Archive for the 'Machines' Category

Finishing and using the pin chuck

Published on March 7, 2011 in Jigs and Fixtures, Machines and Woodturning. 1 Comment Tags: , .

Grinding the flat

Once the shaft slid smoothly into a 7mm pen barrel, it was time to cut a flat for the locking pin. I clamped the shaft in a vise and removed most of the metal with a grindstone in a Dremel rotary tool. Just as in hand sharpening, I locked my arms to my body, then used my legs to traverse the tool back and forth, about 75% of the way along the shaft. I got a fairly even cut.

The shaft, with its locking nail

Once I’d removed about a third of the diameter of the shaft with the grinder, I filed the cut flat. For this job I used a 10″ single-cut mill file. File teeth are graded relative to the length of the file, so a fine-tooth 10″ file has smaller teeth than a fine-tooth 12″ file, and leaves a nicer finish. A double-cut file cuts faster, but rougher. About 15 minutes of work got me a relatively flat surface along most of the shaft, as you see at left.

The nail I’d originally selected as a locking pin proved too large, so I used a #4 finishing nail instead, nipping off its head first. Here is the complete tool, almost ready for use.

Magnetizing

I say “almost” because, if your shop is like mine, having a little loose part such as the pin is a recipe for grief. It’ll get lost in no time, probably falling into the chips under the lathe the first time I pull a pen blank off it. So I ran the pin and shaft through a magnetizer. It doesn’t make them grip tightly—the pin can still roll so it locks, but it keeps the nail from sliding off the shaft.

In use

Here’s the new pin chuck in use. I held it in a Beale collet chuck (they have less runout than scroll chucks or Jacobs chucks), slid the desk pen blank on, and twisted it to lock it in place. I brought up the tailstock to stabilize things for most of the turning, parted off at the end of the bead, and pulled the tailstock out of the way to clean up and sand the part. It worked like a charm.

Comments on Grizzly’s 10″ Wet Grinder

Published on February 18, 2011 in Machines and Reviews. 2 Comments Tags: , .

Tormek's T-7 wet grinder

Maybe you’ve thought about a wet grinder to sharpen your tools. Having used one for over 15 years, I can tell you they’re a wonderful way to put edges on carbon steel chisels and plane blades. You just can’t burn the steel, no matter how ham-handed your grinding. That means you can grind to a feather edge—something you can’t do with a dry grinder without overheating the edge and drawing the temper. Once you see some heat coloring, it’s already too late!

Jet’s JSSG-10 10″ Wet Grinder

Cost is what keeps most people from using these grinders. Tormek, grandaddy of the category, sells their T-7 system for $600. Then there are the accessories… But competition is bringing prices down. Jet sells their version of the tool, the JSSG-10, for $320 (at Amazon, who also sells the Tormek). In a smart move, Jet made their machine accept all the Tormek accessories, so they had a full line of fixtures available before they got all their own on the market.

Grizzly’s T10010 10″ Wet Grinder

Now Grizzly has joined the party with the T10010, its version of the same tool. At less than $200, it’s a new low price point. But how good is it?

Woodworking friend and Sawdust Shop regular Julien Lecomte wrote me about his experiences with the Grizzly. With his permission, I’ve published his message:

“Since you teach the sharpening class at the Sawdust Shop, I thought I would report on my experience with the Grizzly wet grinder.

I use it solely to shape the primary bevel on my chisels and plane irons. I haven’t tried the leather strop yet.

One thing I noticed immediately after unpacking the unit was that the wheel was not true at all! I purchased the Tormek jig to true the wheel (almost all the Tormek jigs fit the Grizzly unit) and was back in business in no time.

Overall, I am very happy with this wet grinder. It misses a few nice features of the Tormek, such as the fine adjustment of the guide rod, but for only $180 (vs $400 for the Tormek), I warmly recommend it.

Starting the jig

Published on January 30, 2011 in Jigs and Fixtures and Machines. 5 Comments Tags: , .

Drilling the melamine

I built this device using scraps of melamine-coated particle board, a flat, low-friction material that’s perfect for jigs.

My design called for two plates, separated by the 3/8″ bolts and nuts shown in the previous post. To drill bolt holes that line up in the two plates, I attached them together with a couple small pieces of double-stick tape, then set the drill press fence and stops so I could drill all four holes.

Above you see the bottom of the jig, which sports four large counter-bores (holes that don’t go through) to accommodate the heads of the carriage bolts, so they won’t drag on the table as I move the jig around. I drilled them first, using a 1″ Forstner bit which drills a flat-bottomed hole.

Forstner bit speed table

A lot of people run Forstner bits too fast, then wonder why they burn the wood and won’t hold an edge. The table at the left came with my set, and it shows that I should run the 1″ bit at around 800 RPM. When I did, it cut smoothly, with no burning.

Forstner bits leave a tiny pit in the center of the hole, and I used that to line up for drilling through both plates with a 3/8″ bit to accept the bolts.

Backer blocks eliminate chipping

Melamine is very brittle, but when I set the drill for the right speed (about 2100 RPM on my machine) and backed up the cut with scrap wood, I got the clean exit holes you see at the left, with no chipping. Note that there is some fraying or chipping around the edges of the plate. This surface faced down when I cut it on the table saw, and I didn’t take the time to set up a zero-clearance throat plate on the saw (it’s just a jig, after all). Therefore, as the blade teeth exited the cut, they pulled a little of the brittle melamine away from the core. The throat plate would have taken care of that. Covering the cut line with masking tape can also help.

Next, assembling and adjusting the jig.

How to hit the high notes

Published on January 27, 2011 in Jigs and Fixtures, Machines and Woodturning. 3 Comments Tags: , , .

