Skew technique with acrylic/acrylester

[putnamm]

I'm trying to do more of my turning with a skew chisel. For one thing, I understand it limits the amount of sanding necessary. And for another, I just want to practice and get better with the skew.

The skew I'm using is a 1" HSS. Nothing fancy; it came in a set from Harbor Freight. I've gotten a good edge on it using a Tormek, so I believe it is good and sharp.

My problem is that I'm having trouble moving the skew along acrylic and acrylester blanks. It seems to require a good deal of force to move the skew while cutting the acrylic, and even then I experience a lot of hitches. (Note that these are not "catches," where the skew bites in to the blank and creates a gash or chip. Rather, these are more like starts and stops where the skew seems no to want to move through the material.)

I'm turning on a Grizzly 10x18 benchtop lathe at the highest speed setting (about 3300 RPM). I'm using the six-inch tool rest that came with the lathe, and it has dawned on me that this may be the problem as the tool rest is not entirely smooth. I have tried a combination of underhand and overhand grips, and I've varied where I place my outside hand along the length of the tool handle. Finally, I'm doing my best and am fairly consistent with the "ABC" method--Approach with the tool on the rest, place the Bevel against the material, and begin to Cut by lifting the handle of the tool while also slightly rotating the tool until "ribbons" begin to appear, then move the skew along the blank to cut.

Not sure what I'm doing wrong, but I'd appreciate some of our more experienced turners pointing me in the right direction. I'd particularly appreciate any videos that I could watch of people using a skew properly on acrylic materials.

Thanks!
-Mark

 

[duncsuss]

The first thing I did to my skews was to "break the corners" -- if the tool has 90 degree corners, either take them to a grinder or use sandpaper to round them over. Also make sure your tool rest is nick-free and smooth (it doesn't cost anything to give the rest a quick rub with the piece you've just used to sand a pen barrel.)

Some people say that it's best to completely round over the sides of the skew, so that it neither rises nor falls as you rotate the tool handle to change the angle it presents to the workpiece. I haven't gone that far (yet).

 

[Charlie_W]

Mark, sounds like you are on the right track.
First, use a flat file to smooth the top of your tool rest. Next rub a little wax on it so your tool will slide easier.

Second, if your skew has square edges, it will not slide well on the tool test. Round the edges of your skew with a grinder, belt sander , or file to ease the edges. Many skews come with a rounded edge or are oval in shape.

Your skew's cutting edge needs to be at an angle to the blank....skewed...perhaps 45 degrees. I like my skews to be ground back leaving a less steep angle by the cutting edge.

I also like to have my skew in forward travel while raising the handle to engage the cutting edge. Less run backs this way.

Also cut low on the skew so your cut is as close to the support of the tool rest.

Hope this helps.

 

[putnamm]

Thank you both.

I think that smoothing out the tool rest and rounding the skew edges will definitely help. I may just go ahead and look for an oval skew chisel, since I don't own one of those.

Another question: What is the proper height of the tool rest for using a skew with a pen blank? Another way to ask this might be: How high on the blank should the cutting edge of the skew be making its cut?

Right now I have the tool rest about mid-height on the blank, such that the skew is making its cuts about a quarter inch higher than the blank's middle. I've watched some videos and noticed a lot of folks appear to be making their cuts higher than that, near say the top quarter of the blank. Any thoughts?

 

[KenV]

Mark,

I suspect the "hitch" may be happening as the depth of cut increases and becomes large for the materials being removed. The thickness of swarf gets thicker and makes the advance of the cutting edge difficult.

The hss steels used by HF are pretty low grade and can have inconsistent heat treat. Try a better grade skew and see if that helps your success. And before the yelps come, yes I have purchased and used HF lathe tools and compared outcomes. I find the better grade steel sharpens less often and is easier to get good cuts, especially finished cuts.

If you are sharpening on a Tormek, odds are extremely good that you are getting sharp edges. With HF skew, you might try a bit steeper bevel angle

 

[Davidh14]

I had this issue on wood and antler. I had finally wore the paint off my tool rest and was getting a rough edge. I tried filing it. It seemed to help for a bit but I would have to file it again after awhile.

Check out Rick Herrells tool rest. Very good quality! http://www.penturners.org/forum/f172/custom-made-penturning-tools-accessories-92501/

 

[Charlie_W]

Thank you both.

I think that smoothing out the tool rest and rounding the skew edges will definitely help. I may just go ahead and look for an oval skew chisel, since I don't own one of those.

Another question: What is the proper height of the tool rest for using a skew with a pen blank? Another way to ask this might be: How high on the blank should the cutting edge of the skew be making its cut?

