making mounting hardware

Tuesday, February 14. 2006

I need some studs and square nuts for my taig mill. I often find myself wanting to clamp

my first batch of parts

the work down rather than put it in a vise, and generally this is a rather challenging task. I used to use 10-32 socket head cap screws with square nuts, but they have to be of the "just right" length - a little too short, and they do not engage in the threads very well. A little too long and you risk damaging the table. You need an assortment of 10-32 screws and lots of washers to have any hope of holding a workpiece like that. 10-32 cap screws are also a bit too small to use with the clamping kit that I picked up a while ago. You need some pretty thick and wide washers that fit 10-32 screws to make that work. In other words, there is technically nothing wrong with using 10-32 screws and square nuts to clamp a workpiece to the table, but it's tedious, takes long to set up and adjust, and is not quite as rigid as it could have been.

It turns out, however, that you can use 1/4" bolts to clamp work. They fit in the table slots just fine. They are big enough to work well with the clamping kit I have. THey are cheap and can be had in a variety of length at any hardware store. And if you have the the head of the bolt in the slot with the threaded part protruding out, there is no risk of damaging the table! There are two small caveats though. One is that the bolt head is not quite as big as I would've wanted it to be. So it can rotate in the slot making it a little hard to tighten the nut (there is no easy way to hold the bolt steady when you are doing this - the head is completely hidden in the slot). The second caveat is somewhat related to the first one - since the underside of the bolt is not flat, and you are not even sure which way the bolt is oriented in the slot when you tighten it, chances are that there are a couple of points where the bolt exerts great pressure on the underside of the slot, while not touching it at all in other places. This can lead to poor holding quality, as well as potential damage to the inside of the slot if you tighten the bolts with sufficient force.

My solution was to cut small aluminum blocks that fit tightly on the bolt heads. The

Cutting blocks

blocks solve both problems - they are square (1.0"x0.5") so they will not rotate in the slot. And they are made of soft aluminum and are very flat. When a bolt with such a block on it is tightened for the first time, it will be pressed into the block and slightly distort. The two essentially become one part. But now we have a nice flat soft surface of the aluminum block to push on the underside of the slot instead of just a couple of small spots on the bolt. That should protect the table, increase holding force and make clamping an easer task in general.

In addition to making a useful thing for my mill, this projst allowed me to learn something about making multiple parts with sheetcam. Each block is 1.0"x0.5"x0.21", and is cut from a 0.21" aluminum sheet. A 4-flute 3/32" HSS endmill was used at 10K RPM and 15 IPM. Passes were 0.05" deep with 50% step-over for pocketing. Each part takes 2.5 minutes to make. I cut 5 of them in a batch, making 5 batches total.

Since I was cutting multiple identical parts in a more or less controlled environment, I experimented with cooling and lubrication a little. I tried:

cutting dry without touching the bit or the part
cutting mostly dry with s squirt of WD-40 at the beginning of the cut
cutting while soaking the milling bit in WD-40
cutting dry while aggressively brushing away the chips as best as I could
cutting with WD-40 while brusing away the chips
using a vacuum cleaner to remove chips while cutting
using a water-based coolant.

The best result, surprisingly, is acheived with the water-based coolant. It both washes away the chips and cools, preventing chip wielding. Even with WD-40 I had problems with chip wielding when milling deep slots around the outside edge of each part. Water cooling left the pieces with an excellent finish. I think water cooling is a must regardless of whether cutting aluminum or steel (I was already using it for all steel work). The only problem I need to resolve now is how to prevent the oil from being washed away from the ways of the mill. I have been ATF for lubricant, and it washes away with water very easily, leaving water-based coolant with a small amount of ATF dissolved in it as my "way oil". Not good. Need to find a better lubricant. I am trying bicycle chain oil at the moment. It appears to have pretty good lubricating qualities, and is designed to 'stick' to the metal and resist being washed away with water. This might be just what I need.

Posted by vlad in metalworking at 09:49 | Comments (3) | Trackback (1)

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Awesome idea.

You wouldn't still happen to have the gcode available to make these blocks?

I'd love to make a set if I ever get the cnc back up after my move to texas.