I belong to a woodturning club, and each month we have a President’s Challenge project, to get us to stretch a bit and try something we wouldn’t normally do. This month’s challenge is “Stemmed”.

The note at an early stage, on the lathe.

I think one of the secrets to success is to figure out what everyone else is doing and don’t do it. In this case, I’m betting a lot of people will turn goblets or pieces of fruit. So I wanted to make a musical note.

I mounted a 3″ diameter chunk of osage orange between centers, and turned the stem down to 5/16″ using classic spindle turning techniques. I left a large round piece at the bottom. At this stage, it looked rather like a top.

The next step was to mount it sideways, gripping that large round section between centers. Then I could turn the section down to become the body of the note. I had to turn very carefully, because that long, thin stem whips around in an almost invisible arc. I turned left-handed so I could cut in close to the stem while keeping my hands clear. You can see the note body (that ball on top) is complete, and I next have to remove the rest of that big wooden round. I’ve remounted it along the original turning axis for the photo.

A Porter Cable trim router is the right size.

Now’s the interesting part. I want to attach a “flag” to the stem, like a musical note would have. That means I need to cut a 1/8″-wide mortise in the stem to accept the end of the flag.

I had a little trim router perfect for the job. But I needed to be able to move it in a controlled way along the centerline of the turning. Time to make a jig.

Here are the guts of the jig.

I started with some scrap melamine-coated particle board, 3/8″ carriage bolts, nuts, and washers. Carriage bolts are nice for jigs because once their square shoulders bite in to the wood, they won’t rotate as you tighten bolts on them. By building the jig as a base and elevated platform, fastened by bolts, I eliminated the need for precision cutting and tricky measurements of router bit height. This jig would be adjustable! (That also means I can adapt it to other routers when this one dies.)

Next—turning that pile of stuff into a jig.

Fixing the Beall Collet Chuck

Published on January 1, 2011 in Machines. 10 Comments Tags: .

The problem, explained in the previous post, was that the cap for the collet chuck was improperly machined, so it had a ridge of metal inside that would push the collet off center before it was clamped down. The solution, just as it would be for a wooden cap, was to turn away that ridge without damaging the precision surface that touches the collet.

Collet cap mounted in a three-jaw scroll chuck.

The necessary turning didn’t demand precision. The ring just had to be turned away. So I mounted the cap on a metal lathe in a three-jaw scroll chuck. This chuck centers work within a few thousandths of an inch, and that was adequate for this job.

I wanted to be able to reach into the cap with a cutting tool, hooking around the threads and cutting away the ridge beyond them, toward the headstock.

The boring bar, ready to go to work.

Fortunately, I had just the tool for the job—a 1/2″ boring bar with a carbide tip brazed on the end. That tip reached a little beyond the bar’s side (toward the camera in the photo), enough to clear the threads and cut the ridge. I mounted the bar in a quick-change tool holder, then measured the tool holder’s position when the bar was just past the ridge, but not yet contacting the precision taper which holds the collet in place.

The final result – no more ridge interference.

After that, it was a simple matter to spin up the part and carefully advance the bar into the collet cap, cutting away a little at a time until the ridge was almost gone.

Here’s the final result. You can still see the remnant of the ridge, but it’s now concentric with the tapered hole, and it’s cut back far enough that it no longer touches the collets as I tighten them up.

What a difference! The properly machined cap pushed the collets in tightly without tilting them. Runout at the collet went from .007″ before to about .0005″. Of course, a metal lathe made the job easy. Otherwise, it would have meant a trip to a machine shop. Shame on you, Beall, for letting this part out the door in the first place.

The moral of the story? Check your tools before you blame yourself for problems. Even good quality gear from reputable manufacturers can have problems.

Don’t trust anybody!

Published on December 29, 2010 in Machines. 4 Comments Tags: .

All right, that’s harsh. But sometimes we blame ourselves for bad results when the fault lies with equipment we just assumed was fine.

I’ve been working with my home made rose engine lathe, learning what it can do. Rose engines (more about them in the future) are slow at removing wood, so I hand-turn blanks to roughly the right shape on my traditional lathe, then use the rose engine for final shaping. To get the best possible registration as I move work from one lathe to the other, I got a Beall Collet Chuck to hold the blanks. Collets are more precise than scroll chucks.

Or, are they?

I chucked a walnut rod into the Collet Chuck and turned it round, then moved it to the rose engine. There was .007″ of runout! What’s up with that?

I know, 7/1000 of an inch doesn’t sound like much. In fact, noted turner John Jordan once told me that runout like that makes no difference at all. But I’m using the rose engine to cut through walnut walls only .014″ thick, to reveal white maple inside. It’s an sgraffito technique (where you cut through one surface to show a surface beneath). .007″ is half the wall thickness, and quite noticeable indeed. The pattern was obviously wider and deeper on one side of the piece than the other.

A collet chuck with runout problems

Time for some detective work.

I first assumed I must have turned the piece carelessly. So, just to be sure, I put the Collet Chuck back on the lathe and chucked a piece of 1/4″ drill rod in it. When I measured the runout with a dial indicator, it was .007″. You can see the setup at the left.

Here's the problem!

I took the Collet Chuck apart and looked at the pieces. These chucks have precision spring collets, held in a tapered hole by a screw-on cap that forces the collets to move into the body and tighten up, rather like router collets. When I turned over that cap, here’s what I saw.

The collet cap in my hand has a tapered opening that bears on the collet, forcing it into the hole. But this cap must have been machined near quitting time on Friday afternoon. Note how there’s a ridge of metal just inside the rear hole, and it’s off center! That meant the collet would be pressed into the chuck body only on one side of the top, virtually guaranteeing it would seat off-center.

Isn’t that often the way it goes? Halfway into a project, we have to stop and repair the machine or build the fixture to make the next step possible. Coming up next, fixing the problem.