| Author | Message | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
I need to tap a blind hole that has been drilled into a 3/8 aluminum plate. I don't want to drill through the plate but rather drill the hole 1/4" deep and then tap it. My taps have a long tapper that won't alow me to cut any threads before it bottoms out. Any suggestions? John | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
What you describe is going to be virtually impossible to do with a tap even if it's made for blind holes... you just don't have enough depth from what you've described. My first suggestion, Try drilling the hole as deep as you can without cutting thru, and make it the exact diameter minus a thousandth or so of a pem-nut that has the thread you want. Then press, pound, or otherwise force the pem nut into the hole and finally put a few punch marks around the edge to lock it in... (pem nuts are a pre-threaded insert that is made for operations almost like this, they are sometimes called pem-serts... if you cant find any and I have the thread you want I'll send you a few) Of course this won't be as strong as threaded aluminum, and it's probably not as easy as I might make it seem if you don't have the right tools, but without knowing what you're actually doing this for, it's my first take... Cheers Gary | ||
| R.C.Bishop (128.123.221.174)
Rating: N/A |
Or try epxoy.....  RCB | ||
| Bill (209.173.121.120) Rating: N/A |
Grind the bottom of the tap off. | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
If you do that (Grind the bottom of the tap off) try it first in a test piece. Usually because there's no taper left, the tap won't catch and instead it'll grind up the inside of your hole as you try to start it, making a mess. It might work but not likely in my opinion, with a hole as shallow as yours in aluminum... Cheers Gary | ||
| Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A |
I have successfully used a bottoming tap (special tap) to get the threads started, and then ground off the bottom of a tap until there is no tapered starting threads left. You can then very carefully start this tap in the threads started by the bottoming tap and tap within one thread to the bottom of the hole. | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
I appreciate the responses. I think I'll try to start the tread and then grind down the tap and tap further etc. Where would I find a bottoming tap? John | ||
| Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A |
Bottoming taps are very similar to regular taps, they just do not have a very long taper, so you have to be careful in starting them and make sure the tap is exactly vertical to the hole. One way to assure the tap is vertical is to put it in a drill press and then turn the quill by hand to get it started. Do not turn the power on! Bottoming taps should be available at any good tool supply house. They are really pretty common but many people are not aware of them. There are really three types of taps. Starting, Running and Bottoming and are generally available in sets. The difference in the three is the length of the taper. Richard | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
Hey, I like the tip about putting in a drill press and tuning it by hand. I'd of never thought to do that but I knew I could use the drill press under power. John | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
OOps, Meant to say "couldn't" use the drill press under power. John | ||
| Scott Whitney (66.82.9.17) Rating: N/A |
Another tip when using the bottoming tap: Try to orient the work piece so the cuttings fall out of the hole. Or back the tap out often and blow the cuttings out of the hole. Otherwise there is nowhere for them to go and they just clog up. Is this for your window screen inserts? Scott | ||
| Craig Craddock (Craigc1) (24.127.59.100)
Rating: N/A |
If you looking for any specialty maching tools In your case Taps of any kind are available from MSC Industrial Direct a Search Engine will get them. Might I also recommend a AL tapping lubrication. Also only turn the tap slowly and when resistance is increased turn backward about 1/4 turn to clear cuttings and then start tapping again. This way you are trying to not strip the threads you are making. If I can I install a center in a drill press. I buy taps that have a center hole on the hand end of the tap. I also use a tap hanlde so I can easily feel the pressure that is being applied. I have tapped hundreds of holes in AL using this method as small as 0-80. A good sharp tap also helps to get clean threads or with small taps not to break one off. Hope this helps a little | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
Hi Scott, No, not for the screens. It's for my slide-out step. John | ||
| Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A |
John, the suggestion for a tapping fluid is very good. I like RapidTap brand and it is available for either Aluminum or Steel and is not messy. If you are tapping a bunch of holes with a variable speed drill (works great), put some fluid in a small container and dip the tap in it before starting each hole. The top of a paint spray can works great for a container. Tap slowly, reverse often and keep the hole clear of chips. Richard | ||