Right now I have the tool rest about mid-height on the blank, such that the skew is making its cuts about a quarter inch higher than the blank's middle. I've watched some videos and noticed a lot of folks appear to be making their cuts higher than that, cnear say the top quarter of the blank. Any thoughts?

If standing at the tail stock end of your lathe looking at the head stock, I cut at about 10:30 position. With some experimenting and practice, you will find what works for you and the particular tool you are using.

 

[low_48]

If you ground to the factory angle, it's way too blunt. Google Alan Lacer for sharpening info. He also suggests a long radius across the bevel. I turn quite high on the blank. Think of the skew as a hand plane.

 

[putnamm]

If you ground to the factory angle, it's way too blunt. Google Alan Lacer for sharpening info. He also suggests a long radius across the bevel.

I've ground to a more acute angle, but it sounds like that might not be enough.

 

[Charlie_W]

Also note that with dense, hard or brittle blanks, you need to take very light cuts to turn these blanks successfully.

As for "Sharp", your skew should not have a burr and be able to shave the hair on your arm. I also use a diamond hone after visiting the grinder. Then you can just hone to keep a sharp edge till time to go back to the grinder.

 

[mecompco]

Never had much luck with my big skew. Switched to the little .5" one and suddenly it works. One or two quick passes on a 120 grit belt puts a razor edge on it. I'll second rounding the edges--all my tools dug into the tool rest before I hit them with the belt grinder.

Now I am having good results using the skew "all wrong". I know about the 45* angle, but I've found that if I get close to my final shape with the small gouge, then I can finish up with the skew by using it flat on the tool rest as a scraper. The finish it leaves is superb--I can go right to the MM pads with no more dry sanding like I used to do. I know it's not the proper use of the skew, but it works for me.

Regards,
Michael

 

[putnamm]

Now I am having good results using the skew "all wrong". I know about the 45* angle, but I've found that if I get close to my final shape with the small gouge, then I can finish up with the skew by using it flat on the tool rest as a scraper. The finish it leaves is superb--I can go right to the MM pads with no more dry sanding like I used to do. I know it's not the proper use of the skew, but it works for me.

Regards,
Michael

It's funny you mention this because I've been doing the exact same thing! For some reason I feel guilty. But you're right. It works really well. Glad I'm not the only one!

 

[TonyL]

If you have a Skype account, I will show you what I do - which is what works for me.

I use a roughing gouge to knock off the corners (I used to sand them as described above), then I use skew (either traditional angle or lacer angle).

I have not used an HF skew, but have used the Benjamin's Best without a problem.

I have found that if the chisel is very sharp, the cutting angle to the blanks is right, and the tools rest is set to the right height, the blank practically cuts itself. And trust me, I am no expert.

I also sharpen my skews several times per barrel. I know guys that sharpen their skews once a year (at least that is what they tell me). I can't get away with that.

I also own an oval skew, and finally learned how to sharpen it freehand (which was drove me nuts). It's a Sorbey. If you lived closer, I would let you try it. It is not my tool of choice, neither is their Spindlemaster. I also see lots of folks (on youtube videos) using oval skews and spindlemasters as scrapers which leaves radial scratches if I were to use them that way. Again, maybe others can get away with doing that, I cannot. I have to ensure that I am shear cutting to reduce the number and depth of radial scratches.

 

[Charlie_W]

Never had much luck with my big skew. Switched to the little .5" one and suddenly it works. One or two quick passes on a 120 grit belt puts a razor edge on it. I'll second rounding the edges--all my tools dug into the tool rest before I hit them with the belt grinder.

Now I am having good results using the skew "all wrong". I know about the 45* angle, but I've found that if I get close to my final shape with the small gouge, then I can finish up with the skew by using it flat on the tool rest as a scraper. The finish it leaves is superb--I can go right to the MM pads with no more dry sanding like I used to do. I know it's not the proper use of the skew, but it works for me.

Regards,
Michael

You can use a skew as a scraper. It will work best if there is a burr raised on whichever will be the top side of the skew/scraper. A burr will not last long at all and will need to be raised to keep a sharp edge cutting.
A flat skew is much easier to control when used as a scraper than an oval blade skew.
You may want to have one skew kept as a scraper and another for skew work.

Remember to wax your tool rest so it can slide effortlessly and not drag.

 

[JimB]

I think you are making a big mistake trying to learn how to use the skew on an acrylic blank. You should learn on something easier. I finally learned how to use a skew back in December and was taught by someone who is an expert with the skew. I learned on a piece of green (fresh cut) cherry. It made a huge difference.

