alan0043 Posted January 24, 2017 Report Share Posted January 24, 2017 Hi Everyone, I am starting to get the truck ready for the air hitch. I will be using 4"x4"x1/2" angle steel to support a 1/2" plate that the hitch will sit on top of. It was suggested that I use a tapered bridge reamer to drill the holes in the truck frame. I have done a search on line with no real luck. I also did a search on You Tube. Looking for, how to use a tapered bridge reamer. My question is, do you drill a pilot hole first then go the tapered reamer. What size pilot do I drill. I am planning on using a 9/16" reamer. Also part of the plan is to use six 1/2" grade 8 bolts per side to hold the angle steel. If the bolts seem to small what use would you use ? All input is welcomed, Al 2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger " Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood " 2006 Smart Car " Killer Frog " Link to comment Share on other sites More sharing options...
Darryl&Rita Posted January 24, 2017 Report Share Posted January 24, 2017 ...I don't even. A reamer is for finish-reaming a hole to a close-tolerance finish, not drilling. I have been wrong before, I'll probably be wrong again. 2000 Kenworth T 2000 w/N-14 and 10 speed Gen1 Autoshift, deck built by Star Fabrication 2006 smart fourtwo cdi cabriolet 2007 32.5' Fleetwood QuantumPlease e-mail us here. Link to comment Share on other sites More sharing options...
jkennell Posted January 24, 2017 Report Share Posted January 24, 2017 Alan--Overkill. Just drill a slightly oversize hole (17/32?) in the first place, and go with your (6) 1/2" bolts. No camper at present. Way too many farm machines to maintain. Link to comment Share on other sites More sharing options...
rickeieio Posted January 24, 2017 Report Share Posted January 24, 2017 Non engineer answer......The strength comes from the clamping force of your bolts, not the shear strength. Thus having the holes a little off is of little consequence. It's more important to use adequate bolts and properly tighten them, than to fuss over getting the holes perfectly round. I'll be staying at a Quality Inn this weekend, so factor that into any wrong answers..... KW T-680, POPEMOBILE Newmar X-Aire, VATICAN Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row Young enough to play in the dirt as a retired farmer. contact me at rickeieio1@comcast.net Link to comment Share on other sites More sharing options...
GeorgiaHybrid Posted January 24, 2017 Report Share Posted January 24, 2017 Rickeieio, the bolts actually have a lower value in slip critical connections (clamping force) than they do in bearing (bolt body placed in shear). The upside is if a bolt does slip into bearing, it is stronger than when figured as slip critical. The value is the same for both methods when in tension but the bolts in this condition are in shear only, no tension loads. 2017 Kenworth T6802015 DRV 38RSSA Elite Suites2016 Smart Prime Link to comment Share on other sites More sharing options...
noteven Posted January 25, 2017 Report Share Posted January 25, 2017 Kenworth trucks use 16mm bolts installed in 17mm holes. "Are we there yet?" asked no motorcycle rider, ever. Link to comment Share on other sites More sharing options...
rickeieio Posted January 25, 2017 Report Share Posted January 25, 2017 Rickeieio, the bolts actually have a lower value in slip critical connections (clamping force) than they do in bearing (bolt body placed in shear). The upside is if a bolt does slip into bearing, it is stronger than when figured as slip critical. The value is the same for both methods when in tension but the bolts in this condition are in shear only, no tension loads. Thanks for the lesson. When in doubt, I just shoot for overkill, so my fuzzy white a$$ is covered. Never put in 3 bolts when there's room for 4. KW T-680, POPEMOBILE Newmar X-Aire, VATICAN Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row Young enough to play in the dirt as a retired farmer. contact me at rickeieio1@comcast.net Link to comment Share on other sites More sharing options...
GeorgiaHybrid Posted January 25, 2017 Report Share Posted January 25, 2017 Rick, Never fear, with us the motto is "When in doubt, make it stout" 2017 Kenworth T6802015 DRV 38RSSA Elite Suites2016 Smart Prime Link to comment Share on other sites More sharing options...
sbslinde Posted January 25, 2017 Report Share Posted January 25, 2017 If you are going to use a twist drill, I would recommend using M42 cobalt drill bits. They will stay sharper longer. You will find them at Production Tool or similar tooling outlets. Drill a pilot hole. My personal choice would be to use a Rotobroach style tool. These look like small hole saws, but more accurate. Jeff Link to comment Share on other sites More sharing options...
phoenix2013 Posted January 25, 2017 Report Share Posted January 25, 2017 We use round shank reamers from McMaster-Carr https://www.mcmaster.com/#bridge-reamers/=162cs3m 1/2 inch, 5/8 and 3/4. They are pricey but worth their cost in gold. The ETs have over 120 holes in them and require a bit of "finish" reaming putting together welded assemblies. McMaster chart shows you what start hole you need for the reamer you purchase. The ET is mounted on 5/8 plate with 4 x 4 x 1/2 inch angles into the frame. The hitch is held to the plate with eight 5/8 bolts, grade 8. The angles are mounted to the frame with six 3/4 inch bolts, grade 8. Is it an overkill, absolutely, do I fill good about it, absolutely. Am I embarrassed about designing in and recommending an overkill, not a bit. Could I save money by using bolts with just enough tension and shear rating, sure, about half a six pack's worth. Link to comment Share on other sites More sharing options...
Star Dreamer Posted January 25, 2017 Report Share Posted January 25, 2017 I thought I remember a requirement by the DOT that bolts need to be 5/8" minimum for structural items on the HDT. We came across thst when we were building our truck bed. Dave 2005 Freightliner Century S/T, Singled, Air ride ET Jr. hitch 2019 46'+ Dune Sport Man Cave custom 5th wheel toy hauler Owner of the 1978 Custom Van "Star Dreamer" which might be seen at a local car show near you! Check out http://www.hhrvresource.com/ for much more info on HDT's. Link to comment Share on other sites More sharing options...
Scrap Posted February 4, 2017 Report Share Posted February 4, 2017 I'm kinda late to the game, but yea, 12mm 5th wheel holes is medium duty stuff. If you want to stay over 66K GCW then it needs to be 16mm. Yea KW does 17.2 holes for 16mm and 13.2 for 12mm. I just ordered two trucks with custom frame drill. Saved me the work of drilling 84 holes on each truck. That option was worth every penny! Link to comment Share on other sites More sharing options...
alan0043 Posted February 4, 2017 Author Report Share Posted February 4, 2017 Hi Everyone, Here is a little update on the truck. The frame is now drilled. Also the angle iron is all drilled and fitted to the truck. Everything bolts up just fine. I had to drill four new holes pre side. The truck will have a total of six holes per side for a grand total of twelve bolts being used. The plan is to use 9/16" grade 8 bolts. The 3/8" steel plate that sit's on top of the angle is also drilled. There is a grand total of twelve 9/16" grade 8 bolts that hold the plate to the angle. Al 2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger " Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood " 2006 Smart Car " Killer Frog " Link to comment Share on other sites More sharing options...
MrSeas Posted February 4, 2017 Report Share Posted February 4, 2017 So what did you end up using to drill all of the holes? Link to comment Share on other sites More sharing options...
alan0043 Posted February 4, 2017 Author Report Share Posted February 4, 2017 So what did you end up using to drill all of the holes? All the holes on the truck I used a carbide 5/16" bit for the pilot holes and then finished up using a tapered bridge reamer. The holes in the angle iron and the steel plate I drill using high speed steel drill bits. Al 2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger " Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood " 2006 Smart Car " Killer Frog " Link to comment Share on other sites More sharing options...
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