| Gary Stadler (68.7.217.217) Rating: N/A |
John, four more questions before I add any more thoughts- (1) What size threads are you talking about here? (2) Why don't you want to drill thru the aluminum all the way? (3) Is your aluminum sheet hard or soft? (4) What will the load direction be, ie will your steps be trying to pull the screws straight out or will the load be trying to shear them off? Gary | ||
| Bradd B. Smith (216.18.141.105) Rating: N/A |
Hi, All good questions Gary. As I am sure everyone knows, taps come taper, plug and bottoming. If the taper will not start the threads, and in a 1/4", it will not. You may be able to start it with the plug and finish it with the bottoming tap. Keep in mind, it will not cut full threads all the way to the bottom either. Within a half a thread or so. The next consideration, as Gary pointed out, is load. A good rule of thumb, and I have 10, is the hole should be 1 1/2 times as deep as the total thickness of what you are securing including the top of the fastener. A 1/4 hole in aluminum won't hold much. The same rule applies to studs. 11/2 in hole to 1 out. Richard is dead on about using lube. Aluminum is much more difficult to deal with than steel. It likes to stick and break small taps. Make sure you use one made for aluminum or you are in for a real ride. The suggestion to use a threaded insert is good as long as the load is not to great. A threaded piece of aluminum could be tigged into a hole large enough to leave you some wall thickness and chamfer and welding room. and then ground smooth. Are we having fun yet? HTH and best luck, Bradd | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
Well, I was 50% successful in my objective. Drilled & tapped 4 holes- Had to go all the way thru on 2. Can I use JB weld (aluminum type) to fill the top of the hole? Gary, I am using 1/4 #20 flat head screws to fasten the upper half of a slide to the bottom of the 5/8 aluminum diamond plate. So, If anything, the screws will want to pull steight out. John | ||
| Jim Ashworth (Jimnh) (172.163.47.250)
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Now that we know what you are trying to do, nobody would probably notice if you went down through the aluminum plate with a stainless countersunk flathead bolt and put the nut on the bottom to hold the step. The tapped holes don't sound like a good idea if a 300 pounder should use the step. Jim | ||
| R.C.Bishop (128.123.221.227)
Rating: N/A |
I agree with Jim about a bolt and nut. On a 3/8 plate, with a shallow countersink, there would not be much left for holding power. As a point, epoxy, properly mixed has more holding strength probably than a # 1/4 inch bolt would have shear strength. FFT (food for thought) RCB | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
John, again without actually seeing it, I have to agree with Jim and RC... from the description you're asking for a fall, (pun intended!) Plus if you had a chance at all with your plan, you'd be better off with hard aluminum. Unfortunately Diamond plate aluminum is pretty soft stuff and all the worse at holding threads. A bolt or threaded insert, or simply some tig welded bosses to do your job with decent structure might be worth considering. Two things you don't want to happen: (1) The steps fall off when your wife takes a step up into the bus (2) You notice in your rear view mirror that your steps have just been flattened by the semi behind you... Cheers! Gary | ||
| Craig Craddock (Craigc1) (24.127.59.100)
Rating: N/A |
John I have used Jim and RC idea on the running boards to a steam locomotive to hold on the steam oil lubricators on. Looks OK and has worked for almost twenty years. They just blend in and no one has ever said anything about them. I would also be afraid if this step is in front of you front tire, what if it fell off and you ran over it. It could be a disaster. Craig C | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
OK, sounds like good advice to drill thru the plate and bolt it. Next question: I'd like to find a air actuated cylinder with about a 10" stroke that will fit under the step. about 1-1/4 hight clearance between the underside of sliding step and floor. Is this available?where would I look for info on this. John | ||
| Dale MC8 (64.66.196.59)
Rating: N/A |
John, Haven't tried it myself, but have been advised by someone whose opinion I respect, that the air cylinder from the restroom door would make a good actuator for a copilot step/floor. FWIW. Dale MC8 | ||
| Jim Ashworth (Jimnh) (172.128.168.62)
Rating: N/A |
That cylinder is a one way cylinder that acts like a door spring. If you had 2" or so, the a/c belt tensioner cylinder would do the job. Schraeder-Bellows has total stainless ones 3/4"x6 for under $30.00. Ingersall Rand/ARO has a 3/4"x10" composite one for $36.00. Check with MSC Industrial Supply Co. www.mscdirect.com Jim | ||
| Peter Broadribb (Madbrit) (170.215.39.82)
Rating: N/A |
Don't forget to make sure that in the event of a loss of air pressure, that the step cover opens up automatically. Otherwise you could be obstructing an emergency exit. Peter. | ||
| Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A |
I am under the impression that when maximum holding strength is desired, the hole should be drilled a few thousands undersize to provide deeper threads. Also I believe 1/4 X 28 (fine thread) would give more threads per inch and provide more holding strength. Richard | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
I'm putting in a sliding step, not a step cover. I want to put an air cylinder that will extend the step when activated and pull it back when deactivated. What do I need for this? John | ||
| RJ Long (24.127.74.29) Rating: N/A |
John - You've never mentioned what brand of bus you're installing this step on, but FYI, a retractable step has been a popular option on MCIs since the early '80's. Air powered, too, and set up in such a way that when you securely close the front door, the step automatically retracts so you won't tear it up by leaving it out when you drive off. One caveat, however: Because it's air powered, if the coach loses all it's air pressure, the step will retract slightly, and WILL move if someone steps on it going in either direction. Not so much a problem getting in the coach, but can be a hazard coming out. With a little imagineering, this can be overcome, however. Check with Luke 1-888-262-2434; Caylor Supply 785-878-6405; or Garry Dean (sorry, don't have his number handy), and one of them should be able to provide you with the entire step assembly, inluding the operating cylinder and other various odds 'n ends. HTH, RJ PD4106-2784 Fresno CA | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
Yes, I've looked into these. I'm converting a GMC 4905. The step and brackets that comprise this unit is to large and would hang down to low. I priced one from MCI and they quoted around $800.00 | ||
| RJ Long (24.127.74.29) Rating: N/A |
Well, then, John, just get the air slave cylinder from one of the MCI units. That should do the trick for you. . . RJ | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
RJ, what is a slave cylinder? Grant at US. Coach said the smallest cylinder that MCI uses that has a 10" throw is 2" dia. John | ||
| RJ Long (24.127.74.29) Rating: N/A |
John - I was talking about the air cylinder that MCI uses for the front step. Just using the generic "slave cylinder" interchangeably. Grant should be able to tell you what the throw is for that unit, if not, then MCI parts should know. IIRC, it's a pretty hefty cylinder, as it has to keep the step in position and immobile when somebody steps on it, including those 300 lb folk that ride Greyhound. . . RJ | ||
| john marbury (Jmarbury) (65.100.118.70)
Rating: N/A |
I'm now thinkig about using a power window motor linked to a worm gear. Any thoughts? John | ||
| Gary Stadler (68.7.217.217) Rating: N/A |
John, if you put in a bid for a hundred bucks at the last seconds of the auction, youre sure to win one of these for around $50-60 bucks: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1873147679 http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1873148037 http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1920076279 They are only 6" travel but you should be able to design to use them. They are hundreds each new, and I've used this make- they're great! The last one in the list isn't as strong as the first two but I think if designed right any owuld work. Ebay also has lots of longer ones from time to time if you're not in a hurry. Certainly a lot easier to use than air stuff... Cheers Gary | ||
| Peter Broadribb (Madbrit) (65.37.89.211)
Rating: N/A |
How about the actuator arm from one of the older style big satelite dishes. They work on 12 volts and are available in various lengths, weather proof, although not as small and neat as the ones that Gary found. Peter. | ||
| Buswarrior (Buswarrior) (64.229.214.55)
Rating: N/A |
John, the retracting steps on the MCI's that have been noted are a giant pain, and are easily ripped off on a high curb when sweeping the front end over the curb on a tight left hand turn. And they don't really stick out far enough. Awful Easy for an able bodied person to trip on the @#$#@$ thing. There's a reason the industry has gone to "kneeling" suspension and given up on the steps. Maybe you want to install a deflation valve for your front suspension instead? Or just build a wooden box to put down when you open the door, like the old time bus drivers did, and still do, in an older coach? happy coaching! buswarrior | ||
| AJB (12.217.194.128) Rating: N/A |
The only problem I can see is that the kneeling function is not reliable. Our company has a new J series from MCI that acts like a yo-yo when it is commanded to kneel. The driver can be outside the bus with the door open and watch it rise and drop a good 10 to 12 inches as they are standing there. One of our drivers has been driving for over 30 years and he says they tried the kneel function years ago. They didn't work then either. On the current yo-yo, they have replaced the valve and the controls for the function and it keeps on going. Mommy, I want to ride on the bus, where do I put the dime in? :-) |