#1 John Zitterkopf (Homepage) on 2006-06-07 21:56 (Reply)

Hi John! I do still have the g-code. I've arranged it in such a way as to cut five nuts in one pass. If you want just one nut, start with line N0100. (this was my first try at cutting multiple identical parts in a row, so my hand-editing of g-code looks quite amateurish at best, but it worked!). Here you go:

N0000 (Filename: bolt_quintuple.tap)

N0010 (Post processor: Mach2.post)

N0020 (Date: 2/10/2006)

N0030 G20 (Units: Inches)

N0040 G40 G90

N0050 F1

N0060 (Part: bolt2)

N0070 M6 T2 (Mill/Router, 0.0937 in diameter)

N0080 G43 H2 F15

G0x0y0z0

G10 G90 L2 P2 X0

G10 G90 L2 P3 X1.1

G10 G90 L2 P4 X2.2

G10 G90 L2 P5 X3.3

G10 G90 L2 P6 X4.4

N0090 M04 S10500

G0 G40 G90 G59

M98 P1234

G0 G40 G90 G58

M98 P1234

G0 G40 G90 G57

M98 P1234

G0 G40 G90 G56

M98 P1234

G0 G40 G90 G55

M98 P1234

M05 M30

O1234

N0100 (Process: Spiral pocket hex, Mill/Router, 0.0937 in diameter, 0.15 in Deep)

N0110 G00 Z0.2000

N0120 X0.4684 Y0.2500

N0130 Z0.0197

N0140 G01 Z-0.0500 F1

N0150 X0.4842 Y0.2774 F15

N0160 X0.5158

N0170 X0.5316 Y0.2500

N0180 X0.5158 Y0.2226

N0190 X0.4842

N0200 X0.4684 Y0.2500

N0210 X0.4143

N0220 X0.4571 Y0.3242

N0230 X0.5429

N0240 X0.5857 Y0.2500

N0250 X0.5429 Y0.1758

N0260 X0.4571 Y0.1758

N0270 X0.4143 Y0.2500

N0280 X0.3602 Y0.2500

N0290 X0.4301 Y0.3711

N0300 X0.5699 Y0.3711

N0310 X0.6398 Y0.2500

N0320 X0.5699 Y0.1289

N0330 X0.4301 Y0.1289

N0340 X0.3602 Y0.2500

N0350 X0.3061

N0360 X0.4030 Y0.4179

N0370 X0.5970 Y0.4179

N0380 X0.6939 Y0.2500

N0390 X0.5970 Y0.0821

N0400 X0.4030 Y0.0821

N0410 X0.3061 Y0.2500

N0420 G00 Z0.2000

N0430 X0.4684 Y0.2500

N0440 Z-0.0303

N0450 G01 Z-0.1000 F1

N0460 X0.4842 Y0.2774 F15

N0470 X0.5158

N0480 X0.5316 Y0.2500

N0490 X0.5158 Y0.2226

N0500 X0.4842

N0510 X0.4684 Y0.2500

N0520 X0.4143

N0530 X0.4571 Y0.3242

N0540 X0.5429

N0550 X0.5857 Y0.2500

N0560 X0.5429 Y0.1758

N0570 X0.4571 Y0.1758

N0580 X0.4143 Y0.2500

N0590 X0.3602 Y0.2500

N0600 X0.4301 Y0.3711

N0610 X0.5699 Y0.3711

N0620 X0.6398 Y0.2500

N0630 X0.5699 Y0.1289

N0640 X0.4301 Y0.1289

N0650 X0.3602 Y0.2500

N0660 X0.3061

N0670 X0.4030 Y0.4179

N0680 X0.5970 Y0.4179

N0690 X0.6939 Y0.2500

N0700 X0.5970 Y0.0821

N0710 X0.4030 Y0.0821

N0720 X0.3061 Y0.2500

N0730 G00 Z0.2000

N0740 X0.4684 Y0.2500

N0750 Z-0.0803

N0760 G01 Z-0.1500 F1

N0770 X0.4842 Y0.2774 F15

N0780 X0.5158

N0790 X0.5316 Y0.2500

N0800 X0.5158 Y0.2226

N0810 X0.4842

N0820 X0.4684 Y0.2500

N0830 X0.4143

N0840 X0.4571 Y0.3242

N0850 X0.5429

N0860 X0.5857 Y0.2500

N0870 X0.5429 Y0.1758

N0880 X0.4571 Y0.1758

N0890 X0.4143 Y0.2500

N0900 X0.3602 Y0.2500

N0910 X0.4301 Y0.3711

N0920 X0.5699 Y0.3711

N0930 X0.6398 Y0.2500

N0940 X0.5699 Y0.1289

N0950 X0.4301 Y0.1289

N0960 X0.3602 Y0.2500

N0970 X0.3061

N0980 X0.4030 Y0.4179

N0990 X0.5970 Y0.4179

N1000 X0.6939 Y0.2500

N1010 X0.5970 Y0.0821

N1020 X0.4030 Y0.0821

N1030 X0.3061 Y0.2500

N1040 M03

N1050 (Process: Inside offset hole, Mill/Router, 0.0937 in diameter, 0.23 in Deep)

