sharpening trouble...

[Faulko]

Hi,

i've got some melton hollowers and I'm struggling to keep them sharp. I've used an ezylap diamond hone and the slipstone along the bevel in an upward action. I am struggling to get a burr. The slip stone seems a little more effective, but i don't think its meant to be this hard to keep them sharp. I have heeded the established wisdom of not trying to sharpen on a grinder.
Anyone have experience with keeping these hollowers sharp?
thanks

[Old Croc]

Hey mate, just did a Google search and no mention of them. Do you want to post a picture for us?
Rgds,
Crocy.

[Faulko]

sorry - keyboard fail...Kelton or McNaughton hollowers.
Kelton Hollowers (http://www.kelton.co.nz/Kelton%20Hollowers.html)

[Skew ChiDAMN!!]

I think you've just discovered why they're not as popular as, say, a Munro or other replaceable tip type hollower. (If I'm thinking of the right type, that is? Basically a negative rake scraper with a down-curved top on the nose?)

Honing keeps an edge fresh for as long as possible, but there comes a time when the cutting edge is rounded over too far for a burr to be created, in which case it needs a touch-up on a grinder. Especially if you didn't raise the burr often enough while working hard timbers. Just the same as any other tool in that regard.

This is one of the reasons I'm an advocate of learning to sharpen free-hand, at least for a beginner, and only buying sharpening jigs to save time later. Once you have already mastered the skill to sharpen tools that can't be handled by a jig. (I have a similar soap-box with regards to chucks. :rolleyes:)

For other scrapers of similar type I would actually grind the top surface to recreate the edge angle, then dress with a hone stone as per usual to rebuild the burr... but I believe that's the one thing Kelton says specifically not to do? I wonder why?

Perhaps they hammer harden that top surface, or do something similar to minimise wear on the top surface while leaving the bevel material softer to assist in honing? Then they certainly wouldn't want you to grind that away... and I wouldn't try. :no: It may just ruin the tool if this is the case.

Sorry I can't be of more help.

Edit: Gak! On rereading I see that I've used both 'honing' & 'raising a burr' interchangeably. They're two different things, I shouldn't have said honing at all in this context. But you know what I mean, right?

[Faulko]

thanks skew. u r right in that kelton are clear in their advice to not use on a grinder. i think i must've had a brain snap one day and ran the diamond hone across the top flat of scraping end of the tool..which would've neen a mistake and made this situation worse. i will try and post a pic or two tonight to show close up....i am pretty sure they have a standard scraper shape but with a layer of better steel on the top/edge..which is why the advice is to avoid the grinder....

[NeilS]

Anyone have experience with keeping these hollowers sharp?


I don't have the Kelton hollowers, but I do have their coring blade sets.

If the tips are made of the same material on both systems (you may need to check that out) then my experience is that they sharpen quite readily on a diamond wheel. I expect CBN would do a similar job.

I have even reshaped the tips on the coring bars without any issues.

I haven't touched the top surface, but wouldn't hesitate to do so if I thought that the top surface wasn't polished enough. That is, of course, different from regularly resharpening the top surface to keep a sharp edge.

I expect the cutting metal is quite thin on that top surface.




Sent from my ZTE T84 using Tapatalk

[Faulko]

442751
442752
442753

here's a few pics

[hughie]

I had a set of Kelton Hollowers, essentially they are Oland tools and they are basically scrapers. I found them to be not what I expected and on-sold them. Now some folk may like them but they are not for me.

[Faulko]

i have been happy with them...when sharp.

[NeilS]

I don't have the Kelton hollowers, but I do have their coring blade sets.



I should add that, as yet, nobody has come up with a coring blade system that doesn't use scraper tips. For hollowing I prefer cutting tools like the Woodcut. But, until somebody comes up with a coring system that cuts rather than scrapes, we will have to make do with scraping tips on corers.

I do, and will continue to, use scrapers for my final light finishing cuts/scrapes, as most (but not all) experienced turners do. So, understanding how to sharpen scraper tips will continue to be important knowledge for most turners.

I ran a thread on some tests I conducted on the durability of scraper burrs raised by various methods back in Feb 2011. Unfortunately that predates the 'great image disappearance', so none of the associated digital microscope images are there any longer, which makes the thread next to useless. But, for what it is worth, here is the original thread; A brief history of the burr (http://www.woodworkforums.com/f8/brief-history-burr-131073). I still have the images from that original thread, however, I'm not sure that I could re-post them in a way that would work, ie add value rather than just confusing everyone.

The thread also provided a link to the article on scraper sharpness by Alan Lacer & Jeryl Wright but that is also now broken. Here it is again on page 67 of https://www.mnwoodturners.com/cms-files/sharpeningturningtoolsbookdo.pdf

As always...

[Acco]

I still have the images from that original thread, however, I'm not sure that I could re-post them in a way that would work, ie add value rather than just confusing everyone.


