Craig Thomas Posted January 17, 2016 Share Posted January 17, 2016 Hi guys. I need some help with a bold size question. A week or so ago now I had a little accident down the field, nothing too bad, just a broken prop. Came home, removed the prop so could replace. I didn't have a prop at the time so I screwed the bolts in the engine so as not to loose them. I should at this point say the engine is a dle35. Next morning, went into the garage to find the whole plane on the floor. The wall bracket came out and the plane hit the deck. Nose diving bolts first on to the floor. Snapped the fuse in 1 section and bent prop bolts. Looked in the engine manual to find they are m4x40mm. So ordered some from hobby King, I've just tried them this morning and they screw in fine, but are slack in the threads. Why is this? The proper doe bolts are solid with no movement in the thread? Can anyone please advise as to what size I need and where to get from? Sorry for the long winded story, but feel I needed to vent a little 🙄🙄🙄 Edited By Craig Thomas on 17/01/2016 14:40:32 Quote Link to comment Share on other sites More sharing options...
Chris Barlow Posted January 17, 2016 Share Posted January 17, 2016 Could be poor manufacturing of the bolts. You could use blue threadlock or order some different bolts.Try model fixings. Co.UK (or .com) for good quality boltsEdited By Chris Barlow on 17/01/2016 14:53:35 Quote Link to comment Share on other sites More sharing options...
A.A. Barry Posted January 17, 2016 Share Posted January 17, 2016 Craig, this the problem that happes a lot, different manufactures have different machine tolerances. So what is needed is bolts that screw in with out the slop, H\K bolts vary in tolerances, bolt per bolt Order new ones from the DLE manufactures and all should be good All the best Barry Quote Link to comment Share on other sites More sharing options...
kc Posted January 17, 2016 Share Posted January 17, 2016 Try a good M4 nut and bolt and see if they are a better fit. The nut should fit both the HK bolts and the good bolt equally welI. The good bolt should fit the engine. Is it a better fit.? I wonder if they are really M4. Might be another thread - 3BA is very close to M4 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted January 17, 2016 Share Posted January 17, 2016 Hi . HK bolts are probably cheap chinese stuff. Could they be 4.5mm bolts or 3 BA as suggested. Measure the originals to make sure . Find a local engineer supplier they will match them upfor you . Make sure the replacement bolts are "High Tensile" as a prop in the face often offends . I Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 17, 2016 Share Posted January 17, 2016 According to this manual, the prop bolts are 4 x 40mm Quote Link to comment Share on other sites More sharing options...
Craig Thomas Posted January 17, 2016 Author Share Posted January 17, 2016 I ordered some 4x40 bolts but they seem very loose in the thread. I'm gonna pop into my local model shop see if they can help me, if not I'll pop into my local nut and bolt specialist. I surprised there can be that much of a variance in bolt sizes. Thanks guys. 👍 Quote Link to comment Share on other sites More sharing options...
bert baker Posted January 17, 2016 Share Posted January 17, 2016 I would recommend ordering the bolts from a DLE agent, it's not worth mucking about with such an important part. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted January 17, 2016 Share Posted January 17, 2016 I'd also recommend Modelfixings for a reliable source of decent quality bolts at a reasonable price in small quantities. Geoff Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 17, 2016 Share Posted January 17, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Shaunie Posted January 17, 2016 Share Posted January 17, 2016 Remember "High tensile" covers a multitude of sins, some call table 8.8 bolts high tensile but to me they are regular bolts. True high tensile bolts are either table 10.9 or table 12.9 with the latter being stronger but more brittle. For your application I would recommend 10.9, nevertheless it would be best to see what the manufacturers spec is. Buy quality bolts for this application. Shaunie. Quote Link to comment Share on other sites More sharing options...
Shaunie Posted January 17, 2016 Share Posted January 17, 2016 Look closely at the bolt heads they are often stamped with the rating. A quick googling found this **LINK** which shows relative strengths. Shaunie. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 17, 2016 Share Posted January 17, 2016 Posted by Craig Thomas on 17/01/2016 19:49:57: I ordered some 4x40 bolts but they seem very loose in the thread. I'm gonna pop into my local model shop see if they can help me, if not I'll pop into my local nut and bolt specialist. I surprised there can be that much of a variance in bolt sizes. Thanks guys. 👍 Did you order 4-40 (UNF) by any chance? They would certainly be very loose! I'm pretty sure they mean 4mm dia. x 40mm length. Quote Link to comment Share on other sites More sharing options...
onetenor Posted January 18, 2016 Share Posted January 18, 2016 He did say the manual said 4x40 mm surely that means 4 mm x 40 mm Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 18, 2016 Share Posted January 18, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.