N1060 G00 Z0.2000

N1070 X0.4219 Y0.2500

N1080 Z-0.1303

N1090 G01 Z-0.2000 F1

N1100 G02 X0.5000 Y0.3281 I0.0781 J0.0000 F15.0

N1110 X0.5781 Y0.2500 I0.0000 J-0.0781

N1120 X0.5000 Y0.1719 I-0.0781 J0.0000

N1130 X0.4219 Y0.2500 I0.0000 J0.0781

N1140 G01 Z-0.2300 F1

N1150 G02 X0.5000 Y0.3281 I0.0781 J0.0000 F15.0

N1160 X0.5781 Y0.2500 I0.0000 J-0.0781

N1170 X0.5000 Y0.1719 I-0.0781 J0.0000

N1180 X0.4219 Y0.2500 I0.0000 J0.0781

N1190 (Process: Outside offset contour, Mill/Router, 0.0937 in diameter, 0.23 in Deep)

N1200 G00 Z0.2000

N1210 X0.0000 Y-0.0469

N1220 Z0.0197

N1230 G01 Z-0.0500 F1

N1240 X1.0000 F15

N1250 G03 X1.0469 Y0.0000 I0.0000 J0.0469

N1260 G01 Y0.5000

N1270 G03 X1.0000 Y0.5469 I-0.0469 J0.0000

N1280 G01 X0.0000

N1290 G03 X-0.0469 Y0.5000 I0.0000 J-0.0469

N1300 G01 Y0.0000

N1310 G03 X0.0000 Y-0.0469 I0.0469 J0.0000

N1320 G01 Z-0.1000 F1

N1330 X1.0000 F15

N1340 G03 X1.0469 Y0.0000 I0.0000 J0.0469

N1350 G01 Y0.5000

N1360 G03 X1.0000 Y0.5469 I-0.0469 J0.0000

N1370 G01 X0.0000

N1380 G03 X-0.0469 Y0.5000 I0.0000 J-0.0469

N1390 G01 Y0.0000

N1400 G03 X0.0000 Y-0.0469 I0.0469 J0.0000

N1410 G01 Z-0.1500 F1

N1420 X1.0000 F15

N1430 G03 X1.0469 Y0.0000 I0.0000 J0.0469

N1440 G01 Y0.5000

N1450 G03 X1.0000 Y0.5469 I-0.0469 J0.0000

N1460 G01 X0.0000

N1470 G03 X-0.0469 Y0.5000 I0.0000 J-0.0469

N1480 G01 Y0.0000

N1490 G03 X0.0000 Y-0.0469 I0.0469 J0.0000

N1500 G01 Z-0.2000 F1

N1510 X1.0000 F15

N1520 G03 X1.0469 Y0.0000 I0.0000 J0.0469

N1530 G01 Y0.5000

N1540 G03 X1.0000 Y0.5469 I-0.0469 J0.0000

N1550 G01 X0.0000

N1560 G03 X-0.0469 Y0.5000 I0.0000 J-0.0469

N1570 G01 Y0.0000

N1580 G03 X0.0000 Y-0.0469 I0.0469 J0.0000

N1590 G01 Z-0.2300 F1

N1600 X1.0000 F15

N1610 G03 X1.0469 Y0.0000 I0.0000 J0.0469

N1620 G01 Y0.5000

N1630 G03 X1.0000 Y0.5469 I-0.0469 J0.0000

N1640 G01 X0.0000

N1650 G03 X-0.0469 Y0.5000 I0.0000 J-0.0469

N1660 G01 Y0.0000

N1670 G03 X0.0000 Y-0.0469 I0.0469 J0.0000

N1680 G00 Z0.2000

N1710 M99

#1.1 Vlad on 2006-06-09 00:20 (Reply)

Thanks.

I look forward to trying out the gcode when I get my cnc back up.

#1.1.1 John Zitterkopf (Homepage) on 2006-06-09 17:13 (Reply)

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