I also have the HF set. If you still have it ground to the original bevel angles you will continue to struggle. You need to get it to about 25 degrees.

I hone my skew very frequently with a diamond credit card. That gives it a very, very sharp edge.

As other have mentioned, file your tool rest to get it smooth and wax it. If it is not smooth you can not get a smooth cut. That stop and go you experience may be your tool rest, not your cutting. Also round the edges on your skew so they do not dig into the tool rest.

 

[putnamm]

I think you are making a big mistake trying to learn how to use the skew on an acrylic blank. You should learn on something easier.

I appreciate the guidance. I have used the skew on a variety of woods, also, just for practice. I've been making beads, etc. to get a feel for the thing. So I'm not entirely unpracticed. But I am still new.

Also, I'm extremely hard-headed and impatient. So I tend to jump in with both feet. Granted, I subject myself to the consequences...

 

[mecompco]

Tony raises a good point--I've never tried an oval skew--mine is double-sided flat. I kind of give it a "swipe" on the belt when sharpening which knocks back the tip of the heel and toe a bit to help eliminate catches.

I take the blank right down to close to the final dimensions with the gouge. Keep the gouge sharp and you can get a very nice finish. Using the skew as a scraper to get down to the final dimensions and smooth out any ripples from the gouge seems to work for me. I take very fine cuts, and it takes practice to keep the tool on the rest and the depth of the cut uniform across the whole blank. I've not notices radial scratches left from the skew. If there were any, a little dry sanding would make quick work of them.

Also as mentioned, the tools have to slide easy over the rest. I spent a couple of hours removing all the crinkle paint that was on my rest, then filing and sanding the whole thing smooth. My cheap tools all had very sharp square edges until I hit them with the belt grinder.

I know you have a bench grinder, but I'm surprised more people don't use a belt grinder. You can do flat grinds, hollow grinds or what I prefer, a slight concave grind (using the slack part of the belt). You also have a vast array of belts you can use, not just the two wheels on a bench grinder.

Keep at it and you'll find the method that works for you.

Regards,
Michael

 

[MTViper]

Mark,

Get an 8' 4x4 at Home Depot, cut it in chunks, and turn with the skew til it's all sawdust. Amazing how much you can learn from that.

Steve

 

[Charlie_W]

Tony raises a good point--I've never tried an oval skew--mine is double-sided flat. I kind of give it a "swipe" on the belt when sharpening which knocks back the tip of the heel and toe a bit to help eliminate catches.

I take the blank right down to close to the final dimensions with the gouge. Keep the gouge sharp and you can get a very nice finish. Using the skew as a scraper to get down to the final dimensions and smooth out any ripples from the gouge seems to work for me. I take very fine cuts, and it takes practice to keep the tool on the rest and the depth of the cut uniform across the whole blank. I've not notices radial scratches left from the skew. If there were any, a little dry sanding would make quick work of them.

Also as mentioned, the tools have to slide easy over the rest. I spent a couple of hours removing all the crinkle paint that was on my rest, then filing and sanding the whole thing smooth. My cheap tools all had very sharp square edges until I hit them with the belt grinder.

I know you have a bench grinder, but I'm surprised more people don't use a belt grinder. You can do flat grinds, hollow grinds or what I prefer, a slight concave grind (using the slack part of the belt). You also have a vast array of belts you can use, not just the two wheels on a bench grinder.

Keep at it and you'll find the method that works for you.

Regards,
Michael

Michael, It is good that you found what works for you. Having the toe and heel taken back a tad helps when using the skew as a scraper.
If you use the skew for other traditional skew cuts you do want crisp sharp toe/heel or you will not be able to do some cuts. An extra skew for this work would be good and keep the other for scraping.

 

[putnamm]

So I bought a new tool rest from Woodcraft that has a rounded bar on top. It made a huge difference. I also made sure my skew was extremely sharp. I will be reshaping the edges in the near future.

 

[mecompco]

Michael, It is good that you found what works for you. Having the toe and heel taken back a tad helps when using the skew as a scraper.

If you use the skew for other traditional skew cuts you do want crisp sharp toe/heel or you will not be able to do some cuts. An extra skew for this work would be good and keep the other for scraping.

Charile, thanks for the advice and I'll keep that in mind.

Regards,
Michael

 

[Charlie_W]

So I bought a new tool rest from Woodcraft that has a rounded bar on top. It made a huge difference. I also made sure my skew was extremely sharp. I will be reshaping the edges in the near future.

Good move on the tool rest! Sounds like you are in good shape now!
Ok you have more questions, just ask.