This is the thumb screw from the DeWalt DW788 scroll saw. The tip of the screw rotates. This helps prevent the blade from twisting when tightening the clamp. I have a question. Does any one know the name for this type of screw. Does anyone know of a source for a rotating tip screw. I don't meant a replacement thumb screw for the DeWalt. I just want a name and source for a generic rotating tip screw.
I have searched McMaster-Carr without finding anything. Maybe this is a special made part but I doubt it.
The next four pictures are the clamps on a couple of my saws. Click them to enlarge. I get a lot of questions about blade slippage and about the knobs. I wanted to talk for a minute about these subjects. The pictures are from my Excalibur and one of my DeWalt DW788's
This first picture shows a clamp that is in need of some maintenance. Look closely at the contact points of the set screw and the thumb screw. Notice the gap at the top. This is probably because the blade chuck has bent from over tightening. It's common to want to over tighten the clam when the blade start slipping out of the clamp. This is not the solutions. What you probably need to do is replace the set screw and thumb screw. I have prolonged the life by lightly sanding the points but you have to be very careful to keep the two point straight. In the case of this clamp assembly I need to replace the set screw, thumb screw and the blade chuck. For the DeWalt that's going to cost around $40 with shipping. that's for upper and lower clamps.
I have in the past shown how to make or buy larger knobs for the thumbscrew. The thumbscrews can be hard on those with weak or sore hands. The above damage can be caused by the extra torque you can gain from the larger knob or lever. That's why I always give the warning that you want to be careful with the larger knob. Just use modest pressure. If the blade is slipping you need maintenance not more torque.
Thisis a picture of the Excalibur upper clamp.The set screw has been sanded a couple times but it's still in decent shape and holding well. The picture is a little off but the blade is centered between the two contact points which is what you want.
Thispicture shows the lower clamp of the Excalibur. Notice a couple things here. The blade is centered and in full contact with the set screw and thumb screw. You can also see a little spec of blue on the left set screw. This is removable Loctite blue. It prevents the setscrew from vibrating out but is removable with hand tools. With out the Loctite the set screw will eventually move. If you notice that it's moved you can just adjust it but sometime that gets over looked. The Loctite keeps it in place once adjusted. You can buy Loctite from most hardware stores.
This last picture shows a badly adjusted lower blade clamp. See how the blade is not centered in the blade chuck. The left set screw needs to be adjusted to recenter the blade.
These tips can apply to other scroll saws as well depending on how their clamps work.
Keep the set screws and thumb screws maintained.
Make sure they are adjusted so the blade rides centered in the chuck.
Do not over tighten the thumb screw. If the blade is slipping check these tips.
If you sand the tips, do it gently. Don't remove material. Just lightly rough up the tips. Get a replacement set when needed. They are not that expensive when you consider the aggravation of slipping blades.
A little removable Loctite on the left set screw can help keep it in place.
