Homemade scraper

[MKepke]

Trying to contribute something in my meager way..

..this is a short explanation of a negative rake scraper I built using a cheap HSS blank (see also thinshavings' thread of a similar name)

I started with a Chineseium HSS blank off Amazon..


I wanted about 3" of the tool inserted into the handle. Rather than lose 3" of good (ish) tool steel, I opted to grind in a 1" long shank on one end. Made fairly quick work of it with a cutting wheel in an angle grinder.

That shank got inserted into a 5/8" x 3" mild steel rod made from a garden variety 5/8" hex bolt (I chopped the head and threads off the bolt and slotted one end to receive the HSS shank). Fitting the HSS shank and the mild steel bolt..err rod..took probably an hour of mucking around (grind, file, hit with hammer, repeat).

Once I was happy with the fit, I preheated with a propane torch, then fluxcore welded the two together..and tada. Looks like it stuck together despite my terrible welding skills.




I had planned to make a Hosaluk-style insert (above), but after I turned one on my metal lathe out of a scrap bolt, I decided it was too heavy. Instead I made an insert out of scrap 1/2" black pipe - the ID is just under 5/8", so easy to bore to the full 5/8 ID. Readily available at the local big box too.

Bought a replacement post-hole digger handle for a tool handle. Bored the end to take the steel insert and gave it a very light profiling. Then epoxied the DIY insert into the wooden handle. Normally there should be some method of securing the tool's shank into the insert, like set-screws but the surface finish on the tool's shank was rough enough that a jam-fit worked fine.

The wooden handle unfortunately is not ash, but cuts like some sort of cheap imported hardwood. Check carefully before you buy replacement garden tool handles if that's important to you.

Next step for the scraper was to spend a lot of time profiling it at the grinder. I opted to make it a so-called negative rake scraper (NRS) to remove tool marks from the interiors of bowls.

This one I ground for an interior curve with 70 degrees on one face and 20 degrees on the other (for a 90 degree included angle). That is a sexy grinding job - look at those curves!

Cutting is done with a burr you raise on the edge, just like a cabinet scraper - you can just barely see it glinting in the picture above right. One can raise a burr by regrinding the edge or by using a burnishing rod. For better or worse, this Chinesium HSS steel comes from the factory with high hardness - like Rc-65-ish hard (my Rc-65 file makes light scratches you can see, but not feel).


For burnishing I tried a rod style burnisher, but wasn't getting a great burr so I switched to using a Veritas carbide jig that I've had for ages.

It did much better raising a burr. It uses an angled carbide rod and when clamped in a vise you can apply a lot more pressure. Will save the rod burnisher for my card scrapers.


So how does this Frankenstein perform at the lathe? Pretty good - it takes very fine shavings and the sweeping curve eliminates those pesky toolmarks from the interior of bowls. Probably ready for 220 grit?

Unfortunately the burr is very short-lived necessitating removing the old burr with a stone and raising a new burr. This is definitely a finishing tool.

Lessons learned:
*The method I used to join the tool steel to the mild steel 5/8" rod had a number of problems including being fussy to cut, hard to align and hard to regrind to roundness. In the future, I'll try simply cutting a 1"x5/8" notch into the HSS blank and weld the mild steel rod into that notch.

*Grind the same bevel angle on both sides of the tool. I got the idea for the 70/20 grind angles from D-way Tools, but in retrospect, it was not a great choice - as it requires two different grinding set-ups. Over time, I'll change to use the same bevel angles on both faces. That'll probably let me raise a bigger burr too.

*Really like being able to remove the tooling from the handle - it makes grinding much easier.

*Use a different style of insert holder to (continue to) avoid setscrews. I'm thinking about using NPT pipe and cheap 5C collets. If I use collets, I may have to switch to proper steel rod and not the cheap bolts - as the bolts are undersized .614 versus a true .625 and may not be held properly in a collet.

-Mark

[Bill Holt]

Great post!
I enjoy the rewards of a scraper; have not tried the negative rake.  Your thoughts on the two different angles make since.  So I am wondering:
1. What advantage does the 70/20 offer?
2. Do you need to regrind both angles each time?

[MKepke]

Great post!
I enjoy the rewards of a scraper; have not tried the negative rake.  Your thoughts on the two different angles make since.  So I am wondering:
1. What advantage does the 70/20 offer?
2. Do you need to regrind both angles each time?

Don't think there's anything particularly special about the 70/20 grind. I chose that one for a first attempt at making a scraper since it matched a factory scraper and secondly, it's easier to take off more metal than put it back.

Like I said tho, I'm going to change the grind over time to use the same angle top and bottom.

In practice, you only need to grind the bottom bevel - at least until you've ground the edge back so far the top bevel needs to be re-ground too.

Hairy mentioned that when he needs to re-do the burr, he only regrinds - no burnishing. I burnish because it extends the time between regrinding.

-Mark

[hairy]

Trying to contribute something in my meager way..

..this is a short explanation of a negative rake scraper I built using a cheap HSS blank (see also thinshavings' thread of a similar name)

I started with a Chineseium HSS blank off Amazon..


