Monthly Archive for January, 2011

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.

A comment on comments

Published on January 10, 2011 in Uncategorized. 2 Comments

I appreciate the comments you send in, and especially questions that suggest directions for future posts. My goal is to build a woodworking community here, and have some fun at the same time. Unfortunately, we bloggers get bombarded with spam comments, which the botnet managers hope I’ll be sleepy enough to approve so they can get a shot at you, my reader.

Here’s how I protect our community.

I use a spam filter to weed out link-choked “comments” so you and I don’t see them. I vet the rest. A lot of those are schemes promising webmasters “…huge amounts of traffic…” or “…make thousands by doing hardly any work.” I got three of those this morning. Peace was just a click away.

The rest of the spams are generic nonsense in broken English. How about, “I think everyone will really like to study this write-up once more & once more and am quite sure that most vsitors of this page will come here once more in future.” (sic). These try to get you to click on their URLs, which take you to sites that try to sell you something. They never relate to the article to which they’re responding. Click. They’re gone.

Finally, there are questionable ones that might be just pats on the back, but don’t mention anything specific about an article or about woodworking. I’ll usually post those if they show a person’s name. Otherwise, they go.

That’s it. Please comment. Please don’t spam.

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.