Used endmills

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Mr Ron
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Used endmills

Post by Mr Ron » Tue Sep 10, 2019 12:16 pm

Buying endmills can be expensive for a home shop, so my question is; if I buy used endmills in lots and buy a tool grinder, and sharpen them myself, will they be as good as a brand new endmill and will it be cost effective? The cost of U.S. made HSS endmills can add up pretty quick.
Mr.Ron from South Mississippi

John Evans
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Re: Used endmills

Post by John Evans » Tue Sep 10, 2019 1:30 pm

Have you priced a tool and cutter grinder? If used it must have all the tooling,more to cutter grinding than first appears. Cost effective ?? I doubt it unless you have hundreds of mills to sharpen. And is it a good use of your time? Personally I would not even consider sharpening anything under 3/8 s to start with even if I had all the needed tooling from my old B&S #13 grinder.
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Glenn Brooks
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Re: Used endmills

Post by Glenn Brooks » Tue Sep 10, 2019 1:37 pm

Mr Ron,

Personally I decided not to take on sharpening end mills. The geometry is complex and each cutting edge needs to be precisely in alignment with all the others on the shanks - seems like a real PITA.

However, I have had good success buying used and NOS end mill lots off eBay. Lots of times CNC high precision and aerospace shops sell off vast quantities of slightly used end mills, that are still perfectly fine for manual machines. Once in a great while I have had to throw away one or two items from a bulk purchase- but mostly they are good to go. IF i inspect the pictures on eBay closely, and watch what I bid on.

(And I only buy cheap, pennies on the dollar, offerings. )

Glenn
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Harold_V
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Re: Used endmills

Post by Harold_V » Tue Sep 10, 2019 3:57 pm

Keep one thing in mind when you consider sharpening end mills. They have a limited lifespan, and can only be sharpened a given number of times, all relating to how much must be removed to restore a keen edge. The problem comes from losing rake as the diameter is reduced, and that happens all too quickly as the diameter of the end mill is reduced. My rule of thumb is that small end mills (<¼") are best not resharpened on the periphery.

The rake angle could be restored if the flute could be reground, but without a CNC cutter grinder, that's not easy to do, so it isn't generally done.

Don't discount the value of rake on end mills. Reduced rake, along with reduced flute volume (needed for chip evacuation) renders such end mills useless, as they perform extremely poorly.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

LIALLEGHENY
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Re: Used endmills

Post by LIALLEGHENY » Tue Sep 10, 2019 4:19 pm

Personally I think Ginsu should get into the endmill manufacturing business. With the perpetual edge it would sharpen as you use it.

Back to reality....I also buy endmills from Ebay. Like Glenn said there are companies that sell lots of slightly used good quality endmills that work quite well in manual machines. Beware, you can spend hours looking for deals, but they are there.

Nyle

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SteveM
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Re: Used endmills

Post by SteveM » Tue Sep 10, 2019 9:06 pm

See if there is a local shop that can sharpen them for you, or look into mail order.

On carbide, the cost to sharpen them is a small fraction of the cost to buy one, so you can come out ahead. The HSS ones aren't as much of a bargain, but can still be cost effective, particularly if you buy a bulk lot of end mills at an auction and get them cheap enough.

Steve

spro
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Re: Used endmills

Post by spro » Tue Sep 10, 2019 11:41 pm

Once at an auction (big one ) There were boxes of end mills and one box looked really good. They were sold in "lots" to where you were getting other boxes. The other open boxes had endmills which were reground too but they were examples. They were examples of others using a T/C grinder for practice. The webs were wrong , edges were wrong and the diameter was way off.
Proper diameter is what we use as a register.

Mr Ron
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Re: Used endmills

Post by Mr Ron » Wed Sep 11, 2019 12:54 pm

Thanks. Doesn't sound like a good idea after all.
Mr.Ron from South Mississippi

pete
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Re: Used endmills

Post by pete » Wed Sep 11, 2019 2:32 pm

Given the cost for new high quality or in other words durable long lasting end mills in a home shop I understand the reasoning behind the question. If Youtube is any example I see many using up there end mills inefficiently. At a certain point moving to a larger diameter replaceable tip face mill for metal removal would be much more cost effective when machining larger areas. Your still limited for just how large any mill can effectively use those face mills though. Unless your taking very light depths of cut an R8 taper Bridgeport or clone is maybe good for a 2.5" - really pushing things 3" diameter face mill. I also see many making multiple fine finishing passes to final size with larger end mills. When I can I'll always change tools and run a fly cutter for that job. That's what they were designed for and will almost always leave a better surface finish anyway. And against the costs for those end mills face mills and fly cutters are a whole lot cheaper when the work allows there use.

Unlike industry for most of us tool life is far more important than maximum rates of metal removal per minute. Dropping your rpm and feed rates 10-20% below what the books recommend will give a far greater increase in tool life than that 10 - 20%. A huge number of the home cnc guy's seem fixated on just how fast they can push there light weight machines and tooling. It might seem impressive, but I'm happy I'm not the one paying there tooling costs. Chip recutting will also drastically shorten tool life for end mills as well. So how your generally using the tooling has a very large effect for the maximum life you can expect before resharpening or replacement.

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tornitore45
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Re: Used endmills

Post by tornitore45 » Thu Sep 12, 2019 6:50 am

I demote the marginal end mill to slogging through on non precision jobs in Aluminum. And when an end mill has finally had it it is a good piece of HSS to make a special tool for the lathe, or cut the shank to use as a dowel to align the spindle with a hole, or a spacer or a pusher in the wise. Nothing goes to waste in my shop, except time.
Mauro Gaetano
in Austin TX

Harold_V
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Re: Used endmills

Post by Harold_V » Thu Sep 12, 2019 3:20 pm

tornitore45 wrote:
Thu Sep 12, 2019 6:50 am
Nothing goes to waste in my shop, except time.
Sounds all too familiar.
I throw almost nothing away, and I've been well rewarded for that practice. For me, to purchase anything involves a considerable amount of travel, with the nearest store 7 miles away, where precious little is available (common fasteners). For anything more, I must travel at least 25 miles, one way, and even then my options are quite limited.

I have ample storage, and it's reasonably well organized, so I can find what I need, when I need it.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

RSG
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Re: Used endmills

Post by RSG » Fri Sep 13, 2019 6:28 am

tornitore45 wrote:
Thu Sep 12, 2019 6:50 am
Nothing goes to waste in my shop, except time.
LOL @ Mauro :lol:

I thought about sharpening mine once but for all the reasons mentioned above I decided not to as I don't have the skill, the machinery nor the time. I found a local place that will sharpen them but will only will send out endmills 5/8" and larger, anything smaller gets tossed in a bucket and replaced with new. I don't mess with correcting for size adjustments and bad finishes on my most used endmills, anything 1/8" to 1/2" as an example.
Vision is not seeing things as they are, but as they will be.

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