If you PM Neil (uBeaut) I’m sure that he can change your settings so that you could re-attach your images in there original spots

[NeilS]

If you PM Neil (uBeaut) I’m sure that he can change your settings so that you could re-attach your images in there original spots

OK, I have manage to add a few of the original images with a new post at #16 of A brief history of the burr (http://www.woodworkforums.com/f8/brief-history-burr-131073).

[Paul39]

I do 95 % bowls. I use bowl gouges, then for finishing, scrapers. I sharpen my scrapers upside down on a 120 grit white wheel, with about an 80 degree undercut. This works well on medium and softer timbers, taking off a tissue paper thin layer. This burr lasts for 30 seconds to a minute, then is gone. For the last, last finishing cuts I sharpen the same way then hone the top on 240 or 320 grit laid flat on the lathe bed. Again good for just a minute.

I think with the hard Aussie timber the burr would be gone in 10 - 20 seconds.

Faulko, If you have a flat plate on your grinder, set it so that your upside down scraper goes into the wheel slightly down. Start at one end, into the wheel and a rotation to give it a swipe over the cutting surface. I hold the scraper flat on the plate with one finger and rotate the scraper with the other hand. Have a look at the end to see the shiney part is all the way to the top. Feel for a burr on top. have ago at a piece of timber.

If you have a rounded scraper to practice with, that would be better than starting with the hollowers. If the method works for you, do the same with the hollowers.

If the hollowers work with the increased sharpening, use them up, and buy better ones. I think there are some that use carbide tips.

[hughie]

I don't have the Kelton hollowers, but I do have their coring blade sets.

If the tips are made of the same material on both systems (you may need to check that out) then my experience is that they sharpen quite readily on a diamond wheel. I expect CBN would do a similar job.

I have even reshaped the tips on the coring bars without any issues.

I haven't touched the top surface, but wouldn't hesitate to do so if I thought that the top surface wasn't polished enough. That is, of course, different from regularly resharpening the top surface to keep a sharp edge.

I expect the cutting metal is quite thin on that top surface.




Sent from my ZTE T84 using Tapatalk


I seem to remember from way back that the tips were stellite a hard facing deposit done with an arc welder.Usually found in the earth moving game to hard face the buckets and teeth.

[Paul39]

Faulko,

Continuing from last night when my brain got fuzzy. In photo #1 of your post #7 that tool looks like a tine from a garden rake that has been used to rake stony ground. That does not look sharp. Is that after use and before sharpening, or after sharpening?

In the light of further posts, it would be best to not touch the top surface of the tool, but do all sharpening on the front, per my post #13.

From this: http://www.kelton.co.nz/Guides/Kelton%20Hollowers%20Guide.pdf

The Cutting Tip is designed for both rapid removal of waste wood and fine finish cuts resulting in a

sanded



like surface. While maintaining their extremely effective cutting edges, these tips, unlike high

speed steel tools, will not back temper or loose hardness with sharpening induced heat. The precision
shaped cutting tips of the Hollowers will easily outlast those of high speed steel tools.

I copied and pasted the above and can't remove all the formatting.




High speed steel was designed for cutting steel on metal lathes and mills at red heat taking off smoking hot blue chips.

https://youtu.be/Bs-CRzXEnM4?t=1505

There are various grades of HSS but I have not experienced any lack of sharpness from any of my purported HSS tools, including cheap Chinese. They do not cut as long as carbide tipped, but are sharper than carbide for finishing cuts.

I am a tool slut, so have tools by Crown, Sorby, Henry Taylor, Thompson, Craftsman, Penn State Industries, Easy Wood carbide, generic Sheffield, cheap Chinese HSS and carbon steel, home made from mystery metal and 5/8 in square file, scraper made from a 2 1/2 X 12 X 3/8 inch HSS planer blade, scraper made from a rotary lawn mower blade for knocking dirt, rocks, bark, etc. off of stumps. Thin parting tool made from a ham slicing knife. All have their purpose.

Except for a 5/8 inch Crown bowl gouge (I had Christmas crazy money) all were purchased used for 1/2 or less price. On the order of 8 HSS with decent handles for $40.

A purpose ground tool does not have to be made from expensive exotic steel to cut a spigot or recess to mount a bowl. A nice chunk of carbon steel works fine.

Hogging out the inside of a 20 inch bowl on a 3 HP lathe is another matter. I would want a 5/8 inch carbide tip on a 3 foot long tool. I own the tool, but not the lathe. Not yet.

[NeilS]

OK, I have manage to add a few of the original images with a new post at #16 of A brief history of the burr (http://www.woodworkforums.com/f8/brief-history-burr-131073).Faulko, you may not have a digital microscope that goes up to 200x magnification (yet), but I would encourage you to get a jeweller's loupe, if you don't already have one... 10x to 15x mag is sufficient. They are not very expensive.

When I saw those photos of your hollowing tips I was reaching for my loupe wanting to have a closer look at their edges (or perhaps lack of edge). I find my loupe is an indispensable tool when I'm sharpening any blade.

As always...

Sent from my ZTE T84 using Tapatalk