I wanted about 3" of the tool inserted into the handle. Rather than lose 3" of good (ish) tool steel, I opted to grind in a 1" long shank on one end. Made fairly quick work of it with a cutting wheel in an angle grinder.

That shank got inserted into a 5/8" x 3" mild steel rod made from a garden variety 5/8" hex bolt (I chopped the head and threads off the bolt and slotted one end to receive the HSS shank). Fitting the HSS shank and the mild steel bolt..err rod..took probably an hour of mucking around (grind, file, hit with hammer, repeat).

Once I was happy with the fit, I preheated with a propane torch, then fluxcore welded the two together..and tada. Looks like it stuck together despite my terrible welding skills.




I had planned to make a Hosaluk-style insert (above), but after I turned one on my metal lathe out of a scrap bolt, I decided it was too heavy.  Instead I made an insert out of scrap 1/2" black pipe -  the ID is just under 5/8", so easy to bore to the full 5/8 ID. Readily available at the local big box too.

Bought a replacement post-hole digger handle for a tool handle.  Bored the end to take the steel insert and gave it a very light profiling.    Then epoxied the DIY insert into the wooden handle. Normally there should be some method of securing the tool's shank into the insert, like set-screws but the surface finish on the tool's shank was rough enough that a jam-fit worked fine.

The wooden handle unfortunately is not ash, but cuts like some sort of cheap imported hardwood. Check carefully before you buy replacement garden tool handles if that's important to you.

Next step for the scraper was to spend a lot of time profiling it at the grinder. I opted to make it a so-called negative rake scraper (NRS) to remove tool marks from the interiors of bowls.

This one I ground for an interior curve with 70 degrees on one face and 20 degrees on the other (for a 90 degree included angle).  That is a sexy grinding job - look at those curves!

Cutting is done with a burr you raise on the edge, just like a cabinet scraper - you can just barely see it glinting in the picture above right. One can raise a burr by regrinding the edge or by using a burnishing rod. For better or worse, this Chinesium HSS steel comes from the factory with high hardness - like Rc-65-ish hard (my Rc-65 file makes light scratches you can see, but not feel).


For burnishing I tried a rod style burnisher, but wasn't getting a great burr so I switched to using a Veritas carbide jig that I've had for ages.

It did much better raising a burr. It uses an angled carbide rod and when clamped in a vise you can apply a lot more pressure.  Will save the rod burnisher for my card scrapers.


So how does this Frankenstein perform at the lathe?  Pretty good - it takes very fine shavings and the sweeping curve eliminates those pesky toolmarks from the interior of bowls. Probably ready for 220 grit?

Unfortunately the burr is very short-lived necessitating removing the old burr with a stone and raising a new burr.  This is definitely a finishing tool.

Lessons learned:
*The method I used to join the tool steel to the mild steel 5/8" rod had a number of problems including being fussy to cut, hard to align and hard to regrind to roundness. In the future, I'll try simply cutting a 1"x5/8" notch into the HSS blank and weld the mild steel rod into that notch.

*Grind the same bevel angle on both sides of the tool. I got the idea for the 70/20 grind angles from D-way Tools, but in retrospect, it was not a great choice - as it requires two different grinding set-ups. Over time, I'll change to use the same bevel angles on both faces. That'll probably let me raise a bigger burr too.

*Really like being able to remove the tooling from the handle - it makes grinding much easier.

*Use a different style of insert holder to (continue to) avoid setscrews. I'm thinking about using NPT pipe and cheap 5C collets. If I use collets, I may have to switch to proper steel rod and not the cheap bolts - as the bolts are undersized .614 versus a true .625 and may not be held properly in a collet.

-Mark

I didn't make mine. I got a Sorby.
 https://www.grizzly.com/products/robert-...YkEALw_wcB

1 and 1/2" wide x 3/8" thick

This  link is just to show the tool, look around, prices are varied for the same thing.

I ground it to 40 degrees on each side. It will do inside and outside very well.

I don't remember the angle as it was delivered. I used an AO 120 wheel and kept going until each side was as the other and met in the middle. Resharpen in about 30 seconds.Straight back to cutting, no burnishing.

It's not a negative rake scraper until the included angle is less than 90 degrees.

This is end grain hard maple. Cut smooth as baby's bottom. No sanding necessary.

I'm struggling trying to get a good pic of the tool

[hairy]

I didn't make mine. I got a Sorby.
 https://www.grizzly.com/products/robert-...YkEALw_wcB

1 and 1/2" wide x 3/8" thick

This  link is just to show the tool, look around, prices are varied for the same thing.

I ground it to 40 degrees on each side. It will do inside and outside very well.

I don't remember the angle as it was delivered. I used an AO 120 wheel and kept going until each side was as the other and met in the middle. Resharpen in about 30 seconds.Straight back to cutting, no burnishing.

It's not a negative rake scraper until the included angle is less than 90 degrees.

This is end grain hard maple. Cut smooth as baby's bottom. No sanding necessary.

I'm struggling trying to get a good pic of the tool


Here's a better view.

[Dave in Denver]

This thread has been really helpful for me- thanks! I think I’ll be taking this project on in the near future. Here’s an additional video I came across that’s also helpful: https://youtu.be/wymTRPilYB4. It’s less than 5 minutes long.

Dave in Denver