge will last many times less.
"Rough" wears compared to smooth more, even when the work piece may be ledloy... rough finish cutters wear exponentially more as the tougher and harder up the scales the work piece is.
https://www.google.com/search?q=lat...X&ved=0ahUKEwjF5-HfianQAhVollQKHXQXCOgQsAQIGg


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## MagicSmoker (Nov 21, 2016)

Reeltor said:


> Take a look at Oxtool and ABomb79's YouTube video series entitled Chip Control.  Tom and Adam go at it trying to take the biggest cut using HSS hand ground bits, showing how they like to grind their tool bits.  IIRC one of them uses a hand grinder with the bit clamped in a vise to rough in the bit then move to the pedestal grinder.



Two thumb's up for the "Chip Control" video series. I was thoroughly confused on how to grind lathe tool bits until I watched the first video in the series.

One other thing I can perhaps add to the discussion: it really is very important to both true and dress the wheels on your bench grinder. Even the stock wheels on a Ryobi 6" grinder do a decent job grinding HSS *after* they are dressed (and of course the grinder shakes-and-bakes if the wheels aren't trued) *. I first bought a single point diamond truing tool off Amazon which did a good job (once I put a 3/8" drill stop on the handle to hold the point a fixed distance from the wheel), but the t-shaped tool with lots of little diamonds on it is far faster and easier to use for only a few dollars more. I bought it on a lark - along with a CGW "soft" 120 grit white wheel - from the local Woodcraft store. I use the usual star wheel type dressing tool (from HF), and it is flat out amazing how much faster the wheel will grind HSS after it is dressed (equally amazing - how quickly dressing reduces the diameter of the wheel and how much grit it throws into the air!).


* - I speak only of the efficacy of the grinder itself, not of my skill at grinding!


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## kwoodhands (Nov 26, 2016)

The grey wheels that come from an import machine are very good for honing your axe. Break it half or quarters for easier handling.
mike


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## MagicSmoker (Nov 26, 2016)

kwoodhands said:


> The grey wheels that come from an import machine are very good for honing your axe. Break it half or quarters for easier handling.
> mike



LOL... The wheels on the HF grinders I tried (both the 6" and 8" models) were, indeed, just that bad, but the stock wheels on the Ryobi (well, the fine wheel at least) do a passable job on HSS. That said, the CGW 120 grit wheel grinds HSS much faster and gives a finer finish than the stock ~60 grit Ryobi wheel, and it doesn't need to be dressed nearly so frequently, but it also cost $25 all by itself compared to $45 for the Ryobi grinder + 2 wheels. 

I'm not ditching the other Ryobi wheel just yet, though; the slower metal removal rate is actually a plus as I learn how to grind lathe tool bits (and, simultaneously learn just how ugly a bit can look and still cut metal just fine... ).


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## Terrywerm (Nov 27, 2016)

I was given an 8" bench grinder that came from HF. It vibrated and shook like the devil, and good luck trying to sharpen anything with it. It quickly became obvious why the previous owner wanted to be rid of it. Once I replaced the wheels with some good ones it was fine!


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## Christian Poulsen (Nov 28, 2016)

My HF 8" snag grinder I took back...the one on display seemed to spin fine by hand but mine looked like 2 potato chips spinning...
...upon turning on and then inspection at home, not only were the wheels molded like potato chips when I took them off but the spindle shafts (I think it's design had 2 separate and not one thru?) didn't run on center (As a matter of fact one side ran so far out it was more than the apx .030 travel one direction of my test indicator!)

No complaints though on the metal cutoff/band saw I bought from them (except the blades aren't the best)

PS: I checked out some of their drill presses last week but this time it was the sound and eyeballing the runout of some of the chucks by hand (maybe it was the spindles too) that scared me away...

It makes one think about the QC of some imported "stuff"...


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## kingmt01 (Nov 30, 2016)

I have a bench & a mini from HF. The mini once I throw away the handheld attachment was great out of the box. The bench grinder has some vibration but most went away with normal use. I finally dressed it & it runs smooth now.


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## Bob Korves (Dec 1, 2016)

Christian Poulsen said:


> My HF 8" snag grinder I took back...the one on display seemed to spin fine by hand but mine looked like 2 potato chips spinning...
> ...upon turning on and then inspection at home, not only were the wheels molded like potato chips when I took them off but the spindle shafts (I think it's design had 2 separate and not one thru?) didn't run on center (As a matter of fact one side ran so far out it was more than the apx .030 travel one direction of my test indicator!)
> 
> No complaints though on the metal cutoff/band saw I bought from them (except the blades aren't the best)
> ...


QC on most Asian stuff that comes to hobby-machinists is outsourced -- to the final purchaser!  The machine tools come with an inspection card that appears photocopied multiple times.  Those tools are going out the door, regardless.


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## kingmt01 (Dec 4, 2016)

Bob Korves said:


> QC on most Asian stuff that comes to hobby-machinists is outsourced -- to the final purchaser!  The machine tools come with an inspection card that appears photocopied multiple times.  Those tools are going out the door, regardless.


That is the best way I've ever heard it put. I actually usually buy this stuff planning to finish it when I get it.


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## Bob Korves (Dec 4, 2016)

kingmt01 said:


> That is the best way I've ever heard it put. I actually usually buy this stuff planning to finish it when I get it.


Yes.  They are all "parts kits" on some level.  Many of them are just fine as purchased, and others require some final work and QC before use, but they can usually be put to good use.  The question is -- what is your time and effort worth?  I am an old retired geezer so I work cheap...

The lack of manufacturer QC is a large part of the low purchase price.


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## kingmt01 (Dec 5, 2016)

Bob Korves said:


> Yes.  They are all "parts kits" on some level.  Many of them are just fine as purchased, and others require some final work and QC before use, but they can usually be put to good use.  The question is -- what is your time and effort worth?  I am an old retired geezer so I work cheap...
> 
> The lack of manufacturer QC is a large part of the low purchase price.


Or you can consider it cheaper then a school education as experience building project.


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## Bob Korves (Dec 5, 2016)

If you want to see some really nice projects turning sow's ears into silk purses, check out Stefan Gotteswinter's channel:
https://www.youtube.com/channel/UCY8gSLTqvs38bR9X061jFWw
He often uses inexpensive Asian import tooling just as raw material to make nice tools that meet his very high standards.  I highly recommend his channel.


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## kingmt01 (Dec 5, 2016)

OK
Last post that is off topic from me(at least I'll try to make it my last).

Speaking of Chinese made crap. I bought two tent garages yesterday. I have only opened one of them so far except for stealing parts from the second one to finish the first one. I couldn't get a nut started on one of the bolts. I noticed a extra thread on the end so I put it in the lathe & cut a little off the end. After cleaning the end up with a file the nut still wouldn't go on. Looking I still seen two threads on the end. So marking the thread with a sharpy I found it actually had a double start thread on the bolt. The nut is only a single start at half the thread pitch. I have no idea how this one strange bolt got in the mix but at quick glance it really looks like the correct bolt. I think I will hold on to this bolt just because I can't figure out how this mistake could ever happen in the first place being it is a formed bolt instead of a turned bolt & there was only one out of the bag of twelve.


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